Validation of the Western Ontario Rotator Cuff Index in Patients With Arthroscopic Rotator Cuff Repair

Reliability of the WORC is tested by comparing the results at T0 with T1. T1 is planned 2-3 weeks after T0, because we expect that the symptoms do not change between these two moments and the time span is large enough to forget initial responses to the questions. In order to signal change in severity of the symptoms, at both moments patients are asked to rate their shoulder hindrance. To determine test-retest reliability, intraclass correlation coefficients (ICC) are used.

Criterion validity is measured by comparing WORC with a general quality of life questionnaire (SF-36) and a commonly used clinical shoulder score (Constant Score) both at T0 and T1. Bland Altman plots will be used to estimate 95% boundaries of concurrence.

Responsiveness will be determined by calculating the standardized response means and effect sizes on T0 and T2 scores on WORC, SF-36 and Constant scores for the subgroups.

A comparison of WORC scores between the three distinct groups is made, to see whether WORC scores can differentiate between them. WORC scores will be compared with SF-36 to investigate whether the noted differences correlate with notable clinical differences and can be expressed as MCID's (minimal clinical important differences).