Conditioning Electrical Stimulation Improves Functional Recover in a Tibial to Peroneal Nerve Transfer
Jenna-Lynn B Senger, MD, PhD1, Karyne Rabey, PhD1, Michael J Morhart, MD, M.Sc2, K. Ming Chan, MD3 and Christine A Webber, PhD1, (1)University of Alberta, Edmonton, AB, Canada, (2)Division of Plastic and Reconstructive Surgery, University of Alberta, Edmonton, AB, Canada, (3)Division of Physical Medicine & Rehabilitation, University of Alberta, Edmonton, AB, Canada
Background: Injury to the common peroneal nerve (CP) results in foot drop, with major effects on patients' function and quality of life. Attempts at reconstruction with distal nerve transfers (DNT) where the distal stump of the degenerated CP nerve is coapted with a branch of the tibial nerve have gained popularity; however, outcomes remain inconsistent due to poor regeneration, reinnervation, and cortical relearning. We hypothesize that delivering one hour of conditioning electrical stimulation (CES) 7 days prior to DNT surgery will significantly improve regeneration and functional outcomes.
Methods: Using a rat model, the CP nerve was crushed to replicate a traumatic CP nerve injury. CES was delivered to the tibial nerve in half the animals one-week post-injury. Fourteen days following CP nerve injury, a DNT was performed. A branch of the tibial nerve innervating the lateral gastrocnemius muscle was divided, and its proximal stump coapted to the distal stump of the injured CP nerve. Length of axonal regeneration was quantified 2 weeks following the injury. Motor reinnervation of the tibialis anterior muscle (neuromuscular junction analysis and muscle weight) and functional outcomes (kinetic/kinematic studies and skilled locomotion) were assessed 6-10 weeks following injury.
Results: Animals treated with CES prior to DNT had significantly greater regeneration and motor recovery compared to animals treated with surgery alone. The length of axon extension in CES-treated animals was 7.8 ±0.8 mm, significantly longer than 3.1 ± 0.5 mm in the non-conditioned controls (p<0.001). By 9 weeks, gait analysis of CES animals identified significant improvements in normalization of the vertical peak, braking, and propulsion forces, gait kinematics, and performance on the horizontal ladder test (p<0.05). The tibialis anterior of the affected limb had greater muscle mass, with significantly more reinnervated neuromuscular junctions on immunofluorescent analysis (p<0.01).
Conclusions: Delivery of CES one week prior to lower limb DNT from a tibial nerve branch to an injured CP nerve significantly improved muscle reinnervation in the tibialis anterior muscle, and is also reflected in superior functional recovery. Previous studies have established electrical stimulation as a clinically feasible method for conditioning, and this study demonstrates its application in potentially significantly improving outcomes in patients with CP nerve injuries undergoing DNT.
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