Reliability, validity and responsiveness of the German short musculoskeletal function assessment questionnaire (SMFA-D) in patients with osteoarthritis of the hip undergoing total hip arthroplasty

Background The aim of the present study was to check for reliability, validity and responsiveness of the Musculoskeletal Function Assessment questionnaire (SMFA-D) in patients with coxarthrosis undergoing total hip replacement. Patients and method In a prospective clinical trial the SMFA-D, the SF-36, the Harris Hip score, test of walking speed and the functional impairment according to the physican assessment were recorded. Results The reliability of the instrument could be demonstrated by a correlation coeffizient of r = 0.78 for the function index and r = 0.84 for the bother index. Patients could be distinguished by the physican's assessment to show discriminative validity. Both indices correlated significantly with the Harris Hip score, scales of the SF-36 and the walking speed supporting the construct validity. The responsiveness could be shown with large effect sizes (1.04 for the function index and 1.02 for the bother index) at the three-month follow-up. Conclusions The SMFA-D was found to be a reliable, valid and responsive instrument in patients with coxarthrosis undergoing hip replacement and the use of this instrument can be recommended.