Preliminary Results of a Clinical Trial to Determine the Efficacy of Regenerative Peripheral Nerve Interfaces for Postamputation Pain after Lower Limb Amputation
Nishant Ganesh Kumar, MD1, Carrie A Kubiak, MD1, Jennifer B Hamill, MPH1, Hyungjin M Kim, ScD1, Stephen WP Kemp, PhD1, Melissa J Tinney, MD1, Randy S Roth, MD, PhD1, Paul S Cederna, MD2, Michael E Geisser, MD, PhD1 and Theodore A Kung, MD3, (1)University of Michigan, Ann Arbor, MI, (2)Plastic Surgery, University of Michigan, Ann Arbor, MI, (3)Section of Plastic & Reconstructive Surgery, University of Michigan, Ann Arbor, MI
Introduction: The regenerative peripheral nerve interface (RPNI) has been previously shown to reduce neuroma and phantom limb pain. We present preliminary findings of a prospective clinical trial examining the efficacy of RPNI surgery to treat and prevent postamputation pain in patients with lower limb amputations. We hypothesize that RPNI surgery will result in a reduction in neuroma pain and phantom limb pain. We also anticipate an associated improvement in prosthetic use and psychosocial wellbeing.
Methods: Participants are recruited into either: Arm 1 (patients with lower limb amputations undergoing RPNI surgery to treat existing painful neuromas); or Arm 2 (patients undergoing RPNI surgery prophylactically at the time of new lower limb amputation with a cohort of controls without RPNI surgery). In Arm 1, postoperative outcomes at 4 months are compared to preoperative values. In Arm 2, postoperative outcomes at 4 months are compared between RPNI patients to controls. Primary outcomes are ascertained using the Short Form McGill Pain Questionnaire (SF-MPQ), Patient-Reported Outcomes Measurement Information System (PROMIS) instruments for Pain Intensity and Pain Interference, Orthotics and Prosthetics Users' Survey (OPUS), PCS (Pain Catastrophizing Scale), PHQ-9 (Patient Health Questionnaire-9), and GAD-7 (Generalized Anxiety Disorder-7). Analyses includes calculation of standardized mean difference (effect size, d) to determine the efficacy of RPNI surgery.
Results: To date, 45 patients have enrolled in the study. Preliminary data are presented in Table 1 and Table 2. There was a trend towards improvement in all outcomes. In Arm 1, the greatest effect size was observed for lessening Pain Interference (d=0.64, p=0.09) and Pain Intensity (d=0.55, p=0.16). In Arm 2, the greatest effect size was noted in better prosthetic use (d=1.14, p=0.06) and reduced phantom limb pain (d=0.71, p=0.05) among RPNI patients compared to controls.
Conclusion: Early results of this clinical trial to determine the efficacy of RPNIs across a range of clinical parameters show favorable trends. RPNI surgery has greatest effects when used to prevent phantom limb pain and associated improvement in prosthetic use. We expect these findings to provide preliminary data to consider adopting RPNI surgery to mitigate and prevent postamputation pain.
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