PMC4875967_01
Schematic drawing of the left thorax and upper limb, demonstrating the chondroepitrochlearis muscle (CEM) inserting into the deep brachial fascia (bf) and the fibrous band (tuberoepicondylar band, tb) (PM: pectoralis major; fs: fascial sling; cj: costochondral junction; and Me: medial epicondyle).
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fig1
At the medial border of the brachium, the muscle belly of CEM bifurcated into two separate slips (Figure 2): one is continuous with the deep brachial fascia (Figure 1) while the other inserted into a distinct fibrous band 16 cm above the medial epicondyle of the humerus (Figures 1 and 2).
Photographs of the left chondroepitrochlearis muscle (CEM): (a) highlights the course of the CEM from its origin in the thorax through to its insertion into the fibrous band (tuberoepicondylar band, tb) (note: pectoralis major (PM) has been reflected cranially). (b) insert from (a) that highlights the course of the CEM in the axilla and its suspension by the fascial sling (fs). The photograph depicts two separate CEM slips at insertion. One slip inserts into the deep brachial fascia (black asterisk) and the other (white asterisk) fuses with the tb.
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fig2
CEM on each side was identified as a separate thin muscular slip, adjacent to the inferolateral border of pectoralis major (PM) measuring 22 cm (muscle belly) in length and 0.7 cm in width at its broadest point (Figure 2). Commencing at the costochondral junction of the 5th rib, fibers of CEM took an initial course parallel to yet independent of the lateral margin of PM. At the axilla, the muscle belly of CEM was suspended to the axillary fascia by a fascial sling (Figures 2 and 3). At the medial border of the brachium, the muscle belly of CEM bifurcated into two separate slips (Figure 2): one is continuous with the deep brachial fascia (Figure 1) while the other inserted into a distinct fibrous band 16 cm above the medial epicondyle of the humerus (Figures 1 and 2).
Photograph demonstrating the neurovascular supply of the left CEM. One branch of medial pectoral nerve (N1) passes though pectoralis minor (PMin) and the other branch (N2) passes deep to PMin. Pectoral branch of thoracoacromial trunk (black arrow) provides its arterial supply and lateral thoracic vein (white arrow) drains its venous blood (PM: pectoralis major; fs: fascial sling).
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fig3
At the axilla, the muscle belly of CEM was suspended to the axillary fascia by a fascial sling (Figures 2 and 3). The nerve supply for CEM was by two small nerves that entered its muscle belly at the lateral border of PM (Figure 3). One nerve could be traced back through pectoralis minor (PMin), while the other nerve ran deep to PMin; however both nerves branched out of brachial plexus from the anterior division of middle trunk (Figure 3). The arterial supply for CEM was from the pectoral branch of thoracoacromial trunk and from the lateral thoracic artery via its fine branches that entered the muscle belly at the lateral chest wall (Figure 3). Venous drainage was traced to the lateral thoracic vein (Figure 3). The lateral pectoral nerve exited from this ansa pectoralis, while medial pectoral nerves branched directly from the anterior division of middle trunk (Figure 3).