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Targeted Muscle Reinnervation versus Regenerative Peripheral Nerve Interface at Time of Below-the-Knee Amputation: Prospective Comparison of Patient-Reported Outcomes and Complications
Brian L Chang, MD1; Alison Hill, BS2; Attinger Christopher, MD, FACS3; Grant M. Kleiber, MD4
1Georgetown University, Washington, DC; 2Georgetown Medical School, Washington, DC; 3Plastic and Reconstructive Surgery/Wound Healing Center, MedStar Georgetown University Hospital, Washington, DC; 4Medstar Georgetown University Hospital, Washington, DC

Introduction Primary physiologic nerve stabilization at the time of major extremity amputation is critical in reducing the risk of post-amputation pain from stump neuromas and phantom limb pain. The two most common techniques are targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI). Each technique has its proponents and critics, and each technique has demonstrated clinical success in reducing post-amputation pain. No studies have compared TMR and RPNI to date. The goal of this study was to compare clinical and patient-reported outcomes in patients undergoing TMR versus RPNI at the time of below-the-knee-amputation (BKA).
Materials and Methods This is a prospective, single-center study of patients undergoing non-traumatic BKAs by a single amputation surgeon and a single peripheral nerve surgeon. Either TMR or RPNI was performed on the superficial peroneal nerve (SPN), tibial nerve, and saphenous nerve. The deep peroneal nerve (DPN) and sural nerve were treated with traction neurectomies. Patient charts were reviewed for demographic information including the medical comorbidities in the Charlson Comorbidity Index (CCI), inpatient pain medications, pain medications at most recent follow-up, and any complications requiring a change in management. Patients were asked to answer the PROMIS Pain Intensity for residual limb pain (RLP) and phantom limb pain (PLP), PROMIS Pain Interference, and were asked about their degree of ambulation.
Results 27 patients were included in this study, 15 in the TMR cohort and 12 in the RPNI cohort. The average age was 61 years and average CCI was 5.1. There were no significant demographic differences between the cohorts. 20% of TMR patients required an operative revision of their amputation stump, compared to 25% of RPNI patients. 6.7% of TMR patients remain on narcotics, compared to 8.3% for the RPNI cohort. Average PROMIS Intensity scores for the TMR cohort were 45.9 for RLP and 48.4 for PLP, compared to 49.9 (P = 0.52) and 46.3 (P = 0.74), respectively, for the RPNI cohort. Average PROMIS Interference scores were 59.6 and 62.3 (P = 0.35). Ambulation rates were 86.7% for the TMR cohort and 83.3% for the RPNI cohort (P = 0.85).
Conclusions This study is the first to demonstrate that both TMR and RPNI have superior patient-reported pain outcomes, relative to rates in the literature, with similar complication profiles. The most important takeaway is that physiologic nerve stabilization at time of major extremity amputation, regardless of technique, should be offered to all patients.


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