Targeted Muscle Reinnervation for Amputees: Mechanism, Outcomes, and Future Applications

Amputation has a significant negative effect on patients' quality of life, and often results in complications including painful neuromas, residual limb pain, and phantom limb pain in up to 75% of patients. At the same time, intuitive control of myoelectric prostheses presents a significant rehabilitation challenge. Targeted muscle reinnervation is an innovative microsurgical procedure that solves both problems. Targeted muscle reinnervation was initially conceived to enhance electromyographic signals for targeted upper-extremity bioprosthetics, and entails the transfer of severed peripheral nerves to redundant motor branches of functionally expendable muscle. This allows for a vascularized scaffold and a target for transected nerves, thus eliminating the formation of disorganized axonal sprouts that may form the basis of a neuroma. In this review, comparative and quantitative data from recent clinical trials, prospective cohorts, and meta-analyses are reviewed to assess the two-fold efficacy of targeted muscle reinnervation. Acute and delayed targeted muscle reinnervation is shown to reduce pain scores, opioid use, and symptomatic neuroma recurrence when compared to traction neurectomy. Moreover, targeted muscle reinnervation dramatically increases walking ability (in lower-extremity amputees) and has high success rates in intuitive myoelectric control (in upper-extremity amputees). This review, which combines quantitative results from several studies, supports consideration of targeted muscle reinnervation as standard-of-care surgery to prevent neuropathic pain and to enhance the performance of prostheses.