Shoulder outcome scoring systems have substantial ceiling effects 2 years after arthroscopic rotator cuff repair.

<bold>Purpose: </bold>Previous studies show no difference in clinical outcomes between patients with healed and structurally failed rotator cuff repairs. The objective of this study was to assess ceiling effects when reporting surgical outcomes of arthroscopic rotator cuff repair using four of the currently most popular clinical shoulder outcome scoring systems.<bold>Methods: </bold>Ninety-two patients who underwent arthroscopic rotator cuff repair were examined. The simple shoulder test (SST), American Shoulder and Elbow Surgeons (ASES) score, University of California at Los Angeles (UCLA) shoulder rating scale, and Constant-Murley shoulder score were completed 2 years postoperatively. Demographic data of the subjects were analysed using descriptive statistics. The ceiling effects in the outcome data assessed for each scale were estimated based on two previously reported definitions.<bold>Results: </bold>The number of patients with the maximum possible score was 31 (33.7%) with the SST, 26 (28.3%) with the ASES score, 28 (30.4%) with the UCLA scale, and 18 (19.6%) with the Constant-Murley score. The standardised distance of the outcome data assessed by the SST, ASES score, UCLA scale, and Constant-Murley scores were 0.92, 0.97, 0.96, and 1.18, respectively.<bold>Conclusion: </bold>The SST, ASES score, and UCLA scale evaluated at 2 years postoperatively have substantial ceiling effects showing that the proportion of patients with the maximum possible score is > 20%, and the standardised distance is < 1.0. Researchers should be aware of possible biases due to ceiling effects when interpreting the results of studies investigating the surgical outcomes of arthroscopic rotator cuff repair. It could increase the likelihood of a type II error.<bold>Level Of Evidence: </bold>IV. [ABSTRACT FROM AUTHOR]