Changes and thresholds in the Oxford Shoulder Score following shoulder arthroplasty: Minimal clinically important difference, minimal important and detectable changes, and patient-acceptable symptom state

Abstract

Background The minimal clinically important difference, minimal important change, minimal detectable change and patient-acceptable symptom state are poorly defined for the Oxford Shoulder Score following shoulder arthroplasty. The study's aim was to calculate their values. Methods One hundred patients underwent shoulder arthroplasty and completed pre and 1-year postoperative Oxford Shoulder Score. Patient satisfaction was assessed at 1-year using a visual analogue scale from 0 to 100: ‘very satisfied’ (>80), ‘satisfied’ (>60–80), and ‘unsatisfied’ (≤60). The difference between patients recording ‘unsatisfied’ ( n  =  11) and ‘satisfied’ ( n  =  16) was used to define the minimal clinically important difference. MICcohort was calculated as the change in Oxford Shoulder Score for those satisfied (>60). Receiver-operating characteristic curve analysis was used to determine the MICindividual and patient-acceptable symptom state. Distribution-based methodology was used for the minimal detectable change. Results The minimal clinically important difference was 6.9 (95% confidence interval 0.7–13.1, p  =  0.039). The MICcohort was 11.6 (95% confidence interval 6.8–16.4) and MICindividual 13. The minimal detectable change was 6.6 and the patient-acceptable symptom state was defined as ≥29. Discussion The minimal clinically important difference and minimal important change can assess whether there is a clinical difference between two groups and whether a cohort/patient has had a meaningful change in their Oxford Shoulder Score, respectively. These were greater than measurement error (minimal detectable change), suggesting a real change. The patient-acceptable symptom state can be used as a marker of achieving satisfaction.