Risk Factors Associated with Secondary Surgical Procedures for Pain following Initial Regenerative Peripheral Nerve Interface (RPNI) Surgery
Jennifer C Lee, MD1, Widya Adidharma, M.D.1, Paul S Cederna, M.D.2, Stephen WP Kemp, Ph.D.1 and 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 an innovative procedure that involves implanting a transected nerve into an autologous free muscle graft. By providing nerves with physiologic targets, RPNI surgery can prevent neuroma formation. Previously, clinical studies demonstrated that RPNI surgery is highly successful with 75-85% of patients having improved pain outcomes. However, these studies did not investigate the subset of patients who had suboptimal outcomes following their initial RPNI surgery for pain. The purpose of this study is to assess the risk factors associated with unsatisfactory RPNI surgical outcomes.
Material & Methods:
This retrospective review included patients who underwent RPNI surgery for treatment or prevention of neuropathic pain at the University of Michigan from 2014 to 2021. Inclusion criteria included pediatric and adult patients with at least a 6 month follow up period. The primary outcome of this study was the need for a secondary surgical procedure for pain after initial RPNI surgery. Chi-square and student t tests were used to assess which clinical risk factors were independently associated with patients undergoing secondary surgery (Table 1). Multivariate regression (MVR) analysis was performed by using clinical factors demonstrating a bivariate analysis p-value of less than 0.1. All analyses were done using SPSS software.
Results
In total, 214 patients met inclusion criteria. Twenty-seven patients (12.6%) underwent a secondary surgical procedure after initial RPNI surgery for the treatment or prevention of neuropathic pain. Sixty-six percent of patients with secondary surgery had the subsequent surgery on different nerves from their initial RPNI surgery. Eleven patients had >=2 subsequent surgery. MVR analysis revealed that female gender, a preoperative history of chronic pain, previous surgical treatment for pain, and phantom limb pain significantly predisposes patients to higher odds of undergoing a secondary surgery (Table 2).
Conclusion
RPNI surgery is effective for treating or preventing neuropathic pain with only 12.6% of patients undergoing secondary surgeries. It is likely that an unmasking effect occurs after initial RPNI surgery which explains why different nerves are commonly the source of persistent pain. This study identifies specific risk factors that can predict potentially suboptimal results after initial RPNI surgery.
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