Objective: Compared to the upper limb, lower limb distal nerve transfer (DNT) outcomes are poor, likely due to the longer length of regeneration required. DNT surgery to treat foot drop entails rerouting a tibial nerve branch to the denervated common fibular nerve stump to reinnervate the tibialis anterior muscle for ankle dorsiflexion. Conditioning electrical stimulation (CES) prior to nerve repair surgery accelerates nerve regeneration and promotes sensorimotor recovery. We hypothesize that CES prior to DNT will promote nerve regeneration to restore ankle dorsiflexion.
Methods: One week following common fibular nerve crush, CES was delivered to the tibial nerve in half the animals, and at 2 weeks, all animals received a DNT. To investigate the effects of CES on nerve regeneration, a series of kinetic, kinematic, skilled locomotion, electrophysiologic, and immunohistochemical outcomes were assessed. The effects of CES on the nerve were investigated.
Results: CES-treated animals had significantly accelerated nerve regeneration (p < 0.001), increased walking speed, and improved skilled locomotion. The injured limb had greater vertical peak forces, with improved duty factor, near-complete recovery of braking, propulsive forces, and dorsiflexion (p < 0.01). Reinnervation of the tibialis anterior muscle was confirmed with nerve conduction studies and immunohistochemical analysis of the neuromuscular junction. Immunohistochemistry demonstrated that CES does not induce Wallerian degeneration, nor does it cause macrophage infiltration of the distal tibial nerve.
Interpretation: Tibial nerve CES prior to DNT significantly improved functional recovery of the common fibular nerve and its muscle targets without inducing injury to the donor nerve. ANN NEUROL 2020;88:363-374.
© 2020 American Neurological Association.