Background and aims: Advanced osteoarthritis of the shoulder joint is associated with significant pain and disability. There is minimal information on substantial clinical benefit (SCB) and responsiveness of the American Shoulder and Elbow Surgery (ASES) score, the relative Constant Murley score (CMS) and the Western Ontario Osteoarthritis of the Shoulder (WOOS) index following shoulder arthroplasty. The purpose of this study was to examine the SCB and responsiveness of these three outcome measures based on patient’s report of change at six months and two years following surgery. 
Methods: Methods: The SCB and responsiveness were calculated based on external anchors related to change in pain, range of motion (ROM) and ability to carry out activities of daily living (ADL). The areas under curve (AUCs) represented responsiveness.  Results: The data of 159 and 131 patients with complete follow-up at six and two years were reviewed. The SCB for pain at 6 months varied from 29.1-39.5 and increased to 48.9-53.3 at 2 years. A similar pattern of increased SCB values was observed for ROM and ADL for all measures over time. Responsiveness of all measures was high (AUCs >0.80) at 6 months and further improved at two years (AUCs >0.86). There were no statistically significant differences between the AUC values of the ASES and CMS when compared with the WOOS (P>0.05). Conclusion: The lack of a difference in responsiveness between the joint-specific outcomes and a diseases-specific measure demonstrates equivalence, as opposed to superiority of the WOOS over the ASES and CMS.

SUBSTANTIAL CLINICAL BENEFIT OF COMMON OUTCOME MEASURES FOLLOWING SHOULDER ARTHROPLASTY