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The soleus muscle, together with the gastrocnemius and plantaris, plantarflexes the foot at the ankle joint. It is innervated by the tibial nerve.
There are four muscles in the deep posterior compartment of the leg (Fig. 6.88)—the popliteus, flexor hallucis longus, flexor digitorum longus, and tibialis posterior (Table 6.7). The popliteus muscle acts on the knee, whereas the other three muscles act mainly on the foot.
The popliteus is the smallest and most superior of the deep muscles in the posterior compartment of the leg. It unlocks the extended knee at the initiation of flexion and stabilizes the knee by resisting lateral (external) rotation of the tibia on the femur. It is flat and triangular in shape, forms part of the floor of the popliteal fossa (Fig. 6.88), and is inserted into a broad triangular region above the soleal line on the posterior surface of the tibia.
The popliteus muscle ascends laterally across the lower aspect of the knee and originates from a tendon, which penetrates the fibrous membrane of the joint capsule of the knee. The tendon ascends laterally around the joint where it passes between the lateral meniscus and the fibrous membrane and then into a groove on the inferolateral aspect of the lateral femoral condyle. The tendon attaches to and originates from a depression at the anterior end of the groove.
When initiating gait from a standing position, contraction of the popliteus laterally rotates the femur on the fixed tibia, unlocking the knee joint. The popliteus muscle is innervated by the tibial nerve.
The flexor hallucis longus muscle originates on the lateral side of the posterior compartment of the leg and inserts into the plantar surface of the great toe on the medial side of the foot (Fig. 6.88). It arises mainly from the lower two-thirds of the posterior surface of the fibula and adjacent interosseous membrane.
The muscle fibers of the flexor hallucis longus converge inferiorly to form a large cord-like tendon, which passes behind the distal head of the tibia and then slips into a distinct groove on the posterior surface of the adjacent tarsal bone (talus) of the foot. The tendon curves anteriorly first under the talus and then under a shelf of bone (the sustentaculum tali), which projects medially from the calcaneus, and then continues anteriorly through the sole of the foot to insert on the inferior surface of the base of the distal phalanx of the great toe.
The flexor hallucis longus flexes the great toe. It is particularly active during the toe-off phase of walking when the body is propelled forward off the stance leg and the great toe is the last part of the foot to leave the ground. It can also contribute to plantarflexion of the foot at the ankle joint and is innervated by the tibial nerve.
The flexor digitorum longus muscle originates on the medial side of the posterior compartment of the leg and inserts into the lateral four digits of the foot (Fig. 6.88). It arises mainly from the medial side of the posterior surface of the tibia inferior to the soleal line.
The flexor digitorum longus descends in the leg and forms a tendon, which crosses posterior to the tendon of the tibialis posterior muscle near the ankle joint. The tendon continues inferiorly in a shallow groove behind the medial malleolus and then swings forward to enter the sole of the foot. It crosses inferior to the tendon of the flexor hallucis longus muscle to reach the medial side of the foot and then divides into four tendons, which insert on the plantar surfaces of the bases of the distal phalanges of digits II to V.
The flexor digitorum longus flexes the lateral four toes. It is involved with gripping the ground during walking and propelling the body forward off the toes at the end of the stance phase of gait. It is innervated by the tibial nerve. |
The tibialis posterior muscle originates from the interosseous membrane and the adjacent posterior surfaces of the tibia and fibula (Fig. 6.88). It lies between and is overlapped by the flexor digitorum longus and the flexor hallucis longus muscles.
Near the ankle, the tendon of the tibialis posterior is crossed superficially by the tendon of the flexor digitorum longus muscle and lies medial to this tendon in the groove on the posterior surface of the medial malleolus. The tendon curves forward under the medial malleolus and enters the medial side of the foot. It wraps around the medial margin of the foot to attach to the plantar surfaces of the medial tarsal bones, mainly to the tuberosity of the navicular and to the adjacent region of the medial cuneiform.
The tibialis posterior inverts and plantarflexes the foot, and supports the medial arch of the foot during walking. It is innervated by the tibial nerve.
The popliteal artery is the major blood supply to the leg and foot and enters the posterior compartment of the leg from the popliteal fossa behind the knee (Fig. 6.89).
The popliteal artery passes into the posterior compartment of the leg between the gastrocnemius and popliteus muscles. As it continues inferiorly it passes under the tendinous arch formed between the fibular and tibial heads of the soleus muscle and enters the deep region of the posterior compartment of the leg where it immediately divides into an anterior tibial artery and a posterior tibial artery.
Two large sural arteries, one on each side, branch from the popliteal artery to supply the gastrocnemius, soleus, and plantaris muscles (Fig. 6.89). In addition, the popliteal artery gives rise to branches that contribute to a collateral network of vessels around the knee joint (see Fig. 6.80).
The anterior tibial artery passes forward through the aperture in the upper part of the interosseous membrane and enters and supplies the anterior compartment of the leg. It continues inferiorly onto the dorsal aspect of the foot.
The posterior tibial artery supplies the posterior and lateral compartments of the leg and continues into the sole of the foot (Fig. 6.89).
The posterior tibial artery descends through the deep region of the posterior compartment of the leg on the superficial surfaces of the tibialis posterior and flexor digitorum longus muscles. It passes through the tarsal tunnel behind the medial malleolus and into the sole of the foot.
In the leg, the posterior tibial artery supplies adjacent muscles and bone and has two major branches, the circumflex fibular artery and the fibular artery:
The circumflex fibular artery passes laterally through the soleus muscle and around the neck of the fibula to connect with the anastomotic network of vessels surrounding the knee (Fig. 6.89; see also Fig. 6.80).
The fibular artery parallels the course of the tibial artery, but descends along the lateral side of the posterior compartment adjacent to the medial crest on the posterior surface of the fibula, which separates the attachments of the tibialis posterior and flexor hallucis longus muscles.
The fibular artery supplies adjacent muscles and bone in the posterior compartment of the leg and also has branches that pass laterally through the intermuscular septum to supply the fibularis muscles in the lateral compartment of the leg.
A perforating branch that originates from the fibular artery distally in the leg passes anteriorly through the inferior aperture in the interosseous membrane to anastomose with a branch of the anterior tibial artery.
The fibular artery passes behind the attachment between the distal ends of the tibia and fibula and terminates in a network of vessels over the lateral surface of the calcaneus.
Deep veins in the posterior compartment generally follow the arteries.
The nerve associated with the posterior compartment of the leg is the tibial nerve (Fig. 6.90), a major branch of the sciatic nerve that descends into the posterior compartment from the popliteal fossa. |
The tibial nerve passes under the tendinous arch formed between the fibular and tibial heads of the soleus muscle and passes vertically through the deep region of the posterior compartment of the leg on the surface of the tibialis posterior muscle with the posterior tibial vessels.
The tibial nerve leaves the posterior compartment of the leg at the ankle by passing through the tarsal tunnel behind the medial malleolus. It enters the foot to supply most intrinsic muscles and skin.
In the leg, the tibial nerve gives rise to: branches that supply all the muscles in the posterior compartment of the leg, and two cutaneous branches, the sural nerve and medial calcaneal nerve.
Branches of the tibial nerve that innervate the superficial group of muscles of the posterior compartment and popliteus muscle of the deep group originate high in the leg between the two heads of the gastrocnemius muscle in the distal region of the popliteal fossa (Fig. 6.91). Branches innervate the gastrocnemius, plantaris, and soleus muscles, and pass more deeply into the popliteus muscle.
Branches to the deep muscles of the posterior compartment originate from the tibial nerve deep to the soleus muscle in the upper half of the leg and innervate the tibialis posterior, flexor hallucis longus, and flexor digitorum longus muscles.
The sural nerve originates high in the leg between the two heads of the gastrocnemius muscle (Fig. 6.90). It descends superficial to the belly of the gastrocnemius muscle and penetrates through the deep fascia approximately in the middle of the leg where it is joined by a sural communicating branch from the common fibular nerve. It passes down the leg, around the lateral malleolus, and into the foot.
The sural nerve supplies skin on the lower posterolateral surface of the leg and the lateral side of the foot and little toe.
The medial calcaneal nerve is often multiple and originates from the tibial nerve low in the leg near the ankle and descends onto the medial side of the heel.
The medial calcaneal nerve innervates skin on the medial surface and sole of the heel (Fig. 6.90).
Lateral compartment of leg
There are two muscles in the lateral compartment of the leg—the fibularis longus and fibularis brevis (Fig. 6.91 and Table 6.8). Both evert the foot (turn the sole outward) and are innervated by the superficial fibular nerve, which is a branch of the common fibular nerve.
The fibularis longus muscle arises in the lateral compartment of the leg, but its tendon crosses under the foot to attach to bones on the medial side (Fig. 6.91). It originates from both the upper lateral surface of the fibula and from the anterior aspect of the fibular head and occasionally up onto the adjacent region of the lateral tibial condyle.
The common fibular nerve passes anteriorly around the fibular neck between the attachments of the fibularis longus to the fibular head and shaft.
Distally, the fibularis longus descends in the leg to form a tendon, which, in order: passes posterior to the lateral malleolus in a shallow bony groove, swings forward to enter the lateral side of the foot, descends obliquely down the lateral side of the foot where it curves forward under a bony tubercle (fibular trochlea) of the calcaneus, enters a deep groove on the inferior surface of one of the other tarsal bones (the cuboid), and swings under the foot to cross the sole and attach to the inferior surfaces of bones on the medial side of the foot (lateral sides of the base of metatarsal I and the distal end of the medial cuneiform).
The fibularis longus everts and plantarflexes the foot. |
In addition, the fibularis longus, tibialis anterior, and tibialis posterior muscles, which all insert on the undersurfaces of bones on the medial side of the foot, together act as a stirrup to support the arches of the foot. The fibularis longus supports mainly the lateral and transverse arches.
The fibularis longus is innervated by the superficial fibular nerve.
The fibularis brevis muscle is deep to the fibularis longus muscle in the leg and originates from the lower two-thirds of the lateral surface of the shaft of the fibula (Fig. 6.91).
The tendon of the fibularis brevis passes behind the lateral malleolus with the tendon of the fibularis longus muscle and then curves forward across the lateral surface of the calcaneus to attach to a tubercle on the lateral surface of the base of metatarsal V (the metatarsal associated with the little toe).
The fibularis brevis assists in eversion of the foot and is innervated by the superficial fibular nerve.
No major artery passes vertically through the lateral compartment of the leg. It is supplied by branches (mainly from the fibular artery in the posterior compartment of the leg) that penetrate into the lateral compartment (Fig. 6.92).
Deep veins generally follow the arteries.
The nerve associated with the lateral compartment of the leg is the superficial fibular nerve. This nerve originates as one of the two major branches of the common fibular nerve, which enters the lateral compartment of the leg from the popliteal fossa (Fig. 6.92B).
The common fibular nerve originates from the sciatic nerve in the posterior compartment of the thigh or in the popliteal fossa (Fig. 6.92A), and follows the medial margin of the biceps femoris tendon over the lateral head of the gastrocnemius muscle and toward the fibula. Here it gives origin to two cutaneous branches, which descend in the leg: the sural communicating nerve, which joins the sural branch of the tibial nerve and contributes to innervation of skin over the lower posterolateral side of the leg; and the lateral sural cutaneous nerve, which innervates skin over the upper lateral leg.
The common fibular nerve continues around the neck of the fibula and enters the lateral compartment by passing between the attachments of the fibularis longus muscle to the head and shaft of the fibula. Here the common fibular nerve divides into its two terminal branches: the superficial fibular nerve, and the deep fibular nerve.
The superficial fibular nerve descends in the lateral compartment deep to the fibularis longus and innervates the fibularis longus and fibularis brevis (Fig. 6.91B). It then penetrates deep fascia in the lower leg and enters the foot where it divides into medial and lateral branches, which supply dorsal areas of the foot and toes except for: the web space between the great and second toes, which is supplied by the deep fibular nerve; and the lateral side of the little toe, which is supplied by the sural branch of the tibial nerve.
The deep fibular nerve passes anteromedially through the intermuscular septum into the anterior compartment of the leg, which it supplies.
Anterior compartment of leg
There are four muscles in the anterior compartment of the leg—the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius (Fig. 6.93 and Table 6.9). Collectively they dorsiflex the foot at the ankle joint, extend the toes, and invert the foot. All are innervated by the deep fibular nerve, which is a branch of the common fibular nerve.
The tibialis anterior muscle is the most anterior and medial of the muscles in the anterior compartment of the leg (Fig. 6.93). It originates mainly from the upper two-thirds of the lateral surface of the shaft of the tibia and adjacent surface of the interosseous membrane. It also originates from deep fascia. |
The muscle fibers of the tibialis anterior converge in the lower one-third of the leg to form a tendon, which descends into the medial side of the foot, where it attaches to the medial and inferior surfaces of one of the tarsal bones (medial cuneiform) and adjacent parts of metatarsal I associated with the great toe.
The tibialis anterior dorsiflexes the foot at the ankle joint and inverts the foot at the intertarsal joints. During walking, it provides dynamic support for the medial arch of the foot.
The tibialis anterior is innervated by the deep fibular nerve.
The extensor hallucis longus muscle lies next to and is partly overlapped by the tibialis anterior muscle (Fig. 6.93). It originates from the middle one-half of the medial surface of the fibula and adjacent interosseous membrane.
The tendon of the extensor hallucis longus appears between the tendons of the tibialis anterior and extensor digitorum longus in the lower one-half of the leg and descends into the foot. It continues anteriorly on the medial side of the dorsal surface of the foot to near the end of the great toe where it inserts on the upper surface of the base of the distal phalanx.
The extensor hallucis longus extends the great toe. Because it crosses anterior to the ankle joint, it also dorsiflexes the foot at the ankle joint. Like all muscles in the anterior compartment of the leg, the extensor hallucis longus muscle is innervated by the deep fibular nerve.
The extensor digitorum longus muscle is the most posterior and lateral of the muscles in the anterior compartment of the leg (Fig. 6.93). It originates mainly from the upper one-half of the medial surface of the fibula lateral to and above the origin of the extensor hallucis longus muscle, and extends superiorly onto the lateral condyle of the tibia. Like the tibialis anterior muscle, it also originates from deep fascia.
The extensor digitorum longus muscle descends to form a tendon, which continues into the dorsal aspect of the foot, where it divides into four tendons, which insert, via dorsal digital expansions, into the dorsal surfaces of the bases of the middle and distal phalanges of the lateral four toes.
The extensor digitorum longus extends the toes and dorsiflexes the foot at the ankle joint, and is innervated by the deep fibular nerve.
The fibularis tertius muscle is normally considered part of the extensor digitorum longus (Fig. 6.93). The fibularis tertius originates from the medial surface of the fibula immediately below the origin of the extensor digitorum longus muscle and the two muscles are normally connected.
The tendon of the fibularis tertius descends into the foot with the tendon of the extensor digitorum longus. On the dorsal aspect of the foot, it deviates laterally to insert into the dorsomedial surface of the base of metatarsal V (the metatarsal associated with the little toe).
The fibularis tertius assists in dorsiflexion and possibly eversion of the foot, and is innervated by the deep fibular nerve.
The artery associated with the anterior compartment of the leg is the anterior tibial artery, which originates from the popliteal artery in the posterior compartment of the leg and passes forward into the anterior compartment of the leg through an aperture in the interosseous membrane.
The anterior tibial artery descends through the anterior compartment on the interosseous membrane (Fig. 6.94). In the distal leg, it lies between the tendons of the tibialis anterior and extensor hallucis longus muscles. It leaves the leg by passing anterior to the distal end of the tibia and ankle joint and continues onto the dorsal aspect of the foot as the dorsalis pedis artery.
In the proximal leg, the anterior tibial artery has a recurrent branch, which connects with the anastomotic network of vessels around the knee joint. |
Along its course, the anterior tibial artery supplies numerous branches to adjacent muscles and is joined by the perforating branch of the fibular artery, which passes forward through the lower aspect of the interosseous membrane from the posterior compartment of the leg.
Distally, the anterior tibial artery gives rise to an anterior medial malleolar artery and an anterior lateral malleolar artery, which pass posteriorly around the distal ends of the tibia and fibula, respectively, and connect with vessels from the posterior tibial and fibular arteries to form an anastomotic network around the ankle.
Deep veins follow the arteries and have similar names.
The nerve associated with the anterior compartment of the leg is the deep fibular nerve (Fig. 6.94). This nerve originates in the lateral compartment of the leg as one of the two divisions of the common fibular nerve.
The deep fibular nerve passes anteromedially through the intermuscular septum that separates the lateral from the anterior compartments of the leg and then passes deep to the extensor digitorum longus. It reaches the anterior interosseous membrane where it meets and descends with the anterior tibial artery.
The deep fibular nerve: innervates all muscles in the anterior compartment; then continues into the dorsal aspect of the foot where it innervates the extensor digitorum brevis, contributes to the innervation of the first two dorsal interossei muscles, and supplies the skin between the great and second toes.
The foot is the region of the lower limb distal to the ankle joint. It is subdivided into the ankle, the metatarsus, and the digits.
There are five digits consisting of the medially placed digits, ending laterally with the little toe (digit V) (Fig. 6.95).
The foot has a superior surface (dorsum of foot) and an inferior surface (sole; Fig. 6.95).
Abduction and adduction of the toes are defined with respect to the long axis of the second digit. Unlike in the hand, where the thumb is oriented 90° to the other fingers, the great toe is oriented in the same position as the other toes. The foot is the body’s point of contact with the ground and provides a stable platform for upright stance. It also levers the body forward during walking.
There are three groups of bones in the foot (Fig. 6.96): the seven tarsal bones, which form the skeletal framework for the ankle; metatarsals (I to V), which are the bones of the metatarsus; and the phalanges, which are the bones of the toes—each toe has three phalanges, except for the great toe, which has two.
The tarsal bones are arranged in a proximal group and a distal group with an intermediate bone between the two groups on the medial side of the foot (Fig. 6.96A).
The proximal group consists of two large bones, the talus (Latin for “ankle”) and the calcaneus (Latin for “heel”):
The talus is the most superior bone of the foot and sits on top of and is supported by the calcaneus (Fig. 6.96B)—it articulates above with the tibia and fibula to form the ankle joint and also projects forward to articulate with the intermediate tarsal bone (navicular) on the medial side of the foot.
The calcaneus is the largest of the tarsal bones—posteriorly it forms the bony framework of the heel and anteriorly it projects forward to articulate with one of the distal group of tarsal bones (cuboid) on the lateral side of the foot.
The talus, when viewed from the medial or lateral sides, is snail-shaped (Fig. 6.97A,B). It has a rounded head, which is projected forward and medially at the end of a short broad neck, which is connected posteriorly to an expanded body.
Anteriorly, the head of the talus is domed for articulation with a corresponding circular depression on the posterior surface of the navicular bone. Inferiorly, this domed articular surface is continuous with an additional three articular facets separated by smooth ridges: |
The anterior and middle facets articulate with adjacent surfaces on the calcaneus bone.
The other facet, medial to the facets for articulation with the calcaneus, articulates with a ligament—the plantar calcaneonavicular ligament (spring ligament)—which connects the calcaneus to the navicular under the head of the talus.
The neck of the talus is marked by a deep groove (the sulcus tali), which passes obliquely forward across the inferior surface from medial to lateral, and expands dramatically on the lateral side. Posterior to the sulcus tali is a large facet (posterior calcaneal surface) for articulation with the calcaneus.
The superior aspect of the body of the talus is elevated to fit into the socket formed by the distal ends of the tibia and fibula to form the ankle joint:
The upper (trochlear) surface of this elevated region articulates with the inferior end of the tibia.
The medial surface articulates with the medial malleolus of the tibia.
The lateral surface articulates with the lateral malleolus of the fibula.
Because the lateral malleolus is larger and projects more inferiorly than the medial malleolus at the ankle joint, the corresponding lateral articular surface on the talus is larger and projects more inferiorly than the medial surface.
The lower part of the lateral surface of the body of the talus, which supports the lower part of the facet for articulation with the fibula, forms a bony projection (the lateral process).
The inferior surface of the body of the talus has a large oval concave facet (the posterior calcaneal articular facet) for articulation with the calcaneus.
The posterior aspect of the body of the talus consists of a backward and medially facing projection (the posterior process). The posterior process is marked on its surface by a lateral tubercle and a medial tubercle, which bracket between them the groove for the tendon of the flexor hallucis longus as it passes from the leg into the foot.
The calcaneus sits under and supports the talus. It is an elongate, irregular, box-shaped bone with its long axis generally oriented along the midline of the foot, but deviating lateral to the midline anteriorly (Fig. 6.98).
The calcaneus projects behind the ankle joint to form the skeletal framework of the heel. The posterior surface of this heel region is circular and divided into upper, middle, and lower parts. The calcaneal tendon (Achilles tendon) attaches to the middle part:
The upper part is separated from the calcaneal tendon by a bursa.
The lower part curves forward, is covered by subcutaneous tissue, is the weight-bearing region of the heel, and is continuous onto the plantar surface of the bone as the calcaneal tuberosity.
The calcaneal tuberosity projects forward on the plantar surface as a large medial process and a small lateral process separated from each other by a V-shaped notch (Fig. 6.98B). At the anterior end of the plantar surface is a tubercle (the calcaneal tubercle) for the posterior attachment of the short plantar ligament of the sole of the foot.
The lateral surface of the calcaneus has a smooth contour except for two slightly raised regions (Fig. 6.98C). One of these raised areas—the fibular trochlea (peroneal tubercle)—is anterior to the middle of the surface and often has two shallow grooves, which pass, one above the other, obliquely across its surface. The tendons of the fibularis brevis and longus muscles are bound to the trochlea as they pass over the lateral side of the calcaneus.
Superior and posterior to the fibular trochlea is a second raised area or tubercle for attachment of the calcaneofibular part of the lateral collateral ligament of the ankle joint. |
The medial surface of the calcaneus is concave and has one prominent feature associated with its upper margin (the sustentaculum tali; Fig. 6.98A), which is a shelf of bone projecting medially and supporting the more posterior part of the head of the talus.
The underside of the sustentaculum tali has a distinct groove running from posterior to anterior and along which the tendon of the flexor hallucis longus muscle travels into the sole of the foot.
The superior surface of the sustentaculum tali has a facet (middle talar articular surface) for articulation with the corresponding middle facet on the head of the talus.
Anterior and posterior talar articular surfaces are on the superior surface of the calcaneus itself (Fig. 6.98A):
The anterior talar articular surface is small and articulates with the corresponding anterior facet on the head of the talus.
The posterior talar articular surface is large and is approximately near the middle of the superior surface of the calcaneus.
Between the posterior talar articular surface, which articulates with the body of the talus, and the other two articular surfaces, which articulate with the head of the talus, is a deep groove (the calcaneal sulcus; Fig. 6.98A,C).
The calcaneal sulcus on the superior surface of the calcaneus and the sulcus tali on the inferior surface of the talus together form the tarsal sinus, which is a large gap between the anterior ends of the calcaneus and talus that is visible when the skeleton of the foot is viewed from its lateral aspect (Fig. 6.99).
The intermediate tarsal bone on the medial side of the foot is the navicular (boat shaped) (Fig. 6.96). This bone articulates behind with the talus and articulates in front and on the lateral side with the distal group of tarsal bones.
One distinctive feature of the navicular is a prominent rounded tuberosity for the attachment of the tibialis posterior tendon, which projects inferiorly on the medial side of the plantar surface of the bone.
From lateral to medial, the distal group of tarsal bones consists of (Fig. 6.96):
The cuboid (Greek for “cube”), which articulates posteriorly with the calcaneus, medially with the lateral cuneiform, and anteriorly with the bases of the lateral two metatarsals—the tendon of the fibularis longus muscle lies in a prominent groove on the anterior plantar surface, which passes obliquely forward across the bone from lateral to medial.
Three cuneiforms (Latin for “wedge”)—the lateral, intermediate, and medial cuneiform bones, in addition to articulating with each other, articulate posteriorly with the navicular bone and anteriorly with the bases of the medial three metatarsals.
There are five metatarsals in the foot, numbered I to V from medial to lateral (Fig. 6.100). Metatarsal I, associated with the great toe, is shortest and thickest. The second is the longest.
Each metatarsal has a head at the distal end, an elongate shaft in the middle, and a proximal base.
The head of each metatarsal articulates with the proximal phalanx of a toe and the base articulates with one or more of the distal group of tarsal bones. The plantar surface of the head of metatarsal I also articulates with two sesamoid bones.
The sides of the bases of metatarsals II to V also articulate with each other. The lateral side of the base of metatarsal V has a prominent tuberosity, which projects posteriorly and is the attachment site for the tendon of the fibularis brevis muscle.
The phalanges are the bones of the toes (Fig. 6.100). Each toe has three phalanges (proximal, middle, and distal), except for the great toe, which has only two (proximal and distal).
Each phalanx consists of a base, a shaft, and a distal head: |
The base of each proximal phalanx articulates with the head of the related metatarsal.
The head of each distal phalanx is nonarticular and flattened into a crescent-shaped plantar tuberosity under the plantar pad at the end of the digit.
In each toe, the total length of the phalanges combined is much shorter than the length of the associated metatarsal.
The ankle joint is synovial in type and involves the talus of the foot and the tibia and fibula of the leg (Fig. 6.102).
The ankle joint mainly allows hinge-like dorsiflexion and plantarflexion of the foot on the leg.
The distal end of the fibula is firmly anchored to the larger distal end of the tibia by strong ligaments. Together, the fibula and tibia create a deep bracket-shaped socket for the upper expanded part of the body of the talus:
The roof of the socket is formed by the inferior surface of the distal end of the tibia.
The medial side of the socket is formed by the medial malleolus of the tibia.
The longer lateral side of the socket is formed by the lateral malleolus of the fibula.
The articular surfaces are covered by hyaline cartilage.
The articular part of the talus is shaped like a short half-cylinder tipped onto its flat side with one end facing lateral and the other end facing medial. The curved upper surface of the half-cylinder and the two ends are covered by hyaline cartilage and fit into the bracket-shaped socket formed by the distal ends of the tibia and fibula.
When viewed from above, the articular surface of the talus is much wider anteriorly than it is posteriorly. As a result, the bone fits tighter into its socket when the foot is dorsiflexed and the wider surface of the talus moves into the ankle joint than when the foot is plantarflexed and the narrower part of the talus is in the joint. The joint is therefore most stable when the foot is dorsiflexed.
The articular cavity is enclosed by a synovial membrane, which attaches around the margins of the articular surfaces, and by a fibrous membrane, which covers the synovial membrane and is also attached to the adjacent bones.
The ankle joint is stabilized by medial (deltoid) and lateral ligaments.
The medial (deltoid) ligament is large, strong (Fig. 6.103), and triangular in shape. Its apex is attached above to the medial malleolus and its broad base is attached below to a line that extends from the tuberosity of the navicular bone in front to the medial tubercle of the talus behind.
The medial ligament is subdivided into four parts based on the inferior points of attachment:
The part that attaches in front to the tuberosity of the navicular and the associated margin of the plantar calcaneonavicular ligament (spring ligament), which connects the navicular bone to the sustentaculum tali of the calcaneus bone behind, is the tibionavicular part of the medial ligament.
The tibiocalcaneal part, which is more central, attaches to the sustentaculum tali of the calcaneus bone.
The posterior tibiotalar part attaches to the medial side and medial tubercle of the talus.
The fourth part (the anterior tibiotalar part) is deep to the tibionavicular and tibiocalcaneal parts of the medial ligament and attaches to the medial surface of the talus.
The lateral ligament of the ankle is composed of three separate ligaments, the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament (Fig. 6.104):
The anterior talofibular ligament is a short ligament, and attaches the anterior margin of the lateral malleolus to the adjacent region of the talus.
The posterior talofibular ligament runs horizontally backward and medially from the malleolar fossa on the medial side of the lateral malleolus to the posterior process of the talus. |
The calcaneofibular ligament is attached above to the malleolar fossa on the posteromedial side of the lateral malleolus and passes posteroinferiorly to attach below to a tubercle on the lateral surface of the calcaneus.
The numerous synovial joints between the individual tarsal bones mainly invert, evert, supinate, and pronate the foot:
Inversion and eversion is turning the whole sole of the foot inward and outward, respectively.
Pronation is rotating the front of the foot laterally relative to the back of the foot, and supination is the reverse movement.
Pronation and supination allow the foot to maintain normal contact with the ground when in different stances or when standing on irregular surfaces.
The major joints at which movements occur include the subtalar, talocalcaneonavicular, and calcaneocuboid joints (Fig. 6.105). The talocalcaneonavicular and calcaneocuboid joints together form what is often referred to as the transverse tarsal joint.
Intertarsal joints between the cuneiforms and between the cuneiforms and the navicular allow only limited movement.
The joint between the cuboid and navicular is normally fibrous.
The subtalar joint is between: the large posterior calcaneal facet on the inferior surface of the talus, and the corresponding posterior talar facet on the superior surface of the calcaneus.
The articular cavity is enclosed by synovial membrane, which is covered by a fibrous membrane.
The subtalar joint allows gliding and rotation, which are involved in inversion and eversion of the foot. Lateral, medial, posterior, and interosseous talocalcaneal ligaments stabilize the joint. The interosseous talocalcaneal ligament lies in the tarsal sinus (Fig. 6.106).
The talocalcaneonavicular joint is a complex joint in which the head of the talus articulates with the calcaneus and plantar calcaneonavicular ligament (spring ligament) below and the navicular in front (Fig. 6.107A).
The talocalcaneonavicular joint allows gliding and rotation movements, which together with similar movements of the subtalar joint are involved with inversion and eversion of the foot. It also participates in pronation and supination.
The parts of the talocalcaneonavicular joint between the talus and calcaneus are: the anterior and middle calcaneal facets on the inferior surface of the talar head, and the corresponding anterior and middle talar facets on the superior surface and sustentaculum tali, respectively, of the calcaneus (Fig. 6.107B).
The part of the joint between the talus and the plantar calcaneonavicular ligament (spring ligament) is between the ligament and the medial facet on the inferior surface of the talar head.
The joint between the navicular and talus is the largest part of the talocalcaneonavicular joint and is between the ovoid anterior end of the talar head and the corresponding concave posterior surface of the navicular.
The capsule of the talocalcaneonavicular joint, which is a synovial joint, is reinforced: posteriorly by the interosseous talocalcaneal ligament, superiorly by the talonavicular ligament, which passes between the neck of the talus and adjacent regions of the navicular, and inferiorly by the plantar calcaneonavicular ligament (spring ligament) (Fig. 6.107C,D).
The lateral part of the talocalcaneonavicular joint is reinforced by the calcaneonavicular part of the bifurcate ligament, which is a Y-shaped ligament superior to the joint. The base of the bifurcate ligament is attached to the anterior aspect of the superior surface of the calcaneus and its arms are attached to: the dorsomedial surface of the cuboid (calcaneocuboid ligament), and the dorsolateral part of the navicular (calcaneonavicular ligament). |
The plantar calcaneonavicular ligament (spring ligament) is a broad thick ligament that spans the space between the sustentaculum tali behind and the navicular bone in front (Fig. 6.107B,C). It supports the head of the talus, takes part in the talocalcaneonavicular joint, and resists depression of the medial arch of the foot.
The calcaneocuboid joint is a synovial joint between: the facet on the anterior surface of the calcaneus, and the corresponding facet on the posterior surface of the cuboid.
The calcaneocuboid joint allows sliding and rotating movements involved with inversion and eversion of the foot, and also contributes to pronation and supination of the forefoot on the hindfoot.
The calcaneocuboid joint is reinforced by the bifurcate ligament (see above) and by the long plantar ligament and the plantar calcaneocuboid ligament (short plantar ligament).
The plantar calcaneocuboid ligament (short plantar ligament) is short, wide, and very strong, and connects the calcaneal tubercle to the inferior surface of the cuboid (Fig. 6.108A). It not only supports the calcaneocuboid joint, but also assists the long plantar ligament in resisting depression of the lateral arch of the foot.
The long plantar ligament is the longest ligament in the sole of the foot and lies inferior to the plantar calcaneocuboid ligament (Fig. 6.108B):
Posteriorly, it attaches to the inferior surface of the calcaneus between the tuberosity and the calcaneal tubercle.
Anteriorly, it attaches to a broad ridge and a tubercle on the inferior surface of the cuboid bone behind the groove for the fibularis longus tendon.
More superficial fibers of the long plantar ligament extend to the bases of the metatarsal bones.
The long plantar ligament supports the calcaneocuboid joint and is the strongest ligament, resisting depression of the lateral arch of the foot.
The tarsometatarsal joints between the metatarsal bones and adjacent tarsal bones are plane joints and allow limited sliding movements (Fig. 6.109).
The range of movement of the tarsometatarsal joint between the metatarsal of the great toe and the medial cuneiform is greater than that of the other tarsometatarsal joints and allows flexion, extension, and rotation. The tarsometatarsal joints, with the transverse tarsal joint, take part in pronation and supination of the foot.
The metatarsophalangeal joints are ellipsoid synovial joints between the sphere-shaped heads of the metatarsals and the corresponding bases of the proximal phalanges of the digits.
The metatarsophalangeal joints allow extension and flexion, and limited abduction, adduction, rotation, and circumduction.
The joint capsules are reinforced by medial and lateral collateral ligaments, and by plantar ligaments, which have grooves on their plantar surfaces for the long tendons of the digits (Fig. 6.109).
Four deep transverse metatarsal ligaments link the heads of the metatarsals together and enable the metatarsals to act as a single unified structure (Fig. 6.109). The ligaments blend with the plantar ligaments of the adjacent metatarsophalangeal joints.
The metatarsal of the great toe is oriented in the same plane as the metatarsals of the other toes and is linked to the metatarsal of the second toe by a deep transverse metatarsal ligament. In addition, the joint between the metatarsal of the great toe and medial cuneiform has a limited range of motion. The great toe therefore has a very restricted independent function—unlike the thumb in the hand, where the metacarpal is oriented 90° to the metacarpals of the fingers, there is no deep transverse metacarpal ligament between the metacarpals of the thumb and index finger, and the joint between the metacarpal and carpal bone allows a wide range of motion. |
The interphalangeal joints are hinge joints that allow mainly flexion and extension. They are reinforced by medial and lateral collateral ligaments and by plantar ligaments (Fig. 6.109).
Tarsal tunnel, retinacula, and arrangement of major structures at the ankle
The tarsal tunnel is formed on the posteromedial side of the ankle by: a depression formed by the medial malleolus of the tibia, the medial and posterior surfaces of the talus, the medial surface of the calcaneus, and the inferior surface of the sustentaculum tali of the calcaneus; and an overlying flexor retinaculum (Fig. 6.110).
The flexor retinaculum is a strap-like layer of connective tissue that spans the bony depression formed by the medial malleolus, the medial and posterior surfaces of the talus, the medial surface of the calcaneus, and the inferior surface of the sustentaculum tali (Fig. 6.110). It attaches above to the medial malleolus and below and behind to the inferomedial margin of the calcaneus.
The retinaculum is continuous above with the deep fascia of the leg and below with the deep fascia (plantar aponeurosis) of the foot.
Septa from the flexor retinaculum convert grooves on the bones into tubular connective tissue channels for the tendons of the flexor muscles as they pass into the sole of the foot from the posterior compartment of the leg (Fig. 6.110). Free movement of the tendons in the channels is facilitated by synovial sheaths, which surround the tendons.
Two compartments on the posterior surface of the medial malleolus are for the tendons of the tibialis posterior and flexor digitorum longus muscles. The tendon of the tibialis posterior is medial to the tendon of the flexor digitorum longus.
Immediately lateral to the tendons of the tibialis posterior and flexor digitorum longus, the posterior tibial artery with its associated veins and the tibial nerve pass through the tarsal tunnel into the sole of the foot. The pulse of the posterior tibial artery can be felt through the flexor retinaculum midway between the medial malleolus and the calcaneus.
Lateral to the tibial nerve is the compartment on the posterior surface of the talus and the undersurface of the sustentaculum tali for the tendon of the flexor hallucis longus muscle.
Two extensor retinacula strap the tendons of the extensor muscles to the ankle region and prevent tendon bowing during extension of the foot and toes (Fig. 6.111):
A superior extensor retinaculum is a thickening of deep fascia in the distal leg just superior to the ankle joint and attached to the anterior borders of the fibula and tibia.
An inferior retinaculum is Y-shaped, attached by its base to the lateral side of the upper surface of the calcaneus, and crosses medially over the foot to attach by one of its arms to the medial malleolus, whereas the other arm wraps medially around the foot and attaches to the medial side of the plantar aponeurosis.
The tendons of the extensor digitorum longus and fibularis tertius pass through a compartment on the lateral side of the proximal foot. Medial to these tendons, the dorsalis pedis artery (terminal branch of the anterior tibial artery), the tendon of the extensor hallucis longus muscle, and finally the tendon of the tibialis anterior muscle pass under the extensor retinacula.
Fibular (peroneal) retinacula bind the tendons of the fibularis longus and fibularis brevis muscles to the lateral side of the foot (Fig. 6.112):
A superior fibular retinaculum extends between the lateral malleolus and the calcaneus. |
An inferior fibular retinaculum attaches to the lateral surface of the calcaneus around the fibular trochlea and blends above with the fibers of the inferior extensor retinaculum.
At the fibular trochlea, a septum separates the compartment for the tendon of the fibularis brevis muscle above from that for the fibularis longus below.
Arches of the foot
The bones of the foot do not lie in a horizontal plane. Instead, they form longitudinal and transverse arches relative to the ground (Fig. 6.113), which absorb and distribute downward forces from the body during standing and moving on different surfaces.
The longitudinal arch of the foot is formed between the posterior end of the calcaneus and the heads of the metatarsals (Fig. 6.113A). It is highest on the medial side, where it forms the medial part of the longitudinal arch, and lowest on the lateral side, where it forms the lateral part.
The transverse arch of the foot is highest in a coronal plane that cuts through the head of the talus and disappears near the heads of the metatarsals, where these bones are held together by the deep transverse metatarsal ligaments (Fig. 6.113B).
