364 - Evaluation of Failed Tendon Transfer after Restoration of Dorsiflexion in Patient with Chronic Right Foot Drop

Case Diagnosis: A 33-year-old man with a twelve-year history of giant cell bone tumors presented for repeat electrodiagnostic testing (EDX) following failed tendon transfer to treat right foot drop.

Case Description: The patient developed right foot drop at age 18 without associated injury. EDX elsewhere at that time showed decreased amplitude in the right fibular nerve (RFN) with positive sharp waves and fibrillations from tibialis anterior (TA) and extensor digitorum brevis (EDB). MRI showed a small RFN lesion, possibly a peripheral nerve sheath tumor but the patient declined further work-up.

At age 32, the patient had a posterior tibial tendon (PTT) transfer to restore right dorsiflexion. Pre-procedure, EDX again showed decreased RFN amplitude at TA and no response at EDB, without motor units from TA or extensor hallucis longus.

Two months post-PTT transfer, the patient regained dorsiflexion. Foot drop recurred five months post-op. Imaging was inconclusive. Exploratory surgery suggested PTT rupture. The patient had persistently visible contraction in his anterior leg but repeat EDX confirmed absence of motor units from TA with motor units firing from tibialis posterior and peroneus longus.

Discussions: The patient’s EDX showed a right deep fibular neuropathy. This remains idiopathic, though prior MRI did suggest a lesion within the nerve. The patient’s visible contraction may be the tibialis posterior, reassigned as a dorsiflexor by the PTT transfer. With the ruptured PTT and lack of function in the TA, the next step is for physiatry to prescribe optimal orthotics to improve his gait pattern.

Conclusions: This case demonstrates a unique presentation of atraumatic foot drop. It illustrates how EDX helps differentiate between mechanical and neurologic etiologies for motor deficits and demonstrates the importance of physiatry in referring patients for orthotics and gait re-training.