Responsiveness and minimal clinically important change: a comparison between 2 shoulder outcome measures

Study Design: A prospective cohort study nested in a randomized controlled trial. Objectives: To determine and compare responsiveness and minimal clinically important change of the modified Constant score (CS) and the Oxford Shoulder Score (OSS). Background: The OSS and the CS are commonly used to assess shoulder outcomes. However, few studies have evaluated the measurement properties of the OSS and CS in terms of responsiveness and minimal clinically important change. Methods: The study included 126 patients who reported having difficulty returning to usual activities 8 to 12 weeks after arthroscopic decompression surgery for subacromial impingement syndrome. The assessment at baseline and at 3 months included the OSS, the CS, and the European Quality of Life-5 Dimensions-3 Level (EQ-5D-3L) index. Responsiveness was assessed as follows: by correlation analysis between the change scores of the OSS, CS, and EQ-5D-3L index, and the Patient Global Impression of Change (PGIC) scale; by receiver-operating-characteristic (ROC) curve analysis using the PGIC scale as an external anchor; and by effect-size statistics. Results: At 3 months, a follow-up assessment of 112 patients (89%) was conducted. The change scores of the CS and the OSS were more strongly correlated with the external anchor (PGIC scale) than the change score of the EQ-5D-3L index. The areas under the ROC curves exceeded 0.80 for both shoulder scores, with no significant differences between them, and comparable effect-size estimates were observed for the CS and the OSS. Minimal clinically important change ROC values were 6 points for the OSS and 11 points for the CS, with upper 95% cutoff limits of 12 and 22 points, respectively. Conclusion: The CS and the OSS were both suitable for assessing improvement after decompression surgery.