Partial Tibial Nerve Transfer to the Tibialis Anterior Motor Branch to Treat Peroneal Nerve Injury After Knee Trauma

Background Injuries to the deep peroneal nerve result in tibialis anterior muscle paralysis and associated loss of ankle dorsiflexion. Nerve grafting of peroneal nerve injuries has led to poor function; therefore, tendon transfers and ankle-foot orthotics have been the standard treatment for foot drop. Questions/purposes We (1) describe an alternative surgical technique to obtain ankle dorsiflexion by partial tibial nerve transfer to the motor branch of the tibialis anterior muscle; (2) evaluate ankle dorsiflexion strength using British Medical Research Council grading after nerve transfer; and (3) qualitatively determine factors that influence functional success of surgery. Methods We retrospectively reviewed 11 patients treated with partial tibial nerve transfers after peroneal nerve injury. Pre- and postoperative motor strength was measured. Patients completed questionnaires regarding pre- and postoperative gait and disability. Results One patient regained Grade 4 ankle dorsiflexion, three patients regained Grade 3, one patient regained Grade 2, and two patients regained Grade 1 ankle dorsiflexion. Four patients did not regain any muscle activity. Clinically apparent motor recovery occurred an average 7.6 months postoperatively. A majority of patients (nine) could walk and participate in activities. Seven patients did not wear ankle-foot orthotics and four patients did not limp. The donor deficits included weak toe flexion (two patients) and reduced calf circumference (seven patients). Conclusion Our observations suggest nerve transfers to the deep peroneal nerve provide inconsistent ankle dorsiflexion strength, possibly related to the mechanism of peroneal nerve injury or delays in surgery. Despite variable strength, four patients achieved M3 or greater motor recovery, which enabled them to walk without assistive devices. Level of Evidence Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.