Ligaments and muscles support the arches of the foot (Fig. 6.114):
Ligaments that support the arches include the plantar calcaneonavicular (spring ligament), plantar calcaneocuboid (short plantar ligament), and long plantar ligaments, and the plantar aponeurosis.
Muscles that provide dynamic support for the arches during walking include the tibialis anterior and posterior and the fibularis longus.
The plantar aponeurosis is a thickening of deep fascia in the sole of the foot (Fig. 6.115). It is firmly anchored to the medial process of the calcaneal tuberosity and extends forward as a thick band of longitudinally arranged connective tissue fibers. The fibers diverge as they pass anteriorly and form digital bands, which enter the toes and connect with bones, ligaments, and dermis of the skin.
Distal to the metatarsophalangeal joints, the digital bands of the plantar aponeurosis are interconnected by transverse fibers, which form superficial transverse metatarsal ligaments.
The plantar aponeurosis supports the longitudinal arch of the foot and protects deeper structures in the sole.
Fibrous sheaths of toes
The tendons of the flexor digitorum longus, flexor digitorum brevis, and flexor hallucis longus muscles enter fibrous digital sheaths or tunnels on the plantar aspect of the digits (Fig. 6.116). These fibrous sheaths begin anterior to the metatarsophalangeal joints and extend to the distal phalanges. They are formed by fibrous arches and cruciate (cross-shaped) ligaments attached posteriorly to the margins of the phalanges and to the plantar ligaments associated with the metatarsophalangeal and interphalangeal joints.
These fibrous tunnels hold the tendons to the bony plane and prevent tendon bowing when the toes are flexed. Within each tunnel, the tendons are surrounded by a synovial sheath.
The tendons of the extensor digitorum longus, extensor digitorum brevis, and extensor hallucis longus pass into the dorsal aspect of the digits and expand over the proximal phalanges to form complex dorsal digital expansions (“extensor hoods”) (Fig. 6.117).
Each extensor hood is triangular in shape with the apex attached to the distal phalanx, the central region attached to the middle (toes II to V) or proximal (toe I) phalanx, and each corner of the base wrapped around the sides of the metatarsophalangeal joint. The corners of the hoods attach mainly to the deep transverse metatarsal ligaments. |
Many of the intrinsic muscles of the foot insert into the free margin of the hood on each side. The attachment of these muscles into the extensor hoods allows the forces from these muscles to be distributed over the toes to cause flexion of the metatarsophalangeal joints while at the same time extending the interphalangeal joints (Fig. 6.117). The function of these movements in the foot is uncertain, but they may prevent overextension of the metatarsophalangeal joints and flexion of the interphalangeal joints when the heel is elevated off the ground and the toes grip the ground during walking.
Intrinsic muscles of the foot originate and insert in the foot: the extensor digitorum brevis and extensor hallucis brevis on the dorsal aspect of the foot; all other intrinsic muscles—the dorsal and plantar interossei, flexor digiti minimi brevis, flexor hallucis brevis, flexor digitorum brevis, quadratus plantae (flexor accessorius), abductor digiti minimi, abductor hallucis, and lumbricals—are on the plantar side of the foot in the sole where they are organized into four layers.
Intrinsic muscles mainly modify the actions of the long tendons and generate fine movements of the toes.
All intrinsic muscles of the foot are innervated by the medial and lateral plantar branches of the tibial nerve except for the extensor digitorum brevis, which is innervated by the deep fibular nerve. The first two dorsal interossei also may receive part of their innervation from the deep fibular nerve.
On the dorsal aspect
The extensor digitorum brevis is attached to a roughened area on the superolateral surface of the calcaneus lateral to the tarsal sinus (Fig. 6.118 and Table 6.10).
The flat muscle belly passes anteromedially over the foot, deep to the tendons of the extensor digitorum longus, and forms three tendons, which enter digits II, III, and IV. The tendons join the lateral sides of the tendons of the extensor digitorum longus. The extensor digitorum brevis extends the middle three toes through attachments to the long extensor tendons and extensor hoods. It is innervated by the deep fibular nerve.
The extensor hallucis brevis originates in conjunction with the extensor digitorum brevis. Its tendon attaches to the base of the proximal phalanx of the great toes. The muscle extends the metatarsophalangeal joint of the great toe and is innervated by the deep fibular nerve.
In the sole
The muscles in the sole of the foot are organized into four layers. From superficial to deep, or plantar to dorsal, these layers are the first, second, third, and fourth layers.
There are three components in the first layer of muscles, which is the most superficial of the four layers and is immediately deep to the plantar aponeurosis (Fig. 6.119 and Table 6.11). From medial to lateral, these muscles are the abductor hallucis, flexor digitorum brevis, and abductor digiti minimi.
The abductor hallucis muscle forms the medial margin of the foot and contributes to a soft tissue bulge on the medial side of the sole (Fig. 6.119). It originates from the medial process of the calcaneal tuberosity and adjacent margins of the flexor retinaculum and plantar aponeurosis. It forms a tendon that inserts on the medial side of the base of the proximal phalanx of the great toe and on the medial sesamoid bone associated with the tendon of the flexor hallucis brevis muscle.
The abductor hallucis abducts and flexes the great toe at the metatarsophalangeal joint and is innervated by the medial plantar branch of the tibial nerve. |
The flexor digitorum brevis muscle lies immediately superior to the plantar aponeurosis and inferior to the tendons of the flexor digitorum longus in the sole of the foot (Fig. 6.119). The flat spindle-shaped muscle belly originates as a tendon from the medial process of the calcaneal tuberosity and from the adjacent plantar aponeurosis.
The muscle fibers of the flexor digitorum brevis converge anteriorly to form four tendons, which each enter one of the lateral four toes. Near the base of the proximal phalanx of the toe, each tendon splits to pass dorsally around each side of the tendon of the flexor digitorum longus and attach to the margins of the middle phalanx.
The flexor digitorum brevis flexes the lateral four toes at the proximal interphalangeal joints and is innervated by the medial plantar branch of the tibial nerve.
The abductor digiti minimi muscle is on the lateral side of the foot and contributes to the large lateral plantar eminence on the sole (Fig. 6.119). It has a broad base of origin, mainly from the lateral and medial processes of the calcaneal tuberosity and from a fibrous band of connective tissue, which connects the calcaneus with the base of metatarsal V.
The abductor digiti minimi forms a tendon, which travels in a shallow groove on the plantar surface of the base of metatarsal V and continues forward to attach to the lateral side of the base of the proximal phalanx of the little toe.
The abductor digiti minimi abducts the little toe at the metatarsophalangeal joint and is innervated by the lateral plantar branch of the tibial nerve.
The second muscle layer in the sole of the foot is associated with the tendons of the flexor digitorum longus muscle, which pass through this layer, and consists of the quadratus plantae and four lumbrical muscles (Fig. 6.120 and Table 6.12).
The quadratus plantae muscle is a flat quadrangular muscle with two heads of origin (Fig. 6.120):
One of the heads originates from the medial surface of the calcaneus inferior to the sustentaculum tali.
The other head originates from the inferior surface of the calcaneus anterior to the lateral process of the calcaneal tuberosity and the attachment of the long plantar ligament.
The quadratus plantae muscle inserts into the lateral side of the tendon of the flexor digitorum longus in the proximal half of the sole of the foot near where the tendon divides.
The quadratus plantae assists the flexor digitorum longus tendon in flexing the toes and may also adjust the “line of pull” of this tendon as it enters the sole of the foot from the medial side. The muscle is innervated by the lateral plantar nerve.
The lumbrical muscles are four worm-like muscles that originate from the tendons of the flexor digitorum longus and pass dorsally to insert into the free medial margins of the extensor hoods of the four lateral toes (Fig. 6.120).
The first lumbrical originates from the medial side of the tendon of the flexor digitorum longus that is associated with the second toe. The remaining three muscles are bipennate and originate from the sides of adjacent tendons.
The lumbrical muscles act through the extensor hoods to resist excessive extension of the metatarsophalangeal joints and flexion of the interphalangeal joints when the heel leaves the ground during walking.
The first lumbrical is innervated by the medial plantar nerve, while the other three are innervated by the lateral plantar nerve.
There are three muscles in the third layer in the sole of the foot (Fig. 6.122 and Table 6.13):
Two (the flexor hallucis brevis and adductor hallucis) are associated with the great toe.
The third (the flexor digiti minimi brevis) is associated with the little toe. |
The flexor hallucis brevis muscle has two tendinous heads of origin (Fig. 6.122):
The lateral head originates from the plantar surfaces of the cuboid, behind the groove for the fibularis longus, and adjacent surface of the lateral cuneiform.
The medial head originates from the tendon of the tibialis posterior muscle as it passes into the sole of the foot.
The medial and lateral heads unite and give rise to a muscle belly, which itself is separated into medial and lateral parts adjacent to the plantar surface of metatarsal I. Each part of the muscle gives rise to a tendon that inserts on either the lateral or medial side of the base of the proximal phalanx of the great toe.
A sesamoid bone occurs in each tendon of the flexor hallucis brevis as it crosses the plantar surface of the head of metatarsal I. The tendon of the flexor hallucis longus passes between the sesamoid bones.
The flexor hallucis brevis flexes the metatarsophalangeal joint of the great toe and is innervated by the medial plantar nerve.
The adductor hallucis muscle originates by two muscular heads, transverse and oblique, which join near their ends to insert into the lateral side of the base of the proximal phalanx of the great toe (Fig. 6.122):
The transverse head originates from the plantar ligaments associated with the metatarsophalangeal joints of the lateral three toes and from the associated deep transverse metatarsal ligaments—the muscle crosses the sole of the foot transversely from lateral to medial and joins the oblique head near the base of the great toe.
The oblique head is larger than the transverse head and originates from the plantar surfaces of the bases of metatarsals II to IV and from the sheath covering the fibularis longus muscle—this head passes anterolaterally through the sole of the foot and joins the transverse head.
The tendon of insertion of the adductor hallucis attaches to the lateral sesamoid bone associated with the tendon of the flexor hallucis brevis muscle in addition to attaching to the proximal phalanx.
The adductor hallucis adducts the great toe at the metatarsophalangeal joint and is innervated by the lateral plantar nerve.
The flexor digiti minimi brevis muscle originates from the plantar surface of the base of metatarsal V and adjacent sheath of the fibularis longus tendon (Fig. 6.122). It inserts on the lateral side of the base of the proximal phalanx of the little toe.
The flexor digiti minimi brevis flexes the little toe at the metatarsophalangeal joint and is innervated by the lateral plantar nerve.
There are two muscle groups in the deepest muscle layer in the sole of the foot, the dorsal and plantar interossei (Fig. 6.123 and Table 6.14).
The four dorsal interossei are the most superior muscles in the sole of the foot and abduct the second to fourth toes relative to the long axis through the second toe (Fig. 6.123). All four muscles are bipennate and originate from the sides of adjacent metatarsals.
The tendons of the dorsal interossei insert into the free margin of the extensor hoods and base of the proximal phalanges of the toes.
The second toe can be abducted to either side of its long axis, so it has two dorsal interossei associated with it, one on each side. The third and fourth toes have a dorsal interosseous muscle on their lateral sides only. The great and little toes have their own abductors (the abductor hallucis and abductor digiti minimi) in the first layer of muscles in the sole of the foot.
In addition to abduction, the dorsal interossei act through the extensor hoods to resist extension of the metatarsophalangeal joints and flexion of the interphalangeal joints. |
The dorsal interossei are innervated by the lateral plantar nerve. The first and second dorsal interossei also receive branches on their superior surfaces from the deep fibular nerve.
The three plantar interossei adduct the third, fourth, and little toes toward the long axis through the second toe (Fig. 6.123).
Each plantar interosseous muscle originates from the medial side of its associated metatarsal and inserts into the medial free margin of the extensor hood and base of the proximal phalanx.
The great toe has its own adductor (the adductor hallucis) in the third layer of muscles in the sole of the foot and the second toe is adducted back to its longitudinal axis by using one of its dorsal interossei.
In addition to adduction, the plantar interossei act through the extensor hoods to resist extension of the metatarsophalangeal joints and flexion of the interphalangeal joints. All are innervated by the lateral plantar nerve.
Blood supply to the foot is by branches of the posterior tibial and dorsalis pedis (dorsal artery of the foot) arteries.
The posterior tibial artery enters the sole and bifurcates into lateral and medial plantar arteries. The lateral plantar artery joins with the terminal end of the dorsalis pedis artery (the deep plantar artery) to form the deep plantar arch. Branches from this arch supply the toes.
The dorsalis pedis artery is the continuation of the anterior tibial artery, passes onto the dorsal aspect of the foot and then inferiorly, as the deep plantar artery, between metatarsals I and II to enter the sole of the foot.
The posterior tibial artery enters the foot through the tarsal tunnel on the medial side of the ankle and posterior to the medial malleolus. Midway between the medial malleolus and the heel, the pulse of the posterior tibial artery is palpable because here the artery is covered only by a thin layer of retinaculum, by superficial connective tissue, and by skin. Near this location, the posterior tibial artery bifurcates into a small medial plantar artery and a much larger lateral plantar artery.
The lateral plantar artery passes anterolaterally into the sole of the foot, first deep to the proximal end of the abductor hallucis muscle and then between the quadratus plantae and flexor digitorum brevis muscles (Fig. 6.124). It reaches the base of metatarsal V where it lies in the groove between the flexor digitorum brevis and abductor digiti minimi muscles. From here, the lateral plantar artery curves medially to form the deep plantar arch, which crosses the deep plane of the sole on the metatarsal bases and the interossei muscles.
Between the bases of metatarsals I and II, the deep plantar arch joins with the terminal branch (deep plantar artery) of the dorsalis pedis artery, which enters the sole from the dorsal side of the foot.
Major branches of the deep plantar arch include: a digital branch to the lateral side of the little toe; four plantar metatarsal arteries, which supply digital branches to adjacent sides of toes I to V and the medial side of the great toe; and three perforating arteries, which pass between the bases of metatarsals II to V to anastomose with vessels on the dorsal aspect of the foot.
The medial plantar artery passes into the sole of the foot by passing deep to the proximal end of the abductor hallucis muscle (Fig. 6.124). It supplies a deep branch to adjacent muscles and then passes forward in the groove between the abductor hallucis and the flexor digitorum brevis muscles. It ends by joining the digital branch of the deep plantar arch, which supplies the medial side of the great toe. |
Near the base of metatarsal I, the medial plantar artery gives rise to a superficial branch, which divides into three vessels that pass superficial to the flexor digitorum brevis muscle to join the plantar metatarsal arteries from the deep plantar arch.
The dorsalis pedis artery is the continuation of the anterior tibial artery and begins as the anterior tibial artery crosses the ankle joint (Fig. 6.125). It passes anteriorly over the dorsal aspect of the talus, navicular, and intermediate cuneiform bones, and then passes inferiorly, as the deep plantar artery, between the two heads of the first dorsal interosseous muscle to join the deep plantar arch in the sole of the foot. The pulse of the dorsalis pedis artery on the dorsal surface of the foot can be felt by gently palpating the vessel against the underlying tarsal bones between the tendons of the extensor hallucis longus and the extensor digitorum longus to the second toe.
Branches of the dorsalis pedis artery include lateral and medial tarsal branches, an arcuate artery, and a first dorsal metatarsal artery:
The tarsal arteries pass medially and laterally over the tarsal bones, supplying adjacent structures and anastomosing with a network of vessels formed around the ankle.
The arcuate artery passes laterally over the dorsal aspect of the metatarsals near their bases and gives rise to three dorsal metatarsal arteries, which supply dorsal digital arteries to adjacent sides of digits II to V, and to a dorsal digital artery that supplies the lateral side of digit V.
The first dorsal metatarsal artery (the last branch of the dorsalis pedis artery before the dorsalis pedis artery continues as the deep plantar artery into the sole of the foot) supplies dorsal digital branches to adjacent sides of the great and second toes.
The dorsal metatarsal arteries connect with perforating branches from the deep plantar arch and similar branches from the plantar metatarsal arteries.
There are interconnected networks of deep and superficial veins in the foot. The deep veins follow the arteries. Superficial veins drain into a dorsal venous arch on the dorsal surface of the foot over the metatarsals (Fig. 6.126):
The great saphenous vein originates from the medial side of the arch and passes anterior to the medial malleolus and onto the medial side of the leg.
The small saphenous vein originates from the lateral side of the arch and passes posterior to the lateral malleolus and onto the back of the leg.
The foot is supplied by the tibial, deep fibular, superficial fibular, sural, and saphenous nerves:
All five nerves contribute to cutaneous or general sensory innervation.
The tibial nerve innervates all intrinsic muscles of the foot except for the extensor digitorum brevis, which is innervated by the deep fibular nerve.
The deep fibular nerve often also contributes to the innervation of the first and second dorsal interossei.
The tibial nerve enters the foot through the tarsal tunnel posterior to the medial malleolus. In the tunnel, the nerve is lateral to the posterior tibial artery, and gives origin to medial calcaneal branches, which penetrate the flexor retinaculum to supply the heel. Midway between the medial malleolus and the heel, the tibial nerve bifurcates with the posterior tibial artery into: a large medial plantar nerve, and a smaller lateral plantar nerve (Fig. 6.127).
The medial and lateral plantar nerves lie together between their corresponding arteries. |
The medial plantar nerve is the major sensory nerve in the sole of the foot (Fig. 6.127). It innervates skin on most of the anterior two-thirds of the sole and adjacent surfaces of the medial three and one-half toes, which includes the great toe. In addition to this large area of plantar skin, the nerve also innervates four intrinsic muscles—the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and first lumbrical.
The medial plantar nerve passes into the sole of the foot deep to the abductor hallucis muscle and forward in the groove between the abductor hallucis and flexor digitorum brevis, supplying branches to both these muscles.
The medial plantar nerve supplies a digital branch (proper plantar digital nerve) to the medial side of the great toe and then divides into three nerves (common plantar digital nerves) on the plantar surface of the flexor digitorum brevis, which continue forward to supply proper plantar digital branches to adjacent surfaces of toes I to IV. The nerve to the first lumbrical originates from the first common plantar digital nerve.
The lateral plantar nerve is an important motor nerve in the foot because it innervates all intrinsic muscles in the sole, except for the muscles supplied by the medial plantar nerve (the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and first lumbrical) (Fig. 6.127). It also innervates a strip of skin on the lateral side of the anterior two-thirds of the sole and the adjacent plantar surfaces of the lateral one and one-half digits.
The lateral plantar nerve enters the sole of the foot by passing deep to the proximal attachment of the abductor hallucis muscle. It continues laterally and anteriorly across the sole between the flexor digitorum brevis and quadratus plantae muscles, supplying branches to both these muscles, and then divides near the head of metatarsal V into deep and superficial branches.
The superficial branch of the lateral plantar nerve gives rise to a proper plantar digital nerve, which supplies skin on the lateral side of the little toe, and to a common plantar digital nerve, which divides to supply proper plantar digital nerves to skin on the adjacent sides of toes IV and V.
The proper plantar digital nerve to the lateral side of the little toe also innervates the flexor digiti minimi brevis and the dorsal and plantar interossei muscles between metatarsals IV and V.
The deep branch of the lateral plantar nerve is motor and accompanies the lateral plantar artery deep to the long flexor tendons and the adductor hallucis muscle. It supplies branches to the second to fourth lumbrical muscles, the adductor hallucis muscle, and all interossei except those between metatarsals IV and V, which are innervated by the superficial branch.
The deep fibular nerve innervates the extensor digitorum brevis, contributes to the innervation of the first two dorsal interossei muscles, and supplies general sensory branches to the skin on the adjacent dorsal sides of the first and second toes and to the web space between them (Fig. 6.128).
The deep fibular nerve enters the dorsal aspect of the foot on the lateral side of the dorsalis pedis artery, and is parallel with and lateral to the tendon of the extensor hallucis longus muscle. Just distal to the ankle joint, the nerve gives origin to a lateral branch, which innervates the extensor digitorum brevis from its deep surface.
The deep fibular nerve continues forward on the dorsal surface of the foot, penetrates deep fascia between metatarsals I and II near the metatarsophalangeal joints, and then divides into two dorsal digital nerves, which supply skin over adjacent surfaces of toes I and II down to the beginning of the nail beds.
Small motor branches, which contribute to the supply of the first two dorsal interossei muscles, originate from the deep fibular nerve before it penetrates deep fascia. |
The superficial fibular nerve is sensory to most skin on the dorsal aspect of the foot and toes except for skin on adjacent sides of toes I and II (which is innervated by the deep fibular nerve) and skin on the lateral side of the foot and little toe (which is innervated by the sural nerve; Fig. 6.128).
The superficial fibular nerve penetrates deep fascia on the anterolateral side of the lower leg and enters the dorsal aspect of the foot in superficial fascia. It gives rise to cutaneous branches and dorsal digital nerves along its course.
The sural nerve is a cutaneous branch of the tibial nerve that originates high in the leg. It enters the foot in superficial fascia posterior to the lateral malleolus close to the short saphenous vein. Terminal branches innervate skin on the lateral side of the foot and dorsolateral surface of the little toe (Fig. 6.128B).
The saphenous nerve is a cutaneous branch of the femoral nerve that originates in the thigh. Terminal branches enter the foot in superficial fascia on the medial side of the ankle and supply skin on the medial side of the proximal foot (Fig. 6.128B).
Tendons, muscles, and bony landmarks in the lower limb are used to locate major arteries, veins, and nerves.
Because vessels are large, they can be used as entry points to the vascular system. In addition, vessels in the lower limb are farthest from the heart and the most inferior in the body. Therefore, the nature of peripheral pulses in the lower limb can give important information about the status of the circulatory system in general.
Sensation and muscle action in the lower limb are tested to assess lumbar and sacral regions of the spinal cord.
Avoiding the sciatic nerve
The sciatic nerve innervates muscles in the posterior compartment of the thigh, muscles in the leg and foot, and an appreciable area of skin. It enters the lower limb in the gluteal region (Fig. 6.129) and passes inferiorly midway between two major palpable bony landmarks, the greater trochanter and the ischial tuberosity. The greater trochanter can be easily felt as a hard bony protuberance about one hand’s width inferior to the midpoint of the iliac crest. The ischial tuberosity is palpable just above the gluteal fold.
The gluteal region can be divided into quadrants by two lines positioned using palpable bony landmarks.
One line descends vertically from the highest point of the iliac crest.
The other line passes horizontally through the first line midway between the highest point of the iliac crest and the horizontal plane through the ischial tuberosity.
The sciatic nerve curves through the upper lateral corner of the lower medial quadrant and descends along the lateral margin of the lower medial quadrant. Injections can be carried out in the anterior corner of the upper lateral quadrant to avoid injury to the sciatic nerve and major vessels in the region (Fig. 6.129B).
Finding the femoral artery in the femoral triangle
The femoral artery passes into the femoral triangle (Fig. 6.130) of the lower limb from the abdomen.
The femoral triangle is the depression formed in the anterior thigh between the medial margin of the adductor longus muscle, the medial margin of the sartorius muscle, and the inguinal ligament.
The tendon of the adductor longus muscle can be palpated as a cord-like structure that attaches to bone immediately inferior to the pubic tubercle.
The sartorius muscle originates from the anterior superior iliac spine and crosses anteriorly over the thigh to attach to the medial aspect of the tibia below the knee joint.
The inguinal ligament attaches to the anterior superior iliac spine laterally and the pubic tubercle medially. |
The femoral artery descends into the thigh from the abdomen by passing under the inguinal ligament and into the femoral triangle. In the femoral triangle, its pulse is easily felt just inferior to the inguinal ligament midway between the pubic symphysis and the anterior superior iliac spine. Medial to the artery is the femoral vein and medial to the vein is the femoral canal, which contains lymphatics and lies immediately lateral to the pubic tubercle. The femoral nerve lies lateral to the femoral artery.
Identifying structures around the knee
The patella is a prominent palpable feature at the knee. The quadriceps femoris tendon attaches superiorly to it and the patellar ligament connects the inferior surface of the patella to the tibial tuberosity (Fig. 6.131). The patellar ligament and the tibial tuberosity are easily palpable. A tap on the patellar ligament (tendon) tests reflex activity mainly at spinal cord levels L3 and L4.
The head of the fibula is palpable as a protuberance on the lateral surface of the knee just inferior to the lateral condyle of the tibia. It can also be located by following the tendon of the biceps femoris inferiorly.
The common fibular nerve passes around the lateral surface of the neck of the fibula just inferior to the head and can often be felt as a cord-like structure in this position.
Another structure that can usually be located on the lateral side of the knee is the iliotibial tract. This flat tendinous structure, which attaches to the lateral tibial condyle, is most prominent when the knee is fully extended. In this position, the anterior edge of the tract raises a sharp vertical fold of skin posterior to the lateral edge of the patella.
Visualizing the contents of the popliteal fossa
The popliteal fossa is a diamond-shaped depression formed between the hamstrings and gastrocnemius muscle posterior to the knee. The inferior margins of the diamond are formed by the medial and lateral heads of the gastrocnemius muscle. The superior margins are formed laterally by the biceps femoris muscle and medially by the semimembranosus and semitendinosus muscles. The tendons of the biceps femoris muscle and the semitendinosus muscle are palpable and often visible.
The head of the fibula is palpable on the lateral side of the knee and can be used as a landmark for identifying the biceps femoris tendon and the common fibular nerve, which curves laterally out of the popliteal fossa and crosses the neck of the fibula just inferior to the head.
The popliteal fossa contains the popliteal artery, the popliteal vein, the tibial nerve, and the common fibular nerve (Fig. 6.132). The popliteal artery is the deepest of the structures in the fossa and descends through the region from the upper medial side. As a consequence of its position, the popliteal artery pulse is difficult to find, but usually can be detected on deep palpation just medial to the midline of the fossa.
The small saphenous vein penetrates deep fascia in the upper part of the posterior leg and joins the popliteal vein.
Finding the tarsal tunnel—the gateway to the foot
The tarsal tunnel (Fig. 6.133) is formed on the medial side of the foot in the groove between the medial malleolus and the heel (calcaneal tuberosity) and by the overlying flexor retinaculum.
The posterior tibial artery and tibial nerve enter the foot through the tarsal tunnel. The tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus also pass through the tarsal tunnel in compartments formed by septa of the flexor retinaculum. |
The order of structures passing through the tunnel from the anteromedial to posterolateral are the tendon of the tibialis posterior, the tendon of the flexor digitorum longus, the posterior tibial artery and associated veins, the tibial nerve, and the tendon of the flexor hallucis longus (“Tom, Dick, and a very nervous Harry”).
The tibial artery is palpable just posteroinferior to the medial malleolus on the anterior face of the visible groove between the heel and medial malleolus.
Identifying tendons around the ankle and in the foot
Numerous tendons can be identified around the ankle and in the foot (Fig. 6.134) and can be used as useful landmarks for locating vessels or testing spinal reflexes.
The tibialis anterior tendon is visible on the medial side of the ankle anterior to the medial malleolus.
The calcaneal tendon is the largest tendon entering the foot and is prominent on the posterior aspect of the foot as it descends from the leg to the heel. A tap with a tendon hammer on this tendon tests reflex activity of spinal cord levels S1 and S2.
When the foot is everted, the tendons of the fibularis longus and fibularis brevis raise a linear fold of skin, which descends from the lower leg to the posterior edge of the lateral malleolus.
The tendon of the fibularis brevis is often evident on the lateral surface of the foot descending obliquely to the base of metatarsal V. The tendons of the fibularis tertius, extensor digitorum longus, and extensor hallucis longus are visible on the dorsal aspect of the foot from lateral to medial.
Finding the dorsalis pedis artery
The nature of the dorsalis pedis pulse (Fig. 6.135) is important for assessing peripheral circulation because the dorsalis pedis artery is the farthest palpable vessel from the heart. Also, it is the lowest palpable artery in the body when a person is standing.
The dorsalis pedis artery passes onto the dorsal aspect of the foot and anteriorly over the tarsal bones where it lies between and is parallel to the tendon of the extensor hallucis longus and the tendon of the extensor digitorum longus to the second toe. It is palpable in this position. The terminal branch of the dorsalis pedis artery passes into the plantar surface of the foot between the two heads of the first dorsal interosseous muscle.
Approximating the position of the plantar arterial arch
The blood supply of the foot is provided by branches of the posterior tibial and dorsalis pedis arteries.
The posterior tibial artery enters the plantar surface of the foot through the tarsal tunnel and divides into a lateral and a medial plantar artery.
The lateral plantar artery curves laterally across the posterior half of the sole and then curves medially as the plantar arch (Fig. 6.136) through the anterior sole. Between the bases of metatarsals I and II, the plantar arch joins the terminal branch (deep plantar artery) of the dorsalis pedis artery. Most of the foot is supplied by the plantar arch.
The medial plantar artery passes anteriorly through the sole, connects with branches of the plantar arch, and supplies the medial side of the great toe.
Superficial veins in the lower limb often become enlarged. Also, because the veins are long, they can be removed and used elsewhere in the body as vascular grafts.
Superficial veins (Fig. 6.137) in the lower limb begin as a dorsal venous arch in the foot. The medial side of the arch curves superiorly anterior to the medial malleolus and passes up the leg and thigh as the great saphenous vein. This vein passes through an aperture in the fascia lata (saphenous ring) to join with the femoral vein in the femoral triangle. |
The lateral side of the dorsal venous arch in the foot passes posterior to the lateral malleolus and up the posterior surface of the leg as the small saphenous vein. This vessel passes through the deep fascia in the upper one-third of the leg and connects with the popliteal vein in the popliteal fossa posterior to the knee.
Peripheral pulses can be felt at four locations in the lower limb (Fig. 6.138): femoral pulse in the femoral triangle—femoral artery inferior to the inguinal ligament and midway between the anterior superior iliac spine and the pubic symphysis; popliteal pulse in the popliteal fossa—popliteal artery deep in the popliteal fossa near the midline; posterior tibial pulse in the tarsal tunnel—posterior tibial artery posteroinferior to the medial malleolus in the groove between the medial malleolus and the heel (calcaneal tuberosity); dorsalis pedis pulse on the dorsal aspect of the foot—dorsalis pedis artery as it passes distally over the tarsal bones between the tendon of the extensor hallucis longus and the tendon of the extensor digitorum longus to the second toe.
Fig. 6.1 Upper margin of the lower limb.
Fig. 6.2 Regions of the lower limb.
Fig. 6.3 Areas of transition.
Inguinal ligamentFemoral trianglePopliteal fossa(posterior to knee)Tarsal tunnel
Fig. 6.4 Center and line of gravity.
Center ofgravityCenterof gravityposterior tohip jointLine of gravityAnterior to kneeAnterior to ankle
Fig. 6.5 Movements of the hip joint. A. Flexion and extension. B. Abduction and adduction. C. External and internal rotation.
D. Circumduction.
Fig. 6.6 Movements of the knee and ankle. A. Knee flexion and extension. B. Ankle dorsiflexion and plantarflexion.
Fig. 6.7 Some of the determinants of gait.
Pelvic rotation in transverse planeminimizes drop in center of gravity byeffectively lengthening the limbsKnee flexion on full stance. Limb minimizes rise incenter of gravity by effectively shortening the limbPelvic tilt (drop) on swing side minimizes rise incenter of gravityMovement of knees toward midline(adduction of hip) minimizes lateralshift in center of gravityAbduction on stanceside controls andlimits the dropLateral shift incenter of gravityWith adductionof hip (kneesmove towardmidline)No adductionof hip (knees donot move towardmidline)Vertical shift incenter of gravityInternal rotationof hip jointExternal rotation of hip jointCenter of gravity with knee not flexedCenter of gravity with knee flexedFlexion
Fig. 6.8 Bones and joints of the lower limb.
Fig. 6.9 Bones of the foot.
Fig. 6.10 Longitudinal and transverse arches of the foot.
Fig. 6.11 Muscles of the gluteal region.
Extensor(gluteus maximus)Abductors(gluteus mediusand gluteus minimus)Rotators(piriformis, obturatorinternus, gemelli,quadratus femoris)
Fig. 6.12 Major flexors of the hip.
Fig. 6.13 Muscle compartments in the thigh and leg.
Fig. 6.14 Apertures of communication between the lower limb and other regions.
Fig. 6.15 Innervation of the lower limb. |
LumbarIliohypogastric (L1)Genitofemoral (L1, L2)Lateral cutaneous nerveof thigh (L2, L3)Obturator nerve (L2 to L4)Femoral nerve (L2 to L4)SacralSuperior gluteal nerve (L4 to S1)Sciatic nerve (L4 to S3)Inferior gluteal nerve (L5 to S2)Pudendal nerve (S2 to S4)Tibial nerve (branch of sciatic)(L4 to S3)Common fibular nerve (branch of sciatic)(L4 to S2)Sacrospinous ligamentIlio-inguinal (L1)LVLIVLIIILIILI
Fig. 6.16 Dermatomes of the lower limb. Dots indicate autonomous zones (i.e., with minimal overlap).
Fig. 6.17 Movements generated by myotomes.
L1, L2L3, L4L5 to S2S1, S2Adduction of toes S2, S3
Fig. 6.18 Major nerves of the lower limb (colors indicate regions of motor innervation).
Femoral nerve(anterior compartmentof thigh)Obturator(medial compartmentof thigh)Commonfibular nerveSuperficial branch(lateral compartment of leg)Deep branch(anterior compartment of leg)Sciatic nerve(posterior compartmentof thigh, leg, andsole of foot)Superior and inferiorgluteal nerves
Fig. 6.19 Regions of skin innervated by peripheral nerves.
Obturator nerveFemoral nerve (anteriorcutaneous nerves of thigh)Femoral nerve (saphenous nerve)Common fibular nerve(lateral cutaneous of calf)Common fibular nerve(superficial branch)Common fibular nerve(deep branch)Medial plantar nervePosterior cutaneous nerve of thigh(from sacral plexus)Posterior rami (L1 to L3)Posterior rami (S1 to S3)Obturator nerveFemoral nerve (saphenous nerve)Tibial nerve (sural nerve)Tibial nerve (sural nerve)Lateral plantar nerveTibial nerve (medial calcanealbranches)Lateral cutaneousnerve of thigh(from lumbar plexus)
Fig. 6.20 Nerves related to bone.
Deep branchCommon fibularnerve (neck of fibula)Superficial branch
Fig. 6.21 Superficial veins.
Fig. 6.22 External surface of the bony pelvis. Lateral view.
LIV spineHorizontal plane through top of iliac crestAnterior gluteal linePosterior gluteal linePosterior superior iliac spineSacrumSacrospinous ligamentIschial spineSacrotuberous ligamentPosterior inferior iliac spineAcetabulumIschial tuberosityIliumInferior gluteal lineIschiumPubisPubic tubercleIliopubic eminenceAnterior inferior iliac spineInguinal ligamentAnterior superior iliac spineAnterior abdominal wallIliac crestTuberculum of iliac crest
Fig. 6.23 Ischial tuberosity. Posterolateral view.
AcetabulumIschial spineFor attachment of sacrotuberous ligamentFor attachment of semitendinosus andlong head of biceps femoris muscleCovered by connective tissue and bursaFor attachment of adductor magnus muscleFor attachment of semimembranosus muscleIschiopubic ramusObturator foramenBody of pubic bone
Fig. 6.24 Acetabulum.
Fig. 6.25 Multiple fractures of the pelvis. Radiograph with contrast in the bladder. A large accumulation of blood is deforming the bladder. |
Fig. 6.26 Proximal end of the femur (right). A. Anterior view. B. Medial view. C. Posterior view. D. Lateral view.
ABTrochanteric fossaHeadNeckNeckAttachment site for piriformis muscleGreater trochanterAttachment site for gluteus minimusShaftLesser trochanterIntertrochanteric lineTubercleGreater trochanterPiriformisFoveaObturator internusTrochanteric fossaEnd of intertrochanteric linePectineal line (spiral line)Lesser trochanterOval depression forobturator externusAttachment ofgluteus mediusQuadrate tubercleGreater trochanterFoveaNeckQuadrate tubercleLesser trochanterPectineal line (spiral line)Medial margin of linea asperaLinea asperaLateral margin of linea asperaGluteal tuberosityAttachment site for gluteus mediusIntertrochanteric crestGluteus minimusGluteus mediusLesser trochanterCD
Fig. 6.27 Shaft of the femur. On the right is a posterior view of proximal shaft of right femur.
Fig. 6.28 This radiograph of the pelvis, anteroposterior view, demonstrates a fracture of the neck of the femur.
Fractured neck of femur
Fig. 6.29 Anteroposterior radiograph showing an intertrochanteric fracture of proximal end of femur.
Fig. 6.30 Hip joint. A. Articular surfaces. Anterior view. B. Movement of the neck of the femur during medial and lateral rotation. Superior view.
Acetabulum of pelvic boneAcetabular labrumHead of femurSuperior viewLateral rotationMedial rotationAB
Fig. 6.31 Hip joint. A. Transverse acetabular ligament. B. Ligament of the head of the femur. The head of the femur has been laterally rotated out of the acetabulum to show the ligament.
ABAcetabular labrum Lunate surfaceTransverseacetabular ligamentAcetabularforamenObturator foramenAcetabular fossaArtery of ligament of headSynovial sleeve around ligamentLigament of head of femurIschial tuberosityObturator membranePubisPubic tubercleObturator arteryAcetabular branchof obturator arteryCut synovial membrane
Fig. 6.32 Synovial membrane of the hip joint.
Synovial membraneLine of attachment around head of femurMembrane reflects back to attach to margin ofacetabulum
Fig. 6.33 Fibrous membrane and ligaments of the hip joint. A. Fibrous membrane of the joint capsule. Anterior view. B. Iliofemoral and pubofemoral ligaments. Anterior view. C. Ischiofemoral ligament. Posterior view.
Fig. 6.34 Blood supply of the hip joint.
