Cross-cultural adaptation and validation of the Italian version of the Western Ontario Osteoarthritis of the Shoulder index (WOOS)

BACKGROUND: The Western Ontario Osteoarthritis of the Shoulder index (WOOS) has been introduced as a disease-specific quality of life measurement in patients with glenohumeral arthritis. The aim of the present study was to perform a cross-cultural adaptation of the English version of the WOOS to Italian and to assess its validity, reliability and responsiveness in patients with glenohumeral joint osteoarthritis treated conservatively. MATERIAL AND METHODS: The adaptation process was carried out following the simplified Guillemin criteria. The English version was translated into Italian by two bilingual orthopaedic surgeons and then translated back into English by two different bilingual orthopaedic surgeons. The original version was compared with the back-translation. The questionnaire was prospectively administered to 30 patients with glenohumeral osteoarthritis at baseline and again after 5 days for retest reliability. After 6 months of conservative treatment, the responsiveness of the questionnaire was assessed in a subsample of 20 patients. The level of statistical significance was set at 0.05. RESULTS: The interclass correlation coefficient between test and retest of the WOOS was 0.99 (P < 0.001). Pearson’s correlation coefficient between the WOOS and disability of the arm, shoulder and hand (DASH) preoperatively was 0.73 (P < 0.01) and the correlation between the changes of score for the WOOS and DASH was 0.75 (P < 0.01). There were no floor or ceiling effects. Responsiveness, calculated by standardized response mean, was 1.1 and effect size was 1.3. CONCLUSIONS: The Italian version of the WOOS questionnaire has shown to be equivalent to its English version and demonstrated good validity, reliability and responsiveness to conservative treatment of glenohumeral osteoarthritis. LEVEL OF EVIDENCE: Level II. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10195-016-0400-4) contains supplementary material, which is available to authorized users.