Traction Sural Neuropathy From Acute Achilles Injury: A Case Report

HISTORY: A 30-year-old male presented with acute onset right posterior lower leg pain that occurred while running, felt a tearing sensation in the posterior heel. Within a few days noted onset of paresthesias and burning in the lateral ankle. PHYSICAL EXAMINATION: Palpable defect in the posterior heel 3-5 cm proximal to calcaneus, with positive Thompson test. Endorsed associated numbness and tingling in the right lateral hindfoot and lower leg. Had weakness with ankle plantarflexion. DIFFERENTIAL DIAGNOSIS: 1. Achilles rupture. 2. Right S1 radiculopathy. 3. Peroneal tendinopathy. 4. Peripheral neuropathy. TEST AND RESULTS: MRI demonstrated complete Achilles tear 84 mm superior to calcaneal insertion. EMG showed isolated axonal sural neuropathy without evidence of radiculopathy. Patient ultimately opted for nonsurgical management with an accelerated functional rehabilitation protocol and returned to sport, although sensory symptoms persisted. FINAL WORKING DIAGNOSIS: Achilles rupture and sural neuropathy. TREATMENT AND OUTCOMES: The sural nerve can be iatrogenically injured during surgical repair of an acute Achilles tendon rupture, as it runs along the tendon's lateral border. Sural nerve injuries due to the Achilles injury are extremely rare, and poorly reported. It is possible that cast immobilization can compress and entrap the sural nerve. However this patient had symptom onset at time of injury, prior to treatment. Extreme traction during rupture is postulated to lead to sural nerve damage in this case. Given the plantarflexion weakness and lateral lower leg paresthesias, the combined symptoms from Achilles injury and sural neuropathy may be misdiagnosed as an S1 radiculopathy. Recovery is possible but the rarity of such injuries underscores the need for more documented cases to enhance understanding. Sural neuropathy, though uncommon, can have long-term effects on physical function. Thus, all patients with Achilles tendon tears should be evaluated for sural nerve injury (regardless of operative or nonsurgical treatment) to assess the need for early intervention.