acute compartment syndrome ( acs ) is defined as high pressure in a closed compartment resulting in decreased capillary blood perfusion . when this high pressure lasts for hours , the circulation and normal function of tissues such as muscles and nerves are disturbed , leading to myoneural necrosis . muscles and nerves tolerate ischemia for up to 4  h with limited sequelae ; however , 8  h of ischemia would result in irreversible damage.2 , 3 an internally expanding or externally compressive force can lead to compartment syndrome . the most common causes of acs are orthopedic conditions , such as fractures and fracture surgery , especially tibial diaphyseal fracture.5 , 6 , 7 mcqueen reported that 23% of acs cases are caused by soft tissue injuries without fracture . in addition , vascular and iatrogenic conditions , and occasionally conditions such as snakebite , can lead to acs . increased intracompartmental pressure ( icp ) reduces capillary perfusion , which eventually leads to arteriolar compression and subsequent tissue ischemia . ischemia - reperfusion and exudation of fluid result in further increases in icp , developing a vicious cycle . the calf contains four compartments ( anterior , lateral / peroneal , deep posterior , and superficial posterior ) . the anterior compartment of the lower leg contains the tibialis muscles and extensors of the toes and is the space in which acs most frequently occurs . timely diagnosis is often difficult because acs can be caused by minimal trauma or masked by concomitant trauma . a delay in diagnosis leads to delayed treatment and can result in ischemic contracture and severe disability . clinical symptoms and physical signs should be considered in combination for diagnosis , and physical examination findings are particularly important . in acs of the calf , for example , patients often report pain that is out of proportion to the injury of the anterior tibialis . the deep peroneal nerve lies in the anterior compartment ; therefore , the sensory territory over the first web space is deficient , and pain in the corresponding toes occurs during passive plantar flexion . ( pain , pallor , paresthesia , paralysis , and pulselessness ) are usually very late signs . when all of these symptoms , especially pulselessness , have developed , the condition is irreversible . a high index of suspicion and awareness of the risk of the syndrome may reduce delays in diagnosis . icp monitoring can facilitate diagnosis based on clinical symptoms and physical examination ; it has shown 94% sensitivity , 98% specificity , 93% positive predictive value , and 99% negative predictive value for the diagnosis of acs . no study to date has reported the performance of imaging modalities in the diagnosis of acs . no time is left for imaging examination , and it is thus difficult to obtain imaging data in patients with acs . we herein report a case of acs in a single compartment in which segmental tissue viability threatened the lower extremities following surgical repair of a ruptured achilles tendon . the diagnosis was almost delayed ; fortunately and coincidentally , we obtained valuable computed tomography angiography ( cta ) and magnetic resonance imaging ( mri ) information in the diagnostic process . we would like to increase awareness and describe the radiographic findings of this uncommon clinical presentation . to our knowledge , this report is the first to provide complete cta and mri information for the diagnosis of acs . the patient was a 24-year - old man with a height of 169  cm and weight of 65  kg ( body mass index , 22.76  kg / m ) . he was admitted to our orthopaedic emergency department with a 1-day history of pain in the right heel . he felt a sudden  pop  in his right ankle region while trying to turn a somersault . inspection revealed slight swelling along the right heel , but no skin change or ecchymosis . palpation revealed discontinuation with a palpable defect of the achilles tendon 4  cm above the calcaneal tuberosity . physical examination showed that the patient had difficulty with active plantar flexion of the right foot , and passive dorsiflexion was painful . therefore , we performed an mri examination , which revealed right achilles tendon rupture ( fig .  1 ) . surgical repair of the achilles tendon rupture was performed 3 days after all preoperative examinations had been completed . after the administration of preoperative antibiotics and general anesthesia , the patient was placed in a prone position . the tourniquet was inflated to 60  kpa for a total of 57  min . a 10-cm incision was made on the medial aspect of the achilles tendon , centered over the palpable defect . a 5- # ethibond suture ( ethicon , shanghai , china ) was used to repair the tendon using the kessler or krakow suture technique . the two ends of the tendon were then reinforced with a 2 - 0 absorbable suture ( vicryl , ethicon ) under no tension . another 2 - 0 absorbable suture was used to suture the plantar tendon over the two ends of the achilles tendon using the lynn technique . the operation was successfully completed , and an anterior short leg cast was applied to maintain the lower leg in a neutral position . the patient 's condition was stable until he complained of pain over the anterior tibialis and around the incision approximately 5  h after surgery . this condition was considered to represent normal postoperative pain at that time . despite the administration of a 100-mg dose of oral tramcontin , he required additional analgesia ( 40  mg parecoxib ) 7  h postoperatively . during rounds the next day , we replaced the anterior short leg cast with a back short leg cast , which eased the patient 's pain . the patient was able to perform active plantar flexion and dorsiflexion of all toes without excessive pain . however , approximately 27  h postoperatively , the patient complained of pain again in the anterior aspect of the lower leg without numbness or toe activity pain . two days later , approximately 38  h after surgery , the patient 's symptoms seemed to progress to intense pain over the anterior aspect of the lower leg . he experienced weakness in dorsiflexion of the great toe , and plantar flexion of the toes aggravated the pain . we then performed emergent mri and cta , which revealed swelling of the extensor hallucis longus ( ehl ) and extensor digitorum longus ( edl ) with distal anterior tibial artery and peroneal artery stenosis ( fig .  2 , fig .  3 , fig .  