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

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. MIC_cohort was calculated as the change in Oxford Shoulder Score for those satisfied (>60). Receiver-operating characteristic curve analysis was used to determine the MIC_individual 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 MIC_cohort was 11.6 (95% confidence interval 6.8-16.4) and MIC_individual 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.