28. Traumatically Injured Muscle Model In Regenerative Peripheral Nerve Interface

PURPOSE: Regenerative Peripheral Nerve Interfaces (RPNIs) enhance prosthetic control and reduce post-amputation neuroma pain through implantation of transected nerves into autologous muscle grafts. Typically, the grafts are harvested from healthy donor muscle distant from the amputation site. However, using injured muscle from the amputated limb could avoid additional donor site risks including infection, pain, and scaring. This study compares the muscle regeneration, synapse formation, and signal amplification in RPNIs constructed with either crushed or non-crushed muscle grafts in rats. The crushed grafts represented traumatically injured muscle. METHODS: We constructed 72 RPNIs by securing the common peroneal (CP) nerve into autologous extensor digitorum longus (EDL) muscle graft. We randomly assigned rats to either crush or non-crush groups. In the crush group, we crushed the EDL graft with a hemostat for 30 seconds before implantation. We evaluated RPNI function by stimulating the CP nerve and recording compound muscle action potentials (CMAPs) from the RPNIs at one, three, and six months postoperative (POM). We evaluated muscle graft regeneration and synapse formation by examining neuromuscular junction (NMJ) morphology, percent embryonic myosin (PEM), percent centralized nuclei (PCN) and percent fibrosis (PF) using immunohistochemistry and hematoxylin and eosin staining. RESULTS: Mean CMAPs, PEM, PCN, and PF for all three POM can be found. Comparison of CMAPs, PEM, PCN and PF using a two-way analysis of variance (ANOVA) for crush vs non-crush RPNIs at all three POMs did not reveal a significant interaction [CMAPs: F (2, 27) = 0.1407, p = 0.2622; PEM: F(2, 27) = 0.1800, p = 0.1846; PCN: F(2, 28) = 0.7159, p = 0.4975; PF: F(2, 28) = 0.1657, p = 0.8481]. Main effect analysis showed that crush vs non-crush RPNIs did not have a statistically significant effect on either CMAPs (p = 0.9757), PEM (p = 0.4357), PCN (p = 0.7361), or PF (p = 0.0768). Qualitatively, NMJ morphology did not appear different between crushed and non-crushed RPNIs. CONCLUSION: Our findings indicate no significant differences in functional or structural outcomes between crushed and non-crushed muscle grafts in RPNIs. These results suggest that crushed muscle from traumatic injury may be used to construct RPNIs, simplifying the surgical process and reducing risks associated with additional donor sites.