Targeted muscle reinnervation after traumatic or elective upper-extremity amputation: a systematic review and meta-analysis.

OBJECTIVE: To systematically evaluate functional recovery and prosthetic control following targeted muscle reinnervation (TMR) or TMR-based reconstruction in patients with upper extremity amputation or severe brachial plexus injury. METHODS: PubMed, Embase, Web of Science, Scopus, and the Cochrane Library were searched for studies reporting standardized functional outcomes before and after TMR. Two reviewers independently performed study selection, data extraction, and methodological quality assessment using the Methodological Index for Non-Randomized Studies (MINORS). Because most studies did not report the standard deviation of paired changes or within-participant correlations, preoperative and postoperative summary data were synthesized using mean differences (MDs) or standardized mean differences (SMDs) as exploratory estimates. Potentially overlapping cohorts were identified by comparing study centers, recruitment periods, authorship, and participant characteristics. RESULTS: Six eligible reports representing five independent patient cohorts were included. MINORS scores ranged from 9 to 12 out of 16, indicating important methodological limitations. Postoperative Southampton Hand Assessment Procedure (SHAP) scores improved significantly (MD = 31.45, 95% CI 6.69-56.21), although substantial heterogeneity was observed (I 2 = 83%). Disabilities of the Arm, Shoulder and Hand (DASH) scores showed a significant reduction in self-reported disability after direction harmonization (MD = 21.91, 95% CI 10.85-32.97; I 2 = 0%). A single study reported a significant improvement in Action Research Arm Test (ARAT) scores (MD = 22.00, 95% CI 10.29-33.71), while another reported an increase in OPUS upper-extremity function scores (mean change = 2.7, 95% CI 2.3-3.2). Sensitivity analysis including combined TMR and osseointegration produced a similar DASH effect. CONCLUSION: Current evidence suggests that TMR-based reconstruction may improve prosthetic task performance and perceived upper-limb function. However, the findings remain preliminary because of small samples, heterogeneous procedures, incomplete paired-data reporting, and the frequent use of TMR within multicomponent reconstructive programmes. Larger prospective multicenter studies using standardized functional outcomes are required. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251002627, identifier (CRD420251002627).