The Current State of Targeted Muscle Reinnervation: A Systematic Review

Background Targeted muscle reinnervation (TMR) is growing in popularity; however, literature evaluating patient characteristics and outcomes is limited. Methods The EMBASE database was queried with the search terms targeted muscle reinnervation OR TMR AND outcomes OR patient outcomes. Clinical human studies in English were eligible for inclusion, yielding 89 articles. After rigorous exclusion criteria, a total of 13 articles were included in this review. Study data including geographic location, patient demographics, TMR indication, amputation level, number of nerve transfers performed, length of follow-up, and reported outcomes were extracted and analyzed. Results The included articles represent 338 patients (341 limbs). Average patient age was 47.4 years. Indication for amputation included trauma (n = 125), infection (n = 76) cancer/tumor resection (n = 71), ischemia (n = 18), failed Charcot reconstruction (n = 15), failed hardware (n = 9), burn (n = 4), and CRPS (n = 4). Five studies included upper extremity TMR only, two included lower extremity TMR only, and six included both upper and lower extremity TMR. TMR was performed in an immediate or delayed fashion, with an average of 2.2 nerve transfers performed per limb overall. Average length of follow-up was 22.3 months. In three studies, patients with phantom limb pain undergoing delayed TMR were found to have significant or trending toward significant reduction in pain after TMR using numeric rating scale and patient-reported outcomes measurement information system scales. One article reported 9/10 patients with improved or complete resolution of phantom limb pain after delayed TMR. Three studies found that patients undergoing immediate TMR had lower pain scores compared with non-TMR controls. Conclusion While there is evidence that TMR reduces neuroma-related pain and improves the quality of life for amputees, further outcomes studies are needed to study the patient experience with TMR on a larger scale. Establishing standardized, validated patient-reported outcomes assessment tools is critical to future investigation in this field.