Validity and Reliability of the Oxford Shoulder Instability Score Translated into Arabic

Background: The Oxford Shoulder Instability Score, abbre-viated OSIS, is a brief, outcome measure self-reported by the patient suffering shoulder instability. Objectives: Our objective was to translate OSIS into Arabic and validate its psychometric properties via test of the reliability, internal consistency, floor and ceiling effects, and validity. Material & Methods: Fifty-five patients were involved in this survey at the baseline and follow-up (14 days after the baseline). We performed the internal consistency test using Cronbach’s α. We calculated Standard Response Mean (SRM) and Pearson’s Correlation to estimate the construct validity and responsiveness of the Arabic OSIS in comparison to Disability of the Arm and Shoulder and Hand (DASH) Score. Results: The Arabic OSIS had a baseline Cronbach’s α of 0.815 and a follow-up value of 0.860. In addition, Intra-class correlation (ICC) of 0.897; (0.813-0.942) indicated high reliability. Arabic versions of OSIS had a strong correlation with DASH score (r = 0.77, p = 0.003) which suggested a good construct validity. Also, moderately correlated changes of baseline to follow-up in OSIS indicated moderate responsiveness. We did not observe any relevant floor and ceiling effect among the responses. Conclusion: Overall, the Arabic version of OSIS proved to be a good and reliable diagnostic tool for patients with shoulder instability.