Internal iliac arteryCommon iliac arteryExternal iliac arteryLateral circumflex femoral artery1st perforating arteryDeep artery of thighMedial circumflex femoral arteryFemoral arteryObturator arteryInferior gluteal arterySuperior gluteal artery
Fig. 6.35 Gateways to the lower limb. |
Sacrospinous ligamentSacrotuberous ligamentPelvic cavityIlio-inguinal nerveAbdominal cavityGap between inguinal ligament and pelvic bone:• Psoas major, iliacus, pectineus muscles• Femoral artery• Femoral vein• Lymphatics• Femoral branch of genitofemoral nerve• Lateral cutaneous nerve of thigh• Femoral nerveObturator canal:• obturator nerve• obturator vesselsLesser sciatic foramen:• Obturator internus muscle tendon• Pudendal nerve and internal pudendal vessels pass into perineum from gluteal regionGreater sciatic foramen below piriformis muscle:• Sciatic nerve• Inferior gluteal nerve, artery, vein• Pudendal nerve• Internal pudendal artery and vein• Posterior femoral cutaneous nerve• Nerve to obturator internus and gemellus superior muscles• Nerve to quadratus femoris and gemellus inferior musclesGreater sciatic foramen abovepiriformis muscle:• Superior gluteal nerve, artery, veinPiriformis muscle
Fig. 6.36 Branches of the lumbosacral plexus.
L3 anterior ramusPerforating cutaneous nerveLumbosacral trunkSuperior gluteal nerveNerves to quadratus femoris and obturator internusInguinal ligamentInferior gluteal nervePosterior cutaneous nerve of thighSciatic nerveS1S2Sacrotuberous ligamentSacrospinous ligamentObturator nerveFemoral branch of genitofemoral nerveFemoral nerveLateral cutaneous nerve of thighIlio-inguinal nerveL1 anterior ramusL2 anterior ramus
Fig. 6.37 Arteries of the lower limb.
Fig. 6.38 Veins of the lower limb.
Fig. 6.39 Lymphatic drainage of the lower limb.
Fig. 6.40 Fascia lata. A. Right limb. Anterior view. B. Lateral view.
ABInguinal ligamentInguinal ligamentDeep fascia of legFascia lataSaphenous openingAnterior superior iliac spineAnterior superior iliac spineTuberculum of iliac crestFascia lataGluteus maximusTensor fascia lataIliotibial tractPubic tuberclePubic tubercle
Fig. 6.41 Saphenous ring. Anterior view.
Fig. 6.42 Boundaries of the femoral triangle.
Fig. 6.43 Contents of the femoral triangle.
Fig. 6.44 Gluteal region. Posterior view.
Fig. 6.45 Deep muscles in the gluteal region. A. Posterior view. B. Function.
ABGemellus superior Gemellus inferiorObturator internusQuadratus femorisGluteus mediusGluteus minimusGreater sciatic foramen abovepiriformisPiriformis muscleGreater sciatic foramen belowpiriformisContraction of gluteus minimus and mediuson stance side prevents excessive pelvic tiltduring swing phase on opposite side
Fig. 6.46 Gluteus maximus muscle. Posterior view.
Gluteus mediusGluteus maximusAttachment of gluteus maximus to iliotibial tractIliotibial tractAttachment of deep fibers to gluteal tuberosity
Fig. 6.47 Tensor fasciae latae. Left gluteal region, lateral view.
Tensor fasciae lataeTubercle of crest of iliumGluteus mediusIliotibial tractGluteus minimusGluteus maximusFascia lataDeep fascia of legTibiaAttachment to tibia
Fig. 6.48 Nerves of the gluteal region. Posterior view. |
Superior gluteal nerveTensor fasciae latae muscleInferior gluteal nerveIliotibial tractPosterior cutaneous nerve of thighNerve to quadratus femorismuscle (deep to gemelli, obturator internus, and quadratus femoris)Gluteus maximusPerforating cutaneous nerveNerve to obturator internusPudendal nervePiriformis muscleSciatic nerve
Fig. 6.49 Site for intramuscular injections in the gluteal region.
Fig. 6.50 Arteries of the gluteal region.
Deep branchLateral femoral circumflex arteryMedial femoral circumflex arteryFirst perforating artery fromdeep artery of thighInferior gluteal artery and veinSuperficial branchSuperior gluteal artery and veinPiriformis muscle
Fig. 6.51 Anastomoses between gluteal arteries and vessels originating from the femoral artery in the thigh. Posterior view.
Superior gluteal arteryFirst perforating arterySecond perforating arteryThird perforating arteryFemoral arteryDeep artery of thighMedial femoral circumflex arteryLateral femoralcircumflex arteryInferior gluteal artery
Fig. 6.52 Thigh. A. Posterior view. B. Anterior view. C. Cross section through the midthigh.
ABCInguinal ligamentAbdominal wallGap between inguinal ligament and pelvic boneObturator canalAnterior superior iliac spinePubic tubercleMedialAnteriorLateral Posterior Anterior compartmentPosterior compartmentMedial compartmentPopliteal fossa(posterior to knee)Popliteal fossaSciatic nerveQuadratus femorisInferior margin of gluteus maximusGluteal fold
Fig. 6.53 Shaft and distal end of femur. A. Lateral view. B. Anterior view. C. Posterior view. D. Cross section through shaft of femur.
Lateral epicondyleMedial epicondyleMedial condyleLateral borderLateral(posterolateral)surfaceMedial(posteromedial)surfaceMedialborderLateral condyleLateral epicondyleFacet for attachment of lateral head of gastrocnemiusFacet for attachment of the tendon of popliteus muscleFacet for attachmentof the tendon ofpopliteus muscleAdductor tubercleAdductor tuberclePatellar surfacePosterior surfaceMedial supracondylar lineLateral supracondylar lineIntercondylar fossaFacet for attachment of posterior cruciate ligamentFacet for attachment of anterior cruciate ligamentRoughened area for attachment of medial head of gastrocnemius muscleFacet for attachmentof lateral head ofgastrocnemius muscleLinea asperaLinea asperaAnterior surfaceABCD
Fig. 6.54 Patella. A. Anterior view. B. Posterior view. C. Superior view.
Fig. 6.55 Proximal end of the tibia. A. Superior view, tibial plateau. B. Anterior view. C. Posterior view. D. Cross section through the shaft of tibia.
AIntercondylar regionAttachment of posterior cruciate ligamentPosterior attachment of lateral meniscusArea of articulation with lateral meniscusAnterior attachment of lateral meniscusAttachment of anterior cruciate ligamentTuberosityTubercles of intercondylar eminenceRoughened and perforated areaAnterior attachment of medial meniscusArea of articulation with medial meniscusPosterior attachment of medial meniscus |
BCLateral condyleRoughened and perforated areaSite of attachment of sartorius, gracilis, and semitendinosus musclesShaft of tibiaGrooveTibial tuberosityMedial condyleAnterior attachment ofmedial meniscusTubercles of intercondylar eminenceAnterior Anterior borderLateral surfaceInterosseous borderPosterior surfacePosteriorMedial borderMedial surfaceAttachment of medial meniscusAttachment of posterior cruciate ligamentSoleal lineArticular facet for proximal head of fibulaD
Fig. 6.56 Proximal end of the fibula. A. Anterior view.
B. Cross section through the shaft of fibula.
ABApexAttachment site for fibular collateral ligament of kneeAttachment site for tendon of biceps femoris muscleCommon fibular nerveLateral surfaceShaftMedial surfaceMedial part of posterior surfaceNeckFacet for articulationwith inferior surfaceof lateral condyle of tibiaHeadInterosseousborderPosterior borderLateral surfaceAnterior borderMedial surfacePosterior surfaceMedial crest onposterior surface
Fig. 6.57 Transverse section through the midthigh.
Fig. 6.58 Psoas major and iliacus muscles.
Fig. 6.59 Muscles of the anterior compartment of thigh.
SartoriusSartoriusStraight head of rectus femorisReflected head of rectus femorisVastus lateralisRectus femorisVastus medialisQuadriceps femoris tendonPatellaPatellar ligamentPes anserinusSartoriusGracilisSemitendinosusAttachment of pes anserinusTibial tuberosityPatellar ligamentQuadriceps femoris tendonSuprapatellar bursaArticularis genusVastus medialisRectus femorisVastus intermediusVastus lateralisSartoriusPosterior compartment of thighVastus lateralisVastus medialisVastus intermediusMedial compartment of thighAdductor canal
Fig. 6.60 Muscles of the medial compartment of thigh. Anterior view.
Obturator externusAdductor magnusPectineusAdductor longusAdductor brevisAnterior compartment of thighSartorius attachmentGracilisGracilisSemitendinosus attachmentAdductor hiatusAdductor canalAdductor longusAdductor magnusPosterior compartment of thighPes anserinus
Fig. 6.61 Pectineus, adductor longus, and adductor brevis muscles. Anterior view.
Fig. 6.62 Adductor magnus and obturator externus muscles. Anterior view.
Obturator externusAdductor magnus (adductor part)Adductor magnus (hamstring part)Adductor tubercleAdductor hiatusPerforations for branches of deep artery of thigh• Terminal end of deep artery of thigh
Fig. 6.63 Muscles of the posterior compartment of thigh. Posterior view.
Ischial tuberosityQuadratus femorisAdductor magnusHamstring part of adductor magnusLong head of biceps femorisShort head of biceps femorisPart of semimembranosus thatinserts into capsule around knee jointOn anterior aspect of tibia attaches to pes anserinusSemimembranosusSemitendinosus
Fig. 6.64 Coronal MRI of the posterior pelvis and thigh showing a hamstring avulsion injury.
Fig. 6.65 Femoral artery. |
Superficial epigastric arterySartorius muscleDeep artery of thighRectus femoris muscleVastus medialis muscleGracilis muscleDeep externalpudendal arterySuperficial externalpudendal arteryVastus lateralis muscleVastus medialis muscleSartorius muscleArtery passes posteriorlythrough adductor hiatus andbecomes popliteal arteryArtery in adductor canalFemoral artery • Midway between anterior superior iliac spine and pubic symphysis inferior to inguinal ligamentExternal iliac arterySuperficial externaliliac arteryPubic symphysis
Fig. 6.66 Deep artery of thigh. A. Anterior view. B. Posterior view.
BSuperior gluteal arteryLateral femoral circumflex arteryCruciate anastomosesMedial circumflex femoral arteryFirst perforating arterySecond perforating arteryThird perforating arteryTerminal end of deepartery of thighPopliteal arteryAdductor magnus muscleAdductor hiatusInferior gluteal arteryPiriformis muscleAPsoas and iliacus musclesSartorius muscleRectus femoris muscleLateral circumflex femoral arteryAscending branchDescending branchVastus lateralis muscleVastus intermedius muscleCut vastus medialis muscleQuadriceps femoris tendonTerminal end of deepartery of thighGracilis muscleSartorius muscleAdductor magnus muscleFirst, second, and third perforating arteriesAdductor brevis muscleAdductor longus musclePectineus muscleMedial circumflex femoral arteryDeep artery of thigh
Fig. 6.67 Obturator artery.
Ligament ofhead offemurObturatorarteryAnterior branchAcetabular branchPosterior branchObturatorexternus muscleArtery of ligament of head of femur
Fig. 6.68 Femoral nerve.
Nerve to pectineusAnterior branchNerves to iliacusNerve to sartoriusRectus femoris muscleVastus lateralis muscleVastus medialis muscleSaphenous nerveSaphenous nervePes anserinusSartorius muscleGracilis muscleAnterior cutaneous branchesAdductor magnus musclePectineus muscleAdductor longus musclePosterior branchFemoral nerve
Fig. 6.69 Obturator nerve.
Posterior branchObturator externus musclePsoas and iliacus musclesPectineus muscleAdductor brevis muscleAdductor longus muscleBranch to adductor magnus from posterior branchAdductor magnus muscleGracilis muscleCutaneous branchAnterior branchObturator nerve
Fig. 6.70 Sciatic nerve.
Piriformis muscleQuadratus femoris muscleSciatic nerveAdductor magnus muscleLong head of biceps femoris muscleLong head of biceps femoris muscleShort head of biceps femoris muscleCommon fibular nerveTibial nervePopliteal artery and veinSemimembranosus muscleSemitendinosus muscleBranch to part of adductor magnus originatingfrom ischial tuberosity
Fig. 6.71 Knee joint. Joint capsule is not shown.
Fig. 6.72 Articular surfaces of the knee joint. A. Extended.
B. Flexed. C. Anterior view (flexed).
Fig. 6.73 Menisci of the knee joint. A. Superior view.
Menisci of the knee joint. B. Normal knee joint showing the medial meniscus. T2-weighted magnetic resonance image in the sagittal plane. C. Normal knee joint showing the lateral meniscus. T2-weighted magnetic resonance image in the sagittal plane. |
APatellar ligamentJoint capsuleMedial meniscusPopliteus tendonLateral meniscusTransverse ligament of the kneeInfrapatellar fat
Fig. 6.74 Meniscal injury and repair. A. Sagittal MRI of a knee joint showing tear of the medial meniscus. B. Coronal MRI of a knee showing a truncated lateral meniscus after partial meniscectomy to treat a tear.
Fig. 6.75 Synovial membrane of the knee joint and associated bursae. A. Superolateral view; patella and femur not shown. B. Paramedial sagittal section through the knee.
Fig. 6.76 Fibrous membrane of the knee joint capsule. A. Anterior view. B. Posterior view.
Fig. 6.77 Collateral ligaments of the knee joint. A. Lateral view. B. Medial view. C. Normal knee joint showing the patellar ligament and the fibular collateral ligament. T1-weighted magnetic resonance image in the sagittal plane. D. Normal knee joint showing the tibial collateral ligament, the medial and lateral menisci, and the anterior and posterior cruciate ligaments. T1-weighted magnetic resonance image in the coronal plane.
Fig. 6.78 Cruciate ligaments of the knee joint. Superolateral view.
Fig. 6.79 Knee “locking” mechanism.
Medial rotation of femur on tibia tightens ligamentsFlat surface offemoral condylesis in contact withtibia and stabilizesjointLine of center of gravity isanterior to knee joint andmaintains extension
Fig. 6.80 Anastomoses of arteries around the knee. Anterior view.
Femoral arteryAdductorhiatusDescendinggenicular arteryAdductormagnusSaphenousbranchSuperior medialgenicular arteryPoplitealarteryInferior medialgenicular arteryPosteriortibial arteryAnteriortibial arteryInterosseousmembraneRecurrent branchof anterior tibialCircumflexfibular arteryInferior lateralgenicular arterySuperior lateralgenicular arteryDescending branch of lateral circumflex femoral artery
Fig. 6.81 Sagittal MRI of knee joint showing rupture of the anterior cruciate ligament.
Fig. 6.82 Tibiofibular joint.
Fig. 6.83 Popliteal fossa. A. Boundaries. B. Nerves and vessels. C. Superficial structures.
ABCLinea asperaBiceps femoris muscle(short head)Biceps femorismuscle(long head)PoplitealfossaPlantarismuscleLateral head ofgastrocnemiusmusclePopliteusmuscleMedial head ofgastrocnemiusmuscleSemitendinosusmuscleSemimembranosus muscleAdductorhiatusAdductor magnus muscleSciatic nerveTibial nerveSmallsaphenousveinSmallsaphenousveinCommonfibular nervePopliteal arteryPopliteal veinFemoral veinFemoral arteryPosteriorcutaneousnerve of thighPosteriorcutaneousnerve of thighLateralNerveVeinArteryMedial
Fig. 6.84 Posterior view of leg; cross section through the left leg (inset).
Fig. 6.85 Tibia and fibula. A. Anterior view. B. Posterior view. C. Cross section through shafts. D. Posteromedial view of distal ends. |
Lateral surfaceLateralsurfaceInterosseousmembraneInterosseousborderMedialsurfaceAnteriorborderMedialborderPosteriorborderPosterior surfacePosterior surfaceMedial crestInterosseous borderInterosseousborderMedialsurfaceAnteriorborderAnteriorborderGroove for fibularis longus and brevis musclesRoughened triangulararea that fits intofibular groove of tibiaABCDFibulaTibiaFibular grooveon tibiaSoleal lineArticular surfaces for talusMedial malleolusGroove for tendon oftibialis posterior muscleMalleolar fossaLateralmalleolusLateral malleolus
Fig. 6.86 Interosseous membrane. A. Anterior view. B. Posteromedial view.
Aperture for anterior tibial vesselsABAperture for perforating branch of fibular arteryAnterior tibiofibular ligamentInterosseous membraneInterosseous membranePosterior tibiofibular ligament
Fig. 6.87 Superficial group of muscles in the posterior compartment of leg. A. Posterior view. B. Lateral view.
APlantarisMedial head ofgastrocnemiusPopliteal vessels and tibial nerveLigament spanning distance betweenfibular and tibial origins of soleusTendon of plantarisCalcaneal (Achilles) tendonCalcaneusGastrocnemiusSoleusLateral head of gastrocnemiusMedialLateralBSoleusCalcaneal tendonGastrocnemiusCalcaneus
Fig. 6.88 Deep group of muscles in the posterior compartment of leg.
PopliteusSoleal lineTibialisposteriorOrigin oftibialisposteriorVerticallineFlexordigitorumlongusOrigin of flexordigitorum longusOrigin of flexorhallucis longusGroove onmedialmalleolusMedialTuberosity ofnavicularMedialcuneiformGroove on inferiorsurface of sustentaculumtali of calcaneus boneGroove on posteriorsurface of talusFlexor hallucislongusLateral
Fig. 6.89 Arteries in the posterior compartment of leg.
Adductor hiatusSuperior medialgenicular arterySuperior lateralgenicular arteryAdductormagnus musclePopliteal arterySural arteriesMedial head ofgastrocnemiusmuscle Popliteus musclePosterior tibial arteryPosterior tibial arteryPerforating terminalbranch of fibular arteryBranches thatperforate intermuscularseptum to enter lateralcompartmentFibular arteryCircumflexfibular arteryAnterior tibial artery(passes throughaperture ininterosseousmembrane)Popliteal vein
Fig. 6.90 Tibial nerve. A. Posterior view. B. Sural nerve.
Fig. 6.91 Muscles in the lateral compartment of leg. A. Lateral view. B. Inferior view of the right foot, with the foot plantarflexed at the ankle.
ABCommon fibular nerveFibularislongusFibularisbrevisFibular trochleaof calcaneus boneAnteriorborder of fibulaInterosseousmembraneMedialcuneiformMetatarsal IGroove oninferior aspectof cuboidFibularisbrevistendonFibularislongustendon
Fig. 6.92 Common fibular nerve, and nerves and arteries of the lateral compartment of leg. A. Posterior view, right leg. B. Lateral view, right leg.
ABSural communicating nervePenetrates deep fasciaSural nervePenetrates deep fasciaLateral sural nerveCommon fibular nerveSuperficial fibular nervePerforating branches of fibular arteryin posterior compartment(vessels in and around fibula)Deep fibularnerve
Fig. 6.93 Muscles of the anterior compartment of leg. |
Anterior surfaceof fibulaExtensordigitorumlongusOrigin of extensordigitorum longusLateral surfaceof fibulaExtensor hallucis longusOrigin of extensorhallucis longusFibularistertiusAttachment to inferior surface of medial cuneiform and metatarsal ISubcutaneoussurface of tibiaTibialisanteriorOrigin of tibialisanterior
Fig. 6.94 Anterior tibial artery and deep fibular nerve.
Fig. 6.95 Foot. A. Dorsal aspect, right foot. B. Plantar aspect, right foot, showing the surface in contact with the ground when standing.
AbductionAdductionGreat toeDigit IDigit IIDigit IIIDigit IVDigit VPhalangesLittle toeMetatarsals (I–V)Tarsal bonesABCut surface of medialmalleolus (tibia)Cut surface of lateralmalleolus (fibula)Calcaneal tendonMedial malleolusLateral malleolusHeelSesamoid bones
Fig. 6.96 Bones of the foot. A. Dorsal view, right foot. B. Lateral view, right foot.
TalusPosteriorprocessof the talusBCalcaneusFibular trochleaGrooveCuboidMedial tubercleCuneiformsNavicularPhalangesMetatarsalsNavicularIntermediatetarsal boneTuberosity (on undersurface)CalcaneusTalusLateral processLateraltubercleGroove for tendon offlexor hallucis longusProximal groupof tarsal bonesMedialIntermediateLateralCuneiformsDistal groupof tarsal bonesCuboidDistalMiddleProximalA
Fig. 6.97 Talus. A. Medial view. B. Inferior view.
ABPosterior AnteriorArticular surfacefor navicularArticular surfacefor navicularNeckHeadBodyAnteriorPosteriorArticular surface withmedial malleolusMedialtubercleLateraltubercleGroove for flexorhallucis longusGroove for flexorhallucis longusArticular surface withdistal end of tibiaAnterior calcanealsurfaceMiddle calcanealsurfaceSulcus taliPosterior processof talusPosteriorcalcaneal surfaceArticular surface forcalcaneonavicularligament
Fig. 6.98 Calcaneus. A. Superior view. B. Inferior view. C. Lateral view.
ABCAnterior talar articular surfacePosterior talararticular surfacePosterior talararticular surfaceAnterior talararticular surfaceMiddle talararticular surfaceMiddle talararticular surfaceSustentaculum taliMedialMedialMiddle part of posterior surface(insertion of calcaneal tendon)Upper part ofposterior surfaceLateralCalcanealsulcusArticular surface with cuboid boneCalcanealtubercleLateralprocessNotchCalcaneal tuberosity(lower part of posterior surface)MedialprocessGroove for tendon offlexor hallucis longusAttachment of calcaneofibularpart of lateral collateral ligamentof ankle jointFibular trochleaCalcaneal sulcus
Fig. 6.99 Tarsal sinus. Lateral view, right foot.
Fig. 6.100 Metatarsals and phalanges. Dorsal view, right foot.
Fig. 6.101 Radiograph of ankle showing talar beak.
Fig. 6.102 Ankle joint. A. Anterior view with right foot plantarflexed. B. Schematic of joint, posterior view. C. Superior view of the talus to show the shape of the articular surface.
ABCInterosseousligamentTibiaMedialmalleolusLateralmalleolusLateral malleolusTalusFibulaFibulaTibiaArticular surface of talusArticular surfacenarrow posteriorlyPosteriorMedial malleolusAnteriorArticular surface wide anteriorly
Fig. 6.103 Medial ligament of the ankle joint, right foot. |
Medialtubercleof talusSustentaculum taliof calcaneus bonePlantar calcaneonavicular ligamentTuberosity ofnavicular bonePosteriortibiotalar partTibiocalcaneal partTibionavicular partAnterior tibiotalar partMedial ligament of the ankle joint
Fig. 6.104 Lateral ligament of the ankle joint. A. Lateral view, right foot. B. Posterior view, right foot.
Malleolar fossaAnterior talofibular ligamentCalcaneofibular ligamentPosteriortalofibularligamentPosteriortalofibular ligamentPosteriorprocess of talusMalleolar fossaFibulaTibiaTalusAB
Fig. 6.105 Intertarsal joints, right foot.
Fig. 6.106 Interosseous talocalcaneal ligament. Lateral view, right foot.
Fig. 6.107 Talocalcaneonavicular joint. A. Medial view, right foot. B. Superior view, right foot, talus removed. C. Ligaments, medial view, right foot. D. Ligaments, lateral view, right foot.
Fig. 6.108 Plantar ligaments, right foot. A. Plantar calcaneocuboid ligament (short plantar ligament). B. Long plantar ligament.
Fig. 6.109 Tarsometatarsal, metatarsophalangeal, and interphalangeal joints, and the deep transverse metatarsal ligaments, right foot.
Fig. 6.110 Tarsal tunnel and flexor retinaculum. Posteromedial view, right foot. A. Bones. B. Tarsal tunnel and flexor retinaculum.
ABTibiaTalusCalcaneusFlexor retinaculumTarsaltunnelTendon of flexordigitorum longusTendon oftibialis posteriorPulse of post-tibial arterymidway between heeland medial malleolusTendon offlexorhallucislongusTibial nervePosteriortibial arteryTibialis posteriorFlexor digitorumlongusTibial arteryTibial veinTibial nerveFlexor hallucislongus
Fig. 6.111 Extensor retinacula, right foot.
Anterior tibial arteryTendon of extensorhallucis longusTendon oftibialis anteriorDorsalispedis arteryFirst dorsalinterosseousmuscleInferior extensorretinaculumSuperior extensorretinaculumExtensordigitorum longusFibularis tertius
Fig. 6.112 Fibular retinacula. Lateral view, right foot.
Tendons of fibularis longus andbrevis musclesSuperior fibular retinaculumInferior fibular retinaculum(at fibular trochlea on calcaneus)
Fig. 6.113 Arches of the foot. A. Longitudinal arches, right foot.
B. Transverse arch, left foot.
Fig. 6.114 Support for arches of the foot. A. Ligaments. Medial view, right foot. B. Cross section through the foot to show tendons of muscles supporting the arches, left foot.
Fig. 6.115 Plantar aponeurosis, right foot.
Superficial transversemetatarsal ligamentsMedial process ofcalcaneal tuberosityPlantar aponeurosisAnterior arm of inferiorextensor retinaculum
Fig. 6.116 Fibrous digital sheaths, right foot.
Fig. 6.117 Extensor hoods.
1st dorsal interosseous muscleExtensor tendonsExtensor hoodDeep transverse metatarsal ligamentLumbricalFlexor digitorum longusExtension of PIP joints prevents overflexionFlexion of MTP jointprevents overextension
Fig. 6.118 Extensor digitorum brevis muscle, right foot. |
Fig. 6.119 First layer of muscles in the sole of the right foot.
Fig. 6.120 Second layer of muscles in the sole of the right foot.
Fig. 6.121 MRI of posterior foot in a patient with plantar fasciitis shows thickening of the plantar aponeurosis at the calcaneal insertion and a calcaneal spur.
Fig. 6.122 Third layer of muscles in the sole of the right foot.
FlexorhallucisbrevisTransverse headOblique headAdductor hallucisFlexor digitiminimi brevisTendon of fibularislongus muscleTendon of tibialisposterior muscleTendon of flexorhallucis longus
Fig. 6.123 Fourth layer of muscles in the sole of the right foot.
Fig. 6.124 Arteries in the sole of the right foot.
Digital branchesDeep plantar artery: terminal branchof dorsalis pedis arteryPlantar metatarsal arteriesPerforatingvesselsDeepplantar archLateral plantararteryPosterior tibial arteryMedial plantarartery
Fig. 6.125 Dorsalis pedis artery right foot.
ExtensorhoodDorsaldigitalarteriesAnterior tibial arteryDorsalis pedisarteryAnterior medialmalleolar arteryAnterior lateralmalleolar arteryMedial and lateraltarsal branchesExtensorhallucislongusDorsalis pedisarteryDeep plantararteryFirst dorsalmetatarsalarteryFirst dorsalinterosseousmuscleArcuate arteryTendon of extensordigitorum longusto toe II
Fig. 6.126 Superficial veins of the right foot.
Fig. 6.127 Lateral and medial plantar nerves. A. Sole of the right foot. B. Cutaneous distribution of right foot.
Fig. 6.128 A.Terminal branches of superficial and deep fibular nerves in the right foot. B. Cutaneous distribution right foot.
Deep fibularnerveABBranches tofirst and seconddorsal interosseiExtensordigitorumbrevisBranch of deepfibular to extensordigitorum brevisSuperficialfibular nerveSaphenous nerveSuperficialfibular nerveDeep fibular nerveSural nerve
Fig. 6.129 Avoiding the sciatic nerve. A. Posterior view of the gluteal region of a man with the position of the sciatic nerve indicated. B. Posterolateral view of the left gluteal region with gluteal quadrants and the position of the sciatic nerve indicated.
Fig. 6.130 Position of the femoral artery in the femoral triangle. Anterior thigh.
Inguinal ligamentAnterior superior iliac spineFemoral nerveFemoral arteryFemoral veinLymphatics passing through femoral canalMedial margin ofsartorius muscleMedial margin of adductor longus musclePubic tuberclePubic symphysis
Fig. 6.131 Identifying structures around the knee. A. Anterior view of the right knee. B. Lateral view of the partially flexed right knee.
C. Lateral view of the extended right knee, thigh, and gluteal region.
ABCVastus lateralisVastus medialisQuadriceps tendonQuadriceps femoris musclePatellaPatellaPatellarligamentPatellar ligamentTibial tuberosityTendon ofbiceps femorisHead of fibulaCommon fibular nerveTensor fasciae lataeIliotibial tractHamstring musclesGluteus maximus
Fig. 6.132 Visualizing the contents of the popliteal fossa. Posterior view of the left knee. |
Popliteal fossaPopliteal arteryPopliteal veinCommon fibular nerveBiceps femoris muscle and tendonHead of fibulaPenetrates deep fasciaLateral head of gastrocnemius muscleMedial head of gastrocnemius muscleTibial nerveSemimembranosus muscleSemitendinosus tendonSmall saphenous vein
Fig. 6.133 Finding the tarsal tunnel—the gateway to the foot.
Fig. 6.134 Identifying tendons around the ankle and in the foot. A. Medial side of the right foot. B. Posterior aspect of the right foot. C. Lateral side of the right foot. D. Dorsal aspect of the right foot.
Fig. 6.135 Finding the dorsalis pedis artery.
Dorsalis pedis arteryExtensor digitorumlongus tendon to second toeExtensor hallucislongus tendon
Fig. 6.136 Position of the plantar arch.
Fig. 6.137 Major superficial veins. A. Dorsal aspect of the right foot. B. Anterior view of right lower limb. C. Posterior aspect of the left thigh, leg, and foot.
Fig. 6.138 Where to feel peripheral arterial pulses in the lower limb.
Fig. 6.139 A. Normal knee joint showing the tibial collateral ligament and the medial and lateral menisci. Proton density (PD)-weighted magnetic resonance image in the coronal plane. B. Knee joint showing a torn tibial collateral ligament. PD-weighted magnetic resonance image in the coronal plane.
Fig. 6.140 A. Knee joint showing an intact anterior cruciate ligament. T2-weighted magnetic resonance image in the sagittal plane.
B. Knee joint showing a torn anterior cruciate ligament. T2-weighted magnetic resonance image in the sagittal plane. C. Knee joint showing a torn medial meniscus (the broken off portion of the posterior horn has moved into the anterior aspect of the joint giving the impression of a ‘double meniscus’ in this location). Proton density-weighted magnetic resonance image in the sagittal plane.
AFemurPatellaAnterior cruciate ligamentTibiaBFemurTorn anteriorcruciate ligamentTibiaAnterior cruciateligament fragmentPatellaCMedial femoral condyleTorn posterior “horn”of medial meniscusTibiaAnterior “horn” of medial meniscusDisplaced fragment of posterior hornof medial meniscus
Fig. 6.141 Radiograph (A) and MRI (B) of soft tissue ulceration and erosion in the adjacent calcaneus. After debridement and placement of antibiotics beads in the wound there is progressive healing (C).
eFig. 6.142 Popliteal fossa showing position of the popliteal artery and vein and sciatic nerve. T1-weighted magnetic resonance image in the axial plane.
eFig. 6.143 Pulmonary embolus. Axial computed tomogram.
Left atriumAortaRight inferior pulmonary artery with embolusEmbolus eFig. 6.144 Ankle showing a ruptured calcaneal tendon. T2-weighted magnetic resonance image in the sagittal plane.
eFig. 6.145 A. Normal ankle joint showing an intact anterior talofibular ligament. T1-weighted magnetic resonance image in the axial plane. B. Ankle joint showing a torn anterior talofibular ligament. T2-weighted magnetic resonance image in the axial plane.
Table 6.1 Branches of the lumbosacral plexus associated with the lower limb
Table 6.2 Muscles of the gluteal region (spinal segments in bold are the major segments innervating the muscle)
Table 6.3 Muscles of the anterior compartment of thigh (spinal segments in bold are the major segments innervating the muscle) |
Table 6.4 Muscles of the medial compartment of thigh (spinal segments in bold are the major segments innervating the muscle)
Table 6.5 Muscles of the posterior compartment of thigh (spinal segments in bold are the major segments innervating the muscle)
Table 6.6 Superficial group of muscles in the posterior compartment of leg (spinal segments in bold are the major segments innervating the muscle)
Table 6.7 Deep group of muscles in the posterior compartment of leg (spinal segments in bold are the major segments innervating the muscle)
Table 6.8 Muscles of the lateral compartment of leg (spinal segments in bold are the major segments innervating the muscle)
Table 6.9 Muscles of the anterior compartment of leg (spinal segments in bold are the major segments innervating the muscle)
Table 6.10 Muscles of the dorsal aspect of the foot (spinal segments in bold are the major segments innervating the muscle)
Table 6.11 First layer of muscles in the sole of the foot (spinal segments in bold are the major segments innervating the muscle)
Table 6.12 Second layer of muscles in the sole of the foot (spinal segments in bold are the major segments innervating the muscle)
Table 6.13 Third layer of muscles in the sole of the foot (spinal segments in bold are the major segments innervating the muscle)
Table 6.14 Fourth layer of muscles in the sole of the foot (spinal segments in bold are the major segments innervating the muscle)
In the clinic
The pelvic bones, sacrum, and associated joints form a bony ring surrounding the pelvic cavity. Soft tissue and visceral organ damage must be suspected when the pelvis is fractured. Patients with multiple injuries and evidence of chest, abdominal, and lower limb trauma should also be investigated for pelvic trauma.
Pelvic fractures can be associated with appreciable blood loss (concealed exsanguination) and blood transfusion is often required. In addition, this bleeding tends to form a significant pelvic hematoma, which can compress nerves, press on organs, and inhibit pelvic visceral function (Fig. 6.25).
There are many ways of classifying pelvic fractures, which enable the surgeon to determine the appropriate treatment and the patient’s prognosis. Pelvic fractures are generally of four types.
Type 1 injuries occur without disruption of the bony pelvic ring (e.g., a fracture of the iliac crest). These types of injuries are unlikely to represent significant trauma, though in the case of a fracture of the iliac crest, blood loss needs to be assessed.
Type 2 injuries occur with a single break in the bony pelvic ring. An example of this would be a single fracture with diastasis (separation) of the symphysis pubis. Again, these injuries are relatively benign in nature, but it may be appropriate to assess for blood loss.
Type 3 injuries occur with double breaks in the bony pelvic ring. These include bilateral fractures of the pubic rami, which may produce urethral damage.
Type 4 injuries occur at and around the acetabulum.
Other types of pelvic ring injuries include fractures of the pubic rami and disruption of the sacro-iliac joint with or without dislocation. This may involve significant visceral pelvic trauma and hemorrhage.
Other general pelvic injuries include stress fractures and insufficiency fractures, as seen in athletes and elderly patients with osteoporosis, respectively.
In the clinic |
Femoral neck fractures (Fig. 6.28) can interrupt the blood supply to the femoral head. The blood supply to the head and neck is primarily from an arterial ring formed by the branches of the medial and lateral circumflex femoral arteries around the base of the femoral neck. From here, vessels course along the neck, penetrate the capsule, and supply the femoral head. The blood supply to the femoral head and femoral neck is further enhanced by the artery of the ligamentum teres, a branch of the obturator artery, which is generally small and variable. Femoral neck fractures may disrupt associated vessels and lead to necrosis of the femoral head. Femoral neck fractures can be divided into three categories depending on the location of the fracture line: subcapital (fracture line passes across the femoral head-neck junction), transcervical (fracture line passes through the midportion of the femoral neck), and basicervical (fracture line passes across the base of the neck). Subcapital fractures have the highest risk of developing necrosis of the femoral head, and basicervical fractures have the lowest risk. Elderly patients with osteoporosis tend to have transverse subcapital fractures following low-energy trauma such as a fall from a standing height. Conversely, younger patients usually sustain more vertical fractures of the distal femoral neck (basicervical) after high-energy trauma such as a fall from a great height or due to axial load applied to an abducted knee, such as during a motor vehicle accident.
In the clinic
In these fractures, the break usually runs from the greater trochanter through to the lesser trochanter and does not involve the femoral neck. Intertrochanteric fractures preserve the femoral neck blood supply and do not render the femoral head ischemic. They are most commonly seen in the elderly and result from low-energy impact (Fig. 6.29).
Sometimes isolated fractures of the greater or the lesser trochanter can occur. An isolated fracture of the lesser trochanter in adults is most commonly pathological and due to an underlying malignant deposit.
In the clinic
An appreciable amount of energy is needed to fracture the femoral shaft. This type of injury is therefore accompanied by damage to the surrounding soft tissues, which include the muscle compartments and the structures they contain.
In the clinic
The normal flow of blood in the lower limbs is from the skin and subcutaneous tissues to the superficial veins, which drain via perforating veins to the deep veins, which in turn drain into the iliac veins and inferior vena cava.
The normal flow of blood in the venous system depends upon the presence of competent valves, which prevent reflux. Venous return is supplemented with contraction of the muscles in the lower limb, which pump the blood toward the heart. When venous valves become incompetent they tend to place extra pressure on more distal valves, which may also become incompetent. This condition produces dilated tortuous superficial veins (varicose veins) in the distribution of the great (long) and small (short) saphenous venous systems.
Varicose veins occur more commonly in women than in men, and symptoms are often aggravated by pregnancy. Some individuals have a genetic predisposition to developing varicose veins. Valves may also be destroyed when a deep vein thrombosis occurs if the clot incorporates the valve into its interstices; during the process of healing and recanalization the valve is destroyed, rendering it incompetent.
Typical sites for valvular incompetence include the junction between the great (long) saphenous vein and the femoral vein, perforating veins in the midthigh, and the junction between the small (short) saphenous vein and the popliteal vein. |
Varicose veins may be unsightly, and soft tissue changes may occur with chronic venous incompetence. As the venous pressure rises, increased venular and capillary pressure damages the cells, and blood and blood products extrude into the soft tissue. This may produce a brown pigmentation in the skin, and venous eczema may develop. Furthermore, if the pressure remains high the skin may break down and ulcerate, and many weeks of hospitalization may be needed for this to heal.
Treatments for varicose veins include tying off the valve, “stripping” (removing) the great (long) and small (short) saphenous systems, and in some cases valvular reconstruction.