4 ) . fasciotomy for decompression was emergently performed . during the operation , after a 10-cm incision of the skin was made and the subcutaneous tissue was sharply dissected down to the level of the fascia , tension over the anterior compartment was found . upon fascial incision , the ehl and edl immediately and prominently herniated through the fascia , and part of the muscle was ischemic and edematous . the sectional muscle 's color appeared ashen gray relative to the others , corresponding with the mri findings . no contraction of the ehl or edl occurred upon stimulation with a diathermy needle ( fig .  5 ) . within a few minutes of compartment release , the color of the ehl and edl muscle bellies had improved , but to a minimal extent . the patient 's pain was relived immediately after surgery , and sensation in the first toe web area was slightly improved . intraoperatively , the ehl and edl muscle bellies were found to be slightly gray and showed no reaction to the diathermy needle ( fig . the patient recovered well and was discharged home 3 days later in a plaster back slab . he returned 3 months later , at which time he had recovered well , with no motor or sensory deficit in the right lower extremity . acs is usually caused by traumatic injuries , such as extremity fracture , crush injury , prolonged tourniquet use under anesthesia , compression by casts , burns , hematoma , anticoagulation therapy , or , in chronic compartment syndrome , exercise . patients complain of pain over the anterior region of the lower leg and feel weakness when trying to pull the foot upward against resistance . furthermore , no obvious preoperative traumatic factor was found that could have resulted in acs . soft - tissue injuries and muscle tears occur frequently in athletes.17 , 18 muscle swelling can reportedly also result from hematoma due to minor injury . in this case , the patient was trying to turn a somersault when his right heel was injured . his anterior tibial muscle might have been strained during sports activities , causing a buildup of pressure in the anterior compartment . muscle swelling may have been delayed by increased muscle ischemia . on the other hand , he had practiced martial arts for more than 6 years , and his muscles were strong with large muscle volumes , while his compartment size was limited . chronic exertional compartment syndrome is commonly seen in physically active military service members and athletes.20 , 21 affected individuals have recurrent , activity - related leg pain of a consistent duration or intensity that is relieved only by rest . as the interval between injury and surgery was only 3 days in our patient , we can not rule out the possibility of an acute episode of chronic exertional compartment syndrome . some authors have considered acs to be related to the operative position , especially when the muscles are compressed , as in the lithotomy position . in our case , we used a pneumatic tourniquet around the proximal leg and placed soft surgical linen under the ankle ; these procedures were performed carefully and checked by several members of the surgical team . the operation time was 57  min , within the permissible range of lower limb tourniquet application . in this patient thrombi and vasospasm resulting from the use of a tourniquet have been implicated as etiologies of compartment ischemia . therefore , based on the patient 's muscular factors and the mechanism of ischemia - reperfusion injury , the tourniquet increased the risk of muscle ischemia and swelling , resulting in elevated pressure in the compartment . an anterior short leg cast was applied to this patient to maintain the lower leg in a neutral position after surgery . masten considered venous obstruction aroused by a long leg brace to be an etiology of anterior tibial compartment syndrome . we replaced the anterior short leg cast with a posterior short leg cast , but the symptoms did not improve . however , external pressure secondary to the cast must not be dismissed as a possible cause . previous studies have found that casts potentially restrict compartment expansion and decrease venous flow , ultimately resulting in acs.25 , 26 throughout this patient 's clinical course , we speculated that the use of the cast was the main factor related to the onset of acs . controversy exists about the identification of critical factors leading to muscle ischemia or tissue necrosis . many researchers have proposed an icp threshold of 30  mmhg as an indication for fasciotomy . in modern medicine compared with the invasiveness of icp monitoring , mri can precisely demonstrate the region of swelling and provide accurate guidance for the operation . thus , mri or cta findings should be taken into account if conditions permit . because acs was considered with the help of radiographic information in most cases of compartment syndrome , no time is available for the acquisition of mri data . muscle edema caused by acs is sometimes difficult to distinguish from that caused by trauma . although some authors consider that mri is not useful and may even be detrimental because of the resultant delay in surgical treatment , it aided the diagnosis of this rare condition in the present case . therefore , it was indeed fortunate that cta and mri data were obtained in our case . to sum up , acute segmental single - compartment syndrome is a rare but serious complication encountered in several fields of medicine , especially orthopedics , sports medicine , and traumatology . high awareness must be maintained at all times when patients complain of pain in the extremities . our report presented the detailed imaging data used for the diagnosis of acs in a patient with extremity pain . our goals are to provide information that will aid the development of additional diagnostic methods and highlight the importance of vigilance for acs .
acute compartment syndrome of the lower extremity is a serious postinjury complication that requires emergency treatment . 
 early diagnosis is of paramount importance for a good outcome . 
 four muscle compartments in the calf ( anterior , lateral , deep posterior , and superficial posterior ) may be individually or collectively affected . 
 acute segmental single - compartment syndrome is an extremely rare condition characterized by high pressure in a single compartment space with threatening of the segmental tissue viability . in this case report 
 , we describe a young man with achilles tendon rupture who complained of postoperative pain in the anterior tibial region . 
 emergent computed tomography angiography and magnetic resonance imaging revealed local muscle edema . 
 segmental anterior compartment syndrome was diagnosed and fasciotomy was performed .