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ASPN #1 Electrical Stimulation Enhances Axon Regeneration And Functional Recovery Following Cubital Tunnel Surgery In Humans - A Randomized Controlled Trial
Hollie A. Power, MD; Michael J. Morhart, MSc, MD; Jaret L. Olson, MD; K. Ming Chan, MD
University of Alberta, Edmonton, AB, Canada

Introduction: Brief post-surgical electrical stimulation (ES) enhances motor and sensory axonal regeneration in animal models following axotomy and crush injury. Although improved physiological outcomes with ES have also been shown in humans following carpal tunnel release, there was no significant difference in functional recovery compared to those who underwent surgery alone. The underlying reason is that thenar muscle strength only plays a small role in hand dexterity. In contrast, the ulnar nerve innervates the majority of hand muscles and makes a vital contribution to hand strength. In this study, we investigated the hypothesis that ES following cubital tunnel surgery in patients with severe ulnar neuropathy would result in better muscle reinnervation and functional recovery compared to surgery alone.

Methods: Patients with severe axonal loss from ulnar nerve compression at the elbow (McGowan grade III) were randomly assigned to the treatment or control group in a 2:1 ratio. Those in the control group received cubital tunnel surgery alone, while patients in the treatment group received 1 hour of 20Hz ES following surgery. Stimulation was delivered via two stainless electrodes placed adjacent to the ulnar nerve intraoperatively. Patients were followed yearly for 3 years. At each visit, axonal regeneration was quantified using motor unit number estimation (MUNE) and functional recovery was evaluated using grip strength and key pinch strength. Statistical analysis was performed using non-parametric tests, with statistical significance set at p<0.05.

Results: Twenty-four patients were enrolled in the study: 8 received surgery alone and 16 received surgery and ES. There was no significant difference in demographics between the two groups. At three years following surgery, MUNE was significantly higher in the treatment group (182±25, mean±SE) compared to controls (93±14, p<0.05). In terms of functional recovery, grip strength was significantly improved in the treatment group (43±3kg) at 3 years post-operatively compared to controls (39±3kg, p<0.05). Key pinch strength was also significantly better in the treatment group (5.2±0.5 kg) compared to controls (4.4±0.8kg, p<0.05).

Conclusions: Our results suggest that post-surgical ES enhances axonal regeneration, muscle reinnervation and functional recovery following cubital tunnel surgery in humans. We propose that ES may be a clinically useful adjunct to surgical decompression for severe ulnar neuropathy, where functional recovery with conventional treatment is poor.


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