In the clinic
Thrombosis may occur in the deep veins of the lower limb and within the pelvic veins. Its etiology was eloquently described by Virchow, who described the classic triad (venous stasis, injury to the vessel wall, and hypercoagulable states) that precipitates thrombosis.
In some patients a deep vein thrombosis (DVT) in the calf veins may propagate into the femoral veins. This clot may break off and pass through the heart to enter the pulmonary circulation, resulting in occlusion of the pulmonary artery, cardiopulmonary arrest, and death.
A significant number of patients undergoing surgery are likely to develop a DVT, so most surgical patients are given specific prophylactic treatment to prevent thrombosis. A typical DVT prophylactic regimen includes anticoagulant injections and graduated stockings (to prevent deep venous stasis and facilitate emptying of the deep veins).
Although physicians aim to prevent the formation of DVT, it is not always possible to detect it because there may be no clinical signs. Calf muscle tenderness, postoperative pyrexia, and limb swelling can be helpful clues. The diagnosis is predominantly made by duplex Doppler sonography or rarely by ascending venography.
If DVT is confirmed, intravenous and oral anticoagulation are started to prevent extension of the thrombus.
In the clinic
Vascular access to the lower limb
Deep and inferior to the inguinal ligament are the femoral artery and femoral vein. The femoral artery is palpable as it passes over the femoral head and may be easily demonstrated using ultrasound. If arterial or venous access is needed rapidly, a physician can use the femoral approach to these vessels.
Many radiological procedures involve catheterization of the femoral artery or the femoral vein to obtain access to the contralateral lower limb, the ipsilateral lower limb, the vessels of the thorax and abdomen, and the cerebral vessels.
Cardiologists also use the femoral artery to place catheters in vessels around the arch of the aorta and into the coronary arteries to perform coronary angiography and angioplasty.
Access to the femoral vein permits catheters to be maneuvered into the renal veins, the gonadal veins, the right atrium, and the right side of the heart, including the pulmonary artery and distal vessels of the pulmonary tree. Access to the superior vena cava and the great veins of the neck is also possible.
In the clinic
Trendelenburg’s sign occurs in people with weak or paralyzed abductor muscles (gluteus medius and gluteus minimus) of the hip. The sign is demonstrated by asking the patient to stand on one limb. When the patient stands on the affected limb, the pelvis severely drops over the swing limb.
Positive signs are typically found in patients with damage to the superior gluteal nerve. Damage to this nerve may occur with associated pelvic fractures, with space-occupying lesions within the pelvis extending into the greater sciatic foramen, and in some cases relating to hip surgery during which there has been disruption of and subsequent atrophy of the insertion of the gluteus medius and gluteus minimus tendons on the greater trochanter. |
In patients with a positive Trendelenburg’s sign, gait also is abnormal. Typically during the stance phase of the affected limb, the weakened abductor muscles allow the pelvis to tilt inferiorly over the swing limb. The patient compensates for the pelvic drop by lurching the trunk to the affected side to maintain the level of the pelvis throughout the gait cycle.
In the clinic
From time to time it is necessary to administer drugs intramuscularly, that is, by direct injection into muscles. This procedure must be carried out without injuring neurovascular structures. A typical site for an intramuscular injection is the gluteal region. The sciatic nerve passes through this region and needs to be avoided. The safest place to inject is the upper outer quadrant of either gluteal region.
The gluteal region can be divided into quadrants by two imaginary lines positioned using palpable bony landmarks (Fig. 6.49). One line descends vertically from the highest point of the iliac crest. Another line is horizontal and passes through the first line midway between the highest point of the iliac crest and the horizontal plane through the ischial tuberosity.
It is important to remember that the gluteal region extends as far forward as the anterior superior iliac spine. The sciatic nerve curves through the upper lateral corner of the lower medial quadrant and descends along the medial margin of the lower lateral quadrant.
Occasionally, the sciatic nerve bifurcates into its tibial and common fibular branches in the pelvis, in which case the common fibular nerve passes into the gluteal region through, or even above, the piriformis muscle.
The superior gluteal nerve and vessels normally enter the gluteal region above the piriformis and pass superiorly and forward.
The anterior corner of the upper lateral quadrant is normally used for injections to avoid injuring any part of the sciatic nerve or other nerves and vessels in the gluteal region. A needle placed in this region enters the gluteus medius anterosuperior to the margin of the gluteus maximus.
In the clinic
Compartment syndrome occurs when there is swelling within a fascial enclosed muscle compartment in the limbs. Typical causes include limb trauma, intracompartment hemorrhage, and limb compression. As pressure within the compartment elevates, capillary blood flow and tissue perfusion is compromised, which can ultimately lead to neuromuscular damage if not treated.
In the clinic
Muscle injuries to the lower limb
Muscle injuries may occur as a result of direct trauma or as part of an overuse syndrome.
Muscle injuries may occur as a minor muscle tear, which may be demonstrated as a focal area of fluid within the muscle. With increasingly severe injuries, more muscle fibers are torn and this may eventually result in a complete muscle tear. The usual muscles in the thigh that tear are the hamstring muscles. Tears in the muscles below the knee typically occur within the soleus muscle, though other muscles may be affected.
Injury to the hamstring muscles is a common source of pain in athletes, particularly in those competing in sports requiring a high degree of power and speed (such as sprinting, track and field, football) where the hamstring muscles are very susceptible to injury from excessive stretching.
The injury can range from a mild muscle strain to a complete tear of a muscle or a tendon. It usually occurs during sudden accelerations and decelerations or rapid change in direction. In adults, the most commonly injured is the muscle-tendon junction, which is a wide transition zone between the muscle and the tendon. An avulsion of the ischial tuberosity with proximal hamstring origin attachment is common in the adolescent population, particularly during sudden hip flexion because the ischial apophysis is the weakest element of the proximal hamstring unit in this age group (Fig. 6.64). Both ultrasound and MRI can be used to assess the hamstring injury with the MRI providing not only the information about the extent of the injury but also give some indication about the prognosis (future risk of re-tear, loss of function, etc).
In the clinic |
Peripheral vascular disease is often characterized by reduced blood flow to the legs. This disorder may be caused by stenoses (narrowing) and/or occlusions (blockages) in the lower aorta and the iliac, femoral, tibial, and fibular vessels. Patients typically have chronic leg ischemia and “acute on chronic” leg ischemia.
Chronic leg ischemia is a disorder in which vessels have undergone atheromatous change, and often there is significant luminal narrowing (usually over 50%). Most patients with peripheral arterial disease have widespread arterial disease (including cardiovascular and cerebrovascular disease), which may be clinically asymptomatic. Some of these patients develop such severe ischemia that the viability of the limb is threatened (critical limb ischemia).
The commonest symptom of chronic leg ischemia is intermittent claudication. Patients typically have a history of pain that develops in the calf muscles (usually associated with occlusions or narrowing in the femoral artery) or the buttocks (usually associated with occlusion or narrowing in the aorto-iliac segments). The pain experienced in these muscles is often cramplike and occurs with walking. The patient rests and is able to continue walking up to the same distance until the pain recurs and stops walking as before.
In some patients with chronic limb ischemia, an acute event blocks the vessels or reduces the blood supply to such a degree that the viability of the limb is threatened.
Occasionally a leg may become acutely ischemic with no evidence of underlying atheromatous disease. In these instances a blood clot is likely to have embolized from the heart. Patients with mitral valve disease and atrial fibrillation are prone to embolic disease.
Critical limb ischemia occurs when the blood supply to the limb is so poor that the viability of the limb is severely threatened, and in this case many patients develop gangrene, ulceration, and severe rest pain in the foot. These patients require urgent treatment, which may be in the form of surgical reconstruction, radiological angioplasty, or even amputation.
In the clinic
Menisci can get torn during forceful rotation or twisting of the knee, but significant trauma is not always necessary for a tear to occur. There are various patterns of meniscal tearing depending on the cleavage plane such as vertical tears (perpendicular to the tibial plateau), horizontal tears (parallel to the long axis of the meniscus and perpendicular to the tibial plateau), or bucket handle tears (longitudinal tear where the torn portion of the meniscus forms a handle shaped fragment which gets displaced into the intercondylar notch).
The patient usually complains of pain localized to the medial or lateral side of the knee, knee locking or clicking, sensation of knee giving way, and swelling, which can be intermittent and usually delayed.
MRI is the modality of choice to assess meniscal tears and detect other associated injuries, such as ligamentous tears and articular cartilage damage (Fig. 6.74A). Arthroscopy is usually performed to repair a tear, debride the damaged meniscal material, or rarely remove the entire torn meniscus (Fig. 6.74B).
In the clinic
The collateral ligaments are responsible for stabilizing the knee joint, controlling its sideway movements, and protecting the knee from excessive motion.
Injury to the fibular collateral ligament occurs when excessive outward force is applied to the medial side of the knee (varus force), and is less common than an injury to the tibial collateral ligament that is damaged when excessive force is applied inward to the lateral side of the joint (valgus force). Injuries to the tibial collateral ligament can be part of a so called “unhappy triad” that also involves tears of the medial meniscus and the anterior cruciate ligament.
The spectrum of injuries to collateral ligaments of the knee range from minor sprains where the ligaments are slightly stretched, but still able to stabilize the knee joint, to full thickness tears where all fibers are torn and the ligaments lose their stabilizing function. |
In the clinic
The anterior cruciate ligament (ACL) is most frequently injured during non-contact activities when there is a sudden change in the direction of movement (cutting or pivoting) (Fig. 6.81). Contact sports may also result in ACL injury due to sudden twisting, hyperextension, and valgus force related to direct collision. The injury usually affects the mid-portion of the ligament and manifests itself as a complete or partial discontinuity of the fibers or abnormal orientation and contour of the ligament. With an acute ACL tear, a sudden click or pop can be heard and the knee becomes rapidly swollen. Several tests are used to clinically assess the injury, and the diagnosis is usually confirmed by MRI. A full thickness ACL tear causes instability of the knee joint. The treatment depends on the desired level of activity of the patient. In those with high activity levels, surgical reconstruction of the ligament is required. Those with low activity levels may opt for knee bracing and physiotherapy; however, in the long term the internal damage to the knee leads to the development of early osteoarthritis.
A tear to the posterior cruciate ligament (PCL) requires significant force, so it rarely occurs in isolation. It usually occurs during hyperextension of the knee or as a result of a direct blow to a bent knee such as when striking the knee against the dashboard in a motor vehicle accident. Typically, the injury presents as posterior displacement of the tibia on physical examination (the so called tibial sag sign). Patients complain of knee pain and swelling, inability to bear weight, and instability. The diagnosis is confirmed on MRI. The management, as in ACL injury, depends on the degree of the injury (sprain, partial thickness, full thickness) and the level of desired activity.
In the clinic
Degenerative joint disease occurs throughout many joints within the body. Articular degeneration may result from an abnormal force across the joint with a normal cartilage or a normal force with abnormal cartilage.
Typically degenerative joint disease occurs in synovial joints and the process is called osteoarthritis. In the joints where osteoarthritis occurs the cartilage and bony tissues are usually involved, with limited change within the synovial membrane. The typical findings include reduction in the joint space, eburnation (joint sclerosis), osteophytosis (small bony outgrowths), and bony cyst formation. As the disease progresses the joint may become malaligned, its movement may become severely limited, and there may be significant pain.
The commonest sites for osteoarthritis include the small joints of the hands and wrist, and in the lower limb, the hip and knee are typically affected, though the tarsometatarsal and metatarsophalangeal articulations may undergo similar changes.
The etiology of degenerative joint disease is unclear, but there are some associations, including genetic predisposition, increasing age (males tend to be affected younger than females), overuse or underuse of joints, and nutritional and metabolic abnormalities. Further factors include joint trauma and pre-existing articular disease or deformity.
The histological findings of osteoarthritis consist of degenerative changes within the cartilage and the subchondral bone. Further articular damage worsens these changes, which promote further abnormal stresses upon the joint. As the disease progresses the typical finding is pain, which is usually worse on rising from bed and at the end of a day’s activity. Commonly it is aggravated by the extremes of movement or unaccustomed exertion. Stiffness and limitation of movement may ensue.
Treatment in the first instance includes alteration of lifestyle to prevent pain and simple analgesia. As symptoms progress a joint replacement may be necessary, but although joint replacement appears to be the panacea for degenerative joint disease, it is not without risks and complications, which include infection and failure in the short and long term.
In the clinic
Examination of the knee joint |
It is important to establish the nature of the patient’s complaint before any examination. The history should include information about the complaint, the signs and symptoms, and the patient’s lifestyle (level of activity). This history may give a significant clue to the type of injury and the likely findings on clinical examination, for example, if the patient was kicked around the medial aspect of the knee, a valgus deformity injury to the tibial collateral ligament might be suspected.
The examination should include assessment in the erect position, while walking, and on the couch. The affected side must be compared with the unaffected side.
There are many tests and techniques for examining the knee joint, including the following.
Lachman’s test—the patient lies on the couch. The examiner places one hand around the distal femur and the other around the proximal tibia and then elevates the knee, producing 20° of flexion. The patient’s heel rests on the couch. The examiner’s thumb must be on the tibial tuberosity. The hand on the tibia applies a brisk anteriorly directed force. If the movement of the tibia on the femur comes to a sudden stop, it is a firm endpoint. If it does not come to a sudden stop, the endpoint is described as soft and is associated with a tear of the anterior cruciate ligament.
Anterior drawer test—a positive anterior drawer test is when the proximal head of a patient’s tibia can be pulled anteriorly on the femur. The patient lies supine on the couch. The knee is flexed to 90° and the heel and sole of the foot are placed on the couch. The examiner sits gently on the patient’s foot, which has been placed in a neutral position. The index fingers are used to check that the hamstrings are relaxed while the other fingers encircle the upper end of the tibia and pull the tibia. If the tibia moves forward, the anterior cruciate ligament is torn. Other peripheral structures, such as the medial meniscus or meniscotibial ligaments, must also be damaged to elicit this sign.
Pivot shift test—there are many variations of this test. The patient’s foot is wedged between the examiner’s body and elbow. The examiner places one hand flat under the tibia pushing it forward with the knee in extension. The other hand is placed against the patient’s thigh pushing it the other way. The lower limb is taken into slight abduction by the examiner’s elbow with the examiner’s body acting as a fulcrum to produce the valgus. The examiner maintains the anterior tibial translation and the valgus and initiates flexion of the patient’s knee. At about 20°–30° the pivot shift will occur as the lateral tibial plateau reduces. This test demonstrates damage to the posterolateral corner of the knee joint and the anterior cruciate ligament.
Posterior drawer test—a positive posterior drawer test occurs when the proximal head of a patient’s tibia can be pushed posteriorly on the femur. The patient is placed in a supine position and the knee is flexed to approximately 90° with the foot in the neutral position. The examiner sits gently on the patient’s foot placing both thumbs on the tibial tuberosity and pushing the tibia backward. If the tibial plateau moves, the posterior cruciate ligament is torn.
Assessment of other structures of the knee
Assessment of the tibial collateral ligament can be performed by placing a valgus stress on the knee.
Assessment of lateral and posterolateral knee structures requires more complex clinical testing.
The knee will also be assessed for: joint line tenderness, patellofemoral movement and instability, presence of an effusion, muscle injury, and popliteal fossa masses.
After the clinical examination has been carried out, further investigations usually include plain radiography and possibly magnetic resonance imaging, which allows the radiologist to assess the menisci, cruciate ligaments, collateral ligaments, bony and cartilaginous surfaces, and soft tissues. |
Arthroscopy may be carried out and damage to any internal structures repaired or trimmed. An arthroscope is a small camera that is placed into the knee joint through the anterolateral or anteromedial aspect of the knee joint. The joint is filled with a saline solution and the telescope is manipulated around the knee joint to assess the cruciate ligaments, menisci, and cartilaginous surfaces.
In the clinic
Anterolateral ligament of the knee
A ligament associated at its origin with the fibular collateral ligament of the knee has been described. This ligament (anterolateral ligament of the knee) courses from the lateral femoral epicondyle to the anterolateral region of the proximal end of the tibia and may control internal rotation of the tibia. (J Anat 2013;223:321–328)
In the clinic
The popliteal artery can become abnormally dilated, forming an aneurysm. The artery is considered aneurysmal when its diameter exceeds 7 mm. Although popliteal artery aneurysms can occur in isolation, they are most commonly associated with aneurysms in other large vessels such as the femoral artery or the thoracic or abdominal aorta. Therefore, once a popliteal aneurysm has been detected, the entire arterial tree needs to be investigated for the presence of coexisting aneurysms elsewhere in the body.
Popliteal artery aneurysms tend to undergo thrombosis and are less likely to rupture than other aneurysms. Therefore the complications are mainly related to distal embolization of the arterial tree and lower limb ischemia, which in the most severe cases can lead to leg amputation.
Ultrasound with duplex Doppler is the most helpful way of diagnosing a popliteal artery aneurysm because it can demonstrate abnormal dilation of the artery, confirm or rule out thrombus within the aneurysm, and help distinguish it from other masses of the popliteal fossa such as a synovial cyst (Baker’s cyst). Popliteal artery aneurysms are usually repaired surgically in view of high risk of thromboembolic complications.
In the clinic
Rupture of the calcaneal tendon is often related to sudden or direct trauma. This type of injury frequently occurs in a normal healthy tendon. In addition, there are certain conditions that may predispose the tendon to rupture. Among these conditions are tendinopathy (due to overuse, or to age-related degenerative changes) and previous calcaneal tendon interventions such as injections of pharmaceuticals and the use of certain antibiotics (quinolone group). The diagnosis of calcaneal tendon rupture is relatively straightforward. The patient typically complains of “being kicked” or “shot” behind the ankle, and clinical examination often reveals a gap in the tendon.
In the clinic
Neurological examination of the legs
Some of the commonest conditions that affect the legs are peripheral neuropathy (particularly associated with diabetes mellitus), lumbar nerve root lesions (associated with pathology of the intervertebral discs), fibular nerve palsy, and spastic paraparesis.
Look for muscle wasting—loss of muscle mass may indicate loss of or reduced innervation. |
Test the power in muscle groups—hip flexion (L1, L2—iliopsoas—straight leg raise); knee flexion (L5 to S2—hamstrings—the patient tries to bend the knee while the examiner applies force to the leg to hold the knee in extension); knee extension (L3, L4—quadriceps femoris—the patient attempts to keep the leg straight while the examiner applies a force to the leg to flex the knee joint); ankle plantarflexion (S1, S2—the patient pushes the foot down while the examiner applies a force to the plantar surface of the foot to dorsiflex the ankle joint); ankle dorsiflexion (L4, L5—the patient pulls the foot upward while the examiner applies a force to the dorsal aspect of the foot to plantarflex the ankle joint).
Examine knee and ankle reflexes—a tap with a tendon hammer on the patellar ligament (tendon) tests reflexes at the L3–L4 spinal levels, and tapping the calcaneal tendon tests reflexes at the S1–S2 spinal levels.
Assess status of general sensory input to lumbar and upper sacral spinal cord levels—test light touch, pin prick, and vibration sense at dermatomes in the lower limb.
In the clinic
Footdrop is an inability to dorsiflex the foot. Patients with footdrop have a characteristic “steppage” gait. As the patient walks, the knee of the affected limb is elevated to an abnormal height during the swing phase to prevent the foot from dragging. At the end of the swing phase, the foot “slaps” the ground. Also, the unaffected limb often acquires a characteristic tiptoe pattern of gait during the stance phase. A typical cause of footdrop is damage to the common fibular nerve, which may occur with fractures of the fibular neck. Other causes include disc protrusion compressing the L5 nerve root, disorders of the sciatic nerve and the lumbosacral plexus, and pathologies of the spinal cord and brain.
In the clinic
The common fibular nerve is susceptible to injury as it passes around the lateral aspect of the neck of the fibula. It can be injured as a result of a direct trauma (blow or laceration), secondary to knee injury (knee dislocation), or as a consequence of a proximal fibular fracture. Sometimes damage to the nerve can be iatrogenic, that is, damaged during arthroscopy or knee surgery.
Symptoms of common fibular nerve injury are often observed in bed-bound patients, particularly in those with decreased levels of consciousness, due to prolonged external pressure to the knee leading to nerve compression and neuropathy. Similarly, application of a tight cast or a brace to the leg can compress the nerve, producing symptoms of fibular muscle palsy.
Apart from a foot drop, other symptoms of common fibular nerve injury include loss of sensation over the lateral aspect of the leg and dorsum of the foot, and wasting of fibular and anterior tibial muscles.
In the clinic
Occasionally there is a superior projection of the distal aspect of the talus, which is beak-shaped (Fig. 6.101). It is often associated with the presence of a bony or fibrous joint between the talus and calcaneus.
In the clinic
Fracture of the talus
The talus is an unusual bone because it ossifies from a single primary ossification center, which initially appears in the neck. The posterior aspect of the talus appears to ossify last, normally after puberty. In up to 50% of people there is a small accessory ossicle (the os trigonum) posterior to the lateral tubercle of the posterior process. Articular cartilage covers approximately 60% of the talar surface and there are no direct tendon or muscle attachments to the bone. |
One of the problems with fractures of the talus is that the blood supply to the bone is vulnerable to damage. The main blood supply to the bone enters the talus through the tarsal sinus from a branch of the posterior tibial artery. This vessel supplies most of the neck and the body of the talus. Branches of the dorsalis pedis artery enter the superior aspect of the talar neck and supply the dorsal portion of the head and neck, and branches from the fibular artery supply a small portion of the lateral talus.
Fractures of the neck of the talus often interrupt the blood supply to the talus, so making the body and posterior aspect of the talus susceptible to osteonecrosis, which may in turn lead to premature osteoarthritis and require extensive surgery.
In the clinic
An appreciation of ankle anatomy is essential to understand the wide variety of fractures that may occur at and around the ankle joint.
The ankle joint and related structures can be regarded as a fibro-osseous ring oriented in the coronal plane.
The upper part of the ring is formed by the joint between the distal ends of the fibula and tibia and by the ankle joint itself.
The sides of the ring are formed by the ligaments that connect the medial malleolus and lateral malleolus to the adjacent tarsal bones.
The bottom of the ring is not part of the ankle joint, but consists of the subtalar joint and the associated ligaments.
Visualizing the ankle joint and surrounding structures as a fibro-osseous ring allows the physician to predict the type of damage likely to result from a particular type of injury. For example, an inversion injury may fracture the medial malleolus and tear ligaments anchoring the lateral malleolus to the tarsal bones.
The ring may be disrupted not only by damage to the bones (which produces fractures), but also by damage to the ligaments. Unlike bone fractures, damage to ligaments is unlikely to be appreciated on plain radiographs. When a fracture is noted on a plain radiograph, the physician must always be aware that there may also be appreciable ligamentous disruption.
The Ottawa ankle rules were developed to assist clinicians in deciding whether patients with acute ankle injuries require investigation with radiographs in order to avoid unnecessary studies. Named after the hospital where they were developed, the rules are highly sensitive and have reduced the utilization of unwarranted ankle radiographs since their implementation.
An ankle x-ray series is required if there is ankle pain and any of the following:
Bone tenderness along the distal 6 cm of the posterior tibia or tip of the medial malleolus
Bone tenderness along the distal 6 cm of the posterior fibula or tip of the lateral malleolus
Inability to bear weight for four steps both immediately after the injury and in the emergency department
A foot x-ray series is required if there is midfoot pain and any of the following:
Bone tenderness at the base of the fifth metatarsal
Bone tenderness at the navicular bone
Inability to bear weight for four steps both immediately after the injury and in the emergency department
In the clinic
A bunion occurs on the medial aspect of the first metatarsophalangeal joint. This is an extremely important area of the foot because it is crossed by tendons and ligaments, which transmit and distribute the body’s weight during movement. It is postulated that abnormal stresses in this region of the joint may produce the bunion deformity.
Clinically, a bunion is a significant protuberance of bone that may include soft tissue around the medial aspect of the first metatarsophalangeal joint. As it progresses, the toe appears to move toward the smaller toes, producing crowding of the digits.
This deformity tends to occur among people who wear high-heeled or pointed shoes, but osteoporosis and a hereditary predisposition are also risk factors.
Typically the patient’s symptoms are pain, swelling, and inflammation. The bunion tends to enlarge and may cause problems in obtaining appropriate footwear. |
Initial treatment is by adding padding to shoes, changing the type of footwear used, and taking anti-inflammatory drugs. Some patients may need surgery to correct the deformity and realign the toe.
In the clinic
The plantar aponeurosis is a flat band of connective tissue that supports the arch of the sole of the foot. It runs from the calcaneal tuberosity to the base of the toes. Overuse and increased strain on the plantar aponeurosis, such as excessive running and standing, and increased body weight, can lead to micro-tears and degeneration within the aponeurosis at the heel with disorganization of the collagen fibers. Patients typically present with mild to severe heel pain, which appears thickened on imaging (Fig. 6.121). It is usually successfully treated with intense physiotherapy, but may require image-guided injection therapies. In severe cases, the diseased section of the fascia needs to be surgically removed.
In the clinic
A Morton’s neuroma is an enlarged common plantar nerve, usually in the third interspace between the third and fourth toes. In this region of the foot the lateral plantar nerve often unites with the medial plantar nerve. As the two nerves join, the resulting nerve is typically larger in diameter than those of the other toes. Also, it is in a relatively subcutaneous position, just above the fat pad of the foot close to the artery and the vein. Above the nerve is the deep transverse metatarsal ligament, which is a broad strong structure holding the metatarsals together. Typically, as the patient enters the “push-off” phase of walking the interdigital nerve is sandwiched between the ground and the deep transverse metatarsal ligament. The forces tend to compress the common plantar nerve, which can be irritated, in which case there is usually some associated inflammatory change and thickening.
Typically, patients experience pain in the third interspace, which may be sharp or dull and is usually worsened by wearing shoes and walking.
Treatment may include injection of anti-inflammatory drugs, or it may be necessary to surgically remove the lesion.
In the clinic
Clubfoot is a congenital deformity in which babies are born with one or both feet pointing inward and downward. It is treated with gentle manipulation of the affected foot and with plaster casts to straighten the foot, which is usually followed by a minor surgical procedure where the calcaneal tendon is cut to release the foot into a better position.
A young man was enjoying a long weekend skiing at a European ski resort. While racing a friend he caught an inner edge of his right ski. He lost his balance and fell. During his tumble he heard an audible “click.” After recovering from his spill, he developed tremendous pain in his right knee. He was unable to carry on skiing for that day, and by the time he returned to his chalet, his knee was significantly swollen. He went immediately to see an orthopedic surgeon.
The orthopedic surgeon carefully reviewed the mechanism of injury.
The man was skiing down the slope with both skis in parallel. The ankles were held rigid in the boots and the knees were slightly flexed. A momentary loss of concentration led to the skier catching the inner edge of his right ski. This effect was to force the boot and calf into external rotation. Furthermore, the knee was forced into a valgus position (bowed laterally away from the midline) and the skier tumbled. Both skis were detached from the boots as the bindings released them.
A series of structures within the knee joint were damaged sequentially.
As the knee went into external rotation and valgus, the anterior cruciate ligament became taut, acting as a fulcrum. The tibial collateral ligament was stressed and the lateral compartment of the knee compressed. As the force increased, the tibial collateral ligament was torn (Fig. 6.139A,B), as was the medial meniscus (Fig. 6.140C). Finally, the anterior cruciate ligament, which was taut, gave way (Fig. 6.140A,B).
The joint became swollen some hours afterward. |
Disruption of the anterior cruciate ligament characteristically produces marked joint swelling. The ligament is extrasynovial and intracapsular and has a rich blood supply. As the ligament was torn it ruptured into the joint. Blood from the tear irritates the synovial membrane and also enters the joint. These factors produce gradual swelling of the joint over the ensuing hours with significant fluid accumulation in the joint cavity.
The patient had a surgical reconstruction of the anterior cruciate ligament.
It is difficult to find a man-made substance that can act in the same way as the anterior cruciate ligament and demonstrate the same physical properties. Surgeons have devised ingenious ways of reconstructing the anterior cruciate ligament. Two of the commonest methods use the patellar ligament (tendon) and hamstrings to reconstruct the ligament.
The patient had further surgical procedures.
The tibial collateral ligament was explored and resutured. Using arthroscopic techniques, the tear in the medial meniscus was débrided to prevent further complications.
A 45-year-old man with diabetes mellitus visited his nurse because he had an ulcer on his foot that was not healing despite daily dressings.
Diabetes can lead to vascular disease of large and medium arteries, narrowing the lumen and reducing blood supply to the extremities, thereby impairing healing. In addition, diabetes can also affect blood supply to nerves, which leads to peripheral neuropathy. Peripheral neuropathy results in reduced sensation, and therefore minor injuries can often go unnoticed.
This patient has developed an ulcer on his heel, which is a pressure point and likely to be under repeated strain. The nurse examined the ulcer and found that the ulcer was looking infected with pus at the base of the ulcer and asked for a specialist orthopedic opinion, who requested an x-ray and an MRI. The MRI and x-ray both demonstrated infection invading into the calcaneus with destruction of the bone (Fig. 6.141A,B).
The patient required surgical washout with removal of the dead and infected bone (debridement) and was given long-term antibiotic treatment (Fig. 6.141C).
A young woman came to a vascular surgeon with a series of large dilated tortuous veins in her right leg. The rest of her leg was otherwise unremarkable.
A diagnosis of varicose veins was made and the surgeon needed to determine the site of valvular incompetence.
There are typical points where incompetent valves occur between the superficial and the deep veins. In these regions the varicosities tend to become marked. The typical sites are: at the saphena varix—the saphenofemoral junction where the femoral vein is joined by the great saphenous vein; in the midthigh perforating vein between the great saphenous vein and the femoral vein; in the calf the three sites where perforators occur, 5, 10, and 15 cm above the medial malleolus between the great saphenous vein and the deep veins of the calf; and at the junction of the small saphenous vein and the popliteal vein.
The surgeon asked the patient to lie supine on the bed and elevated the leg. A tourniquet was placed around the upper thigh below the saphenofemoral junction and the patient was asked to stand up. No veins were demonstrated filling on the medial aspect of the thigh and lower limb.
The effect of the tourniquet is to compress the great saphenous vein while permitting blood to flow in the deep venous system of the femoral vein and the deep femoral vein.
Because there was no filling of the medial varicose veins below the level of the tourniquet, the surgeon assumed that the valve at the saphenofemoral junction was incompetent and would require surgical treatment.
However, during the tourniquet maneuver the surgeon also noted some veins around the posterior and posterolateral aspect of the calf. |
A similar technique was performed by application of a tourniquet just below the level of the knee joint while the leg was elevated. The patient stood up and no veins were demonstrated filling in the posterior and posterolateral aspect of the calf. These findings suggested to the surgeon that there was also incompetence of the valve for the small saphenous system where it anastomoses with the popliteal vein.
Surgery was planned.
A small transverse incision was made below the level of the inguinal ligament where the great saphenous vein passes through the saphenous ring in the deep fascia. This can be easily palpated as a small circular defect in the fascia. The saphenofemoral junction was identified and the great saphenous vein was ligated, at its anastomosis with the femoral vein. The great saphenous vein was stripped using special surgical techniques and removed.
The patient was placed prone for the second part of the operation.
A small incision was made transversely at the level of the skin crease in the popliteal fossa. However, the surgeon had difficulty identifying the junction between the small saphenous vein and the popliteal vein. After considerable time the surgeon located what he thought was the small saphenous vein and the structure was ligated and the wound closed.
The following day the patient was sent home, but returned to the clinic after 2 weeks complaining of problems walking. On examination there was absence of dorsiflexion, a sensory disturbance over the lateral aspect of the leg and foot, and obvious wasting of the fibular muscles. As the patient walked, the foot was dragged between steps. A clinical diagnosis of footdrop was made and a common fibular nerve injury was diagnosed. The injury occurred at the time of surgery.
Within the popliteal fossa are the popliteal artery, popliteal vein, and sciatic nerve (and its divisions). The popliteal artery is the deepest structure. The popliteal vein is superficial to the artery and the sciatic nerve is superficial to the vein (eFig. 6.142). Importantly, the sciatic nerve divides at the apex of the popliteal fossa. The tibial nerve continues into the lower popliteal fossa. The common fibular nerve passes laterally adjacent to the biceps femoris muscle to become superficial and wrap around the fibula neck.
It was concluded that the surgeon had accidentally ligated the common fibular nerve rather than the small saphenous vein, thus producing this patient’s symptoms.
A 72-year-old woman was admitted to the emergency room after falling at home. She complained of a severe pain in her right hip and had noticeable bruising on the right side of the face.
On admission it was noted that the patient’s right leg was shorter than her left leg and externally rotated.
An initial series of investigations was carried out, including a plain radiograph of the pelvis.
The plain radiograph of the pelvis demonstrated a displaced fracture through the right neck of the femur.
The apparent shortening and external rotation of the leg on clinical examination were accounted for by spasm of the muscles connecting the pelvis to the trochanters and proximal femur. Of the muscles that surround the hip joint the largest group is the adductor group (adductor longus, brevis, and magnus) and the psoas major. The psoas major inserts onto the lesser trochanter and its action is to externally rotate and flex the hip. The fulcrum of action of the psoas major is the femoral head in the acetabulum. However, when the femoral neck is detached its overriding action pulls the femur proximally and into external rotation. The external rotation is exacerbated by the spasm in the adductor muscles.
Extensive medical testing was necessary before surgery. It is important to remember that elderly patients may have a number of coexisting diseases.
The patient then underwent a hemiarthroplasty. |
Hemiarthroplasty is a surgical procedure in which the femoral head is removed from the acetabulum. The femoral neck is trimmed close to the trochanters and the medullary cavity of the femoral shaft is reamed. A metal hip prosthesis is inserted into the medullary cavity of the femur and the head of the prosthesis is placed into the acetabulum, in which it articulates. Importantly, the acetabulum is not replaced in straightforward cases, though a prosthetic acetabulum may be inserted if clinically appropriate.
An arthroplasty was the only procedure that could be performed.
The blood supply to the femoral head is from three sources—the artery within the ligament of the head of the femur, vessels in the medullary cavity, and vessels deep to the synovium running in the retinacula of the fibrous capsule of the hip joint. With increasing age, the medullary cavity undergoes fatty replacement of the normal red marrow, thus attenuating the medullary blood supply. The artery within the ligament of the head of the femur also becomes attenuated and this is often associated with atherosclerotic arterial disease.
Unfortunately for this patient, the sole blood supply to the head of the femur was via the vessels in the retinacula fibers, which were transected at the time of the fracture. If the patient had an intertrochanteric fracture instead, the vessels of the retinacula fibers would not have been damaged and a different approach to surgical fixation could be undertaken without the need for a hemiarthroplasty.
The patient has osteoporosis.
Osteoporosis is a common condition affecting older people, but is significantly more frequent in postmenopausal women. Many fractures of the femoral neck in elderly patients occur because the strength of the bone is significantly reduced when it is osteoporotic. Other common sites for osteoporotic fractures include the distal radius and the thoracic and lumbar vertebrae.
A 28-year-old woman was seen by her family practitioner for a routine pregnancy checkup at 36 weeks’ gestational age. Neither the patient nor the family physician had any concerns about the pregnancy. However, the patient did complain of unilateral swelling of her left leg, which had gradually increased over the previous 2 days. Furthermore, the evening before her visit she developed some sharp chest pain, which was exacerbated by deep breaths.
The family physician ordered a duplex ultrasound scan of the left leg venous system.
Ultrasound scanning of the vascular tree can demonstrate flow and occlusion of arteries and veins.
The probe was placed over the left femoral vein and no flow was demonstrated. Furthermore, the vein could not be compressed, and no alteration of flow with breathing could be demonstrated. Some flow was demonstrated in the deep femoral vein and in the great saphenous vein. No flow was demonstrated throughout the length of the left femoral vein, the popliteal vein, and the tibial veins.
The technician scanned the opposite side, where excellent flow was demonstrated within the right femoral venous system. In addition, when the calf was gently massaged an augmentation to the flow was noted. It was possible to demonstrate alteration of flow with respiratory excursion and venous compression was satisfactory. A diagnosis of extensive left-sided deep vein thrombosis was made.
Certain patients are more prone to deep vein thrombosis.
Three major factors predispose a patient to thrombosis: reduced or stagnant blood flow in the veins—significant stasis of blood (which may be due to lack of movement), reduced muscular calf pump effect, and obstruction to flow may occur; injury to the vein wall—venous trauma may damage the vessel walls, promoting thrombus formation; hypercoagulability of the blood—hypercoagulable states are often associated with abnormal levels of certain clotting factors, such as antithrombin III, protein C, and protein S.
In this patient, compression of the left external iliac veins by the gravid uterus was the likely cause of stasis, which led to the deep vein thrombosis. |
The chest pain was due to pulmonary emboli.
Small emboli were thrown off from the leading edge of the thrombus through the heart to lodge in the lungs. Small emboli cause typical pleuritic chest pain, which is exacerbated by breathing. In isolation these small pulmonary emboli may affect respiratory function, but they may be the precursor to a large and potentially fatal pulmonary embolus (eFig. 6.143).
Anticoagulation was instituted and the patient had an uneventful delivery.
A 45-year-old man had recently taken up squash. During a game he attempted a forehand shot and noticed severe sudden pain in his heel. He thought his opponent had hit him with his racket. When he turned, though, he realized his opponent was too far away to have hit him.
Within minutes there was marked swelling of the ankle. The patient was unable to plantarflex his foot and had to stop the game. Afterward an appreciable subcutaneous hematoma developed in the ankle.
The diagnostic possibilities include a bone or soft tissue injury.
A bony injury was excluded because there was no bone tenderness.
The patient had a significant soft tissue injury. On examination he had significant swelling of the ankle with a subcutaneous hematoma. He was unable to stand on tiptoe on the right leg, and in the prone position a palpable defect was demonstrated within the calcaneal tendon.
A diagnosis of calcaneal tendon rupture was made.
