139 Evaluating the Evidence: A Systematic Review of Targeted Muscle Reinnervation for Post-Amputation Phantom and Residual Limb Pain

Abstract

INTRODUCTION: Over 2 million amputees in the US suffer from chronic pain related to their residual or phantom limb. Nerve ablation and neuroma excisions with transposition of remaining nerve fascicles into a more favorable microenvironment are two current pain-reducing procedures for post-amputation phantom and residual limb pain (PAP). Targeted Muscle Reinnervation (TMR) is an emerging technique that removes the terminal neuroma and attaches the nerve to a nearby motor neuron. This approach has gained wide acceptance for PAP, despite no clear consensus on the superiority of TMR over other approaches. METHODS: Eligible studies were attained using the PRISMA guidelines including those that evaluated TMR for treatment of PAP. The primary outcome was pain resolution. A computerized search of MEDLINE/ PubMed, Ovid and Embase from inception to March 2021 was conducted for the terms “Targeted Muscle Reinnervation” AND (“pain” OR “neuroma”). Two independent researchers evaluated each study, assigning a level of evidence according to the American Association of Neurology (AAN) algorithm; a third independent researcher resolved any discrepancies with assignments. Data extracted included the level of amputation, time from amputation to TMR, time from TMR to follow-up and reported pain scale(s). RESULTS: Of the 23 studies included in the analysis, only one study was a randomized controlled study (level I) with 28 patients, and three studies were level II evidence. The remaining 19 studies were found to be level IV evidence. The RCT results demonstrated that the difference in pain scale scores in the TMR versus the standard of care group was not statistically significant. The low-level studies suffered from high selection bias, lack of comparison cohorts, inconsistent outcomes, variable procedure locations, and variable time from amputation to TMR. Only 16 (69.6%) studies used validated patient-reported pain scales, including numerical rating scale and/ or PROMIS. CONCLUSION: There is insufficient and poor evidence to recommend TMR over standard neuroma excision for the reduction of PAP. The literature remains inconsistent due to the lack of validated pain scale data and variable results based on the amputation/ TMR site. This highlights the importance for a national registry to compare outcomes across surgical techniques.