Cross-cultural adaptation and validation of the Japanese version of the Toronto Extremity Salvage Score (TESS) for patients with malignant musculoskeletal tumors in the lower extremities

Before this work a Japanese version of the Toronto Extremity Salvage Score (TESS), a disease-specific patient-completed questionnaire widely used to assess the physical function of patients with musculoskeletal tumors, had not been developed. The purpose of this study was cross-cultural adaptation and validation of the English-language version of the TESS to facilitate international comparisons of treatment results. The TESS was translated into Japanese, back-translated into English, and reviewed by a committee to develop a consensus Japanese version of the TESS. One hundred and two patients were assessed by use of this Japanese version to examine its reliability and validity. Test-retest reliability and internal consistency determined by using the intraclass correlation coefficient (0.941) and Cronbach's alpha test (0.978), respectively, were excellent. Factor analysis showed that the structure consisted of a three-item cluster; the Akaike information criterion (AIC) network also demonstrated that the items could be divided into three domains in accordance with their content. The Japanese version of the TESS correlated with the Musculoskeletal Tumor Society rating scale (r = 0.811; P < 0.001) and the Short Form-36 physical component summary (r = 0.785; P < 0.001). Our study suggested that the Japanese version of the TESS is a reliable and valid instrument for measuring patient-reported functional outcome for patients with lower extremity sarcoma, and that it enables international comparisons of treatment results. The spatial association of each item demonstrated by using the AIC network also suggested that the underlying structure of the TESS reflected its coverage of a wide range of physical functions.