Comparison of the responsiveness of the SF-36 and WOMAC in patients undergoing total hip arthroplasty

This study examines the responsiveness of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Short Form-36 (SF-36) in patients undergoing total hip arthroplasty. Eighty-nine patients completed the WOMAC and SF-36 preoperatively and postoperatively. Standardized response means (SRMs) and effect sizes (ES) were used to measure responsiveness. Mean follow-up was 17 months. The SRMs for the WOMAC ranged from -0.93 to -1.49, and the ES ranged from -1.02 to -1.53. The SRMs for the SF-36 ranged from 0.22 to 1.64, and the ES ranged from 0.20 to 1.97. The highest values occurred with the physical functioning, bodily pain, and Physical Component Summary Scales. This study demonstrates a similar level of responsiveness of the WOMAC and several components of the SF-36. This suggests that the isolated use of the SF-36 may be adequate to monitor outcomes after total hip arthroplasty. There may still be a role for the WOMAC when comparing outcomes of specific designs or techniques of total hip arthroplasty.