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

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.