421 - Common Peroneal Nerve Injury secondary to High Velocity Tibial Plateau Fracture: A Case Report

This patient was admitted following a motor vehicle accident and was found to have subarachnoid hemorrhage, pneumothorax, bilateral rib fractures, left grade 3 open tibial plateau fracture, left acetabular fracture, and right pelvic fracture. The patient underwent left open bicondylar tibial plateau fracture closed reduction and external fixation followed by bicondylar tibial fracture open reduction and internal fixation. During his rehabilitation course, he was unable to dorsiflex his left ankle which did not improve. Outpatient electromyography showed evidence of severe left common peroneal nerve (CPN) neuropathy at the level of the knee with no motor units firing in the tibialis anterior and peroneus longus muscles. With therapy, the patient showed improvement in his mobility and deferred evaluation for orthotic support.

Discussions:

CPN and its branches have both sensory and motor functions which involves foot dorsiflexion, great toe extension, ankle eversion and sensation to the dorsum of the foot. Peroneal neuropathy is the third most common focal neuropathy. Etiology includes structural and external compression, trauma, and iatrogenic injury. Knee dislocation can cause CPN injury in 16- 40% of cases and tibial plateau fractures are estimated to have a 1-2% incidence. Imaging can evaluate for presence of a structural cause and electrodiagnostic studies can be used for confirmation and localization of the injury.

Conclusions:

CPN injury is a rare but significant complication following knee trauma. CPN injury following trauma has a poor prognosis for long term recovery especially with knee dislocations. However, studies have shown positive prognosis in CPN palsy resulting from tibial plateau fractures. Timely diagnosis utilizing physical exam and electrodiagnostic studies can aid in early targeted physical therapy and orthotic fitting which can improve risk of future injury and contracture.