Early Post-operative Pain Course Following Primary and Secondary Targeted Muscle Reinnervation - a Temporal Description of Pain Outcomes.

Introduction: Targeted muscle reinnervation (TMR) is an effective surgical treatment of neuropathic pain for amputees. However, limited data exists regarding the early post-operative pain course for patients who undergo either Primary (<14 days since amputation) or Secondary (≥14 days) TMR. This study aims to outline the post-operative pain course for Primary and Secondary TMR during the first six post-operative months, to aid in patient education and expectation management.

Methods: Patients were eligible if they underwent TMR surgery between 2017 and 2023. Prospectively collected patient-reported outcome measures of pain scores, Pain Interference, and Pain Intensity were analyzed. Multilevel mixed-effect models were utilized to visualize and compare pain courses between Primary and Secondary TMR patients.

Results: A total of 203 amputees were included, with 40.9% being Primary and 59.1% being Secondary TMR patients. Primary TMR patients reported significantly lower pain scores over the full 6-month post-operative trajectory (p<0.001) compared to Secondary TMR patients, with a difference of Δ-1.0 at day of TMR (Primary=4.5, Secondary=5.5), and a difference of Δ-1.4 at the 6-month mark (Primary=3.6, Secondary=5.0). Primary TMR patients also reported significantly lower Pain Interference (p<0.001) and Pain Intensity scores (p<0.001) over the complete trajectory of their care.

Conclusion: Primary TMR patients report lower pain during the first six months post-operatively compared to secondary TMR patients. This may reflect how pre-existing neuropathic pain is more challenging to mitigate through peripheral nerve surgery. The current trends may assist in both understanding the post-operative pain course and in managing patient expectations following TMR.