Longitudinal Durability of Patient-Reported Pain Outcomes after Targeted Muscle Reinnervation at the Time of Major Limb Amputation

Background: Phantom limb pain (PLP) and residual limb pain (RLP) are debilitating sequelae of major limb amputation. Targeted muscle reinnervation (TMR), when performed at the time of amputation, has been shown to be effective for management of this pain; however, its long-term effects and the longitudinal trend of patient-reported outcomes is unknown. The purpose of this study was to characterize the longitudinal patient-reported outcomes of pain and quality of life following TMR at the time of initial amputation.

Study design: A prospective case series of patients undergoing major limb amputation with TMR performed at the time of amputation were followed from October 2015 to December 2020 with outcomes measured 3, 6, 12, and 18 months or longer after amputation and TMR. Outcomes included patient-reported severity of PLP and RLP as measured by the numeric rating scale (NRS). Secondary outcomes included the Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference and Pain Behavior Questionnaires.

Results: Eighty-one patients with 83 treated limbs were included in the study, and 23 patients completed surveys at 18 months or later, with an average follow-up time of 2.4 years. By 3 months after operation, all patient-reported outcomes for PLP and RLP were consistent with previously reported data that demonstrated superiority to non-TMR amputees. Mixed-model linear regression analysis showed that PLP NRS severity scores continued to improve over the study period (p = 0.022). The remaining outcomes for RLP severity and PROMIS quality-of-life measures demonstrated that these scores remained stable over the study period (p > 0.05).

Conclusion: TMR is an effective surgical procedure that improves the chances of having reduced RLP and PLP when performed at the time of amputation, and our study demonstrates the long-term durability of its efficacy.