Comparative responsiveness of measures of pain and function after total hip replacement

Objective. To compare the responsiveness of the Functional Assessment System (FAS), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the Medical Outcomes Study 36-item Short Form (SF-36) in patients with osteoarthritis (OA) scheduled for total hip replacement. Method. Twenty patients with a mean age at surgery of 72.6 years, with primary OA of the hip, were investigated preoperatively and at 3, 6, and 12 months postoperatively with the FAS, WOMAC, and SF-36. The responsiveness was calculated as standardized response mean, effect size, and relative efficiency. Results. The pain and function scores of WOMAC and SF-36 showed greater responsiveness than FAS at 3 months. These differences remained at 6 and 12 months postoperatively. The differences between these 3 outcome measures were found to be similar using several methods for calculating responsiveness. Conclusion. Self-administered questionnaires like WOMAC and SF-36 are more responsive measures of pain and function than ran-e of motion, performance tests, and observer-administered questions (FAS) following total hip replacement.