A review of pain outcomes following targeted muscle reinnervation in lower extremity limb pain

Abstract

Approximately 75% experience phantom (PLP), residual (RLP), or general (GLP) limb pain following lower extremity amputation. Targeted muscle reinnervation (TMR) is a peripheral nerve transfer that reroutes amputated nerves to motor endplates that can prevent or treat limb pain. This systematic review summarizes pain outcomes following primary and secondary treatment of lower extremity PLP, RLP, and GLP. Primary literature review of three databases - PubMed, EMBASE, MEDLINE - were used for all articles related to TMR and lower extremity limb pain, querying the same keywords: “targeted muscle reinnervation” AND “pain”. Citations were then reviewed and eliminated if only upper extremities were studied or the study lacked pain outcomes. Citations were categorized as primary or secondary TMR. Pain outcomes, including Numerical Rating Scales (NRS) and Patient-Reported Outcome Measurement Information System (PROMIS) Pain scores, were aggregated when appropriate. Ten studies met all inclusion and exclusion criteria after formal review for a total of 431 extremities, of which 79.1% (n = 341 limbs) were lower extremities. Average primary TMR PROMIS scores for PLP and RLP were lower than amputees without primary TMR. Average NRS scores and PROMIS Pain scores in secondary TMR demonstrated improvements in PLP, RLP, and GLP. Primary and Secondary TMR does prevent and improve PLP, RLP, and GLP; however, a minority of studies report quantifiable pain outcomes. All future TMR studies should include validated pain outcomes to better quantify the expected pain and quality of life improvements after lower extremity TMR.