Responsiveness and clinically important differences of the Western Ontario Rotator Cuff (WORC) Index in surgical and non-surgical treatment groups with different follow-up periods: A systematic review and meta-analysis

Background: This study reviews and meta-analyzes the responsiveness and minimal clinically important difference (MCID) of the Western Ontario Rotator Cuff (WORC) Index for various patient populations and treatment durations. Methods: A comprehensive search in PubMed, Embase, Web of Science, and CINAHL identified studies on the responsiveness or MCID of the WORC in shoulder conditions. Two authors independently screened articles. Study quality was appraised using COSMIN and GRADE guidelines. Responsiveness was evaluated using anchor-based MCID and distribution-based standardized mean differences (SMDs) computed with Hedges' g. A random-effect model addressed study variability, and heterogeneity was assessed with the chi-squared test and I² statistic. Results: The 12 studies yielded high-quality evidence supporting the WORC's responsiveness. A meta-analysis of 1326 observations revealed a significant overall effect size (SMD) of 0.91 (95% CI: 0.56 to 1.26; p < 0.0001), with high heterogeneity (I² = 91.2%). Subgroup analyses showed larger effect sizes for long-term follow-ups (SMD = 1.28) and surgical treatments (SMD = 1.14). The average MCID was 17 for conservative treatments within six months, 26 for surgical procedures, and 29 for follow-ups over six months. Conclusion: The WORC measures improvements in rotator cuff conditions, with varying MCID values for different treatments and durations.