DEFINING CLINICALLY IMPORTANT IMPROVEMENT FOR THE OXFORD SHOULDER SCORE: DATA FROM THE AUSTRALIAN ORTHOPAEDIC ASSOCIATION NATIONAL JOINT REPLACEMENT REGISTRY PATIENT-REPORTED OUTCOMES MEASURES PROGRAM

While clinically important improvements in Oxford Shoulder Scores have been defined for patients with general shoulder problems or those undergoing subacromial decompression, no threshold has been reported for classifying improvement after shoulder replacement surgery. This study aimed to establish the minimal clinically important change (MCIC) for the Oxford Shoulder Score in patients undergoing primary total shoulder replacement (TSR). Patient-reported outcomes data were sourced from the Australian Orthopaedic Association National Joint Replacement Registry Patient-Reported Outcome Measures Program. These included pre- and 6-month post-operative Oxford Shoulder Scores and a rating of patient-perceived change after surgery (5-point scale ranging from ‘much worse’ to ‘much better’). Two anchor-based methods (using patient-perceived improvement as the anchor) were used to calculate the MCIC: 1) mean change method; and 2) predictive modelling, with and without adjustment for the proportion of improved patients. The analysis included 612 patients undergoing primary TSR who provided pre- and post-operative data (58% female; mean (SD) age 70 (8) years). Most patients (93%) reported improvement after surgery. The MCIC derived from the mean change method was 6.8 points (95%CI 4.7 to 8.9). Predictive modelling produced an MCIC estimate of 11.6 points (95%CI 8.9 to 15.6), which reduced to 8.7 points (95%CI 6.0 to 12.7) after adjustment for the proportion of improved patients. For patient-reported outcome measures to provide valuable information that can support clinical care, we need to understand the magnitude of change that matters to patients. Using contemporary psychometric methods, this analysis has generated MCIC estimates for the Oxford Shoulder Score. These estimates can be used by clinicians and researchers to interpret important changes in pain and function after TSR from the patient's perspective. We conclude that an increase in Oxford Shoulder Scores of at least 9 points can be considered a meaningful improvement in shoulder-related pain and function after TSR.