Background: The Western Ontario Rotator Cuff Index (WORC) is a self-report, disease-specific, quality-of-life assessment tool. Good reliability and validity have been demonstrated with several language versions of the WORC. In this study, the WORC was translated into Japanese, and its reproducibility and validity for use in Japanese patients with rotator cuff disorder were determined.
Materials and methods: The translated version of the WORC was certified by the developer of the original version. Of 78 consecutive Japanese patients with rotator cuff disorder, 75 completed the following questionnaires: the WORC; the Disabilities of the Arm, Shoulder, and Hand (DASH); and the Short Form 36 (SF-36). In total, 50 patients completed the WORC twice within 2-14 days. Internal consistency, test-retest reliability, absolute reliability, and construct validity were assessed.
Results: Cronbach's alpha coefficients ranged from 0.78-0.95, and intraclass correlation coefficients ranged from 0.72-0.84 for the total score as well as scores on all WORC domains. A fixed bias was revealed between the test and retest for the total score and scores of some domains. Limits of agreement (LOA) ranged from -19.0-27.9% for the total score on the WORC. Furthermore, the WORC scores correlated with those of DASH (r = 0.63-0.78) and SF-36 (r = -0.24 to -0.69).
Conclusions: Good test-retest reliability and construct validity were demonstrated for the Japanese WORC, but relatively high absolute measurement errors were observed. LOA values must be considered when using the WORC for individual patients with rotator cuff disorder.