Cross-cultural adaptation of the German version of the spinal stenosis measure

Abstract

PURPOSE To validate the German version of the spinal stenosis measure (SSM), a disease-specific questionnaire assessing symptom severity, physical function, and satisfaction with treatment in patients with lumbar spinal stenosis. METHODS After translation, cross-cultural adaptation, and pilot testing, we assessed internal consistency, test-retest reliability, construct validity, and responsiveness of the SSM subscales. Data from a large Swiss multi-center prospective cohort study were used. Reference scales for the assessment of construct validity and responsiveness were the numeric rating scale, pain thermometer, and the Roland Morris Disability Questionnaire. RESULTS One hundred and eight consecutive patients were included in this validation study, recruited from five different centers. Cronbach's alpha was above 0.8 for all three subscales of the SSM. The objectivity of the SSM was assessed using a partial credit approach. The model showed a good global fit to the data. Of the 108 patients 78 participated in the test-retest procedure. The ICC values were above 0.8 for all three subscales of the SSM. Correlations with reference scales were above 0.7 for the symptom and function subscales. For satisfaction subscale, it was 0.66 or above. Clinically meaningful changes of the reference scales over time were associated with significantly more improvement in all three SSM subscales (p < 0.001). Conclusion: The proposed version of the SSM showed very good measurement properties and can be considered validated for use in the German language.