357 - Uncommon Sciatic Nerve Injury Secondary to Nerve Block During Ankle Pin Revision Surgery

Case Diagnosis: Sciatic Nerve Injury Secondary to Peripheral Nerve Block

Case Description: A 59-year-old male presents right foot pain, paresthesia, and foot drop post-operatively following an ankle pin revision surgery two months prior. Physical examination reveals weakness of right dorsiflexion, plantarflexion, eversion, and big toe extension with decreased sensation of digits 1-4, medial arch, and dorsum of the foot. Nerve conduction studies revealed diminished amplitude in the deep peroneal nerve from the fibular head to the extensor digitorium brevis (EDB), but not from the ankle to EDB. Electromyography demonstrated denervation of the right tibialis anterior, peroneus longus, and medial head of the gastrocnemius with fibrillation and positive sharp waves with decreased recruitment.

Discussions: Complications from nerve blocks are rare. Retrospective studies estimate perioperative peripheral nerve injury incidences to be between 0.5-1.0%. Popliteal nerve blocks are commonly used for perioperative pain control in foot and ankle surgery. The sciatic nerve is anesthetized proximal to the division tibial nerve and common peroneal nerve. This case is unique because the presentation of the symptoms is immediately downstream of the ankle surgery, leading to a clinical suspicion of intraoperative nerve damage from the surgical procedure itself. However, electrodiagnostic testing reveals the pathology to be further upstream. The right tibialis anterior, peroneus longus, and medial head of the gastrocnemius are innervated by branches of the common peroneal nerve and the tibial nerve. Their involvement is consistent with a sciatic pathology. The constellation of symptoms, chronology of events, and electrodiagnostic correlate with peripheral nerve damage at the injection site.

Conclusions: As peripheral nerve blocks become the preferred anesthetic over general anesthesia, it is crucial to consider peripheral nerve injuries secondary to nerve blocks as post-operative complications. Electrodiagnostics can help distinguish between etiologies and should be used to characterize nerve injuries.