Targeted Muscle Reinnervation: Factors Predisposing to Successful Pain Score Reduction

Introduction: Targeted muscle reinnervation (TMR) has demonstrated efficacy in reducing neuroma and phantom limb pain. Here we investigated postoperative outcomes in our patient cohort, with a focus on the role of nonmodifiable factors such as patient age and gender. Methods: Patients who had extremity TMR from April 2018 to October 2022 were reviewed. Outcomes of interest included patient age, gender, cause and type of amputation, delayed vs immediate TMR, as well as postoperative improvement in pain as assessed by numerical rating score (NRS). Results: A total of 39 patients underwent 46 TMR with a mean age of 45.9 ± 17.2 years. Delayed TMR (27, 58.7%) was most commonly performed, followed by immediate and delayed-immediate at 10 (21.7%) and 9 (19.6%), respectively. Amputation level was most commonly above-knee in 20 (43.5%) patients, followed by below-knee (11, 23.9%), transhumeral (9, 19.6%), and transradial (6, 13.0%). The median time interval between amputation and TMR was 12 months. The median preoperative NRS score for patients that underwent delayed TMR was 10. At the last follow-up, 33 (71.7%) patients had more than 50% resolution of pain. The median postoperative NRS for all patients was 0 (IQR25-75: 0-4) and significantly improved compared to preoperative NRS (P <0.001). There was a significant difference in median postoperative NRS by gender (3.5 in men and 0 in women) (P<0.05). Postoperative median NRS also favored younger patients (0, <50 yrs; 4, >50 yrs; P<0.05). Conclusion: TMR showed high efficacy in our cohort, with improved outcomes in women and younger patients.