Reliability and validity of the Turkish version of lumbar stiffness disability index.

Objective: Post-lumbar fusion surgery often restricts daily activities due to lumbar stiffness. The validity and reliability of the lumbar stiffness disability index (LSDI) in Türkiye, which measures the impact of lumbar stiffness on functional abilities, have not yet been confirmed. This study aims to test the validity and reliability of the Turkish version of LSDI (Tr-LSDI).

Methods: Sixty-six patients who underwent lumbar fusion surgery were included in this methodological study. The Tr-LSDI was developed using a forward-backward translation. Using the Davis technique and expert feedback, we confirmed the content validity (CV) of the Tr-LSDI. The construct validity of the Tr-LSDI was assessed with exploratory factor analysis (EFA) and convergent validity. Convergent validity was examined by correlation analysis between Tr-LSDI, the Oswestry disability index (ODI) scores, and the number of fusion levels. Internal consistency was determined using Cronbach's alpha coefficients, and test-retest reliability was assessed with the intraclass correlation coefficient (ICC).

Results: Expert evaluation yielded CV indexes > 0.8 for all items. Exploratory factor analysis revealed a one-factor structure for Tr-LSDI, comprising 10 items that accounted for 63.7% of the variance. Factor loadings spanned from 0.371 to 0.926. Notably, the Tr-LSDI score correlated with fusion levels (r=0.386, P=.001) and demonstrated a robust correlation with ODI (r=0.899, P < .001), affirming its convergent validity. The Tr-LSDI displayed excellent internal consistency with a Cronbach's alpha coefficient of 0.934. The ICC was 0.980.

Conclusion: The Tr-LSDI is a validated, reliable tool for measuring lumbar stiffness in Türkiye. Its consistency, validity, and alignment with the original LSDI make it suitable for clinical and research use.

Level of evidence: Level II, Diagnostic Study.