This patient has a typical history of ruptured calcaneal tendon and the clinical findings support this. Magnetic resonance imaging was carried out and confirmed the diagnosis (eFig. 6.144).
The patient underwent an operative repair.
The tendon healed well, though the patient has not gone back to playing squash.
A 67-year-old man was noted to have a mass at the back of his knee. The mass measured approximately 4 cm in transverse diameter. The patient was otherwise fit and well and had no other history of note.
The mass was arising from one of the structures in the popliteal fossa.
Within the popliteal fossa there is a neurovascular bundle that contains the sciatic nerve (and its two divisions), the popliteal artery and the popliteal vein. There are also numerous small bursae associated with the posterior aspect of the knee joint and the muscles and tendons in this region. It is possible that this mass is arising from the posterior structures of the knee joint, which include synovial outpouchings, the menisci, and the muscles and tendons of this region.
The commonest masses demonstrated within the popliteal fossa are a popliteal cyst, a popliteal aneurysm, and an arterial adventitial cyst.
Further clinical examination revealed that this mass was pulsatile and demonstrated a bruit (an audible rumbling made by turbulent blood flow) on auscultation.
A diagnosis of popliteal artery aneurysm was made.
A popliteal artery aneurysm is an abnormal dilation of the popliteal artery. It is unusual for it to be greater than 5 cm because symptoms usually develop before it reaches this size.
Unlike aneurysms elsewhere in the body, the natural history of popliteal aneurysms is to embolize, with the mural thrombus producing ischemia distal to the lesion, rather than rupture. It is mandatory to examine the rest of the arterial tree in patients with a popliteal aneurysm because aneurysms may be bilateral and there is an association with abdominal aortic aneurysms.
The other diagnostic possibilities include a popliteal cyst and an adventitial cyst. |
A popliteal cyst (Baker’s cyst) is a synovial outpouching that arises from the posteromedial aspect of the knee joint. The synovial membrane of the knee joint outpouches between the medial head of the gastrocnemius and the semimembranosus tendon to lie medially within the popliteal fossa. Occasionally it tracks inferiorly to lie in and around the tendons that form the pes anserinus (sartorius, gracilis, and semitendinosus).
An arterial adventitial cyst is an uncommon cystic structure that arises from the wall of the artery.
An ultrasound investigation was carried out.
Using real-time ultrasound the dimensions of the popliteal aneurysm were characterized and the flow in the vessels was demonstrated. Furthermore, a popliteal cyst and adventitial cyst were completely excluded.
The patient underwent a surgical excision and graft interposition and has made an uneventful recovery.
A young long-distance runner came to her physician with acute swelling around the lateral aspect of her ankle. This injury occurred directly after accidentally running into a pothole in the pavement.
A fractured ankle was suspected.
Plain anteroposterior and lateral radiographs of the ankle revealed no evidence of any bone injury to account for the patient’s soft tissue swelling.
The patient was given a pair of crutches and analgesics and told to rest. A diagnosis of a simple sprain was made.
Over the ensuing weeks the swelling and edema within the soft tissue of the ankle decreased and the patient began to run, but noted that the ankle kept “giving way.” She went to an orthopedic surgeon for further assessment.
There was a positive anterior drawer test of the ankle joint.
At this stage it is important to review the mechanism of injury. Typically when running on a hard surface the final phase of push-off involves supination of the foot. If the foot is caught in a pothole or divot, this supinating maneuver continues and inverts the ankle joint in plantarflexion. This puts significant strain on the lateral ligament complex and, given the appropriate circumstances, disruption (in order) of the ligament structures occurs from anterior to posterior. First, the anterior talofibular ligament is disrupted, followed by the calcaneofibular ligament, and then the posterior talofibular ligament. As each of these ligaments is disrupted, the severity of the soft tissue injury is significantly enhanced and the chance of permanent ankle instability is increased.
On examination any positive anterior drawer test of the ankle (4–5 mm compared to the opposite side) suggests an injury to the anterior talofibular ligament.
The anterior talofibular ligament can be assessed by placing the foot in marked plantarflexion. If there is over 10° of difference between the affected foot and nonaffected foot, an anterior talofibular ligament disruption is suspected.
It is extremely rare for all three ligaments to be disrupted, and if so there are usually other significant ankle injuries.
Magnetic resonance imaging (MRI) was carried out to assess ligament damage.
MRI is excellent for demonstrating the medial and lateral ligament complexes of the ankle as well as the soft tissues that support the bones of the posterior foot.
Unfortunately for this patient there was a tear of the anterior talofibular ligament (eFig. 6.145), which had to be repaired surgically.
670.e2 670.e1
In the clinic—cont’d
Table 6.1 Branches of the lumbosacral plexus associated with the lower limb—cont’d
Regional Anatomy • Deep Fascia and the Saphenous Opening
Fig. 6.73, cont’d
Surface Anatomy • Avoiding the Sciatic Nerve
Surface Anatomy • Identifying Structures Around the Knee
Surface Anatomy • Finding the Tarsal Tunnel—the Gateway to the Foot |
Surface Anatomy • Approximating the Position of the Plantar Arterial Arch
Anterior compartment of the forearm 766
Posterior compartment of the forearm 775
Carpal tunnel and structures at the wrist 788
Bony landmarks and muscles of the posterior scapular region 810
Visualizing the axilla and locating contents and related structures 811
Locating the brachial artery in the arm 812
The triceps brachii tendon and position of the radial nerve 813
Identifying tendons and locating major vessels and nerves in the distal forearm 815
Normal appearance of the hand 816
Position of the flexor retinaculum and the recurrent branch of the median nerve 817
Motor function of the median and ulnar nerves in the hand 817
Visualizing the positions of the superficial and deep palmar arches 818
The upper limb is associated with the lateral aspect of the lower portion of the neck and with the thoracic wall. It is suspended from the trunk by muscles and a small skeletal articulation between the clavicle and the sternum—the sternoclavicular joint. Based on the position of its major joints and component bones, the upper limb is divided into shoulder, arm, forearm, and hand (Fig. 7.1A).
The shoulder is the area of upper limb attachment to the trunk (Fig. 7.1B).
The arm is the part of the upper limb between the shoulder and the elbow joint; the forearm is between the elbow joint and the wrist joint; and the hand is distal to the wrist joint.
The axilla, cubital fossa, and carpal tunnel are significant areas of transition between the different parts of the limb (Fig. 7.2). Important structures pass through, or are related to, each of these areas.
The axilla is an irregularly shaped pyramidal area formed by muscles and bones of the shoulder and the lateral surface of the thoracic wall. The apex or inlet opens directly into the lower portion of the neck. The skin of the armpit forms the floor. All major structures that pass between the neck and arm pass through the axilla.
The cubital fossa is a triangularly shaped depression formed by muscles anterior to the elbow joint. The major artery, the brachial artery, passing from the arm to the forearm passes through this fossa, as does one of the major nerves of the upper limb, the median nerve.
The carpal tunnel is the gateway to the palm of the hand. Its posterior, lateral, and medial walls form an arch, which is made up of small carpal bones in the proximal region of the hand. A thick band of connective tissue, the flexor retinaculum, spans the distance between each side of the arch and forms the anterior wall of the tunnel. The median nerve and all the long flexor tendons passing from the forearm to the digits of the hand pass through the carpal tunnel.
Positioning the hand
Unlike the lower limb, which is used for support, stability, and locomotion, the upper limb is highly mobile for positioning the hand in space.
The shoulder is suspended from the trunk predominantly by muscles and can therefore be moved relative to the body. Sliding (protraction and retraction) and rotating the scapula on the thoracic wall changes the position of the glenohumeral joint (shoulder joint) and extends the reach of the hand (Fig. 7.3). The glenohumeral joint allows the arm to move around three axes with a wide range of motion. Movements of the arm at this joint are flexion, extension, abduction, adduction, medial rotation (internal rotation), lateral rotation (external rotation), and circumduction (Fig. 7.4). |
The major movements at the elbow joint are flexion and extension of the forearm (Fig. 7.5A). At the other end of the forearm, the distal end of the lateral bone, the radius, can be flipped over the adjacent head of the medial bone, the ulna. Because the hand is articulated with the radius, it can be efficiently moved from a palm-anterior position to a palm-posterior position simply by crossing the distal end of the radius over the ulna (Fig. 7.5B). This movement, termed pronation, occurs solely in the forearm. Supination returns the hand to the anatomical position.
At the wrist joint, the hand can be abducted, adducted, flexed, extended, and circumducted (Fig. 7.6). These movements, combined with those of the shoulder, arm, and forearm, enable the hand to be placed in a wide range of positions relative to the body.
The hand as a mechanical tool
One of the major functions of the hand is to grip and manipulate objects. Gripping objects generally involves flexing the fingers against the thumb. Depending on the type of grip, muscles in the hand act to: modify the actions of long tendons that emerge from the forearm and insert into the digits of the hand, and produce combinations of joint movements within each digit that cannot be generated by the long flexor and extensor tendons alone coming from the forearm.
The hand as a sensory tool
The hand is used to discriminate between objects on the basis of touch. The pads on the palmar aspect of the fingers contain a high density of somatic sensory receptors. Also, the sensory cortex of the brain devoted to interpreting information from the hand, particularly from the thumb, is disproportionately large relative to that for many other regions of skin.
The bones of the shoulder consist of the scapula, clavicle, and proximal end of the humerus (Fig. 7.7).
The clavicle articulates medially with the manubrium of the sternum and laterally with the acromion of the scapula, which arches over the joint between the glenoid cavity of the scapula and the head of the humerus (the glenohumeral joint).
The humerus is the bone of the arm (Fig. 7.7). The distal end of the humerus articulates with the bones of the forearm at the elbow joint, which is a hinge joint that allows flexion and extension of the forearm.
The forearm contains two bones:
The lateral bone is the radius.
The medial bone is the ulna (Fig. 7.7).
At the elbow joint, the proximal ends of the radius and ulna articulate with each other as well as with the humerus.
In addition to flexing and extending the forearm, the elbow joint allows the radius to spin on the humerus while sliding against the head of the ulna during pronation and supination of the hand.
The distal portions of the radius and the ulna also articulate with each other. This joint allows the end of the radius to flip from the lateral side to the medial side of the ulna during pronation of the hand.
The wrist joint is formed between the radius and carpal bones of the hand and between an articular disc, distal to the ulna, and carpal bones.
The bones of the hand consist of the carpal bones, the metacarpals, and the phalanges (Fig. 7.7).
The five digits in the hand are the thumb and the index, middle, ring, and little fingers.
Joints between the eight small carpal bones allow only limited amounts of movement; as a result, the bones work together as a unit.
The five metacarpals, one for each digit, are the primary skeletal foundation of the palm (Fig. 7.7).
The joint between the metacarpal of the thumb (metacarpal I) and one of the carpal bones allows greater mobility than the limited sliding movement that occurs at the carpometacarpal joints of the fingers. |
Distally, the heads of metacarpals II to V (i.e., except that of the thumb) are interconnected by strong ligaments. Lack of this ligamentous connection between the metacarpal bones of the thumb and index finger together with the biaxial saddle joint between the metacarpal bone of the thumb and the carpus provide the thumb with greater freedom of movement than the other digits of the hand.
The bones of the digits are the phalanges (Fig. 7.7). The thumb has two phalanges, while each of the other digits has three.
The metacarpophalangeal joints are biaxial condylar joints (ellipsoid joints) that allow abduction, adduction, flexion, extension, and circumduction (Fig. 7.8). Abduction and adduction of the fingers is defined in reference to an axis passing through the center of the middle finger in the anatomical position. The middle finger can therefore abduct both medially and laterally and adduct back to the central axis from either side. The interphalangeal joints are primarily hinge joints that allow only flexion and extension.
Some muscles of the shoulder, such as the trapezius, levator scapulae, and rhomboids, connect the scapula and clavicle to the trunk. Other muscles connect the clavicle, scapula, and body wall to the proximal end of the humerus. These include the pectoralis major, pectoralis minor, latissimus dorsi, teres major, and deltoid (Fig. 7.9A,B). The most important of these muscles are the four rotator cuff muscles—the subscapularis, supraspinatus, infraspinatus, and teres minor muscles—which connect the scapula to the humerus and provide support for the glenohumeral joint (Fig. 7.9C).
Muscles in the arm and forearm are separated into anterior (flexor) and posterior (extensor) compartments by layers of fascia, bones, and ligaments (Fig. 7.10).
The anterior compartment of the arm lies anteriorly in position and is separated from muscles of the posterior compartment by the humerus and by medial and lateral intermuscular septa. These intermuscular septa are continuous with the deep fascia enclosing the arm and attach to the sides of the humerus.
In the forearm, the anterior and posterior compartments are separated by a lateral intermuscular septum, the radius, the ulna, and an interosseous membrane, which joins adjacent sides of the radius and ulna (Fig. 7.10).
Muscles in the arm act mainly to move the forearm at the elbow joint, while those in the forearm function predominantly to move the hand at the wrist joint and the fingers and thumb.
Muscles found entirely in the hand, the intrinsic muscles, generate delicate movements of the digits of the hand and modify the forces produced by tendons coming into the fingers and thumb from the forearm. Included among the intrinsic muscles of the hand are three small thenar muscles, which form a soft tissue mound, called the thenar eminence, over the palmar aspect of metacarpal I. The thenar muscles allow the thumb to move freely relative to the other fingers.
The upper limb is directly related to the neck. Lying on each side of the superior thoracic aperture at the base of the neck is an axillary inlet, which is formed by: the lateral margin of rib I, the posterior surface of the clavicle, the superior margin of the scapula, and the medial surface of the coracoid process of the scapula (Fig. 7.11).
The major artery and vein of the upper limb pass between the thorax and the limb by passing over rib I and through the axillary inlet. Nerves, predominantly derived from the cervical portion of the spinal cord, also pass through the axillary inlet and the axilla to supply the upper limb.
Muscles that attach the bones of the shoulder to the trunk are associated with the back and the thoracic wall and include the trapezius, levator scapulae, rhomboid major, rhomboid minor, and latissimus dorsi (Fig. 7.12). |
The breast on the anterior thoracic wall has a number of significant relationships with the axilla and upper limb. It overlies the pectoralis major muscle, which forms most of the anterior wall of the axilla and attaches the humerus to the chest wall (Fig. 7.13). Often, part of the breast known as the axillary process extends around the lateral margin of the pectoralis major into the axilla.
of the breast is predominantly into lymph nodes in the axilla. Several arteries and veins that supply or drain the gland also originate from, or drain into, major axillary vessels.
Innervation of the upper limb is by the brachial plexus, which is formed by the anterior rami of cervical spinal nerves C5 to C8, and T1 (Fig. 7.14). This plexus is initially formed in the neck and then continues through the axillary inlet into the axilla. Major nerves that ultimately innervate the arm, forearm, and hand originate from the brachial plexus in the axilla.
As a consequence of this innervation pattern, clinical testing of lower cervical and T1 nerves is carried out by examining dermatomes, myotomes, and tendon reflexes in the upper limb. Another consequence is that the clinical signs of problems related to lower cervical nerves—pain; pins-and-needles sensations, or paresthesia; and muscle twitching—appear in the upper limb.
Dermatomes of the upper limb (Fig. 7.15A) are often tested for sensation. Areas where overlap of dermatomes is minimal include the: upper lateral region of the arm for spinal cord level C5, palmar pad of the thumb for spinal cord level C6, pad of the index finger for spinal cord level C7, pad of the little finger for spinal cord level C8, and skin on the medial aspect of the elbow for spinal cord level T1.
Selected joint movements are used to test myotomes (Fig. 7.15B):
Abduction of the arm at the glenohumeral joint is controlled predominantly by C5.
Flexion of the forearm at the elbow joint is controlled primarily by C6.
Extension of the forearm at the elbow joint is controlled mainly by C7.
Flexion of the fingers is controlled mainly by C8.
Abduction and adduction of the index, middle, and ring fingers is controlled predominantly by T1.
In an unconscious patient, both somatic sensory and motor functions of spinal cord levels can be tested using tendon reflexes:
A tap on the tendon of the biceps in the cubital fossa tests mainly for spinal cord level C6.
A tap on the tendon of the triceps posterior to the elbow tests mainly for C7.
The major spinal cord level associated with innervation of the diaphragm, C4, is immediately above the spinal cord levels associated with the upper limb.
Evaluation of dermatomes and myotomes in the upper limb can provide important information about potential breathing problems that might develop as complications of damage to the spinal cord in regions just below the C4 spinal level.
Each of the major muscle compartments in the arm and forearm and each of the intrinsic muscles of the hand is innervated predominantly by one of the major nerves that originate from the brachial plexus in the axilla (Fig. 7.16A):
All muscles in the anterior compartment of the arm are innervated by the musculocutaneous nerve.
The median nerve innervates the muscles in the anterior compartment of the forearm, with two exceptions—one flexor of the wrist (the flexor carpi ulnaris muscle) and part of one flexor of the fingers (the medial half of the flexor digitorum profundus muscle) are innervated by the ulnar nerve.
Most intrinsic muscles of the hand are innervated by the ulnar nerve, except for the thenar muscles and two lateral lumbrical muscles, which are innervated by the median nerve. |
All muscles in the posterior compartments of the arm and forearm are innervated by the radial nerve.
In addition to innervating major muscle groups, each of the major peripheral nerves originating from the from patches of skin quite different from dermatomes (Fig. 7.16B). Sensation in these areas can be used to test for peripheral nerve lesions:
The musculocutaneous nerve innervates skin on the anterolateral side of the forearm.
The median nerve innervates the palmar surface of the lateral three and one-half digits, and the ulnar nerve innervates the medial one and one-half digits.
The radial nerve supplies skin on the posterior surface of the forearm and the dorsolateral surface of the hand.
Nerves related to bone
Three important nerves are directly related to parts of the humerus (Fig. 7.17):
The axillary nerve, which supplies the deltoid muscle, a major abductor of the humerus at the glenohumeral joint, passes around the posterior aspect of the upper part of the humerus (the surgical neck).
The radial nerve, which supplies all of the extensor muscles of the upper limb, passes diagonally around the posterior surface of the middle of the humerus in the radial groove.
The ulnar nerve, which is ultimately destined for the hand, passes posteriorly to a bony protrusion, the medial epicondyle, on the medial side of the distal end of the humerus.
Fractures of the humerus in any one of these three regions can endanger the related nerve.
Large veins embedded in the superficial fascia of the upper limb are often used to access a patient’s vascular system and to withdraw blood. The most significant of these veins are the cephalic, basilic, and median cubital veins (Fig. 7.18).
The cephalic and basilic veins originate from the dorsal venous network on the back of the hand.
The cephalic vein originates over the anatomical snuffbox at the base of the thumb, passes laterally around the distal forearm to reach the anterolateral surface of the limb, and then continues proximally. It crosses the elbow, then passes up the arm into a triangular depression—the clavipectoral triangle (deltopectoral triangle)—between the pectoralis major muscle, deltoid muscle, and clavicle. In this depression, the vein passes into the axilla by penetrating deep fascia just inferior to the clavicle.
The basilic vein originates from the medial side of the dorsal venous network of the hand and passes proximally up the posteromedial surface of the forearm. It passes onto the anterior surface of the limb just inferior to the elbow and then continues proximally to penetrate deep fascia about midway up the arm.
At the elbow, the cephalic and basilic veins are connected by the median cubital vein, which crosses the roof of the cubital fossa.
Orientation of the thumb
The thumb is positioned at right angles to the orientation of the index, middle, ring, and little fingers (Fig. 7.19). As a result, movements of the thumb occur at right angles to those of the other digits. For example, flexion brings the thumb across the palm, whereas abduction moves it away from the fingers at right angles to the palm.
Importantly, with the thumb positioned at right angles to the palm, only a slight rotation of metacarpal I on the wrist brings the pad of the thumb into a position directly facing the pads of the other fingers. This opposition of the thumb is essential for normal hand function.
The shoulder is the region of upper limb attachment to the trunk.
The bone framework of the shoulder consists of: the clavicle and scapula, which form the pectoral girdle (shoulder girdle), and the proximal end of the humerus.
The superficial muscles of the shoulder consist of the trapezius and deltoid muscles, which together form the smooth muscular contour over the lateral part of the shoulder. These muscles connect the scapula and clavicle to the trunk and to the arm, respectively. |
The clavicle is the only bony attachment between the trunk and the upper limb. It is palpable along its entire length and has a gentle S-shaped contour, with the forward-facing convex part medial and the forward-facing concave part lateral. The acromial (lateral) end of the clavicle is flat, whereas the sternal (medial) end is more robust and somewhat quadrangular in shape (Fig. 7.20).
The acromial end of the clavicle has a small oval facet on its surface for articulation with a similar facet on the medial surface of the acromion of the scapula.
The sternal end has a much larger facet for articulation mainly with the manubrium of the sternum, and to a lesser extent, with the first costal cartilage.
The inferior surface of the lateral third of the clavicle possesses a distinct tuberosity consisting of a tubercle (the conoid tubercle) and lateral roughening (the trapezoid line), for attachment of the important coracoclavicular ligament.
In addition, the surfaces and margins of the clavicle are roughened by the attachment of muscles that connect the clavicle to the thorax, neck, and upper limb. The superior surface is smoother than the inferior surface.
The scapula is a large, flat triangular bone with: three angles (lateral, superior, and inferior), three borders (superior, lateral, and medial), two surfaces (costal and posterior), and three processes (acromion, spine, and coracoid process) (Fig. 7.21).
The lateral angle of the scapula is marked by a shallow, somewhat comma-shaped glenoid cavity, which articulates with the head of the humerus to form the glenohumeral joint (Fig. 7.21B,C).
A large triangular-shaped roughening (the infraglenoid tubercle) inferior to the glenoid cavity is the site of attachment for the long head of the triceps brachii muscle.
A less distinct supraglenoid tubercle is located superior to the glenoid cavity and is the site of attachment for the long head of the biceps brachii muscle.
A prominent spine subdivides the posterior surface of the scapula into a small, superior supraspinous fossa and a much larger, inferior infraspinous fossa (Fig. 7.21A).
The acromion, which is an anterolateral projection of the spine, arches over the glenohumeral joint and articulates, via a small oval facet on its distal end, with the clavicle.
The region between the lateral angle of the scapula and the attachment of the spine to the posterior surface of the scapula is the greater scapular notch (spinoglenoid notch).
Unlike the posterior surface, the costal surface of the scapula is unremarkable, being characterized by a shallow concave subscapular fossa over much of its extent (Fig. 7.21B). The costal surface and margins provide for muscle attachment, and the costal surface, together with its related muscle (subscapularis), moves freely over the underlying thoracic wall.
The lateral border of the scapula is strong and thick for muscle attachment, whereas the medial border and much of the superior border is thin and sharp.
The superior border is marked on its lateral end by: the coracoid process, a hook-like structure that projects anterolaterally and is positioned directly inferior to the lateral part of the clavicle; and the small but distinct suprascapular notch, which lies immediately medial to the root of the coracoid process.
The spine and acromion can be readily palpated on a patient, as can the tip of the coracoid process, the inferior angle, and much of the medial border of the scapula.
The proximal end of the humerus consists of the head, the anatomical neck, the greater and lesser tubercles, the surgical neck, and the superior half of the shaft of the humerus (Fig. 7.22). |
The head is half-spherical in shape and projects medially and somewhat superiorly to articulate with the much smaller glenoid cavity of the scapula.
The anatomical neck is very short and is formed by a narrow constriction immediately distal to the head. It lies between the head and the greater and lesser tubercles laterally, and between the head and the shaft more medially.
The greater and lesser tubercles are prominent landmarks on the proximal end of the humerus and serve as attachment sites for the four rotator cuff muscles of the glenohumeral joint.
The greater tubercle is lateral in position. Its superior surface and posterior surface are marked by three large smooth facets for muscle tendon attachments:
The superior facet is for attachment of the supraspinatus muscle.
The middle facet is for attachment of the infraspinatus.
The inferior facet is for attachment of the teres minor.
The lesser tubercle is anterior in position and its surface is marked by a large smooth impression for attachment of the subscapularis muscle.
A deep intertubercular sulcus (bicipital groove) separates the lesser and greater tubercles and continues inferiorly onto the proximal shaft of the humerus (Fig. 7.22). The tendon of the long head of the biceps brachii passes through this sulcus.
Roughenings on the lateral and medial lips and on the floor of the intertubercular sulcus mark sites for the attachment of the pectoralis major, teres major, and latissimus dorsi muscles, respectively.
The lateral lip of the intertubercular sulcus is continuous inferiorly with a large V-shaped deltoid tuberosity on the lateral surface of the humerus midway along its length (Fig. 7.22), which is where the deltoid muscle inserts onto the humerus.
In approximately the same position, but on the medial surface of the bone, there is a thin vertical roughening for attachment of the coracobrachialis muscle.
One of the most important features of the proximal end of the humerus is the surgical neck (Fig. 7.22). This region is oriented in the horizontal plane between the expanded proximal part of the humerus (head, anatomical neck, and tubercles) and the narrower shaft. The axillary nerve and the posterior circumflex humeral artery, which pass into the deltoid region from the axilla, do so immediately posterior to the surgical neck. Because the surgical neck is weaker than more proximal regions of the bone, it is one of the sites where the humerus commonly fractures. The associated nerve (axillary) and artery (posterior circumflex humeral) can be damaged by fractures in this region.
The three joints in the shoulder complex are the sternoclavicular, acromioclavicular, and glenohumeral joints.
The sternoclavicular joint and the acromioclavicular joint link the two bones of the pectoral girdle to each other and to the trunk. The combined movements at these two joints enable the scapula to be positioned over a wide range on the thoracic wall, substantially increasing “reach” by the upper limb.
The glenohumeral joint (shoulder joint) is the articulation between the humerus of the arm and the scapula.
The sternoclavicular joint occurs between the proximal end of the clavicle and the clavicular notch of the manubrium of the sternum together with a small part of the first costal cartilage (Fig. 7.23). It is synovial and saddle shaped. The articular cavity is completely separated into two compartments by an articular disc. The sternoclavicular joint allows movement of the clavicle, predominantly in the anteroposterior and vertical planes, although some rotation also occurs.
The sternoclavicular joint is surrounded by a joint capsule and is reinforced by four ligaments:
The anterior and posterior sternoclavicular ligaments are anterior and posterior, respectively, to the joint.
An interclavicular ligament links the ends of the two clavicles to each other and to the superior surface of the manubrium of the sternum. |
The costoclavicular ligament is positioned laterally to the joint and links the proximal end of the clavicle to the first rib and related costal cartilage.
The acromioclavicular joint is a small synovial joint between an oval facet on the medial surface of the acromion and a similar facet on the acromial end of the clavicle (Fig. 7.24, also see Fig. 7.31). It allows movement in the anteroposterior and vertical planes together with some axial rotation.
The acromioclavicular joint is surrounded by a joint capsule and is reinforced by: a small acromioclavicular ligament superior to the joint and passing between adjacent regions of the clavicle and acromion, and a much larger coracoclavicular ligament, which is not directly related to the joint, but is an important strong accessory ligament, providing much of the weight-bearing support for the upper limb on the clavicle and maintaining the position of the clavicle on the acromion—it spans the distance between the coracoid process of the scapula and the inferior surface of the acromial end of the clavicle and comprises an anterior trapezoid ligament (which attaches to the trapezoid line on the clavicle) and a posterior conoid ligament (which attaches to the related conoid tubercle).
The glenohumeral joint is a synovial ball and socket articulation between the head of the humerus and the glenoid cavity of the scapula (Fig. 7.25). It is multiaxial with a wide range of movements provided at the cost of skeletal stability. Joint stability is provided, instead, by the rotator cuff muscles, the long head of the biceps brachii muscle, related bony processes, and extracapsular ligaments. Movements at the joint include flexion, extension, abduction, adduction, medial rotation, lateral rotation, and circumduction.
The articular surfaces of the glenohumeral joint are the large spherical head of the humerus and the small glenoid cavity of the scapula (Fig. 7.25). Each of the surfaces is covered by hyaline cartilage.
The glenoid cavity is deepened and expanded peripherally by a fibrocartilaginous collar (the glenoid labrum), which attaches to the margin of the fossa. Superiorly, this labrum is continuous with the tendon of the long head of the biceps brachii muscle, which attaches to the supraglenoid tubercle and passes through the articular cavity superior to the head of the humerus.
The synovial membrane attaches to the margins of the articular surfaces and lines the fibrous membrane of the joint capsule (Fig. 7.26). The synovial membrane is loose inferiorly. This redundant region of synovial membrane and related fibrous membrane accommodates abduction of the arm.
The synovial membrane protrudes through apertures in the fibrous membrane to form bursae, which lie between the tendons of surrounding muscles and the fibrous membrane. The most consistent of these is the subtendinous bursa of the subscapularis, which lies between the subscapularis muscle and the fibrous membrane. The synovial membrane also folds around the tendon of the long head of the biceps brachii muscle in the joint and extends along the tendon as it passes into the intertubercular sulcus. All these synovial structures reduce friction between the tendons and adjacent joint capsule and bone.
In addition to bursae that communicate with the articular cavity through apertures in the fibrous membrane, other bursae are associated with the joint but are not connected to it. These occur: between the acromion (or deltoid muscle) and supraspinatus muscle (or joint capsule) (the subacromial or subdeltoid bursa), between the acromion and skin, between the coracoid process and the joint capsule, and in relationship to tendons of muscles around the joint (coracobrachialis, teres major, long head of triceps brachii, and latissimus dorsi muscles). |
The fibrous membrane of the joint capsule attaches to the margin of the glenoid cavity, outside the attachment of the glenoid labrum and the long head of the biceps brachii muscle, and to the anatomical neck of the humerus (Fig. 7.27).
On the humerus, the medial attachment occurs more inferiorly than the neck and extends onto the shaft. In this region, the fibrous membrane is also loose or folded in the anatomical position. This redundant area of the fibrous membrane accommodates abduction of the arm.
Openings in the fibrous membrane provide continuity of the articular cavity with bursae that occur between the joint capsule and surrounding muscles and around the tendon of the long head of the biceps brachii muscle in the intertubercular sulcus.
The fibrous membrane of the joint capsule is thickened: anterosuperiorly in three locations to form superior, middle, and inferior glenohumeral ligaments, which pass from the superomedial margin of the glenoid cavity to the lesser tubercle and inferiorly related anatomical neck of the humerus (Fig. 7.27); superiorly between the base of the coracoid process and the greater tubercle of the humerus (the coracohumeral ligament); and between the greater and lesser tubercles of the humerus (transverse humeral ligament)—this holds the tendon of the long head of the biceps brachii muscle in the intertubercular sulcus (Fig. 7.27).
Joint stability is provided by surrounding muscle tendons and a skeletal arch formed superiorly by the coracoid process and acromion and the coraco-acromial ligament (Fig. 7.28).
Tendons of the rotator cuff muscles (the supraspinatus, infraspinatus, teres minor, and subscapularis muscles) blend with the joint capsule and form a musculotendinous collar that surrounds the posterior, superior, and anterior aspects of the glenohumeral joint (Figs. 7.28 and 7.29). This cuff of muscles stabilizes and holds the head of the humerus in the glenoid cavity of the scapula without compromising the arm’s flexibility and range of motion. The tendon of the long head of the biceps brachii muscle passes superiorly through the joint and restricts upward movement of the humeral head on the glenoid cavity.
Vascular supply to the glenohumeral joint is predominantly through branches of the anterior and posterior circumflex humeral and suprascapular arteries.
The glenohumeral joint is innervated by branches from the posterior cord of the brachial plexus, and from the suprascapular, axillary, and lateral pectoral nerves.
The two most superficial muscles of the shoulder are the trapezius and deltoid muscles (Fig. 7.35 and Table 7.1). Together, they provide the characteristic contour of the shoulder:
The trapezius attaches the scapula and clavicle to the trunk.
The deltoid attaches the scapula and clavicle to the humerus.
Both the trapezius and deltoid are attached to opposing surfaces and margins of the spine of the scapula, acromion, and clavicle. The scapula, acromion, and clavicle can be palpated between the attachments of the trapezius and deltoid.
Deep to the trapezius the scapula is attached to the vertebral column by three muscles—the levator scapulae, rhomboid minor, and rhomboid major. These three muscles work with the trapezius (and with muscles found anteriorly) to position the scapula on the trunk. |
The trapezius muscle has an extensive origin from the axial skeleton, which includes sites on the skull and the vertebrae, from CI to TXII (Fig. 7.36). From CI to CVII, the muscle attaches to the vertebrae through the ligamentum nuchae. The muscle inserts onto the skeletal framework of the shoulder along the inner margins of a continuous U-shaped line of attachment oriented in the horizontal plane, with the bottom of the U directed laterally. Together, the left and right trapezius muscles form a diamond or trapezoid shape, from which the name is derived.
The trapezius muscle is a powerful elevator of the shoulder and also rotates the scapula to extend the reach superiorly.
Innervation of the trapezius muscle is by the accessory nerve [XI] and the anterior rami of cervical nerves C3 and C4 (Fig. 7.36). These nerves pass vertically along the deep surface of the muscle. The accessory nerve can be evaluated by testing the function of the trapezius muscle. This is most easily done by asking patients to shrug their shoulders against resistance.
The deltoid muscle is large and triangular in shape, with its base attached to the scapula and clavicle and its apex attached to the humerus (Fig. 7.36). It originates along a continuous U-shaped line of attachment to the clavicle and the scapula, mirroring the adjacent insertion sites of the trapezius muscle. It inserts into the deltoid tuberosity on the lateral surface of the shaft of the humerus.
The major function of the deltoid muscle is abduction of the arm.
The deltoid muscle is innervated by the axillary nerve, which is a branch of the posterior cord of the brachial plexus. The axillary nerve and associated blood vessels (the posterior circumflex humeral artery and vein) enter the deltoid by passing posteriorly around the surgical neck of the humerus.
The levator scapulae originates from the transverse processes of CI to CIV vertebrae (Fig. 7.36). It descends laterally to attach to the posterior surface of the medial border of the scapula from the superior angle to the smooth triangular area of bone at the root of the spine.
The levator scapulae muscle is innervated by the dorsal scapular nerve and directly from C3 and C4 spinal nerves.
The levator scapulae elevates the scapula.
The rhomboid minor and major muscles attach medially to the vertebral column and descend laterally to attach to the medial border of the scapula inferior to the levator scapulae muscle (Fig. 7.36).
The rhomboid minor originates from the lower end of the ligamentum nuchae and the spines of CVII and TI vertebrae. It inserts laterally into the smooth triangular area of bone at the root of the spine of the scapula on the posterior surface.
The rhomboid major originates from the spines of vertebrae TII to TV and from the intervening supraspinous ligaments. It descends laterally to insert along the posterior surface of the medial border of the scapula from the insertion of the rhomboid minor to the inferior angle.
The rhomboid muscles are innervated by the dorsal scapular nerve, which is a branch of the brachial plexus.
The rhomboid minor and major retract and elevate the scapula.
The posterior scapular region occupies the posterior aspect of the scapula and is located deep to the trapezius and deltoid muscles (Fig. 7.37 and Table 7.2). It contains four muscles, which pass between the scapula and proximal end of the humerus: the supraspinatus, infraspinatus, teres minor, and teres major muscles. |
The posterior scapular region also contains part of one additional muscle, the long head of the triceps brachii, which passes between the scapula and the proximal end of the forearm. This muscle, along with other muscles of the region and the humerus, participates in forming a number of spaces through which nerves and vessels enter and leave the region.
The supraspinatus, infraspinatus, and teres minor muscles are components of the rotator cuff, which stabilizes the glenohumeral joint.
The supraspinatus and infraspinatus muscles originate from two large fossae, one above and one below the spine, on the posterior surface of the scapula (Fig. 7.37). They form tendons that insert on the greater tubercle of the humerus.
The tendon of the supraspinatus passes under the acromion, where it is separated from the bone by a subacromial bursa, passes over the glenohumeral joint, and inserts on the superior facet of the greater tubercle.
The tendon of the infraspinatus passes posteriorly to the glenohumeral joint and inserts on the middle facet of the greater tubercle.
The supraspinatus participates in abduction of the arm. The infraspinatus laterally rotates the humerus.
The teres minor muscle is a cord-like muscle that originates from a flattened area of the scapula immediately adjacent to its lateral border below the infraglenoid tubercle (Fig. 7.37). Its tendon inserts on the inferior facet of the greater tubercle of the humerus. The teres minor laterally rotates the humerus and is a component of the rotator cuff.
The teres major muscle originates from a large oval region on the posterior surface of the inferior angle of the scapula (Fig. 7.37). This broad cord-like muscle passes superiorly and laterally and ends as a flat tendon that attaches to the medial lip of the intertubercular sulcus on the anterior surface of the humerus. The teres major medially rotates and extends the humerus.
Long head of triceps brachii
The long head of the triceps brachii muscle originates from the infraglenoid tubercle and passes somewhat vertically down the arm to insert, with the medial and lateral heads of this muscle, on the olecranon of the ulna (Fig. 7.37).
The triceps brachii is the primary extensor of the forearm at the elbow joint. Because the long head crosses the glenohumeral joint, it can also extend and adduct the humerus.
The importance of the triceps brachii in the posterior scapular region is that its vertical course between the teres minor and teres major, together with these muscles and the humerus, forms spaces through which nerves and vessels pass between regions.
Gateways to the posterior scapular region
The suprascapular foramen is the route through which structures pass between the base of the neck and the posterior scapular region (Fig. 7.37). It is formed by the suprascapular notch of the scapula and the superior transverse scapular (suprascapular) ligament, which converts the notch into a foramen.
The suprascapular nerve passes through the suprascapular foramen; the suprascapular artery and the suprascapular vein follow the same course as the nerve, but normally pass immediately superior to the superior transverse scapular ligament and not through the foramen (Fig. 7.38).
The quadrangular space provides a passageway for nerves and vessels passing between more anterior regions (the axilla) and the posterior scapular region (Fig. 7.37). In the posterior scapular region, its boundaries are formed by: the inferior margin of the teres minor, the surgical neck of the humerus, the superior margin of the teres major, and the lateral margin of the long head of the triceps brachii.
