Metformin use and outcomes after arthroscopic full thickness rotator cuff repair: a real-world, propensity score-matched cohort study.

Abstract

PURPOSE: Evaluate the impact of preoperative metformin use on surgical outcomes and reoperation rates following arthroscopic rotator cuff repair. METHODS: Using the TriNetX database, patients with full-thickness rotator cuff tears undergoing arthroscopic repair were identified and stratified by preoperative metformin use (within 6 months to 2 weeks before surgery). Cohorts were matched 1:1 via propensity scores for comorbidities. Outcomes including stiffness, bursitis, reoperation, total shoulder arthroplasty (TSA), manipulation under anesthesia (MUA), and adhesive capsulitis were assessed at 3 months, 6 months, 1 year, and 2 years. RESULTS: Each cohort included 3049 patients. At 90 days, metformin users had lower cuff revision rates [1.41% vs. 2.16%, risk ratio RR 0.65 (95% confidence interval CI 0.45,0.95), p = 0.026)]. Postoperative stiffness remained consistently higher in the metformin group at all timepoints, including 90 days [11.58% vs. 7.77%, risk ratio RR 1.49 (1.27,1.74)], 6 months [12.66% vs. 9.12%, RR 1.39 (1.2,1.61)], 1 year [13.48% vs. 10.07%, RR 1.34 (1.17, 1.54)], and 2 years [13.91% vs. 10.56%; RR 1.32 (1.15, 1.51); all p < 0.0001]. Bursitis was more frequent at 1 year [9.77% vs. 8.17%, RR 1.20 (1.02, 1.41), p = 0.028] and 2 years [11.68% vs. 10.04%, RR 1.16 (1.01,1.34), p = 0.040]. Rates of TSA, MUA, and adhesive capsulitis were similar at all time points. CONCLUSION: Preoperative metformin is associated with increased postoperative stiffness but lower early cuff revision rates after RCR. These associations appear limited to the short term, while long-term outcomes suggest no increased risk of cuff revision surgery. Further studies are needed to explore underlying mechanisms. LEVEL OF EVIDENCE III: Retrospective study.