Background: Modern patient based outcome measures like the SMFA-D (German Short Musculoskeletal Function Assessment Questionnaire) are able to detect the impairment and functional capacity of patients with musculoskeletal extremity disorders. The SMFA-D was successfully evaluated in several cohorts treated operatively for osteoarthritis of the knee and hip, rotator cuff tears and rheumatoid arthritis. The aim of the present study was the evaluation of the SMFA-D in patients with conservative treatment for hip osteoarthritis.
Patients and methods: 69 patients with osteoarthritis of the hip were enrolled in a prospective controlled clinical trial. All patients completed the SMFA-D, SF-36, WOMAC, FFbH-OA. A standardized test of walking speed and the functional status of the patient as judged by the physician were recorded. Statistical analysis were done for the following: re-test reliability (ICC), internal consistency (Cronbach's alpha), validity and responsiveness.
Results: Internal consistency (Cronbach's alpha) was alpha = 0.89 and alpha = 0.97 for the SMFA-D scales. The retest reliability (ICC, unjust, mixed effect) was 0.91 (p < 0.001) for the function index and 0.73 (p < 0.001) for the bother index. Both indices correlated significantly with the FFbH-OA (r = 0.66 to r = 0.84), the WOMAC (r = 0.55 to r = 0.86) and the scales of the SF-36 (r = - 0.34 to r = - 0.85) on all three time points, which supports construct validity. There was mainly a significant correlation between the SMFA-D scales and the functional status of the patient (r = 0.21 to r = 0.44), pain reported by the patient (r = 0.43 to = 0.54) and the self selected walking speed (r = 0.28 to r = 0.51), which supports external validity. We were able to differentiate operatively and conservatively treated patients (discriminant construct validity). At the end of the rehabilitation program we were able to demonstrate small to medium treatment effects in SMFA-D and SF-36. The WOMAC and FFbH-OA were not able to demonstrate these treatment effects.
Conclusion: Even in patients with conservative treatment of hip osteoarthritis the SMFA-D represents a reliable, valid and responsive measure. The use of the SMFA-D can be recommended as a patient based outcome measure.