Outcomes of primary reverse total shoulder arthroplasty in patients younger than 65 years: A systematic review.

BACKGROUND: Reverse total shoulder arthroplasty (RTSA) is increasingly performed in younger patients, yet prior studies frequently include heterogeneous cohorts and revision cases. This systematic review evaluated outcomes of primary RTSA in patients <65 years. METHODS: Embase, PubMed, and CENTRAL were queried through October 2025. Methodological quality was assessed using the Newcastle-Ottawa Scale (level III) and NIH Quality Assessment Tool for Case Series (level IV). Random-effects meta-analysis generated pooled estimates for range-of-motion (ROM), patient-reported outcome measures (PROMs), and complication/revision rates. RESULTS: Thirteen studies (nine level III, four level IV; fair-to-good quality) were included. Weighted mean age was 55.4 years (60.9% female; follow-up 2-7.8 years). Forward flexion = 133.2° (95% CI 126-140.4); external rotation = 38.1° (95% CI 32-44.2); abduction = 118.2° (95% CI 111.2-125.2); internal rotation = 3.7 (95% CI 2.7-4.7, 0-7 scale). ASES = 69.5 (95% CI 64.7-74.4); VAS = 2.6 (95% CI 1.3-3.9); Constant-Murley = 62.9 (95% CI 60.3-65.5); SST = 7.5 (95% CI 5.9-9.1); SPADI = 38 (95% CI 33.3-42.7); UCLA = 27.9 (95% CI 26.9-28.8). Complication rate was 13% (95% CI 6%-23%) and revision rate 8% (95% CI 5%-14%), most commonly for instability. Sensitivity analyses demonstrated significant pre-to-postoperative improvements in forward flexion (+46.6°; 95% CI 34.9-58.3) and external rotation (+16.6°; 95% CI 13.6-19.5). DISCUSSION: Primary RTSA in patients <65 years improves ROM and PROMs. Although complication/revision risk increases over time, these findings support RTSA in appropriately selected younger patients and provide benchmarks for outcome counseling.