Predictive Value of Preoperative Pain Sketches in Lower Extremity Amputees Undergoing Secondary Targeted Muscle Reinnervation for Treatment of Neuropathic Pain

Early Postoperative Pain Course following Primary and Secondary Targeted Muscle Reinnervation: A Temporal Description of Pain Outcomes

BACKGROUND

 Targeted muscle reinnervation (TMR) is an effective surgical treatment of neuropathic pain for amputees. However, limited data exist regarding the early postoperative pain course for patients who undergo either primary (<14 days since amputation) or secondary (≥14 days) TMR. This study aims to outline the postoperative pain course for primary and secondary TMR during the first 6 postoperative 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-effects 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 postoperative trajectory (p < 0.001) compared with secondary TMR patients, with a difference of Δ -1.0 at the 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 6 months postoperatively compared with 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 postoperative pain course and managing patient expectations following TMR.

LEVEL OF EVIDENCE

 Therapeutic - IV.

Targeted muscle reinnervation at the time of amputation to prevent the development of neuropathic pain

INTRODUCTION

Targeted muscle reinnervation (TMR) is an established modality for the surgical management of neuropathic pain. Although the preventive effect of primary (acute) TMR at the time of amputation has been demonstrated previously, it remains unclear how many and which patients benefit most. Therefore, this study investigated the proportion of patients achieving sustained pain prophylaxis following amputation, as well as factors associated with its efficacy.

METHODS

Primary patients who underwent TMR with a minimum follow-up of 6 months between 2018 and 2023 were enrolled. Pain outcomes (numeric rating scale [NRS], 0-10), comorbidities, and surgical factors were collected from chart review. Patients achieving sustained pain prophylaxis (NRS of ≤3 for ≥3 months until final follow-up) were identified. Multilevel mixed-effect models and multivariable regression were used to visualize pain courses and identify associated factors.

RESULTS

Seventy-five patients who underwent primary TMR were included (median follow-up: 2.0 years), of whom 57.3% achieved sustained pain prophylaxis whereas 26.7% reported pain disappearance. Distal amputation levels (p = 0.036), a lower Elixhauser Comorbidity Index (p = 0.001), and the absence of psychiatric comorbidities (p = 0.039) were associated with pain prophylaxis.

CONCLUSION

This study demonstrates that more than half of all patients undergoing primary TMR achieved sustained pain prophylaxis, and approximately a quarter of patients achieved sustained pain disappearance. Several factors associated with these favorable outcomes are described. These results will aid in preoperative counseling, managing patient expectations, and selecting patients who may benefit most from primary TMR surgery.

LEVEL OF EVIDENCE

IV - Therapeutic.