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Partial Tibial Nerve Transfer For Pediatric Peroneal Nerve Palsy
Christopher S. Crowe, MD, Raymond Tse, MD.
University of Washington, Seattle, WA, USA.

PURPOSE:
Peroneal nerve palsy with resultant foot drop has a devastating impact on gait mechanics and quality of life. Meaningful recovery of peroneal-innervated muscle groups cannot reliably be expected in proximal injuries and those characterized by segmental nerve loss. Traditional management of foot drop includes the use of an ankle-foot orthosis, tendon transfer, and arthrodesis - each with considerable disadvantages and historically unsatisfactory results. Reestablishing ankle dorsiflexion by nerve transfer to the deep peroneal nerve or a branch of tibialis anterior has been reported in adults, but has not yet been described in the pediatric population.
METHODS:
Between 2017 and 2018, three pediatric patients with peroneal nerve palsy with associated foot drop underwent partial tibial nerve transfer. The same operative technique was utilized in all cases by a single surgeon. Following a formal decompression of the common peroneal nerve, denervation of tibialis anterior was confirmed by intraoperative stimulation. The tibial nerve was explored and branches to the flexor digitorum longus and flexor hallucis longus identified for transfer. Branches producing the greatest contractile strength were selected for transfer while still preserving at least one branch to each donor muscle group. Coaptation was performed end-to-end in all cases. Outcome measures included Medical Research Council (MRC) grades for ankle dorsiflexion, postoperative use of an orthosis, and additional procedures to correct foot drop.
RESULTS:
Peroneal nerve palsy was secondary to a number of injury mechanisms (Table 1). Lesions were localized to the sciatic nerve in 2 cases and the common peroneal in 1. Patients were monitored for spontaneous recovery for an average of 7 months prior to nerve transfer (range 4 - 9 months), and none demonstrated clinical or electrodiagnostic evidence of improvement. The average age at the time of surgery was 9 (range 4 - 14 years). Donor fascicles included branches to FDL, FHL, and both in combination. Recipient nerve included direct branches to tibialis anterior in 2 cases and deep peroneal nerve in 1. Both patients who underwent direct coaptation to a tibialis anterior branch experienced good functional recovery (MRC 4 and 5) and no longer required orthosis 12 months after surgery. The patient who underwent transfer to the deep peroneal nerve experienced minimal recovery of tibialis anterior, though developed reinnervation of extensor hallucis longus and ultimately required a tibialis posterior tendon transfer. All patients retained active plantar flexion of the toes after surgery.
CONCLUSION:
Active ankle dorsiflexion can be restored by partial transfer of tibial nerve fascicles for pediatric patients with peroneal nerve palsy. Donor muscle remains functional as long as not all branches are sacrificed. Coaptation directly to tibialis anterior motor nerve branch is preferable to more proximal deep peroneal nerve as it ensures axons will be directed to the intended muscle group. Overall, partial tibial nerve transfer for peroneal palsy is safe, effective, and does not interfere with subsequent tendon transfer if needed.

Table 1. Patient Demographics, Injury Characteristics, Management, and Outcome
PatientAge (years)Site of InjuryMechanism of InjuryPreoperative Ankle Dorsiflexion (MRC grade)Donor Nerve FasciclesFollow-up (months)Postoperative Ankle Dorsiflexion (MRC grade)Orthosis at 12 monthsAdditional Procedures
14Right sciatic nerveBlunt injury0FDL x2135NoNo
214Left sciatic nerveGunshot wound0FDL x1, FHL x1134NoNo
38Right common peroneal nerveLaceration0FDL x1282YesTibialis posterior tendon transfer


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