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3 A Direct Comparison of Targeted Muscle Reinnervation (TMR) and Regenerative Peripheral Nerve Interfaces (RPNI) to Prevent Neuroma Pain
Jenna-Lynn Senger, MD PhD FRCSC1; Aline Thorkelsson, BSc1; Mithun Rajshekar, Ph.D1; Shirley Duia, BSc1; Bradley Kerr, PhD1; K. Ming Chan, MD, FRCPC2; Stephen WP Kemp, PhD3; Christine A Webber, MD1
1University of Alberta, Edmonton, AB, Canada; 2Division of Physical Medicine and Rehabilitation, University of Alberta, Edmonton, AB, Canada; 3University of Michigan, Ann Arbor, MI

Introduction: Targeted muscle reinnervation (TMR) and regenerative peripheral nerve interfaces (RPNIs) have revolutionized neuroma pain management. Though each surgical technique is well-reported to decrease neuropathic pain following nerve injury, there remains considerable discord regarding the best treatment strategy. Our study provides the first head-to-head comparison of outcomes following TMR and RPNI surgery for the management of neuroma pain.
Methods: The tibial nerve of 30 Fisher rats was transected to allow for neuroma formation. Behavioural testing consisting of a ‘tap test’ to the site of the neuroma was performed weekly. Once painful neuromas were detected, animals were randomized to a) RPNI with a EDL muscle graft, b) TMR to the motor branch to biceps femoris, c) neuroma excision, and d) no further treatment where the neuroma was left in situ. Postoperatively weekly behaviour tests continued for an additional ten weeks. The TMR/RPNIs were harvested to quantify muscle reinnervation, and the dorsal root ganglia were harvested to assess for markers of injury (GFAP, ATF-3) and pain (TRPV1, CGRP, NP-Y).
Results: The thigh neuroma scores were documented for all animals. By ten weeks postoperative, animals that were treated with either TMR or RPNI had significantly decreased pain scores compared to the controls (p<0.01). Neuroma excision alone was insufficient to provide a significant analgesic effect. The neuromuscular interfaces of both TMR and RPNI specimens showed immunohistochemical evidence of motor reinnervation. In all cohorts, the sensory neuronal cell bodies maintained an upregulation of injury markers GFAP and AT3; however, the pain markers TRPV1, CGRP, and neuropeptide-Y similarly and significantly decreased in the TMR and RPNI groups (p<0.05).
Conclusion: Both RPNI and TMR similarly significantly improve pain outcomes following neuroma resection. RPNI and TMRs are clinically feasible techniques for improving outcomes for patients with nerve injuries or undergoing amputation.


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