Responsiveness and internal validity of common patient-reported outcome measures following total shoulder arthroplasty

The Constant-Murley (Constant) score, Western Ontario Osteoarthritis of the Shoulder (WOOS) index, American Shoulder and Elbow Surgeons (ASES) score, and Single Assessment Numeric Evaluation (SANE) score are commonly used to assess patient-reported function following shoulder surgery. However, psychometric properties for these tools are mostly unknown for patients with primary glenohumeral arthritis who have undergone anatomic total shoulder arthroplasty (TSA). The purposes of this study were to (1) compare the responsiveness and internal validity between the 4 patient-reported outcomes (PROs) and (2) identify PRO score values associated with patient satisfaction after TSA. A total of 234 primary TSAs were performed for primary glenohumeral osteoarthritis with a 2-year or greater follow-up. The Constant score, WOOS index, ASES score, SANE score, and patient satisfaction were assessed preoperatively and 2 to 5 years postoperatively. Effect sizes, standardized response means, and relative efficiency were calculated to determine responsiveness, and internal validity was determined via the presence of floor and/or ceiling effects. Receiver operator characteristic (ROC) curves were constructed to identify the minimum outcome score that could correctly identify a satisfied patient. At final follow-up, 88% of patients were satisfied. The PROs had large effect sizes and standardized response means (≥0.83). The minimum score that most correctly identified a patient as satisfied was 78 for ASES score, 18 for WOOS index, 73 for Constant score, and 58 for SANE score. However, the ASES score, WOOS index, and SANE score had marked postoperative ceiling effects, whereas the Constant score was the most responsive and internally valid tool. These results suggest that the Constant score should serve as the primary PRO for patients with primary glenohumeral arthritis, whereas the WOOS index, ASES score, and SANE score could be supplementary assessments.