The axillary nerve and the posterior circumflex humeral artery and vein pass through this space (Fig. 7.38). |
The triangular space is an area of communication between the axilla and the posterior scapular region (Fig. 7.37). When viewed from the posterior scapular region, the triangular space is formed by: the medial margin of the long head of the triceps brachii, the superior margin of the teres major, and the inferior margin of the teres minor.
The circumflex scapular artery and vein pass through this gap (Fig. 7.38).
The triangular interval is formed by: the lateral margin of the long head of the triceps brachii, the shaft of the humerus, and the inferior margin of the teres major (Fig. 7.37).
Because this space is below the inferior margin of the teres major, which defines the inferior boundary of the axilla, the triangular interval serves as a passageway between the anterior and posterior compartments of the arm and between the posterior compartment of the arm and the axilla. The radial nerve, the profunda brachii artery (deep artery of arm), and associated veins pass through it (Fig. 7.38).
The two major nerves of the posterior scapular region are the suprascapular and axillary nerves, both of which originate from the brachial plexus in the axilla (Fig. 7.38).
The suprascapular nerve originates in the base of the neck from the superior trunk of the brachial plexus. It passes posterolaterally from its origin, through the suprascapular foramen to reach the posterior scapular region, where it lies in the plane between bone and muscle (Fig. 7.38).
It innervates the supraspinatus muscle and then passes through the greater scapular (spinoglenoid) notch, between the root of the spine of the scapula and the glenoid cavity, to terminate in and innervate the infraspinatus muscle.
Generally, the suprascapular nerve has no cutaneous branches.
The axillary nerve originates from the posterior cord of the brachial plexus. It exits the axilla by passing through the quadrangular space in the posterior wall of the axilla, and enters the posterior scapular region (Fig. 7.38). Together with the posterior circumflex humeral artery and vein, it is directly related to the posterior surface of the surgical neck of the humerus.
The axillary nerve innervates the deltoid and teres minor muscles. In addition, it has a cutaneous branch, the superior lateral cutaneous nerve of the arm, which carries general sensation from the skin over the inferior part of the deltoid muscle.
Three major arteries are found in the posterior scapular region: the suprascapular, posterior circumflex humeral, and circumflex scapular arteries. These arteries contribute to an interconnected vascular network around the scapula (Fig. 7.39).
The suprascapular artery originates in the base of the neck as a branch of the thyrocervical trunk, which, in turn, is a major branch of the subclavian artery (Figs. 7.38 and 7.39). The vessel may also originate directly from the third part of the subclavian artery.
The suprascapular artery normally enters the posterior scapular region superior to the suprascapular foramen, whereas the nerve passes through the foramen. In the posterior scapular region, the vessel runs with the suprascapular nerve.
In addition to supplying the supraspinatus and infraspinatus muscles, the suprascapular artery contributes branches to numerous structures along its course.
The posterior circumflex humeral artery originates from the third part of the axillary artery in the axilla (Figs. 7.38 and 7.39).
The posterior circumflex humeral artery and axillary nerve leave the axilla through the quadrangular space in the posterior wall and enter the posterior scapular region. The vessel supplies the related muscles and the glenohumeral joint. |
The circumflex scapular artery is a branch of the subscapular artery that also originates from the third part of the axillary artery in the axilla (Figs. 7.38 and 7.39). The circumflex scapular artery leaves the axilla through the triangular space and enters the posterior scapular region, passes through the origin of the teres minor muscle, and forms anastomotic connections with other arteries in the region.
Veins in the posterior scapular region generally follow the arteries and connect with vessels in the neck, back, arm, and axilla.
The axilla is the gateway to the upper limb, providing an area of transition between the neck and the arm (Fig. 7.40A). Formed by the clavicle, the scapula, the upper thoracic wall, the humerus, and related muscles, the axilla is an irregularly shaped pyramidal space with: four sides, an inlet, and a floor (base) (Fig. 7.40A,B).
The axillary inlet is continuous superiorly with the neck, and the lateral part of the floor opens into the arm.
All major structures passing into and out of the upper limb pass through the axilla (Fig. 7.40C). Apertures formed between muscles in the anterior and posterior walls enable structures to pass between the axilla and immediately adjacent regions (the posterior scapular, pectoral, and deltoid regions).
The axillary inlet is oriented in the horizontal plane and is somewhat triangular in shape, with its apex directed laterally (Fig. 7.40A,B). The margins of the inlet are completely formed by bone:
The medial margin is the lateral border of rib I.
The anterior margin is the posterior surface of the clavicle.
The posterior margin is the superior border of the scapula up to the coracoid process.
The apex of the triangularly shaped axillary inlet is lateral in position and is formed by the medial aspect of the coracoid process.
Major vessels and nerves pass between the neck and the axilla by crossing over the lateral border of rib I and through the axillary inlet (Fig. 7.40A).
The subclavian artery, the major blood vessel supplying the upper limb, becomes the axillary artery as it crosses the lateral margin of rib I and enters the axilla. Similarly, the axillary vein becomes the subclavian vein as it passes over the lateral margin of rib I and leaves the axilla to enter the neck.
At the axillary inlet, the axillary vein is anterior to the axillary artery, which, in turn, is anterior to the trunks of the brachial plexus.
The inferior trunk (lower trunk) of the brachial plexus lies directly on rib I in the neck, as does the subclavian artery and vein. As they pass over rib I, the vein and artery are separated by the insertion of the anterior scalene muscle (Fig. 7.40A).
The anterior wall of the axilla is formed by the lateral part of the pectoralis major muscle, the underlying pectoralis minor and subclavius muscles, and the clavipectoral fascia (Table 7.3).
The pectoralis major muscle is the largest and most superficial muscle of the anterior wall (Fig. 7.41). Its inferior margin underlies the anterior axillary fold, which marks the anteroinferior border of the axilla. The muscle has two heads:
The clavicular head originates from the medial half of the clavicle.
The sternocostal head originates from the medial part of the anterior thoracic wall—often, fibers from this head continue inferiorly and medially to attach to the anterior abdominal wall, forming an additional abdominal part of the muscle.
The muscle inserts into the lateral lip of the intertubercular sulcus of the humerus. The parts of the muscle that have a superior origin on the trunk insert lower and more anteriorly on the lateral lip of the intertubercular sulcus than the parts of the muscle that originate inferiorly. |
Acting together, the two heads of the pectoralis major flex, adduct, and medially rotate the arm at the glenohumeral joint. The clavicular head flexes the arm from an extended position, whereas the sternocostal head extends the arm from a flexed position, particularly against resistance.
The pectoralis major is innervated by the lateral and medial pectoral nerves, which originate from the brachial plexus in the axilla.
The subclavius muscle is a small muscle that lies deep to the pectoralis major muscle and passes between the clavicle and rib I (Fig. 7.42). It originates medially, as a tendon, from rib I at the junction between the rib and its costal cartilage. It passes laterally and superiorly to insert via a muscular attachment into an elongate shallow groove on the inferior surface of the middle third of the clavicle.
The function of the subclavius is not entirely clear, but it may act to pull the shoulder down by depressing the clavicle and may also stabilize the sternoclavicular joint by pulling the clavicle medially.
The subclavius muscle is innervated by a small branch from the superior trunk of the brachial plexus.
The pectoralis minor muscle is a small triangular-shaped muscle that lies deep to the pectoralis major muscle and passes from the thoracic wall to the coracoid process of the scapula (Fig. 7.42). It originates as three muscular slips from the anterior surfaces and upper margins of ribs III to V and from the fascia overlying muscles of the related intercostal spaces. The muscle fibers pass superiorly and laterally to insert into the medial and upper aspects of the coracoid process.
The pectoralis minor muscle protracts the scapula (by pulling the scapula anteriorly on the thoracic wall) and depresses the lateral angle of the scapula.
The pectoralis minor is innervated by the medial pectoral nerve, which originates from the brachial plexus in the axilla.
The clavipectoral fascia is a thick sheet of connective tissue that connects the clavicle to the floor of the axilla (Fig. 7.42). It encloses the subclavius and pectoralis minor muscles and spans the gap between them.
Structures travel between the axilla and the anterior wall of the axilla by passing through the clavipectoral fascia either between the pectoralis minor and subclavius muscles or inferior to the pectoralis minor muscle.
Important structures that pass between the subclavius and pectoralis minor muscles include the cephalic vein, the thoraco-acromial artery, and the lateral pectoral nerve.
The lateral thoracic artery leaves the axilla by passing through the fascia inferior to the pectoralis minor muscle.
The medial pectoral nerve leaves the axilla by penetrating directly through the pectoralis minor muscle to supply this muscle and to reach the pectoralis major muscle.
Occasionally, branches of the medial pectoral nerve pass around the lower margin of the pectoralis minor to reach and innervate the overlying pectoralis major muscle.
The medial wall of the axilla consists of the upper thoracic wall (the ribs and related intercostal tissues) and the serratus anterior muscle (Fig. 7.43 and Table 7.4, and see Fig. 7.40).
The serratus anterior muscle originates as a number of muscular slips from the lateral surfaces of ribs I to IX and the intervening deep fascia overlying the related intercostal spaces (Fig. 7.43). The muscle forms a flattened sheet, which passes posteriorly around the thoracic wall to insert primarily on the costal surface of the medial border of the scapula.
The serratus anterior pulls the scapula forward over the thoracic wall and facilitates scapular rotation. It also keeps the costal surface of the scapula closely opposed to the thoracic wall. |
The serratus anterior is innervated by the long thoracic nerve, which is derived from the roots of the brachial plexus, passes through the axilla along the medial wall, and passes vertically down the serratus anterior muscle on its external surface, just deep to skin and superficial fascia.
The only major structure that passes directly through the medial wall and into the axilla is the intercostobrachial nerve (Fig. 7.43). This nerve is the lateral cutaneous branch of the second intercostal nerve (anterior ramus of T2). It communicates with a branch of the brachial plexus (the medial cutaneous nerve of the arm) in the axilla and supplies skin on the upper posteromedial side of the arm, which is part of the T2 dermatome.
The lateral wall of the axilla is narrow and formed entirely by the intertubercular sulcus of the humerus (Fig. 7.44). The pectoralis major muscle of the anterior wall attaches to the lateral lip of the intertubercular sulcus. The latissimus dorsi and teres major muscles of the posterior wall attach to the floor and medial lip of the intertubercular sulcus, respectively (Table 7.5).
The posterior wall of the axilla is complex (Fig. 7.45 and see Fig. 7.50). Its bone framework is formed by the costal surface of the scapula. Muscles of the wall are: the subscapularis muscle (associated with the costal surface of the scapula), the distal parts of the latissimus dorsi and teres major muscles (which pass into the wall from the back and posterior scapular region), and the proximal part of the long head of the triceps brachii muscle (which passes vertically down the wall and into the arm).
Gaps between the muscles of the posterior wall form apertures through which structures pass between the axilla, posterior scapular region, and posterior compartment of the arm.
The subscapularis muscle forms the largest component of the posterior wall of the axilla. It originates from, and fills, the subscapular fossa and inserts on the lesser tubercle of the humerus (Figs. 7.45 and 7.46). The tendon crosses immediately anterior to the joint capsule of the glenohumeral joint.
Together with three muscles of the posterior scapular region (the supraspinatus, infraspinatus, and teres minor muscles), the subscapularis is a member of the rotator cuff muscle group, which stabilizes the glenohumeral joint.
The subscapularis is innervated by branches of the brachial plexus (the superior and inferior subscapular nerves), which originate in the axilla.
The inferolateral aspect of the posterior wall of the axilla is formed by the terminal part of the teres major muscle and the tendon of the latissimus dorsi muscle (Fig. 7.45). These two structures lie under the posterior axillary fold, which marks the posteroinferior border of the axilla.
The flat tendon of the latissimus dorsi muscle curves around the inferior margin of the teres major muscle on the posterior wall to insert into the floor of the intertubercular sulcus of the humerus, anterior to and slightly above the most distal attachment of the teres major muscle to the medial lip of the intertubercular sulcus. As a consequence, the inferior margin of the teres major muscle defines the inferior limit of the axilla laterally.
The axillary artery becomes the brachial artery of the arm as it crosses the inferior margin of the teres major muscle.
Long head of the triceps brachii
The long head of the triceps brachii muscle passes vertically through the posterior wall of the axilla, and, together with surrounding muscles and adjacent bones, results in the formation of three apertures through which major structures pass through the posterior wall: the quadrangular space, the triangular space, and the triangular interval (Fig. 7.45). |
Gateways in the posterior wall (See also “Gateways to the posterior scapular region,” pp. 706–710, and Figs. 7.37 and 7.38.)
The quadrangular space provides a passageway for nerves and vessels passing between the axilla and the more posterior scapular and deltoid regions (Fig. 7.45). When viewed from anteriorly, its boundaries are formed by: the inferior margin of the subscapularis muscle, the surgical neck of the humerus, the superior margin of the teres major muscle, and the lateral margin of the long head of the triceps brachii muscle.
Passing through the quadrangular space are the axillary nerve and the posterior circumflex humeral artery and vein.
The triangular space is an area of communication between the axilla and the posterior scapular region (Fig. 7.45). When viewed from anteriorly, it is formed by: the medial margin of the long head of the triceps brachii muscle, the superior margin of the teres major muscle, and the inferior margin of the subscapularis muscle.
The circumflex scapular artery and vein pass into this space.
This triangular interval is formed by: the lateral margin of the long head of the triceps brachii muscle, the shaft of the humerus, and the inferior margin of the teres major muscle (Fig. 7.45).
The radial nerve passes out of the axilla traveling through this interval to reach the posterior compartment of the arm.
The floor of the axilla is formed by fascia and a dome of skin that spans the distance between the inferior margins of the walls (Fig. 7.47 and see Fig. 7.40B). It is supported by the clavipectoral fascia. On a patient, the anterior axillary fold is more superior in position than is the posterior axillary fold.
Inferiorly, structures pass into and out of the axilla immediately lateral to the floor where the anterior and posterior walls of the axilla converge and where the axilla is continuous with the anterior compartment of the arm.
Contents of the axilla
Passing through the axilla are the major vessels, nerves, and lymphatics of the upper limb. The space also contains the proximal parts of two muscles of the arm, the axillary process of the breast, and collections of lymph nodes, which drain the upper limb, chest wall, and breast.
The proximal parts of the biceps brachii and coracobrachialis muscles pass through the axilla (Table 7.6).
The biceps brachii muscle originates as two heads (Fig. 7.48):
The short head originates from the apex of the coracoid process of the scapula and passes vertically through the axilla and into the arm where it joins the long head.
The long head originates as a tendon from the supraglenoid tubercle of the scapula, passes over the head of the humerus deep to the joint capsule of the glenohumeral joint, and enters the intertubercular sulcus where it is held in position by a ligament, the transverse humeral ligament, which spans the distance between the greater and lesser tubercles; the tendon passes through the axilla in the intertubercular sulcus and forms a muscle belly in the proximal part of the arm.
The long and short heads of the muscle join in distal regions of the arm and primarily insert as a single tendon into the radial tuberosity in the forearm.
The biceps brachii muscle is primarily a powerful flexor of the forearm at the elbow joint and a powerful supinator in the forearm. Because both heads originate from the scapula, the muscle also acts as an accessory flexor of the arm at the glenohumeral joint. In addition, the long head prevents superior movement of the humerus on the glenoid cavity.
The biceps brachii muscle is innervated by the musculocutaneous nerve. |
The coracobrachialis muscle, together with the short head of the biceps brachii muscle, originates from the apex of the coracoid process (Fig. 7.48). It passes vertically through the axilla to insert on a small linear roughening on the medial aspect of the humerus, approximately midshaft.
The coracobrachialis muscle flexes the arm at the glenohumeral joint.
In the axilla, the medial surface of the coracobrachialis muscle is pierced by the musculocutaneous nerve, which innervates and then passes through the muscle to enter the arm.
The axillary artery supplies the walls of the axilla and related regions, and continues as the major blood supply to the more distal parts of the upper limb (Fig. 7.49).
The subclavian artery in the neck becomes the axillary artery at the lateral margin of rib I and passes through the axilla, becoming the brachial artery at the inferior margin of the teres major muscle.
The axillary artery is separated into three parts by the pectoralis minor muscle, which crosses anteriorly to the vessel (Fig. 7.49):
The first part is proximal to the pectoralis minor.
The second part is posterior to the pectoralis minor.
The third part is distal to the pectoralis minor.
Generally, six branches arise from the axillary artery:
One branch, the superior thoracic artery, originates from the first part.
Two branches, the thoraco-acromial artery and the lateral thoracic artery, originate from the second part.
Three branches, the subscapular artery, the anterior circumflex humeral artery, and the posterior circumflex humeral artery, originate from the third part (Fig. 7.50).
The superior thoracic artery is small and originates from the anterior surface of the first part of the axillary artery (Fig. 7.50). It supplies upper regions of the medial and anterior axillary walls.
The thoraco-acromial artery is short and originates from the anterior surface of the second part of the axillary artery just posterior to the medial (superior) margin of the pectoralis minor muscle (Fig. 7.50). It curves around the superior margin of the muscle, penetrates the clavipectoral fascia, and immediately divides into four branches—the pectoral, deltoid, clavicular, and acromial branches, which supply the anterior axillary wall and related regions.
Additionally, the pectoral branch contributes vascular supply to the breast, and the deltoid branch passes into the clavipectoral triangle where it accompanies the cephalic vein and supplies adjacent structures (see Fig. 7.41).
The lateral thoracic artery arises from the anterior surface of the second part of the axillary artery posterior to the lateral (inferior) margin of the pectoralis minor (Fig. 7.50). It follows the margin of the muscle to the thoracic wall and supplies the medial and anterior walls of the axilla. In women, branches emerge from around the inferior margin of the pectoralis major muscle and contribute to the vascular supply of the breast.
The subscapular artery is the largest branch of the axillary artery and is the major blood supply to the posterior wall of the axilla (Fig. 7.50). It also contributes to the blood supply of the posterior scapular region.
The subscapular artery originates from the posterior surface of the third part of the axillary artery, follows the inferior margin of the subscapularis muscle for a short distance, and then divides into its two terminal branches, the circumflex scapular artery and the thoracodorsal artery. |
The circumflex scapular artery passes through the triangular space between the subscapularis, teres major, and long head of the triceps muscle. Posteriorly, it passes inferior to, or pierces, the origin of the teres minor muscle to enter the infraspinous fossa. It anastomoses with the suprascapular artery and the deep branch (dorsal scapular artery) of the transverse cervical artery, thereby contributing to an anastomotic network of vessels around the scapula.
The thoracodorsal artery approximately follows the lateral border of the scapula to the inferior angle. It contributes to the vascular supply of the posterior and medial walls of the axilla.
The anterior circumflex humeral artery is small compared to the posterior circumflex humeral artery, and originates from the lateral side of the third part of the axillary artery (Fig. 7.50). It passes anterior to the surgical neck of the humerus and anastomoses with the posterior circumflex humeral artery.
This anterior circumflex humeral artery supplies branches to surrounding tissues, which include the glenohumeral joint and the head of the humerus.
The posterior circumflex humeral artery originates from the lateral surface of the third part of the axillary artery immediately posterior to the origin of the anterior circumflex humeral artery (Fig. 7.50). With the axillary nerve, it leaves the axilla by passing through the quadrangular space between the teres major, teres minor, and long head of the triceps brachii muscle and the surgical neck of the humerus.
The posterior circumflex humeral artery curves around the surgical neck of the humerus and supplies the surrounding muscles and the glenohumeral joint. It anastomoses with the anterior circumflex humeral artery and with branches from the profunda brachii, suprascapular, and thoraco-acromial arteries.
The axillary vein begins at the lower margin of the teres major muscle and is the continuation of the basilic vein (Fig. 7.51), which is a superficial vein that drains the posteromedial surface of the hand and forearm and penetrates the deep fascia in the middle of the arm.
The axillary vein passes through the axilla medial and anterior to the axillary artery and becomes the subclavian vein as the vessel crosses the lateral border of rib I at the axillary inlet. Tributaries of the axillary vein generally follow the branches of the axillary artery. Other tributaries include brachial veins that follow the brachial artery and the cephalic vein.
The cephalic vein is a superficial vein that drains the lateral and posterior parts of the hand, the forearm, and the arm. In the area of the shoulder, it passes into an inverted triangular cleft (the clavipectoral triangle) between the deltoid muscle, pectoralis major muscle, and clavicle. In the superior part of the clavipectoral triangle, the cephalic vein passes deep to the clavicular head of the pectoralis major muscle and pierces the clavipectoral fascia to join the axillary vein. Many patients who are critically ill have lost blood or fluid, which requires replacement. Access to a peripheral vein is necessary to replace the fluid. The typical sites for venous access are the cephalic vein in the hand or veins that lie within the superficial tissues of the cubital fossa.
The brachial plexus is a somatic nerve plexus formed by the anterior rami of C5 to C8, and most of the anterior ramus of T1 (Fig. 7.52). The plexus originates in the neck, passes laterally and inferiorly over rib I, and enters the axilla. |
The parts of the brachial plexus, from medial to lateral, are roots, trunks, divisions, and cords. All major nerves that innervate the upper limb originate from the brachial plexus, mostly from the cords. Proximal parts of the brachial plexus are posterior to the subclavian artery in the neck, while more distal regions of the plexus surround the axillary artery.
The roots of the brachial plexus are the anterior rami of C5 to C8, and most of T1. Close to their origin, the roots receive gray rami communicantes from the sympathetic trunk (Fig. 7.52). These carry postganglionic sympathetic fibers onto the roots for distribution to the periphery. The roots and trunks enter the posterior triangle of the neck by passing between the anterior scalene and middle scalene muscles and lie superior and posterior to the subclavian artery.
The three trunks of the brachial plexus originate from the roots, pass laterally over rib I, and enter the axilla (Fig. 7.52):
The superior trunk is formed by the union of C5 and C6 roots.
The middle trunk is a continuation of the C7 root.
The inferior trunk is formed by the union of the C8 and T1 roots.
The inferior trunk lies on rib I posterior to the subclavian artery; the middle and superior trunks are more superior in position.
Each of the three trunks of the brachial plexus divides into an anterior and a posterior division (Fig. 7.52):
The three anterior divisions form parts of the brachial plexus that ultimately give rise to peripheral nerves associated with the anterior compartments of the arm and forearm.
The three posterior divisions combine to form parts of the brachial plexus that give rise to nerves associated with the posterior compartments.
No peripheral nerves originate directly from the divisions of the brachial plexus.
The three cords of the brachial plexus originate from the divisions and are related to the second part of the axillary artery (Fig. 7.52):
The lateral cord results from the union of the anterior divisions of the upper and middle trunks and therefore has contributions from C5 to C7—it is positioned lateral to the second part of the axillary artery.
The medial cord is medial to the second part of the axillary artery and is the continuation of the anterior division of the inferior trunk—it contains contributions from C8 and T1.
The posterior cord occurs posterior to the second part of the axillary artery and originates as the union of all three posterior divisions—it contains contributions from all roots of the brachial plexus (C5 to T1).
Most of the major peripheral nerves of the upper limb originate from the cords of the brachial plexus. Generally, nerves associated with the anterior compartments of the upper limb arise from the medial and lateral cords and nerves associated with the posterior compartments originate from the posterior cord.
Branches (Table 7.7)
Branches of the roots
In addition to small segmental branches from C5 to C8 to muscles of the neck and a contribution of C5 to the phrenic nerve, the roots of the brachial plexus give rise to the dorsal scapular and long thoracic nerves (Fig. 7.53).
The dorsal scapular nerve: originates from the C5 root of the brachial plexus, passes posteriorly, often piercing the middle scalene muscle in the neck, to reach and travel along the medial border of the scapula (Fig. 7.54), and innervates the rhomboid major and minor muscles from their deep surfaces.
The long thoracic nerve: originates from the anterior rami of C5 to C7, passes vertically down the neck, through the axillary inlet, and down the medial wall of the axilla to supply the serratus anterior muscle (Fig. 7.54), and lies on the superficial aspect of the serratus anterior muscle.
Branches of the trunks |
The only branches from the trunks of the brachial plexus are two nerves that originate from the superior trunk (upper trunk): the suprascapular nerve and the nerve to the subclavius muscle (Fig. 7.53).
The suprascapular nerve (C5 and C6): originates from the superior trunk of the brachial plexus, passes laterally through the posterior triangle of the neck (Fig. 7.54) and through the suprascapular foramen to enter the posterior scapular region, innervates the supraspinatus and infraspinatus muscles, and is accompanied in the lateral parts of the neck and in the posterior scapular region by the suprascapular artery.
The nerve to the subclavius muscle (C5 and C6) is a small nerve that: originates from the superior trunk of the brachial plexus, passes anteroinferiorly over the subclavian artery and vein, and innervates the subclavius muscle.
Branches of the lateral cord
Three nerves originate entirely or partly from the lateral cord (Fig. 7.53).
The lateral pectoral nerve is the most proximal of the branches from the lateral cord. It passes anteriorly, together with the thoraco-acromial artery, to penetrate the clavipectoral fascia that spans the gap between the subclavius and pectoralis minor muscles (Fig. 7.55), and innervates the pectoralis major muscle.
The musculocutaneous nerve is a large terminal branch of the lateral cord. It passes laterally to penetrate the coracobrachialis muscle and pass between the biceps brachii and brachialis muscles in the arm, and innervates all three flexor muscles in the anterior compartment of the arm, terminating as the lateral cutaneous nerve of the forearm.
The lateral root of the median nerve is the largest terminal branch of the lateral cord and passes medially to join a similar branch from the medial cord to form the median nerve (Fig. 7.55).
Branches of the medial cord
The medial cord has five branches (Fig. 7.55).
The medial pectoral nerve is the most proximal branch. It receives a communicating branch from the lateral pectoral nerve and then passes anteriorly between the axillary artery and axillary vein. Branches of the nerve penetrate and supply the pectoralis minor muscle. Some of these branches pass through the muscle to reach and supply the pectoralis major muscle. Other branches occasionally pass around the inferior or lateral margin of the pectoralis minor muscle to reach the pectoralis major muscle.
The medial cutaneous nerve of the arm (medial brachial cutaneous nerve) passes through the axilla and into the arm where it penetrates deep fascia and supplies skin over the medial side of the distal third of the arm. In the axilla, the nerve communicates with the intercostobrachial nerve of T2. Fibers of the medial cutaneous nerve of the arm innervate the upper part of the medial surface of the arm and floor of the axilla.
The medial cutaneous nerve of the forearm (medial antebrachial cutaneous nerve) originates just distal to the origin of the medial cutaneous nerve of the arm. It passes out of the axilla and into the arm where it gives off a branch to the skin over the biceps brachii muscle, and then continues down the arm to penetrate the deep fascia with the basilic vein, continuing inferiorly to supply the skin over the anterior surface of the forearm. It innervates skin over the medial surface of the forearm down to the wrist.
The medial root of the median nerve passes laterally to join with a similar root from the lateral cord to form the median nerve anterior to the third part of the axillary artery. |
The ulnar nerve is a large terminal branch of the medial cord (Fig. 7.55). However, near its origin, it often receives a communicating branch from the lateral root of the median nerve originating from the lateral cord and carrying fibers from C7 (see Fig. 5.73B). The ulnar nerve passes through the arm and forearm into the hand where it innervates all intrinsic muscles of the hand (except for the three thenar muscles and the two lateral lumbrical muscles). On passing through the forearm, branches of the ulnar nerve innervate the flexor carpi ulnaris muscle and the medial half of the flexor digitorum profundus muscle. The ulnar nerve innervates skin over the palmar surface of the little finger, medial half of the ring finger, and associated palm and wrist, and the skin over the dorsal surface of the medial part of the hand.
Median nerve. The median nerve is formed anterior to the third part of the axillary artery by the union of lateral and medial roots originating from the lateral and medial cords of the brachial plexus (Fig. 7.55). It passes into the arm anterior to the brachial artery and through the arm into the forearm, where branches innervate most of the muscles in the anterior compartment of the forearm (except for the flexor carpi ulnaris muscle and the medial half of the flexor digitorum profundus muscle, which are innervated by the ulnar nerve).
The median nerve continues into the hand to innervate: the three thenar muscles associated with the thumb, the two lateral lumbrical muscles associated with movement of the index and middle fingers, and the skin over the palmar surface of the lateral three and one-half digits and over the lateral side of the palm and middle of the wrist.
The musculocutaneous nerve, the lateral root of the median nerve, the median nerve, the medial root of the median nerve, and the ulnar nerve form an M over the third part of the axillary artery (Fig. 7.55). This feature, together with penetration of the coracobrachialis muscle by the musculocutaneous nerve, can be used to identify components of the brachial plexus in the axilla.
Branches of the posterior cord
Five nerves originate from the posterior cord of the brachial plexus: the superior subscapular nerve, the thoracodorsal nerve, the inferior subscapular nerve, the axillary nerve, and the radial nerve (Fig. 7.53).
All these nerves except the radial nerve innervate muscles associated with the shoulder region or the posterior wall of the axilla; the radial nerve passes into the arm and forearm.
The superior subscapular, thoracodorsal, and inferior subscapular nerves originate sequentially from the posterior cord and pass directly into muscles associated with the posterior axillary wall (Fig. 7.56). The superior subscapular nerve is short and passes into and supplies the subscapularis muscle. The thoracodorsal nerve is the longest of these three nerves and passes vertically along the posterior axillary wall. It penetrates and innervates the latissimus dorsi muscle. The inferior subscapular nerve also passes inferiorly along the posterior axillary wall and innervates the subscapularis and teres major muscles.
The axillary nerve originates from the posterior cord and passes inferiorly and laterally along the posterior wall to exit the axilla through the quadrangular space (Fig. 7.56). It passes posteriorly around the surgical neck of the humerus and innervates both the deltoid and teres minor muscles. A superior lateral cutaneous nerve of the arm originates from the axillary nerve after passing through the quadrangular space and loops around the posterior margin of the deltoid muscle to innervate skin in that region. The axillary nerve is accompanied by the posterior circumflex humeral artery. |
The radial nerve is the largest terminal branch of the posterior cord (Fig. 7.56). It passes out of the axilla and into the posterior compartment of the arm by passing through the triangular interval between the inferior border of the teres major muscle, the long head of the triceps brachii muscle, and the shaft of the humerus. It is accompanied through the triangular interval by the profunda brachii artery, which originates from the brachial artery in the anterior compartment of the arm. The radial nerve and its branches innervate: all muscles in the posterior compartments of the arm and forearm, and the skin on the posterior aspect of the arm and forearm, the lower lateral surface of the arm, and the dorsal lateral surface of the hand.
The posterior cutaneous nerve of the arm (posterior brachial cutaneous nerve) originates from the radial nerve in the axilla and innervates skin on the posterior surface of the arm.
All lymphatics from the upper limb drain into lymph nodes in the axilla (Fig. 7.57).
In addition, axillary nodes receive drainage from an extensive area on the adjacent trunk, which includes regions of the upper back and shoulder, the lower neck, the chest, and the upper anterolateral abdominal wall. Axillary nodes also receive drainage from approximately 75% of the mammary gland.
The 20–30 axillary nodes are generally divided into five groups on the basis of location.
Humeral (lateral) nodes posteromedial to the axillary vein receive most of the lymphatic drainage from the upper limb.
Pectoral (anterior) nodes occur along the inferior margin of the pectoralis minor muscle along the course of the lateral thoracic vessels and receive drainage from the abdominal wall, the chest, and the mammary gland.
Subscapular (posterior) nodes on the posterior axillary wall in association with the subscapular vessels drain the posterior axillary wall and receive lymphatics from the back, the shoulder, and the neck.
Central nodes are embedded in axillary fat and receive tributaries from humeral, subscapular, and pectoral groups of nodes.
Apical nodes are the most superior group of nodes in the axilla and drain all other groups of nodes in the region. In addition, they receive lymphatic vessels that accompany the cephalic vein as well as vessels that drain the superior region of the mammary gland.
Efferent vessels from the apical group converge to form the subclavian trunk, which usually joins the venous system at the junction between the right subclavian vein and the right internal jugular vein in the neck. On the left, the subclavian trunk usually joins the thoracic duct in the base of the neck.
Axillary process of the mammary gland
Although the mammary gland is in superficial fascia overlying the thoracic wall, its superolateral region extends along the inferior margin of the pectoralis major muscle toward the axilla. In some cases, this may pass around the margin of the muscle to penetrate deep fascia and enter the axilla (Fig. 7.58). This axillary process rarely reaches as high as the apex of the axilla.
The arm is the region of the upper limb between the shoulder and the elbow (Fig. 7.59). The superior aspect of the arm communicates medially with the axilla. Inferiorly, a number of important structures pass between the arm and the forearm through the cubital fossa, which is positioned anterior to the elbow joint.
The arm is divided into two compartments by medial and lateral intermuscular septa, which pass from each side of the humerus to the outer sleeve of deep fascia that surrounds the limb (Fig. 7.59).
The anterior compartment of the arm contains muscles that predominantly flex the elbow joint; the posterior compartment contains muscles that extend the joint. Major nerves and vessels supply and pass through each compartment. |
The skeletal support for the arm is the humerus (Fig. 7.60). Most of the large muscles of the arm insert into the proximal ends of the two bones of the forearm, the radius and the ulna, and flex and extend the forearm at the elbow joint. In addition, the muscles predominantly situated in the forearm that move the hand originate at the distal end of the humerus.
Shaft and distal end of the humerus
In cross section, the shaft of the humerus is somewhat triangular with: anterior, lateral, and medial borders, and anterolateral, anteromedial, and posterior surfaces (Fig. 7.60).
The posterior surface of the humerus is marked on its superior aspect by a linear roughening for the attachment of the lateral head of the triceps brachii muscle, beginning just inferior to the surgical neck and passing diagonally across the bone to the deltoid tuberosity.
The middle part of the posterior surface and adjacent part of the anterolateral surface are marked by the shallow radial groove, which passes diagonally down the bone and parallel to the sloping posterior margin of the deltoid tuberosity. The radial nerve and the profunda brachii artery lie in this groove.
Approximately in the middle of the shaft, the medial border is marked by thin elongate roughening for the attachment of the coracobrachialis muscle.
Intermuscular septa, which separate the anterior compartment from the posterior compartment, attach to the medial and lateral borders (Fig. 7.61).
Distally, the bone becomes flattened, and these borders expand as the lateral supraepicondylar ridge (lateral supracondylar ridge) and the medial supraepicondylar ridge (medial supracondylar ridge). The lateral supraepicondylar ridge is more pronounced than the medial ridge and is roughened for the attachment of muscles found in the posterior compartment of the forearm.
The distal end of the humerus, which is flattened in the anteroposterior plane, bears a condyle, two epicondyles, and three fossae, as follows (Fig. 7.61).
The condyle
The two articular parts of the condyle, the capitulum and the trochlea, articulate with the two bones of the forearm.
The capitulum articulates with the radius of the forearm. Lateral in position and hemispherical in shape, it projects anteriorly and somewhat inferiorly and is not visible when the humerus is viewed from the posterior aspect.
The trochlea articulates with the ulna of the forearm. It is pulley shaped and lies medial to the capitulum. Its medial edge is more pronounced than its lateral edge and, unlike the capitulum, it extends onto the posterior surface of the bone.
The two epicondyles
The two epicondyles lie adjacent, and somewhat superior, to the trochlea and capitulum (Fig. 7.61).
The medial epicondyle, a large bony protuberance, is the major palpable landmark on the medial side of the elbow, and projects medially from the distal end of the humerus. On its surface, it bears a large oval impression for the attachment of muscles in the anterior compartment of the forearm. The ulnar nerve passes from the arm into the forearm around the posterior surface of the medial epicondyle and can be palpated against the bone in this location.
The lateral epicondyle is much less pronounced than the medial epicondyle. It is lateral to the capitulum and has a large irregular impression for the attachment of muscles in the posterior compartment of the forearm.
The three fossae
Three fossae occur superior to the trochlea and capitulum on the distal end of the humerus (Fig. 7.61).
The radial fossa is the least distinct of the fossae and occurs immediately superior to the capitulum on the anterior surface of the humerus.
The coronoid fossa is adjacent to the radial fossa and is superior to the trochlea. |
The largest of the fossae, the olecranon fossa, occurs immediately superior to the trochlea on the posterior surface of the distal end of the humerus.
These three fossae accommodate projections from the bones in the forearm during movements of the elbow joint.
Proximal end of the radius
The proximal end of the radius consists of a head, a neck, and the radial tuberosity (Fig. 7.62A,B).
The head of the radius is a thick disc-shaped structure oriented in the horizontal plane. The circular superior surface is concave for articulation with the capitulum of the humerus. The thick margin of the disc is broad medially where it articulates with the radial notch on the proximal end of the ulna.
The neck of the radius is a short and narrow cylinder of bone between the expanded head and the radial tuberosity on the shaft.
The radial tuberosity is a large blunt projection on the medial surface of the radius immediately inferior to the neck. Much of its surface is roughened for the attachment of the biceps brachii tendon. The oblique line of the radius continues diagonally across the shaft of the bone from the inferior margin of the radial tuberosity.
Proximal end of the ulna
The proximal end of the ulna is much larger than the proximal end of the radius and consists of the olecranon, the coronoid process, the trochlear notch, the radial notch, and the tuberosity of the ulna (Fig. 7.63A,B).
The olecranon is a large projection of bone that extends proximally from the ulna. Its anterolateral surface is articular and contributes to the formation of the trochlear notch, which articulates with the trochlea of the humerus. The superior surface is marked by a large roughened impression for the attachment of the triceps brachii muscle. The posterior surface is smooth, shaped somewhat triangularly, and can be palpated as the “tip of the elbow.”
The coronoid process projects anteriorly from the proximal end of the ulna (Fig. 7.63). Its superolateral surface is articular and participates, with the olecranon, in forming the trochlear notch. The lateral surface is marked by the radial notch for articulation with the head of the radius.
