Reliability and Validity of a Japanese-language and Culturally Adapted Version of the Musculoskeletal Tumor Society Scoring System for the Lower Extremity

The Musculoskeletal Tumor Society (MSTS) scoring system is a widely used functional evaluation tool for patients treated for musculoskeletal tumors. Although the MSTS scoring system has been validated in English and Brazilian Portuguese, a Japanese version of the MSTS scoring system has not yet been validated. We sought to determine whether a Japanese-language translation of the MSTS scoring system for the lower extremity had (1) sufficient reliability and internal consistency, (2) adequate construct validity, and (3) reasonable criterion validity compared with the Toronto Extremity Salvage Score (TESS) and SF-36 using psychometric analysis. The Japanese version of the MSTS scoring system was developed using accepted guidelines, which included translation of the English version of the MSTS into Japanese by five native Japanese bilingual musculoskeletal oncology surgeons and integrated into one document. One hundred patients with a diagnosis of intermediate or malignant bone or soft tissue tumors located in the lower extremity and who had undergone tumor resection with or without reconstruction or amputation participated in this study. Reliability was evaluated by test-retest analysis, and internal consistency was established by Cronbach's alpha coefficient. Construct validity was evaluated using the principal factor analysis and Akaike information criterion network. Criterion validity was evaluated by comparing the MSTS scoring system with the TESS and SF-36. Test-retest analysis showed a high intraclass correlation coefficient (0.92; 95% CI, 0.88-0.95), indicating high reliability of the Japanese version of the MSTS scoring system, although a considerable ceiling effect was observed, with 23 patients (23%) given the maximum score. Cronbach's alpha coefficient was 0.87 (95% CI, 0.82-0.90), suggesting a high level of internal consistency. Factor analysis revealed that all items had high loading values and communalities; we identified a central role for the items walking and gait according to the Akaike information criterion network. The total MSTS score was correlated with that of the TESS (r = 0.81; 95% CI, 0.73-0.87; p < 0.001) and the physical component summary and physical functioning of the SF-36. The Japanese-language translation of the MSTS scoring system for the lower extremity has sufficient reliability and reasonable validity. Nevertheless, the observation of a ceiling effect suggests poor ability of this system to discriminate from among patients who have a high level of function.