Muscle Stimulation Intervention for Preventing Degeneration in Denervated Wrist Extensor Muscles After Radial Nerve Transection in Non-Human Primates.

Introduction: Multiple stimulation therapies have been explored in the context of nerve surgery. However, electrical muscle stimulation (EMS), a specific approach that delivers energy directly to the muscle using high intensities and prolonged pulse durations, remains unexplored.

Methods: A radial nerve transection was performed in three non-human primate models, resulting in denervation of the wrist extensor muscles for a period of 6 months. To assess muscle integrity, a strength-duration curve (SDC) was generated monthly to determine the minimum intensity threshold required to activate the muscles. The left arm (experimental arm) was stimulated for 1 hour, 5 days per week, while the right arm (control arm) remained unstimulated. To compare both arms and the changes over time, the average normalized excitability (ANE) before EMS was calculated based on the SDC.

Results: In the control arm, ANE required for muscle stimulation progressively increased over time following denervation, as anticipated, suggesting a rising energy demand due to ongoing muscle degeneration. Conversely, in the experimental arm, ANE remained stable in two primates and even decreased in one, indicating that EMS may help maintain or reduce the energy needed for muscle activation, thereby potentially mitigating degenerative changes.

Conclusion : These findings suggest that EMS may help preserve integrity of denervated muscles following nerve injury, as evidenced by the lower activation thresholds in the experimental arm compared to the control. Further clinical studies are needed to explore the application of EMS before nerve repair surgery.