Responsiveness of the SF-36 and WOMAC following periacetabular osteotomy for acetabular dysplasia.

ABSTRACT

BACKGROUND: Periacetabular osteotomy is a relatively common reconstructive procedure for the adolescent or young adult with acetabular dysplasia. Although several measures have been used to characterize the outcome, the responsiveness of these measures in this population has not been determined. The purpose of this study was to estimate the responsiveness of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Short Form-36 (SF-36) in patients with acetabular dysplasia treated with periacetabular osteotomy. METHODS: Eighty-three patients with acetabular dysplasia treated with periacetabular osteotomy between 2000 and 2005 completed the WOMAC and SF-36 both preoperatively and postoperatively. The scores on each domain of these outcome measures were calculated and analyzed to determine the parameters of responsiveness, including the minimal detectable change at the 90% confidence level. RESULTS: The mean duration of follow-up was 1.9 years. Comparison of the effect size, standardized response mean, and minimal detectable change for the SF-36 and WOMAC demonstrated that the WOMAC was more sensitive to change than the SF-36 was, particularly in the physical function domain (minimal detectable change, 9.1) and the pain domain (minimal detectable change, 5.5). Only one of the eight domains of the SF-36, bodily pain, demonstrated a change in outcome that exceeded the minimal detectable change, which was 2.38. CONCLUSIONS: Both the WOMAC and the SF-36 demonstrated adequate responsiveness to change over time in patients with acetabular dysplasia treated with periacetabular osteotomy, although the WOMAC was more sensitive to change. These results indicate that the WOMAC is sufficiently responsive to be used as a joint-specific measure for assessing changes following periacetabular osteotomy for the treatment of acetabular dysplasia.