Abstract 12: Strategies To Optimize Functional Recovery In Distal Nerve Transfers For Common Fibular Nerve Injuries

Abstract

Purpose: Footdrop secondary to injury of the common fibular nerve has significant implications on patient function and quality of life. Outcomes following distal nerve transfers (DNT) for restoration of common fibular nerve function are unsatisfactory and often unpredictable. A perioperative technique to improve regeneration and reinnervation of end-targets is therefore of significant clinical interest. We investigated the effects of conditioning electrical stimulation (CES) and daily exercise therapy on regeneration and functional recovery in a rodent model of a DNT. Methods: Sprague Dawley rats were equally divided into a) CES, b) training, c) CES + training, and d) DNT. One week prior to DNT, animals randomized to a CES-cohort received one hour of intermittent electrical stimulation. In keeping with current clinical practice, DNT was performed by identifying the branch of the tibial nerve supplying the lateral gastrocnemius muscle, which was transected and coapted to the distal stump of the denervated common fibular nerve. Post-operatively, animals randomized to a training cohort had one-hour of treadmill training daily for 1 month at 10m/min. Length of axonal extension was quantified after two weeks of regeneration, and motor reinnervation was evaluated weekly by gait analysis of kinetic and kinematic outcomes and skilled locomotion testing. Results: Animals treated with CES prior to DNT had significantly greater regeneration and functional recovery. Two weeks postoperative, the length of axon extension in CES-treated nerves was, significantly longer than in non-conditioned control DNTs (p<0.001). By 8 weeks of regeneration, animals treated with CES+training had significantly higher foot placement scores on the horizontal ladder test (4.3 + 0.3) than DNT-controls (2.6 + 0.2, p<0.001)Animals treated with CES+training had the earliest return of dorsiflexion. By 12 weeks of regeneration, animals treated with CES+training (12.6 ± 2.8o) or with CES (11.2 ± 3.5o), had significantly greater recovery of dorsiflexion when compared to those animals trained only (3.9 ± 2.5o, p<0.001) or DNT controls (no dorsiflexion, p<0.001). Restoration to a more symmetrical gait pattern was significantly improved (p<0.001) among CES+training treated animals; with increased weight bearing (vertical peak forces 0.7 ± 0.03) and increased contact time of the affected limb (duty factor= contralateral - ipsilateral contact time; 0.039 ± 0.007) compared to the other groups (p<0.001). By week 12 of regeneration, CES treated animals exhibited a recovery to symmetry with increased vertical peak forces injured limb (0.65 + 0.02) and reduced differences between limb duty factors (0.046 + 0.05) compared to all other cohorts (p<0.05). Conclusion: Preoperative CES with and without exercise enhances functional recovery with improved dorsiflexion and accelerated restoration of normal gait following DNT for reinnervating common fibular nerve targets. As electrical stimulation has already been proven to be safe in a human patient population, and given that DNTs are performed electively and thus preoperative intervention is possible, delivery of CES in the footdrop patient population may significantly improve the efficacy and reliability in patients undergoing a distal nerve transfer.