Background: Outcome assessment after orthopaedic interventions is becoming more and more important. However, there are no disease-specific instruments for patient self-assessment of shoulder instability. The goal of our study was to translate and test the Western Ontario Shoulder Instability Index (WOSI) using a standardised approach. The guidelines of the American Association of Orthopedic Surgeons were used for the translation and cross-cultural adaptation process.
Material and method: Understanding was tested in 20 healthy subjects, and reliability and validity were quantified in 30 patients with shoulder instability. The quality of the translated version was described using the criteria of homogeneity, reliability, and construct validity.
Results: The test-retest reliability of the total score [intraclass correlation coefficient (ICC), 0.87] and of the subscores with the ICC (sports, leisure, and work 0.73; sensitivity 0.81; physical symptoms 0.82; and behaviour 0.90) was high. The internal consistency of the total scale was also high (Cronbach's alpha 0.89).
Conclusions: The WOSI covers a broad range of symptoms and impaired functioning in patients with shoulder instability. The German translation shows good results regarding understanding, homogeneity, reliability, and validity. Therefore, it is a useful instrument for self-assessment in patients with shoulder instability.