Just inferior to the radial notch is a fossa that allows the radial tuberosity to change position during pronation and supination. The posterior margin of this fossa is broadened to form the supinator crest. The anterior surface of the coronoid process is triangular, with the apex directed distally, and has a number of roughenings for muscle attachment. The largest of these roughenings, the tuberosity of the ulna, is at the apex of the anterior surface and is the attachment site for the brachialis muscle.
The anterior compartment of the arm contains three muscles—the coracobrachialis, brachialis, and biceps brachii muscles—which are innervated predominantly by the musculocutaneous nerve.
The posterior compartment contains one muscle—the triceps brachii muscle—which is innervated by the radial nerve.
The coracobrachialis muscle extends from the tip of the coracoid process of the scapula to the medial side of the midshaft of the humerus (Fig. 7.64 and Table 7.8). It passes through the axilla and is penetrated and innervated by the musculocutaneous nerve.
The coracobrachialis muscle flexes the arm.
The biceps brachii muscle has two heads:
The short head of the muscle originates from the coracoid process in conjunction with the coracobrachialis.
The long head originates as a tendon from the supraglenoid tubercle of the scapula (Fig. 7.64 and Table 7.8). |
The tendon of the long head passes through the glenohumeral joint superior to the head of the humerus and then passes through the intertubercular sulcus and enters the arm. In the arm, the tendon joins with its muscle belly and, together with the muscle belly of the short head, overlies the brachialis muscle.
The long and short heads converge to form a single tendon, which inserts onto the radial tuberosity.
As the tendon enters the forearm, a flat sheet of connective tissue (the bicipital aponeurosis) fans out from the medial side of the tendon to blend with deep fascia covering the anterior compartment of the forearm.
The biceps brachii muscle is a powerful flexor of the forearm at the elbow joint; it is also the most powerful supinator of the forearm when the elbow joint is flexed. Because the two heads of the biceps brachii muscle cross the glenohumeral joint, the muscle can also flex the glenohumeral joint.
The biceps brachii muscle is innervated by the musculocutaneous nerve. A tap on the tendon of the biceps brachii at the elbow is used to test predominantly spinal cord segment C6.
The brachialis muscle originates from the distal half of the anterior aspect of the humerus and from adjacent parts of the intermuscular septa, particularly on the medial side (Fig. 7.64 and Table 7.8). It lies beneath the biceps brachii muscle, is flattened dorsoventrally, and converges to form a tendon, which attaches to the tuberosity of the ulna.
The brachialis muscle flexes the forearm at the elbow joint.
Innervation of the brachialis muscle is predominantly by the musculocutaneous nerve. A small component of the lateral part is innervated by the radial nerve.
The only muscle of the posterior compartment of the arm is the triceps brachii muscle (Fig. 7.65 and Table 7.9). The triceps brachii muscle has three heads:
The long head originates from the infraglenoid tubercle of the scapula.
The medial head originates from the extensive area on the posterior surface of the shaft of the humerus inferior to the radial groove.
The lateral head originates from a linear roughening superior to the radial groove of the humerus.
The three heads converge to form a large tendon, which inserts on the superior surface of the olecranon of the ulna.
The triceps brachii muscle extends the forearm at the elbow joint.
Innervation of the triceps brachii is by branches of the radial nerve. A tap on the tendon of the triceps brachii tests predominantly spinal cord segment C7.
The major artery of the arm, the brachial artery, is found in the anterior compartment (Fig. 7.66A). Beginning as a continuation of the axillary artery at the lower border of the teres major muscle, it terminates just distal to the elbow joint where it divides into the radial and ulnar arteries.
In the proximal arm, the brachial artery lies on the medial side. In the distal arm, it moves laterally to assume a position midway between the lateral epicondyle and the medial epicondyle of the humerus. It crosses anteriorly to the elbow joint where it lies immediately medial to the tendon of the biceps brachii muscle. The brachial artery is palpable along its length. In proximal regions, the brachial artery can be compressed against the medial side of the humerus.
Branches of the brachial artery in the arm include those to adjacent muscles and two ulnar collateral vessels, which contribute to a network of arteries around the elbow joint (Fig. 7.66B). Additional branches are the profunda brachii artery and nutrient arteries to the humerus, which pass through a foramen in the anteromedial surface of the humeral shaft. |
The profunda brachii artery, the largest branch of the brachial artery, passes into and supplies the posterior compartment of the arm (Fig. 7.66A,B). It enters the posterior compartment with the radial nerve and together they pass through the triangular interval, which is formed by the shaft of the humerus, the inferior margin of the teres major muscle, and the lateral margin of the long head of the triceps muscle. They then pass along the radial groove on the posterior surface of the humerus deep to the lateral head of the triceps brachii muscle.
Branches of the profunda brachii artery supply adjacent muscles and anastomose with the posterior circumflex humeral artery. The artery terminates as two collateral vessels, which contribute to an anastomotic network of arteries around the elbow joint (Fig. 7.66B).
Paired brachial veins pass along the medial and lateral sides of the brachial artery, receiving tributaries that accompany branches of the artery (Fig. 7.67).
In addition to these deep veins, two large subcutaneous veins, the basilic vein and the cephalic vein, are located in the arm.
The basilic vein passes vertically in the distal half of the arm, penetrates deep fascia to assume a position medial to the brachial artery, and then becomes the axillary vein at the lower border of the teres major muscle. The brachial veins join the basilic, or axillary, vein.
The cephalic vein passes superiorly on the anterolateral aspect of the arm and through the anterior wall of the axilla to reach the axillary vein.
The musculocutaneous nerve leaves the axilla and enters the arm by passing through the coracobrachialis muscle (Fig. 7.68). It passes diagonally down the arm in the plane between the biceps brachii and brachialis muscles. After giving rise to motor branches in the arm, it emerges laterally to the tendon of the biceps brachii muscle at the elbow, penetrates deep fascia, and continues as the lateral cutaneous nerve of the forearm.
The musculocutaneous nerve provides: motor innervation to all muscles in the anterior compartment of the arm, and sensory innervation to skin on the lateral surface of the forearm.
The median nerve enters the arm from the axilla at the inferior margin of the teres major muscle (Fig. 7.68). It passes vertically down the medial side of the arm in the anterior compartment and is related to the brachial artery throughout its course:
In proximal regions, the median nerve is immediately lateral to the brachial artery.
In more distal regions, the median nerve crosses to the medial side of the brachial artery and lies anterior to the elbow joint.
The median nerve has no major branches in the arm, but a branch to one of the muscles of the forearm, the pronator teres muscle, may originate from the nerve immediately proximal to the elbow joint.
The ulnar nerve enters the arm with the median nerve and axillary artery (Fig. 7.68). It passes through proximal regions medial to the axillary artery. In the middle of the arm, the ulnar nerve penetrates the medial intermuscular septum and enters the posterior compartment where it lies anterior to the medial head of the triceps brachii muscle. It passes posterior to the medial epicondyle of the humerus and then into the anterior compartment of the forearm.
The ulnar nerve has no major branches in the arm.
The radial nerve originates from the posterior cord of the brachial plexus and enters the arm by crossing the inferior margin of the teres major muscle (Fig. 7.69). As it enters the arm, it lies posterior to the brachial artery. Accompanied by the profunda brachii artery, the radial nerve enters the posterior compartment of the arm by passing through the triangular interval. |
As the radial nerve passes diagonally, from medial to lateral, through the posterior compartment, it lies in the radial groove directly on bone. On the lateral side of the arm, it passes anteriorly through the lateral intermuscular septum and enters the anterior compartment where it lies between the brachialis muscle and a muscle of the posterior compartment of the forearm—the brachioradialis muscle, which attaches to the lateral supraepicondylar ridge of the humerus. The radial nerve enters the forearm anterior to the lateral epicondyle of the humerus, just deep to the brachioradialis muscle.
In the arm, the radial nerve has muscular and cutaneous branches (Fig. 7.69).
Muscular branches include those to the triceps brachii, brachioradialis, and extensor carpi radialis longus muscles. In addition, the radial nerve contributes to the innervation of the lateral part of the brachialis muscle. One of the branches to the medial head of the triceps brachii muscle arises before the radial nerve’s entrance into the posterior compartment and passes vertically down the arm in association with the ulnar nerve.
Cutaneous branches of the radial nerve that originate in the posterior compartment of the arm are the inferior lateral cutaneous nerve of the arm and the posterior cutaneous nerve of the forearm, both of which penetrate through the lateral head of the triceps brachii muscle and the overlying deep fascia to become subcutaneous.
The elbow joint is a complex joint involving three separate articulations, which share a common synovial cavity (Fig. 7.71).
The joints between the trochlear notch of the ulna and the trochlea of the humerus and between the head of the radius and the capitulum of the humerus are primarily involved with hinge-like flexion and extension of the forearm on the arm and, together, are the principal articulations of the elbow joint.
The joint between the head of the radius and the radial notch of the ulna, the proximal radio-ulnar joint, is involved with pronation and supination of the forearm.
The articular surfaces of the bones are covered with hyaline cartilage.
The synovial membrane originates from the edges of the articular cartilage and lines the radial fossa, the coronoid fossa, the olecranon fossa, the deep surface of the joint capsule, and the medial surface of the trochlea (Fig. 7.72).
The synovial membrane is separated from the fibrous membrane of the joint capsule by pads of fat in regions overlying the coronoid fossa, the olecranon fossa, and the radial fossa. These fat pads accommodate the related bony processes during extension and flexion of the elbow. Attachments of the brachialis and triceps brachii muscles to the joint capsule overlying these regions pull the attached fat pads out of the way when the adjacent bony processes are moved into the fossae.
The fibrous membrane of the joint capsule overlies the synovial membrane, encloses the joint, and attaches to the medial epicondyle and the margins of the olecranon, coronoid, and radial fossae of the humerus (Fig. 7.73). It also attaches to the coronoid process and olecranon of the ulna. On the lateral side, the free inferior margin of the joint capsule passes around the neck of the radius from an anterior attachment to the coronoid process of the ulna to a posterior attachment to the base of the olecranon.
The fibrous membrane of the joint capsule is thickened medially and laterally to form collateral ligaments, which support the flexion and extension movements of the elbow joint (Fig. 7.73). |
In addition, the external surface of the joint capsule is reinforced laterally where it cuffs the head of the radius with a strong anular ligament of the radius. Although this ligament blends with the fibrous membrane of the joint capsule in most regions, they are separate posteriorly. The anular ligament of the radius also blends with the radial collateral ligament.
The anular ligament of the radius and related joint capsule allow the radial head to slide against the radial notch of the ulna and pivot on the capitulum during pronation and supination of the forearm.
The deep surface of the fibrous membrane of the joint capsule and the related anular ligament of the radius that articulate with the sides of the radial head are lined by cartilage. A pocket of synovial membrane (sacciform recess) protrudes from the inferior free margin of the joint capsule and facilitates rotation of the radial head during pronation and supination.
Vascular supply to the elbow joint is through an anastomotic network of vessels derived from collateral and recurrent branches of the brachial, profunda brachii, radial, and ulnar arteries.
The elbow joint is innervated predominantly by branches of the radial and musculocutaneous nerves, but there may be some innervation by branches of the ulnar and median nerves.
The cubital fossa is an important area of transition between the arm and the forearm. It is located anterior to the elbow joint and is a triangular depression formed between two forearm muscles: the brachioradialis muscle originating from the lateral supra-epicondylar ridge of the humerus, and the pronator teres muscle originating from the medial epicondyle of the humerus (Fig. 7.77A).
The base of the triangle is an imaginary horizontal line between the medial and lateral epicondyles. The bed or floor of the fossa is formed mainly by the brachialis muscle.
The major contents of the cubital fossa, from lateral to medial, are: the tendon of the biceps brachii muscle, the brachial artery, and the median nerve (Fig. 7.77B).
The brachial artery normally bifurcates into the radial and ulnar arteries in the apex of the fossa (Fig. 7.77B), although this bifurcation may occur much higher in the arm, even in the axilla. When taking a blood pressure reading from a patient, the clinician places the stethoscope over the brachial artery in the cubital fossa.
The median nerve lies immediately medial to the brachial artery and leaves the fossa by passing between the ulnar and humeral heads of the pronator teres muscle (Fig. 7.77C).
The brachial artery and the median nerve are covered and protected anteriorly in the distal part of the cubital fossa by the bicipital aponeurosis (Fig. 7.77B). This flat connective tissue membrane passes between the medial side of the tendon of the biceps brachii muscle and deep fascia of the forearm. The sharp medial margin of the bicipital aponeurosis can often be felt.
The radial nerve lies just under the lip of the brachioradialis muscle, which forms the lateral margin of the fossa (Fig. 7.77C). In this position, the radial nerve divides into superficial and deep branches:
The superficial branch continues into the forearm just deep to the brachioradialis muscle.
The deep branch passes between the two heads of the supinator muscle (see pp. 778–780 and Fig. 7.92) to access the posterior compartment of the forearm.
The ulnar nerve does not pass through the cubital fossa. Instead, it passes posterior to the medial epicondyle. |
The roof of the cubital fossa is formed by superficial fascia and skin. The most important structure within the roof is the median cubital vein (Fig. 7.77D), which passes diagonally across the roof and connects the cephalic vein on the lateral side of the upper limb with the basilic vein on the medial side. The bicipital aponeurosis separates the median cubital vein from the brachial artery and median nerve. Other structures within the roof are cutaneous nerves—the medial cutaneous and lateral cutaneous nerves of the forearm.
The forearm is the part of the upper limb that extends between the elbow joint and the wrist joint. Proximally, most major structures pass between the arm and forearm through, or in relation to, the cubital fossa, which is anterior to the elbow joint (Fig. 7.79). The exception is the ulnar nerve, which passes posterior to the medial epicondyle of the humerus.
Distally, structures pass between the forearm and the hand through, or anterior to, the carpal tunnel (Fig. 7.79). The major exception is the radial artery, which passes dorsally around the wrist to enter the hand posteriorly.
The bone framework of the forearm consists of two parallel bones, the radius and the ulna (Figs. 7.79 and 7.80B). The radius is lateral in position and is small proximally, where it articulates with the humerus, and large distally, where it forms the wrist joint with the carpal bones of the hand.
The ulna is medial in the forearm, and its proximal and distal dimensions are the reverse of those for the radius: the ulna is large proximally and small distally. Proximal and distal joints between the radius and the ulna allow the distal end of the radius to swing over the adjacent end of the ulna, resulting in pronation and supination of the hand.
As in the arm, the forearm is divided into anterior and posterior compartments (Fig. 7.79). In the forearm, these compartments are separated by: a lateral intermuscular septum, which passes from the anterior border of the radius to deep fascia surrounding the limb; an interosseous membrane, which links adjacent borders of the radius and ulna along most of their length; and the attachment of deep fascia along the posterior border of the ulna.
Muscles in the anterior compartment of the forearm flex the wrist and digits and pronate the hand. Muscles in the posterior compartment extend the wrist and digits and supinate the hand. Major nerves and vessels supply or pass through each compartment.
Shaft and distal end of radius
The shaft of the radius is narrow proximally, where it is continuous with the radial tuberosity and neck, and much broader distally, where it expands to form the distal end (Fig. 7.80).
Throughout most of its length, the shaft of the radius is triangular in cross section, with: three borders (anterior, posterior, and interosseous), and three surfaces (anterior, posterior, and lateral).
The anterior border begins on the medial side of the bone as a continuation of the radial tuberosity. In the superior third of the bone, it crosses the shaft diagonally, from medial to lateral, as the oblique line of the radius. The posterior border is distinct only in the middle third of the bone. The interosseous border is sharp and is the attachment site for the interosseous membrane, which links the radius to the ulna.
The anterior and posterior surfaces of the radius are generally smooth, whereas an oval roughening for the attachment of the pronator teres marks approximately the middle of the lateral surface of the radius.
Viewed anteriorly, the distal end of the radius is broad and somewhat flattened anteroposteriorly (Fig. 7.80). Consequently, the radius has expansive anterior and posterior surfaces and narrow medial and lateral surfaces. Its anterior surface is smooth and unremarkable, except for the prominent sharp ridge that forms its lateral margin. |
The posterior surface of the radius is characterized by the presence of a large dorsal tubercle, which acts as a pulley for the tendon of one of the extensor muscles of the thumb (extensor pollicis longus). The medial surface is marked by a prominent facet for articulation with the distal end of the ulna (Fig. 7.80). The lateral surface of the radius is diamond shaped and extends distally as a radial styloid process.
The distal end of the bone is marked by two facets for articulation with two carpal bones (the scaphoid and lunate).
Shaft and distal end of ulna
The shaft of the ulna is broad superiorly where it is continuous with the large proximal end and narrow distally to form a small distal head (Fig. 7.81). Like the radius, the shaft of the ulna is triangular in cross section and has: three borders (anterior, posterior, and interosseous), and three surfaces (anterior, posterior, and medial).
The anterior border is smooth and rounded. The posterior border is sharp and palpable along its entire length. The interosseous border is also sharp and is the attachment site for the interosseous membrane, which joins the ulna to the radius.
The anterior surface of the ulna is smooth, except distally where there is a prominent linear roughening for the attachment of the pronator quadratus muscle. The medial surface is smooth and unremarkable. The posterior surface is marked by lines, which separate different regions of muscle attachments to bone.
The distal end of the ulna is small and characterized by a rounded head and the ulnar styloid process (Fig. 7.81). The anterolateral and distal part of the head is covered by articular cartilage. The ulnar styloid process originates from the posteromedial aspect of the ulna and projects distally.
The distal radio-ulnar joint occurs between the articular surface of the head of the ulna, with the ulnar notch on the end of the radius, and with a fibrous articular disc, which separates the radio-ulnar joint from the wrist joint (Fig. 7.82).
The triangular-shaped articular disc is attached by its apex to a roughened depression on the ulna between the styloid process and the articular surface of the head, and by its base to the angular margin of the radius between the ulnar notch and the articular surface for the carpal bones.
The synovial membrane is attached to the margins of the distal radio-ulnar joint and is covered on its external surface by a fibrous joint capsule.
The distal radio-ulnar joint allows the distal end of the radius to move anteromedially over the ulna.
The interosseous membrane is a thin fibrous sheet that connects the medial and lateral borders of the radius and ulna, respectively (Fig. 7.82). Collagen fibers within the sheet pass predominantly inferiorly from the radius to the ulna.
The interosseous membrane has a free upper margin, which is situated just inferior to the radial tuberosity, and a small circular aperture in its distal third. Vessels pass between the anterior and posterior compartments superior to the upper margin and through the inferior aperture.
The interosseous membrane connects the radius and ulna without restricting pronation and supination and provides attachment for muscles in the anterior and posterior compartments. The orientation of fibers in the membrane is also consistent with its role in transferring forces from the radius to the ulna and ultimately, therefore, from the hand to the humerus.
Pronation and supination of the hand occur entirely in the forearm and involve rotation of the radius at the elbow and movement of the distal end of the radius over the ulna (Fig. 7.83). |
At the elbow, the superior articular surface of the radial head spins on the capitulum while, at the same time, the articular surface on the side of the head slides against the radial notch of the ulna and adjacent areas of the joint capsule and anular ligament of the radius. At the distal radio-ulnar joint, the ulnar notch of the radius slides anteriorly over the convex surface of the head of the ulna. During these movements, the bones are held together by: the anular ligament of the radius at the proximal radio-ulnar joint, the interosseous membrane along the lengths of the radius and ulna, and the articular disc at the distal radio-ulnar joint (Fig. 7.83).
Because the hand articulates predominantly with the radius, the translocation of the distal end of the radius medially over the ulna moves the hand from the palm-anterior (supinated) position to the palm-posterior (pronated) position.
Two muscles supinate and two muscles pronate the hand (Fig. 7.83).
Biceps brachii. The biceps brachii muscle, the largest of the four muscles that supinate and pronate the hand, is a powerful supinator as well as a flexor of the elbow joint. It is most effective as a supinator when the forearm is flexed.
Supinator. The second of the muscles involved with supination is the supinator muscle. Located in the posterior compartment of the forearm, it has a broad origin, from the supinator crest of the ulna and the lateral epicondyle of the humerus and from ligaments associated with the elbow joint.
The supinator muscle curves around the posterior surface and the lateral surface of the upper third of the radius to attach to the shaft of the radius superior to the oblique line.
The tendon of the biceps brachii muscle and the supinator muscle both become wrapped around the proximal end of the radius when the hand is pronated (Fig. 7.83). When they contract, they unwrap from the bone, producing supination of the hand.
Pronator teres and pronator quadratus. Pronation results from the action of the pronator teres and pronator quadratus muscles (Fig. 7.83). Both these muscles are in the anterior compartment of the forearm:
The pronator teres runs from the medial epicondyle of the humerus to the lateral surface of the radius, approximately midway along the shaft.
The pronator quadratus extends between the anterior surfaces of the distal ends of the radius and ulna.
When these muscles contract, they pull the distal end of the radius over the ulna, resulting in pronation of the hand (Fig. 7.83).
Anconeus. In addition to hinge-like flexion and extension at the elbow joint, some abduction of the distal end of the ulna also occurs and maintains the position of the palm of the hand over a central axis during pronation (Fig. 7.84). The muscle involved in this movement is the anconeus muscle, which is a triangular muscle in the posterior compartment of the forearm that runs from the lateral epicondyle to the lateral surface of the proximal end of the ulna.
Muscles in the anterior (flexor) compartment of the forearm occur in three layers: superficial, intermediate, and deep. Generally, these muscles are associated with: movements of the wrist joint, flexion of the fingers including the thumb, and pronation.
All muscles in the anterior compartment of the forearm are innervated by the median nerve, except for the flexor carpi ulnaris muscle and the medial half of the flexor digitorum profundus muscle, which are innervated by the ulnar nerve.
All four muscles in the superficial layer—the flexor carpi ulnaris, palmaris longus, flexor carpi radialis, and pronator teres—have a common origin from the medial epicondyle of the humerus, and, except for the pronator teres, extend distally from the forearm into the hand (Fig. 7.85 and
Table 7.10). |
The flexor carpi ulnaris muscle is the most medial of the muscles in the superficial layer of flexors, having a long linear origin from the olecranon and posterior border of the ulna, in addition to an origin from the medial epicondyle of the humerus (Fig. 7.85A,B).
The ulnar nerve enters the anterior compartment of the forearm by passing through the triangular gap between the humeral and ulnar heads of the flexor carpi ulnaris (Fig. 7.85B). The muscle fibers converge on a tendon that passes distally and attaches to the pisiform bone of the wrist. From this point, force is transferred to the hamate bone of the wrist and to the base of metacarpal V by the pisohamate and pisometacarpal ligaments.
The flexor carpi ulnaris muscle is a powerful flexor and adductor of the wrist and is innervated by the ulnar nerve (Table 7.10).
The palmaris longus muscle, which is absent in about 15% of the population, lies between the flexor carpi ulnaris and the flexor carpi radialis muscles (Fig. 7.85A). It is a spindle-shaped muscle with a long tendon, which passes into the hand and attaches to the flexor retinaculum and to a thick layer of deep fascia, the palmar aponeurosis, which underlies and is attached to the skin of the palm and fingers.
In addition to its role as an accessory flexor of the wrist joint, the palmaris longus muscle also opposes shearing forces on the skin of the palm during gripping (Table 7.10).
The flexor carpi radialis muscle is lateral to the palmaris longus and has a large and prominent tendon in the distal half of the forearm (Fig. 7.85A and Table 7.10). Unlike the tendon of the flexor carpi ulnaris, which forms the medial margin of the distal forearm, the tendon of the flexor carpi radialis muscle is positioned just lateral to the midline. In this position, the tendon can be easily palpated, making it an important landmark for finding the pulse in the radial artery, which lies immediately lateral to it.
The tendon of the flexor carpi radialis passes through a compartment formed by bone and fascia on the lateral side of the anterior surface of the wrist and attaches to the anterior surfaces of the bases of metacarpals II and III.
The flexor carpi radialis is a powerful flexor of the wrist and can also abduct the wrist.
The pronator teres muscle originates from the medial epicondyle and supraepicondylar ridge of the humerus and from a small linear region on the medial edge of the coronoid process of the ulna (Fig. 7.85A). The median nerve often exits the cubital fossa by passing between the humeral and ulnar heads of this muscle. The pronator teres crosses the forearm and attaches to an oval roughened area on the lateral surface of the radius approximately midway along the bone.
The pronator teres forms the medial border of the cubital fossa and rotates the radius over the ulna during pronation (Table 7.10).
The muscle in the intermediate layer of the anterior compartment of the forearm is the flexor digitorum superficialis muscle (Fig. 7.86). This large muscle has two heads: the humero-ulnar head, which originates mainly from the medial epicondyle of the humerus and from the adjacent medial edge of the coronoid process of the ulna; and the radial head, which originates from the anterior oblique line of the radius.
The median nerve and ulnar artery pass deep to the flexor digitorum superficialis between the two heads.
In the distal forearm, the flexor digitorum superficialis forms four tendons, which pass through the carpal tunnel of the wrist and into the four fingers. The tendons for the ring and middle fingers are superficial to the tendons for the index and little fingers. |
In the forearm, carpal tunnel, and proximal regions of the four fingers, the tendons of the flexor digitorum superficialis are anterior to the tendons of the flexor digitorum profundus muscle.
Near the base of the proximal phalanx of each finger, the tendon of the flexor digitorum superficialis splits into two parts to pass posteriorly around each side of the tendon of the flexor digitorum profundus and ultimately attach to the margins of the middle phalanx (Fig. 7.86).
The flexor digitorum superficialis flexes the metacarpophalangeal joint and proximal interphalangeal joint of each finger; it also flexes the wrist joint (Table 7.11).
There are three deep muscles in the anterior compartment of the forearm: the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus (Fig. 7.87).
The flexor digitorum profundus muscle originates from the anterior and medial surfaces of the ulna and from the adjacent half of the anterior surface of the interosseous membrane (Fig. 7.87). It gives rise to four tendons, which pass through the carpal tunnel into the four medial fingers. Throughout most of their course, the tendons are deep to the tendons of the flexor digitorum superficialis muscle.
Opposite the proximal phalanx of each finger, each tendon of the flexor digitorum profundus passes through a split formed in the overlying tendon of the flexor digitorum superficialis muscle and passes distally to insert into the anterior surface of the base of the distal phalanx.
In the palm, the lumbrical muscles originate from the sides of the tendons of the flexor digitorum profundus (see Fig. 7.108).
Innervation of the medial and lateral halves of the flexor digitorum profundus varies as follows:
The lateral half (associated with the index and middle fingers) is innervated by the anterior interosseous nerve (branch of the median nerve).
The medial half (the part associated with the ring and little fingers) is innervated by the ulnar nerve.
The flexor digitorum profundus flexes the metacarpophalangeal joints and the proximal and distal interphalangeal joints of the four fingers. Because the tendons cross the wrist, it can flex the wrist joint as well (Table 7.12).
The flexor pollicis longus muscle originates from the anterior surface of the radius and the adjacent half of the anterior surface of the interosseous membrane (Fig. 7.87). It is a powerful muscle and forms a single large tendon, which passes through the carpal tunnel, lateral to the tendons of the flexor digitorum superficialis and flexor digitorum profundus muscles, and into the thumb where it attaches to the base of the distal phalanx.
The flexor pollicis longus flexes the thumb and is innervated by the anterior interosseous nerve (branch of the median nerve) (Table 7.12).
The pronator quadratus muscle is a flat square-shaped muscle in the distal forearm (Fig. 7.87). It originates from a linear ridge on the anterior surface of the lower end of the ulna and passes laterally to insert onto the flat anterior surface of the radius. It lies deep to, and is crossed by, the tendons of the flexor digitorum profundus and flexor pollicis longus muscles.
The pronator quadratus muscle pulls the distal end of the radius anteriorly over the ulna during pronation and is innervated by the anterior interosseous nerve (branch of the median nerve) (Table 7.12).
The largest arteries in the forearm are in the anterior compartment, pass distally to supply the hand, and give rise to vessels that supply the posterior compartment (Fig. 7.88). |
The brachial artery enters the forearm from the arm by passing through the cubital fossa. At the apex of the cubital fossa, it divides into its two major branches, the radial and ulnar arteries.
The radial artery originates from the brachial artery at approximately the neck of the radius and passes along the lateral aspect of the forearm (Fig. 7.88). It is: just deep to the brachioradialis muscle in the proximal half of the forearm, related on its lateral side to the superficial branch of the radial nerve in the middle third of the forearm, and medial to the tendon of the brachioradialis muscle and covered only by deep fascia, superficial fascia, and skin in the distal forearm.
In the distal forearm, the radial artery lies immediately lateral to the large tendon of the flexor carpi radialis muscle and directly anterior to the pronator quadratus muscle and the distal end of the radius (Fig. 7.88). In the distal forearm, the radial artery can be located using the flexor carpi radialis muscle as a landmark. The radial pulse can be felt by gently palpating the radial artery against the underlying muscle and bone.
The radial artery leaves the forearm, passes around the lateral side of the wrist, and penetrates the posterolateral aspect of the hand between the bases of metacarpals I and II (Fig. 7.88). Branches of the radial artery in the hand often provide the major blood supply to the thumb and lateral side of the index finger.
Branches of the radial artery originating in the forearm include: a radial recurrent artery, which contributes to an anastomotic network around the elbow joint and to numerous vessels that supply muscles on the lateral side of the forearm (see Fig. 7.66B); a small palmar carpal branch, which contributes to an anastomotic network of vessels that supply the carpal bones and joints; a somewhat larger branch, the superficial palmar branch, which enters the hand by passing through, or superficial to, the thenar muscles at the base of the thumb (Fig. 7.88) and anastomoses with the superficial palmar arch formed by the ulnar artery.
The ulnar artery is larger than the radial artery and passes down the medial side of the forearm (Fig. 7.88). It leaves the cubital fossa by passing deep to the pronator teres muscle, and then passes through the forearm in the fascial plane between the flexor carpi ulnaris and flexor digitorum profundus muscles.
In the distal forearm, the ulnar artery often remains tucked under the anterolateral lip of the flexor carpi ulnaris tendon, and is therefore not easily palpable.
In distal regions of the forearm, the ulnar nerve is immediately medial to the ulnar artery.
The ulnar artery leaves the forearm, enters the hand by passing lateral to the pisiform bone and superficial to the flexor retinaculum of the wrist, and arches over the palm (Fig. 7.88). It is often the major blood supply to the medial three and one-half digits.
Branches of the ulnar artery that arise in the forearm include: the ulnar recurrent artery with anterior and posterior branches, which contribute to an anastomotic network of vessels around the elbow joint (see Fig. 7.66B); numerous muscular arteries, which supply surrounding muscles; the common interosseous artery, which divides into anterior and posterior interosseous arteries (Fig. 7.88); and two small carpal arteries (dorsal carpal branch and palmar carpal branch), which supply the wrist.
The posterior interosseous artery passes dorsally over the proximal margin of the interosseous membrane into the posterior compartment of the forearm. |
The anterior interosseous artery passes distally along the anterior aspect of the interosseous membrane and supplies muscles of the deep compartment of the forearm and the radius and ulna. It has numerous branches, which perforate the interosseous membrane to supply deep muscles of the posterior compartment; it also has a small branch, which contributes to the vascular network around the carpal bones and joints. Perforating the interosseous membrane in the distal forearm, the anterior interosseous artery terminates by joining the posterior interosseous artery.
Deep veins of the anterior compartment generally accompany the arteries and ultimately drain into brachial veins associated with the brachial artery in the cubital fossa.
Nerves in the anterior compartment of the forearm are the median and ulnar nerves and the superficial branch of the radial nerve (Fig. 7.89).
The median nerve innervates the muscles in the anterior compartment of the forearm except for the flexor carpi ulnaris and the medial part of the flexor digitorum profundus (ring and little fingers). It leaves the cubital fossa by passing between the two heads of the pronator teres muscle and passing between the humero-ulnar and radial heads of the flexor digitorum superficialis muscle (Fig. 7.89).
The median nerve continues a straight linear course distally down the forearm in the fascia on the deep surface of the flexor digitorum superficialis muscle. Just proximal to the wrist, it moves around the lateral side of the muscle and becomes more superficial in position, lying between the tendons of the palmaris longus and flexor carpi radialis muscles. It leaves the forearm and enters the palm of the hand by passing through the carpal tunnel deep to the flexor retinaculum.
Most branches to the muscles in the superficial and intermediate layers of the forearm originate medially from the nerve just distal to the elbow joint.
The largest branch of the median nerve in the forearm is the anterior interosseous nerve, which originates between the two heads of the pronator teres, passes distally down the forearm with the anterior interosseous artery, innervates the muscles in the deep layer (the flexor pollicis longus, the lateral half of the flexor digitorum profundus, and the pronator quadratus) and terminates as articular branches to joints of the distal forearm and wrist.
A small palmar branch originates from the median nerve in the distal forearm immediately proximal to the flexor retinaculum (Fig. 7.89), passes superficially into the hand, and innervates the skin over the base and central palm. This palmar branch is spared in carpal tunnel syndrome because it passes into the hand superficial to the flexor retinaculum of the wrist.
The ulnar nerve passes through the forearm and into the hand, where most of its major branches occur. In the forearm, the ulnar nerve innervates only the flexor carpi ulnaris muscle and the medial part (ring and little fingers) of the flexor digitorum profundus muscle (Fig. 7.89).
The ulnar nerve enters the anterior compartment of the forearm by passing posteriorly around the medial epicondyle of the humerus and between the humeral and ulnar heads of the flexor carpi ulnaris muscle. After passing down the medial side of the forearm in the plane between the flexor carpi ulnaris and the flexor digitorum profundus muscles, it lies under the lateral lip of the tendon of the flexor carpi ulnaris proximal to the wrist.
The ulnar artery is lateral to the ulnar nerve in the distal two-thirds of the forearm, and both the ulnar artery and nerve enter the hand by passing superficial to the flexor retinaculum and immediately lateral to the pisiform bone (Fig. 7.89). |
In the forearm the ulnar nerve gives rise to: muscular branches to the flexor carpi ulnaris and to the medial half of the flexor digitorum profundus that arise soon after the ulnar nerve enters the forearm; and two small cutaneous branches—the palmar branch originates in the middle of the forearm and passes into the hand to supply skin on the medial side of the palm; the larger dorsal branch originates from the ulnar nerve in the distal forearm and passes posteriorly deep to the tendon of the flexor carpi ulnaris and innervates skin on the posteromedial side of the back of the hand and most skin on the posterior surfaces of the medial one and one-half digits.
The radial nerve bifurcates into deep and superficial branches under the margin of the brachioradialis muscle in the lateral border of the cubital fossa (Fig. 7.89).
The deep branch is predominantly motor and passes between the superficial and deep layers of the supinator muscle to access and supply muscles in the posterior compartment of the forearm.
The superficial branch of the radial nerve is sensory. It passes down the anterolateral aspect of the forearm deep to the brachioradialis muscle and in association with the radial artery. Approximately two-thirds of the way down the forearm, the superficial branch of the radial nerve passes laterally and posteriorly around the radial side of the forearm deep to the tendon of the brachioradialis. The nerve continues into the hand where it innervates skin on the posterolateral surface.
Muscles in the posterior compartment of the forearm occur in two layers: a superficial and a deep layer. The muscles are associated with: movement of the wrist joint, extension of the fingers and thumb, and supination.
All muscles in the posterior compartment of the forearm are innervated by the radial nerve.
The seven muscles in the superficial layer are the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and anconeus (Fig. 7.90). All have a common origin from the supraepicondylar ridge and lateral epicondyle of the humerus and, except for the brachioradialis and anconeus, extend as tendons into the hand.
The brachioradialis muscle originates from the proximal part of the supraepicondylar ridge of the humerus and passes through the forearm to insert on the lateral side of the distal end of the radius just proximal to the radial styloid process (Fig. 7.90).
In the anatomical position, the brachioradialis is part of the muscle mass overlying the anterolateral surface of the forearm and forms the lateral boundary of the cubital fossa.
Because the brachioradialis is anterior to the elbow joint, it acts as an accessory flexor of this joint even though it is in the posterior compartment of the forearm. Its action is most efficient when the forearm is midpronated and it forms a prominent bulge as it acts against resistance.
The radial nerve emerges from the posterior compartment of the arm just deep to the brachioradialis in the distal arm and innervates the brachioradialis. Lateral to the cubital fossa, the brachioradialis lies over the radial nerve and its bifurcation into deep and superficial branches. In more distal regions, the brachioradialis lies over the superficial branch of the radial nerve and radial artery (Table 7.13).
The extensor carpi radialis longus muscle originates from the distal part of the supraepicondylar ridge and the lateral epicondyle of the humerus; its tendon inserts on the dorsal surface of the base of metacarpal II (Fig. 7.90). In proximal regions, it is deep to the brachioradialis muscle. |
The extensor carpi radialis longus muscle extends and abducts the wrist, and is innervated by the radial nerve before the nerve divides into superficial and deep branches (Table 7.13).
The extensor carpi radialis brevis muscle originates from the lateral epicondyle of the humerus, and the tendon inserts onto adjacent dorsal surfaces of the bases of metacarpals II and III (Fig. 7.90). Along much of its course, the extensor carpi radialis brevis lies deep to the extensor carpi radialis longus.
The extensor carpi radialis brevis muscle extends and abducts the wrist, and is innervated by the deep branch of the radial nerve before the nerve passes between the two heads of the supinator muscle (Table 7.13).
The extensor digitorum muscle is the major extensor of the four fingers (index, middle, ring, and little fingers).
It originates from the lateral epicondyle of the humerus and forms four tendons, each of which passes into a finger (Fig. 7.90).
On the dorsal surface of the hand, adjacent tendons of the extensor digitorum are interconnected. In the fingers, each tendon inserts, via a triangular-shaped connective tissue aponeurosis (the extensor hood), into the base of the dorsal surfaces of the middle and distal phalanges.
The extensor digitorum muscle is innervated by the posterior interosseous nerve, which is the continuation of the deep branch of the radial nerve after it emerges from the supinator muscle (Table 7.13).
