Validation and reliability of a Japanese version of the Simple Shoulder Test: a cross-sectional study

Background The Simple Shoulder Test (SST) is a widely used patient-reported outcome assessment. The purpose of this study was to develop and validate a Japanese version of the SST (SST-Jp). Methods A two-stage observational study was conducted to validate the cross-cultural adaptation of the SST. A total of 100 patients with shoulder disorders completed the SST-Jp; the Disability of Arm, Shoulder, and Hand assessment; and the Medical Outcomes Short-Form 36 (SF-36) at an initial visit. Thirty-four of the patients repeated the SST-Jp one week after the first examination. The test-retest reliability was quantified using the interclass correlation coefficient, and Cronbach’s alpha (α) was calculated to assess internal consistency. Construct validity was assessed using Spearman’s rank correlation coefficient. Results The internal consistency of the SST-Jp was very high (α = 0.826). The interclass correlation coefficient of the SST-Jp was also high (0.859). There was a strong, positive correlation between the Disability of Arm, Shoulder, and Hand and the SST-Jp (r = 0.717, P < .001). The SST-Jp was significantly correlated with most of the SF-36 subscales. The correlations of the SST-Jp with physical subscales of the SF-36 were stronger than those with the other subscales. Conclusions The SST-Jp was found to be a valid and reliable measurement for shoulder joint pain and function assessment among the Japanese population.