American Society for Peripheral Nerve
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1 Four-Year Pain and Medication Intake Outcomes Following Regenerative Peripheral Nerve Interface (RPNI) Surgery for Treatment or Prevention of Postamputation Pain
Jennifer C Lee, MSE1; Nishant Ganesh Kumar, MD1; Stephen WP Kemp, PhD1; Paul S Cederna, MD2; 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: Regenerative peripheral nerve interface (RPNI) surgery is a validated method for mitigating pain in postamputation patients. However, the long-term efficacy of RPNI surgery has yet to be fully characterized. The purpose of this clinical study was to assess long-term pain outcomes and opioid medication intake in amputation patients who have undergone RPNI surgery for the treatment or prevention of postamputation pain.
Materials and Methods: Patients included in this study underwent RPNI surgery between 2014 and 2021 for the treatment or prevention of postamputation pain and had at least one-year follow-up. A retrospective review was performed to collect preoperative demographic and clinical information. Outcomes for neuroma pain and PLP were assessed from the medical records at both the 1-year and the most recent follow-up visits. Postoperative pain was compared to preoperative pain and categorized into the following outcomes: no symptoms, improved symptoms, stable symptoms, or worsened symptoms. Opioid prescriptions were obtained through the EMR at preoperative and follow-up visits and converted to morphine milliequivalents (MME) based on dosage and type of opioid medication.
Results Seventy-seven patients met inclusion criteria in this study. Thirty-seven patients underwent RPNI surgery to treat preexisting postamputation pain (treatment group) and 40 patients underwent prophylactic RPNI surgery at the time of amputation (prophylactic group). Fifty-five patients (26 in the treatment group and 29 in the prophylactic group) had additional follow-up visits after the one-year postop time frame. Average time from surgery at most recent follow-up was 50 months (4.2 years). For the treatment group, at time of most recent follow-up, favorable neuroma pain and PLP outcomes (no reported symptoms or improved symptoms) were seen in 77% and 61% of patients, respectively (Table 1). For patients treated prophylactically, 97% of patients had no recorded neuroma pain or PLP at time of most recent follow-up visit (Table 2). Average MME at time of most recent follow-up was also lower for both the treatment group (-12 +/- 83) and prophylactic group (-40 +/- 103).
Conclusion This study demonstrates the long-term clinical benefits of RPNI surgery on improving neuroma pain and PLP as well as a reduction of opioid intake for amputation patients who underwent the procedure. These findings suggest that the benefits of RPNI surgery on pain outcomes are highly favorable, and thus this surgery should be considered for all amputation patients.


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