The extensor digiti minimi muscle is an accessory extensor of the little finger and is medial to the extensor digitorum in the forearm (Fig. 7.90). It originates from the lateral epicondyle of the humerus and inserts, together with the tendon of the extensor digitorum, into the extensor hood of the little finger.
The extensor digiti minimi is innervated by the posterior interosseous nerve (Table 7.13).
The extensor carpi ulnaris muscle is medial to the extensor digiti minimi (Fig. 7.90). It originates from the lateral epicondyle, and its tendon inserts into the medial side of the base of metacarpal V.
The extensor carpi ulnaris extends and adducts the wrist, and is innervated by the posterior interosseous nerve (Table 7.13).
The anconeus muscle is the most medial of the superficial extensors and has a triangular shape. It originates from the lateral epicondyle of the humerus and has a broad insertion into the posterolateral surface of the olecranon and related posterior surface of the ulna (see Fig. 7.84).
The anconeus abducts the ulna during pronation to maintain the center of the palm over the same point when the hand is flipped. It is also considered to be an accessory extensor of the elbow joint.
The anconeus is innervated by the branch of the radial nerve that innervates the medial head of the triceps brachii muscle (Table 7.13).
The deep layer of the posterior compartment of the forearm consists of five muscles: supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis (Fig. 7.91).
Except for the supinator muscle, all these deep layer muscles originate from the posterior surfaces of the radius, ulna, and interosseous membrane and pass into the thumb and fingers.
Three of these muscles—the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus—emerge from between the extensor digitorum and the extensor carpi radialis brevis tendons of the superficial layer and pass into the thumb. |
Two of the three “outcropping” muscles (the abductor pollicis longus and extensor pollicis brevis) form a distinct muscular bulge in the distal posterolateral surface of the forearm.
All muscles of the deep layer are innervated by the posterior interosseous nerve, the continuation of the deep branch of the radial nerve.
The supinator muscle has two layers, which insert together on the proximal aspect of the radius (Fig. 7.91):
The more superficial (humeral) layer originates mainly from the lateral epicondyle of the humerus and the related anular ligament and the radial collateral ligament of the elbow joint.
The deep (ulnar) layer originates mainly from the supinator crest on the posterolateral surface of the ulna.
From their sites of origin, the two layers wrap around the posterior and lateral aspect of the head, neck, and proximal shaft of the radius to insert on the lateral surface of the radius superior to the anterior oblique line and to the insertion of the pronator teres muscle.
The supinator muscle supinates the forearm and hand.
The deep branch of the radial nerve innervates the supinator muscle and passes to the posterior compartment of the forearm by passing between the two heads of this muscle (Table 7.14).
The abductor pollicis longus muscle originates from the proximal posterior surfaces of the radius and the ulna and from the related interosseous membrane (Fig. 7.91). In the distal forearm, it emerges between the extensor digitorum and extensor carpi radialis brevis muscles to form a tendon that passes into the thumb and inserts on the lateral side of the base of metacarpal I. The tendon contributes to the lateral border of the anatomical snuffbox at the wrist.
The major function of the abductor pollicis longus is to abduct the thumb at the joint between the metacarpal I and trapezium bones (Table 7.14).
The extensor pollicis brevis muscle arises distal to the origin of the abductor pollicis longus from the posterior surface of the radius and interosseous membrane (Fig. 7.91). Together with the abductor pollicis longus, it emerges between the extensor digitorum and extensor carpi radialis brevis muscles to form a bulge on the posterolateral surface of the distal forearm. The tendon of the extensor pollicis brevis passes into the thumb and inserts on the dorsal surface of the base of the proximal phalanx. At the wrist, the tendon contributes to the lateral border of the anatomical snuffbox.
The extensor pollicis brevis extends the metacarpophalangeal and carpometacarpal joints of the thumb (Table 7.14).
The extensor pollicis longus muscle originates from the posterior surface of the ulna and adjacent interosseous membrane and inserts via a long tendon into the dorsal surface of the distal phalanx of the thumb (Fig. 7.91).
Like the abductor pollicis longus and extensor pollicis brevis, the tendon of this muscle emerges between the extensor digitorum and the extensor carpi radialis brevis muscles. However, it is held away from the other two deep muscles of the thumb by passing medially around the dorsal tubercle on the distal end of the radius. The tendon forms the medial margin of the anatomical snuffbox at the wrist.
The extensor pollicis longus extends all joints of the thumb (Table 7.14).
The extensor indicis muscle is an accessory extensor of the index finger. It originates distal to the extensor pollicis longus from the posterior surface of the ulna and adjacent interosseous membrane (Fig. 7.91). The tendon passes into the hand and inserts into the extensor hood of the index finger with the tendon of the extensor digitorum (Table 7.14). |
The blood supply to the posterior compartment of the forearm occurs predominantly through branches of the radial, posterior interosseous, and anterior interosseous arteries (Fig. 7.92).
The posterior interosseous artery originates in the anterior compartment from the common interosseous branch of the ulnar artery and passes posteriorly over the proximal margin of the interosseous membrane and into the posterior compartment of the forearm. It contributes a branch, the recurrent interosseous artery (see Fig. 7.66B), to the vascular network around the elbow joint and then passes between the supinator and abductor pollicis longus muscles to supply the superficial extensors. After receiving the terminal end of the anterior interosseous artery, the posterior interosseous artery terminates by joining the dorsal carpal arch of the wrist.
The anterior interosseous artery, also a branch of the common interosseous branch of the ulnar artery, is situated in the anterior compartment of the forearm on the interosseous membrane. It has numerous perforating branches, which pass directly through the interosseous membrane to supply deep muscles of the posterior compartment. The terminal end of the anterior interosseous artery passes posteriorly through an aperture in the interosseous membrane in distal regions of the forearm to join the posterior interosseous artery.
The radial artery has muscular branches, which contribute to the supply of the extensor muscles on the radial side of the forearm.
Deep veins of the posterior compartment generally accompany the arteries. They ultimately drain into brachial veins associated with the brachial artery in the cubital fossa.
The nerve of the posterior compartment of the forearm is the radial nerve (Fig. 7.92). Most of the muscles are innervated by the deep branch, which originates from the radial nerve in the lateral wall of the cubital fossa deep to the brachioradialis muscle and becomes the posterior interosseous nerve after emerging from between the superficial and deep layers of the supinator muscle in the posterior compartment of the forearm.
In the lateral wall of the cubital fossa, and before dividing into superficial and deep branches, the radial nerve innervates the brachioradialis and extensor carpi radialis longus muscles.
The deep branch innervates the extensor carpi radialis brevis, then passes between the two layers of the supinator muscle and follows the plane of separation between the two layers dorsally and laterally around the proximal shaft of the radius to the posterior aspect of the forearm. It supplies the supinator muscle and then emerges, as the posterior interosseous nerve, from the muscle to lie between the superficial and deep layers of muscles.
The posterior interosseous nerve supplies the remaining muscles in the posterior compartment and terminates as articular branches, which pass deep to the extensor pollicis longus muscle to reach the wrist.
The hand (Fig. 7.93) is the region of the upper limb distal to the wrist joint. It is subdivided into three parts: the wrist (carpus), the metacarpus, and the digits (five fingers including the thumb).
The five digits consist of the laterally positioned thumb and, medial to the thumb, the four fingers—the index, middle, ring, and little fingers.
In the normal resting position, the fingers form a flexed arcade, with the little finger flexed most and the index finger flexed least. In the anatomical position, the fingers are extended.
The hand has an anterior surface (palm) and a dorsal surface (dorsum of hand).
Abduction and adduction of the fingers are defined with respect to the long axis of the middle finger (Fig. 7.93). In the anatomical position, the long axis of the thumb is rotated 90° to the rest of the digits so that the pad of the thumb points medially; consequently, movements of the thumb are defined at right angles to the movements of the other digits of the hand.
The hand is a mechanical and sensory tool. Many of the features of the upper limb are designed to facilitate positioning the hand in space. |
There are three groups of bones in the hand:
The eight carpal bones are the bones of the wrist.
The five metacarpals (I to V) are the bones of the metacarpus.
The phalanges are the bones of the digits—the thumb has only two; the rest of the digits have three (Fig. 7.94).
The carpal bones and metacarpals of the index, middle, ring, and little fingers (metacarpals II to V) tend to function as a unit and form much of the bony framework of the palm. The metacarpal of the thumb functions independently and has increased flexibility at the carpometacarpal joint to provide opposition of the thumb to the fingers.
The small carpal bones of the wrist are arranged in two rows, a proximal and a distal row, each consisting of four bones (Fig. 7.94).
From lateral to medial and when viewed from anteriorly, the proximal row of bones consists of: the boat-shaped scaphoid, the lunate, which has a crescent shape, the three-sided triquetrum bone, and the pea-shaped pisiform (Fig. 7.94).
The pisiform is a sesamoid bone in the tendon of the flexor carpi ulnaris and articulates with the anterior surface of the triquetrum.
The scaphoid has a prominent tubercle on its lateral palmar surface that is directed anteriorly.
From lateral to medial and when viewed from anteriorly, the distal row of carpal bones consists of: the irregular four-sided trapezium bone, the four-sided trapezoid, the capitate, which has a head, and the hamate, which has a hook (Fig. 7.94).
The trapezium articulates with the metacarpal bone of the thumb and has a distinct tubercle on its palmar surface that projects anteriorly.
The largest of the carpal bones, the capitate, articulates with the base of metacarpal III.
The hamate, which is positioned just lateral and distal to the pisiform, has a prominent hook (hook of hamate) on its palmar surface that projects anteriorly.
The carpal bones have numerous articular surfaces (Fig. 7.94). All of them articulate with each other, and the carpal bones in the distal row articulate with the metacarpals of the digits. With the exception of the metacarpal of the thumb, all movements of the metacarpal bones on the carpal bones are limited.
The expansive proximal surfaces of the scaphoid and lunate articulate with the radius to form the wrist joint.
The carpal bones do not lie in a flat plane; rather, they form an arch, whose base is directed anteriorly (Fig. 7.94). The lateral side of this base is formed by the tubercles of the scaphoid and trapezium. The medial side is formed by the pisiform and the hook of the hamate.
The flexor retinaculum attaches to, and spans the distance between, the medial and lateral sides of the base to form the anterior wall of the so-called carpal tunnel. The sides and roof of the carpal tunnel are formed by the arch of the carpal bones.
Each of the five metacarpals is related to one digit:
Metacarpal I is related to the thumb.
Metacarpals II to V are related to the index, middle, ring, and little fingers, respectively (Fig. 7.94).
Each metacarpal consists of a base, a shaft (body), and distally, a head.
All of the bases of the metacarpals articulate with the carpal bones; in addition, the bases of the metacarpal bones of the fingers articulate with each other.
All of the heads of the metacarpals articulate with the proximal phalanges of the digits. The heads form the knuckles on the dorsal surface of the hand when the fingers are flexed.
The phalanges are the bones of the digits (Fig. 7.94):
The thumb has two—a proximal and a distal phalanx. |
The rest of the digits have three—a proximal, a middle, and a distal phalanx.
Each phalanx has a base, a shaft (body), and distally, a head.
The base of each proximal phalanx articulates with the head of the related metacarpal bone.
The head of each distal phalanx is nonarticular and flattened into a crescent-shaped palmar tuberosity, which lies under the palmar pad at the end of the digit.
The wrist joint is a synovial joint between the distal end of the radius and the articular disc overlying the distal end of the ulna, and the scaphoid, lunate, and triquetrum (Fig. 7.94). Together, the articular surfaces of the carpals form an oval shape with a convex contour, which articulates with the corresponding concave surface of the radius and articular disc.
The wrist joint allows movement around two axes. The hand can be abducted, adducted, flexed, and extended at the wrist joint.
Because the radial styloid process extends further distally than does the ulnar styloid process, the hand can be adducted to a greater degree than it can be abducted.
The capsule of the wrist joint is reinforced by palmar radiocarpal, palmar ulnocarpal, and dorsal radiocarpal ligaments. In addition, radial and ulnar collateral ligaments of the wrist joint span the distance between the styloid processes of the radius and ulna and the adjacent carpal bones. These ligaments reinforce the medial and lateral sides of the wrist joint and support them during flexion and extension.
The synovial joints between the carpal bones share a common articular cavity. The joint capsule of the joints is reinforced by numerous ligaments.
Although movement at the carpal joints (intercarpal joints) is limited, the joints do contribute to the positioning of the hand in abduction, adduction, flexion, and, particularly, extension.
There are five carpometacarpal joints between the metacarpals and the related distal row of carpal bones (Fig. 7.94).
The saddle joint, between metacarpal I and the trapezium, imparts a wide range of mobility to the thumb that is not a feature of the rest of the digits. Movements at this carpometacarpal joint are flexion, extension, abduction, adduction, rotation, and circumduction.
The carpometacarpal joints between metacarpals II to V and the carpal bones are much less mobile than the carpometacarpal joint of the thumb, allowing only limited gliding movements. Movement of the joints increases medially, so metacarpal V slides to the greatest degree. This can be best observed on the dorsal surface of the hand as it makes a fist.
The joints between the distal heads of the metacarpals and the proximal phalanges of the digits are condylar joints, which allow flexion, extension, abduction, adduction, circumduction, and limited rotation (Fig. 7.94). The capsule of each joint is reinforced by the palmar ligament and by medial and lateral collateral ligaments.
The three deep transverse metacarpal ligaments (Fig. 7.95) are thick bands of connective tissue connecting the palmar ligaments of the metacarpophalangeal joints of the fingers to each other. They are important because, by linking the heads of the metacarpal bones together, they restrict the movement of these bones relative to each other. As a result, they help form a unified skeletal framework for the palm of the hand.
Significantly, a deep transverse metacarpal ligament does not occur between the palmar ligament of the metacarpophalangeal joint of the thumb and the palmar ligament of the index finger. The absence of this ligament, and the presence of a saddle joint between metacarpal I and the trapezium, are responsible for the increased mobility of the thumb relative to the rest of the digits of the hand.
Interphalangeal joints of hand |
The interphalangeal joints of the hand are hinge joints that allow mainly flexion and extension. They are reinforced by medial and lateral collateral ligaments and palmar ligaments.
Carpal tunnel and structures at the wrist
The carpal tunnel is formed anteriorly at the wrist by a deep arch formed by the carpal bones and the flexor retinaculum (see Fig. 7.94).
The base of the carpal arch is formed medially by the pisiform and the hook of the hamate and laterally by the tubercles of the scaphoid and trapezium.
The flexor retinaculum is a thick connective tissue ligament that bridges the space between the medial and lateral sides of the base of the arch and converts the carpal arch into the carpal tunnel.
The four tendons of the flexor digitorum profundus, the four tendons of the flexor digitorum superficialis, and the tendon of the flexor pollicis longus pass through the carpal tunnel, as does the median nerve (Fig. 7.98).
The flexor retinaculum holds the tendons to the bony plane at the wrist and prevents them from “bowing.”
Free movement of the tendons in the carpal tunnel is facilitated by synovial sheaths, which surround the tendons. All the tendons of the flexor digitorum profundus and flexor digitorum superficialis are surrounded by a single synovial sheath; a separate sheath surrounds the tendon of the flexor pollicis longus. The median nerve is anterior to the tendons in the carpal tunnel.
The tendon of the flexor carpi radialis is surrounded by a synovial sheath and passes through a tubular compartment formed by the attachment of the lateral aspect of the flexor retinaculum to the margins of a groove on the medial side of the tubercle of the trapezium.
The ulnar artery, ulnar nerve, and tendon of the palmaris longus pass into the hand anterior to the flexor retinaculum and therefore do not pass through the carpal tunnel (Fig. 7.98). The tendon of the palmaris longus is not surrounded by a synovial sheath.
The radial artery passes dorsally around the lateral side of the wrist and lies adjacent to the external surface of the scaphoid.
The extensor tendons pass into the hand on the medial, lateral, and posterior surfaces of the wrist in six compartments defined by an extensor retinaculum and lined by synovial sheaths (Fig. 7.98):
The tendons of the extensor digitorum and extensor indicis share a compartment and synovial sheath on the posterior surface of the wrist.
The tendons of the extensor carpi ulnaris and extensor digiti minimi have separate compartments and sheaths on the medial side of the wrist.
The tendons of the abductor pollicis longus and extensor pollicis brevis muscles, the extensor carpi radialis longus and extensor carpi radialis brevis muscles, and the extensor pollicis longus muscle pass through three compartments on the lateral surface of the wrist.
The palmar aponeurosis is a triangular condensation of deep fascia that covers the palm and is anchored to the skin in distal regions (Fig. 7.99).
The apex of the triangle is continuous with the palmaris longus tendon, when present; otherwise, it is anchored to the flexor retinaculum. From this point, fibers radiate to extensions at the bases of the digits that project into each of the index, middle, ring, and little fingers and, to a lesser extent, the thumb.
Transverse fibers interconnect the more longitudinally arranged bundles that continue into the digits.
Vessels, nerves, and long flexor tendons lie deep to the palmar aponeurosis in the palm. |
The palmaris brevis, a small intrinsic muscle of the hand, is a quadrangular-shaped subcutaneous muscle that overlies the hypothenar muscles, ulnar artery, and superficial branch of the ulnar nerve at the medial side of the palm (Fig. 7.99). It originates from the palmar aponeurosis and flexor retinaculum and inserts into the dermis of the skin on the medial margin of the hand.
The palmaris brevis deepens the cup of the palm by pulling on skin over the hypothenar eminence and forming a distinct ridge. This may improve grip.
The palmaris brevis is innervated by the superficial branch of the ulnar nerve.
The “anatomical snuffbox” is a term given to the triangular depression formed on the posterolateral side of the wrist and metacarpal I by the extensor tendons passing into the thumb (Fig. 7.100). Historically, ground tobacco (snuff) was placed in this depression before being inhaled into the nose. The base of the triangle is at the wrist and the apex is directed into the thumb. The impression is most apparent when the thumb is extended:
The lateral border is formed by the tendons of the abductor pollicis longus and extensor pollicis brevis.
The medial border is formed by the tendon of the extensor pollicis longus.
The floor of the impression is formed by the scaphoid and trapezium, and the distal ends of the tendons of the extensor carpi radialis longus and extensor carpi radialis brevis.
The radial artery passes obliquely through the anatomical snuffbox, deep to the extensor tendons of the thumb and lies adjacent to the scaphoid and trapezium.
Terminal parts of the superficial branch of the radial nerve pass subcutaneously over the snuffbox as does the origin of the cephalic vein from the dorsal venous arch of the hand.
After exiting the carpal tunnel, the tendons of the flexor digitorum superficialis and profundus muscles cross the palm and enter fibrous sheaths on the palmar aspect of the digits (Fig. 7.101). These fibrous sheaths: begin proximally, anterior to the metacarpophalangeal joints, and extend to the distal phalanges; are formed by fibrous arches and cruciate (cross-shaped) ligaments, which are attached posteriorly to the margins of the phalanges and to the palmar ligaments associated with the metacarpophalangeal and interphalangeal joints; and hold the tendons to the bony plane and prevent the tendons from bowing when the digits are flexed.
Within each tunnel, the tendons are surrounded by a synovial sheath. The synovial sheaths of the thumb and little finger are continuous with the sheaths associated with the tendons in the carpal tunnel (Fig. 7.101).
The tendons of the extensor digitorum and extensor pollicis longus muscles pass onto the dorsal aspect of the digits and expand over the proximal phalanges to form complex “extensor hoods” or “dorsal digital expansions” (Fig. 7.103A). The tendons of the extensor digiti minimi, extensor indicis, and extensor pollicis brevis muscles join these hoods.
Each extensor hood is triangular, with: the apex attached to the distal phalanx, the central region attached to the middle phalanx (index, middle, ring, and little fingers) or proximal phalanx (thumb), and each corner of the base wrapped around the sides of the metacarpophalangeal joint—in the index, middle, ring, and little fingers, the corners of the hoods attach mainly to the deep transverse metacarpal ligaments; in the thumb, the hood is attached on each side to muscles. |
In addition to other attachments, many of the intrinsic muscles of the hand insert into the free margin of the hood on each side. By inserting into the extensor hood, these intrinsic muscles are responsible for complex delicate movements of the digits that could not be accomplished with the long flexor and extensor tendons alone.
In the index, middle, ring, and little fingers, the lumbrical, interossei, and abductor digiti minimi muscles attach to the extensor hoods. In the thumb, the adductor pollicis and abductor pollicis brevis muscles insert into and anchor the extensor hood.
Because force from the small intrinsic muscles of the hand is applied to the extensor hood distal to the fulcrum of the metacarpophalangeal joints, the muscles flex these joints (Fig. 7.103B). Simultaneously, the force is transferred dorsally through the hood to extend the interphalangeal joints. This ability to flex the metacarpophalangeal joints, while at the same time extending the interphalangeal joints, is entirely due to the intrinsic muscles of the hand working through the extensor hoods. This type of precision movement is used in the upstroke when writing a t (Fig. 7.103C).
The intrinsic muscles of the hand are the palmaris brevis (described on p. 791; see Fig. 7.99), interossei, adductor pollicis, thenar, hypothenar, and lumbrical muscles (Figs. 7.104 to 7.108). Unlike the extrinsic muscles that originate in the forearm, insert in the hand, and function in forcefully gripping (“power grip”) with the hand, the intrinsic muscles occur entirely in the hand and mainly execute precision movements (“precision grip”) with the fingers and thumb.
All of the intrinsic muscles of the hand are innervated by the deep branch of the ulnar nerve except for the three thenar and two lateral lumbrical muscles, which are innervated by the median nerve. The intrinsic muscles are predominantly innervated by spinal cord segment T1 with a contribution from C8.
The interossei are muscles between and attached to the metacarpals (Figs. 7.104 and 7.105). They insert into the proximal phalanx of each digit and into the extensor hood and are divided into two groups, the dorsal interossei and the palmar interossei. All of the interossei are innervated by the deep branch of the ulnar nerve. Collectively, the interossei abduct and adduct the digits and contribute to the complex flexion and extension movements generated by the extensor hoods.
Dorsal interossei are the most dorsally situated of all of the intrinsic muscles and can be palpated through the skin on the dorsal aspect of the hand (Fig. 7.104). There are four bipennate dorsal interosseous muscles between, and attached to, the shafts of adjacent metacarpal bones (Fig. 7.104). Each muscle inserts both into the base of the proximal phalanx and into the extensor hood of its related digit.
The tendons of the dorsal interossei pass dorsal to the deep transverse metacarpal ligaments:
The first dorsal interosseous muscle is the largest and inserts into the lateral side of the index finger.
The second and third dorsal interossei insert into the lateral and medial sides, respectively, of the middle finger.
The fourth dorsal interosseous muscle inserts into the medial side of the ring finger.
In addition to generating flexion and extension movements of the fingers through their attachments to the extensor hoods, the dorsal interossei are the major abductors of the index, middle, and ring fingers, at the metacarpophalangeal joints (Table 7.15). |
The middle finger can abduct medially and laterally with respect to the long axis of the middle finger and consequently has a dorsal interosseous muscle on each side. The thumb and little finger have their own abductors in the thenar and hypothenar muscle groups, respectively, and therefore do not have dorsal interossei.
The radial artery passes between the two heads of the first dorsal interosseous muscle as it passes from the anatomical snuffbox on the posterolateral side of the wrist into the deep aspect of the palm.
The three (or four) palmar interossei are anterior to the dorsal interossei, and are unipennate muscles originating from the metacarpals of the digits with which each is associated (Fig. 7.105).
The first palmar interosseous muscle is rudimentary and often considered part of either the adductor pollicis or the flexor pollicis brevis. When present, it originates from the medial side of the palmar surface of metacarpal I and inserts into both the base of the proximal phalanx of the thumb and into the extensor hood. A sesamoid bone often occurs in the tendon attached to the base of the phalanx.
The second palmar interosseous muscle originates from the medial surface of metacarpal II and inserts into the medial side of the extensor hood of the index finger.
The third and fourth palmar interossei originate from the lateral surfaces of metacarpals IV and V and insert into the lateral sides of the respective extensor hoods.
Like the tendons of the dorsal interossei, the tendons of the palmar interossei pass dorsal to the deep transverse metacarpal ligaments.
The palmar interossei adduct the thumb, index, ring, and little fingers with respect to a long axis through the middle finger. The movements occur at the metacarpophalangeal joints. Because the muscles insert into the extensor hoods, they also produce complex flexion and extension movements of the digits (Table 7.15).
The adductor pollicis is a large triangular muscle anterior to the plane of the interossei that crosses the palm (Fig. 7.106). It originates as two heads: a transverse head from the anterior aspect of the shaft of metacarpal III, and an oblique head, from the capitate and adjacent bases of metacarpals II and III.
The two heads converge laterally to form a tendon, which often contains a sesamoid bone, that inserts into both the medial side of the base of the proximal phalanx of the thumb and into the extensor hood.
The radial artery passes anteriorly and medially between the two heads of the muscle to enter the deep plane of the palm and form the deep palmar arch.
The adductor pollicis is a powerful adductor of the thumb and opposes the thumb to the rest of the digits in gripping (Table 7.15).
The three thenar muscles (the opponens pollicis, flexor pollicis brevis, and abductor pollicis brevis muscles) are associated with opposition of the thumb to the fingers and with delicate movements of the thumb (Fig. 7.107) and are responsible for the prominent swelling (thenar eminence) on the lateral side of the palm at the base of the thumb.
The thenar muscles are innervated by the recurrent branch of the median nerve.
The opponens pollicis muscle is the largest of the thenar muscles and lies deep to the other two (Fig. 7.107). Originating from the tubercle of the trapezium and the adjacent flexor retinaculum, it inserts along the entire length of the lateral margin and adjacent lateral palmar surface of metacarpal I.
The opponens pollicis rotates and flexes metacarpal
I on the trapezium, so bringing the pad of the thumb into a position facing the pads of the fingers (Table 7.15). |
The abductor pollicis brevis muscle overlies the opponens pollicis and is proximal to the flexor pollicis brevis muscle (Fig. 7.107). It originates from the tubercles of the scaphoid and trapezium and from the adjacent flexor retinaculum, and inserts into the lateral side of the base of the proximal phalanx of the thumb and into the extensor hood.
The abductor pollicis brevis abducts the thumb, principally at the metacarpophalangeal joint. Its action is most apparent when the thumb is maximally abducted and the proximal phalanx is moved out of line with the long axis of the metacarpal bone (Table 7.15).
The flexor pollicis brevis muscle is distal to the abductor pollicis brevis (Fig. 7.107). It originates mainly from the tubercle of the trapezium and adjacent flexor retinaculum, but it may also have deeper attachments to other carpal bones and associated ligaments. It inserts into the lateral side of the base of the proximal phalanx of the thumb. The tendon often contains a sesamoid bone.
The flexor pollicis brevis flexes the metacarpophalangeal joint of the thumb (Table 7.15).
The hypothenar muscles (the opponens digiti minimi, abductor digiti minimi, and flexor digiti minimi brevis) contribute to the swelling (hypothenar eminence) on the medial side of the palm at the base of the little finger (Fig. 7.107). The hypothenar muscles are similar to the thenar muscles in name and in organization.
Unlike the thenar muscles, the hypothenar muscles are innervated by the deep branch of the ulnar nerve and not by the recurrent branch of the median nerve.
The opponens digiti minimi muscle lies deep to the other two hypothenar muscles (Fig. 7.107). It originates from the hook of the hamate and from the adjacent flexor retinaculum and it inserts into the medial margin and palmar surface of metacarpal V. Its base is penetrated by the deep branches of the ulnar nerve and ulnar artery.
The opponens digiti minimi rotates metacarpal V toward the palm; however, because of the simple shape of the carpometacarpal joint and the presence of a deep transverse metacarpal ligament, which attaches the head of metacarpal V to that of the ring finger, the movement is much less dramatic than that of the thumb (Table 7.15).
The abductor digiti minimi muscle overlies the opponens digiti minimi (Fig. 7.107). It originates from the pisiform bone, the pisohamate ligament, and the tendon of the flexor carpi ulnaris, and inserts into the medial side of the base of the proximal phalanx of the little finger and into the extensor hood.
The abductor digiti minimi is the principal abductor of the little finger (Table 7.15).
The flexor digiti minimi brevis muscle is lateral to the abductor digiti minimi (Fig. 7.107). It originates from the hook of the hamate bone and the adjacent flexor retinaculum and inserts with the abductor digiti minimi muscle into the medial side of the base of the proximal phalanx of the little finger.
The flexor digiti minimi brevis flexes the metacarpophalangeal joint.
There are four lumbrical (worm-like) muscles, each of which is associated with one of the fingers. The muscles originate from the tendons of the flexor digitorum profundus in the palm:
The medial two lumbricals are bipennate and originate from the flexor digitorum profundus tendons associated with the middle and ring fingers and the ring and little fingers, respectively.
The lateral two lumbricals are unipennate muscles, originating from the flexor digitorum profundus tendons associated with the index and middle fingers, respectively. |
The lumbricals pass dorsally around the lateral side of each finger, and insert into the extensor hood (Fig. 7.108). The tendons of the muscles are anterior to the deep transverse metacarpal ligaments.
The lumbricals are unique because they link flexor tendons with extensor tendons. Through their insertion into the extensor hoods, they participate in flexing the metacarpophalangeal joints and extending the interphalangeal joints.
The medial two lumbricals are innervated by the deep branch of the ulnar nerve; the lateral two lumbricals are innervated by digital branches of the median nerve (Table 7.15).
The blood supply to the hand is by the radial and ulnar arteries, which form two interconnected vascular arches (superficial and deep) in the palm (Fig. 7.109). Vessels to the digits, muscles, and joints originate from the two arches and the parent arteries:
The radial artery contributes substantially to the supply of the thumb and the lateral side of the index finger.
The remaining digits and the medial side of the index finger are supplied mainly by the ulnar artery.
The ulnar artery and ulnar nerve enter the hand on the medial side of the wrist (Fig. 7.110). The vessel lies between the palmaris brevis and the flexor retinaculum and is lateral to the ulnar nerve and the pisiform bone. Distally, the ulnar artery is medial to the hook of the hamate bone and then swings laterally across the palm, forming the superficial palmar arch, which is superficial to the long flexor tendons of the digits and just deep to the palmar aponeurosis. On the lateral side of the palm, the arch communicates with a palmar branch of the radial artery.
One branch of the ulnar artery in the hand is the deep palmar branch (Figs. 7.109 and 7.110), which arises from the medial aspect of the ulnar artery, just distal to the pisiform, and penetrates the origin of the hypothenar muscles. It curves medially around the hook of the hamate to access the deep plane of the palm and to anastomose with the deep palmar arch derived from the radial artery.
Branches from the superficial palmar arch include: a palmar digital artery to the medial side of the little finger, and three large, common palmar digital arteries, which ultimately provide the principal blood supply to the lateral side of the little finger, both sides of the ring and middle fingers, and the medial side of the index finger (Fig. 7.110); they are joined by palmar metacarpal arteries from the deep palmar arch before bifurcating into the proper palmar digital arteries, which enter the fingers.
The radial artery curves around the lateral side of the wrist and passes over the floor of the anatomical snuffbox and into the deep plane of the palm by penetrating anteriorly through the back of the hand (Figs. 7.109 and 7.111). It passes between the two heads of the first dorsal interosseous muscle and then between the two heads of the adductor pollicis to access the deep plane of the palm and form the deep palmar arch.
The deep palmar arch passes medially through the palm between the metacarpal bones and the long flexor tendons of the digits. On the medial side of the palm, it communicates with the deep palmar branch of the ulnar artery (Figs. 7.109 and 7.111).
Before penetrating the back of the hand, the radial artery gives rise to two vessels: a dorsal carpal branch, which passes medially as the dorsal carpal arch, across the wrist and gives rise to three dorsal metacarpal arteries, which subsequently divide to become small dorsal digital arteries, which enter the fingers; and the first dorsal metacarpal artery, which supplies adjacent sides of the index finger and thumb. |
Two vessels, the princeps pollicis artery and the radialis indicis artery, arise from the radial artery in the plane between the first dorsal interosseous and adductor pollicis. The princeps pollicis artery is the major blood supply to the thumb, and the radialis indicis artery supplies the lateral side of the index finger.
The deep palmar arch gives rise to: three palmar metacarpal arteries, which join the common palmar digital arteries from the superficial palmar arch; and three perforating branches, which pass posteriorly between the heads of origin of the dorsal interossei to anastomose with the dorsal metacarpal arteries from the dorsal carpal arch.
As generally found in the upper limb, the hand contains interconnected networks of deep and superficial veins. The deep veins follow the arteries; the superficial veins drain into a dorsal venous network on the back of the hand over the metacarpal bones (Fig. 7.112).
The cephalic vein originates from the lateral side of the dorsal venous network and passes over the anatomical snuffbox into the forearm.
The basilic vein originates from the medial side of the dorsal venous network and passes into the dorsomedial aspect of the forearm.
The hand is supplied by the ulnar, median, and radial nerves (Figs. 7.113 to 7.115). All three nerves contribute to cutaneous or general sensory innervation. The ulnar nerve innervates all intrinsic muscles of the hand except for the three thenar muscles and the two lateral lumbricals, which are innervated by the median nerve. The radial nerve only innervates skin on the dorsolateral side of the hand.
The ulnar nerve enters the hand lateral to the pisiform and posteromedially to the ulnar artery (Fig. 7.113). Immediately distal to the pisiform, it divides into a deep branch, which is mainly motor, and a superficial branch, which is mainly sensory.
The deep branch of the ulnar nerve passes with the deep branch of the ulnar artery (Fig. 7.113). It penetrates and supplies the hypothenar muscles to reach the deep aspect of the palm, arches laterally across the palm, deep to the long flexors of the digits, and supplies the interossei, the adductor pollicis, and the two medial lumbricals. In addition, the deep branch of the ulnar nerve contributes small articular branches to the wrist joint.
As the deep branch of the ulnar nerve passes across the palm, it lies in a fibro-osseous tunnel (Guyon’s canal) between the hook of the hamate and the flexor tendons. Occasionally, small outpouchings of synovial membrane (ganglia) from the joints of the carpus compress the nerve within this canal, producing sensory and motor symptoms.
The superficial branch of the ulnar nerve innervates the palmaris brevis muscle and continues across the palm to supply skin on the palmar surface of the little finger and the medial half of the ring finger (Fig. 7.113).
The median nerve is the most important sensory nerve in the hand because it innervates skin on the thumb, index and middle fingers, and lateral side of the ring finger (Fig. 7.115). The nervous system, using touch, gathers information about the environment from this area, particularly from the skin on the thumb and index finger. In addition, sensory information from the lateral three and one-half digits enables the fingers to be positioned with the appropriate amount of force when using precision grip.
The median nerve also innervates the thenar muscles that are responsible for opposition of the thumb to the other digits.
The median nerve enters the hand by passing through the carpal tunnel and divides into a recurrent branch and palmar digital branches (Fig. 7.115). |
The recurrent branch of the median nerve innervates the three thenar muscles. Originating from the lateral side of the median nerve near the distal margin of the flexor retinaculum, it curves around the margin of the retinaculum and passes proximally over the flexor pollicis brevis muscle. The recurrent branch then passes between the flexor pollicis brevis and abductor pollicis brevis to end in the opponens pollicis.
The palmar digital nerves cross the palm deep to the palmar aponeurosis and the superficial palmar arch and enter the digits. They innervate skin on the palmar surfaces of the lateral three and one-half digits and cutaneous regions over the dorsal aspects of the distal phalanges (nail beds) of the same digits. In addition to skin, the digital nerves supply the lateral two lumbrical muscles.
Superficial branch of the radial nerve
The only part of the radial nerve that enters the hand is the superficial branch (Fig. 7.116). It enters the hand by passing over the anatomical snuffbox on the dorsolateral side of the wrist. Terminal branches of the nerve can be palpated or “rolled” against the tendon of the extensor pollicis longus as they cross the anatomical snuffbox.
The superficial branch of the radial nerve innervates skin over the dorsolateral aspect of the palm and the dorsal aspects of the lateral three and one-half digits distally to approximately the terminal interphalangeal joints.
Tendons, muscles, and bony landmarks in the upper limb are used to locate major arteries, veins, and nerves. Asking patients to maneuver their upper limbs in specific ways is essential for performing neurological examinations.
Tendons are used to test reflexes associated with specific spinal cord segments.
Vessels are used clinically as points of entry into the vascular system (for collecting blood and administering pharmaceuticals and nutrients), and for taking blood pressure and pulses.
Nerves can become entrapped or be damaged in regions where they are related to bone or pass through confined spaces.
Bony landmarks and muscles of the posterior scapular region
The medial border, inferior angle, and part of the lateral border of the scapula can be palpated on a patient, as can the spine and acromion. The superior border and angle of the scapula are deep to soft tissue and are not readily palpable. The supraspinatus and infraspinatus muscles can be palpated above and below the spine, respectively (Fig. 7.117).
The trapezius muscle is responsible for the smooth contour of the lateral side of the neck and over the superior aspect of the shoulder.
The deltoid muscles form the muscular eminence inferior to the acromion and around the glenohumeral joint. The axillary nerve passes posteriorly around the surgical neck of the humerus deep to the deltoid muscle.
The latissimus dorsi muscle forms much of the muscle mass underlying the posterior axillary skin fold extending obliquely upward from the trunk to the arm. The teres major muscle passes from the inferior angle of the scapula to the upper humerus and contributes to this posterior axillary skin fold laterally.
Visualizing the axilla and locating contents and related structures
The axillary inlet and outlet and walls of the axilla can be established using skin folds and palpable bony landmarks (Fig. 7.118).
The anterior margin of the axillary inlet is the clavicle, which can be palpated along its entire length. The lateral limit of the axillary inlet is approximated by the tip of the coracoid process, which is palpable immediately below the lateral third of the clavicle and deep to the medial margin of the deltoid muscle.
The inferior margin of the anterior axillary wall is the anterior axillary skin fold, which overlies the lower margin of the pectoralis major muscle. |
Subsets and Splits