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Regenerative Peripheral Nerve Interface Surgery at the time of Major Lower Limb Amputations: One-Year Outcomes
Nishant Ganesh Kumar, MD1; Carrie A Kubiak, MD1; Jennifer B Hamill, MPH1; Hyungjin M Kim, ScD1; Melissa J Tinney, MD1; Randy S Roth, MD, PhD1; Michael E Geisser, MD, PhD1; Paul S Cederna, MD2; Stephen WP Kemp, PhD1; Theodore A Kung, MD3
1University of Michigan, Ann Arbor, MI; 2Plastic Surgery, University of Michigan, Ann Arbor, MI; 3Section of Plastic & Reconstructive Surgery, University of Michigan, Ann Arbor, MI

Introduction: Postamputation pain is a debilitating condition that affects individuals with amputation. Regenerative peripheral nerve interface (RPNI) surgery has been performed prophylactically at the time of major lower limb amputation to prevent postamputation pain. We present 1-year preliminary findings of a prospective clinical trial examining the efficacy of prophylactic RPNI surgery. We hypothesized better patient reported outcomes (PROs) for neuroma pain, phantom limb pain, prosthetic use, and psychosocial wellbeing for patients undergoing prophylactic RPNI surgery at the time of major lower limb amputation than for patients undergoing standard of care amputation.

Methods: Patients undergoing major lower limb amputation were assigned to either the prophylactic RPNI group or control group based on if they underwent standard of care major lower limb amputation (control group) or amputation with prophylactic RPNI surgery (prophylactic group). Postoperative outcomes at 1-year were compared between the prophylactic and control groups. PROs were collected using the Patient-Reported Outcomes Measurement Information System (PROMIS) instruments for Pain Intensity and Pain Interference, Neuropathic Pain Score (NPS), Short-Form McGill Pain Questionnaire (SF-MPQ), Amputation Pain Survey, Phantom Pain Survey, PCS (Pain Catastrophizing Scale), PHQ-9 (Patient Health Questionnaire-9), GAD-7 (Generalized Anxiety Disorder-7), and Orthotics and Prosthetics Users’ Survey (OPUS). Statistical analysis includes calculation of standardized mean difference (effect size, d) and t-tests.

Results: In total, 49 patients are included in the analytic cohort. One-year post-operative outcomes are presented in Table 1. In general, PROs in the prophylactic group were superior compared to the control group. Greatest effect sizes were noted in the domains of amputation pain (d=-1.19, p<0.01) and phantom limb pain (d=-1.15, p=0.01) among prophylactic RPNI patients compared to controls. Prophylactic RPNI surgery was also associated with better patient-reported scores on measures for pain (PROMIS), depression (PHQ-9), and prosthetic use (OPUS).

Conclusion: Prophylactic RPNI surgery is advantageous for patients undergoing major lower limb amputation. At 1-year following major lower limb amputation with prophylactic RPNI surgery, the greatest effects were noted for patients on outcomes measuring amputation pain and phantom limb pain compared to controls. Furthermore, RPNI surgery is associated with better prosthetic use and psychosocial wellbeing. These findings should encourage surgeons to consider performing RPNI surgery prophylactically at the time of major lower limb amputation.

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