To identify whether patients have symptomatic improvement 12 months following total hip replacement (THR) surgery.


The European Collaborative Database of Cost and Practice Patterns of Total Hip Replacement study consists of 1,327 patients receiving primary THR for osteoarthritis (OA) across 20 European orthopedic centers. The primary outcome was the difference in Western Ontario and McMaster Universities OA Index (WOMAC) score between preoperative and 12-month postoperative measurements. To classify whether patients responded to THR at 12 months, we used return to normal, Outcome Measures in Rheumatology Clinical Trials (OMERACT)–OA Research Society International (OARSI) criteria, minimum important difference (MID), and minimum clinically important difference. Exposures were age, sex, obesity, employment, educational attainment, American Society of Anesthesiologists status, and radiographs.


On average, there was a large improvement in WOMAC scores 12 months after surgery, but whereas some patients improved, others got worse. The OMERACT-OARSI method classified 85.7% of patients as responders, MID 70.1%, and return to normal 64.1%. In general, each approach classified the same groups of patients as responding to THR. Based on total WOMAC score, patients who were younger, morbidly obese, employed, and better educated were more likely to respond to THR, but the effects were attenuated after adjustment for confounding, with only the effect of education remaining important.


The overall average response to THR was good, but ∼14–36% of patients did not improve, or were worse, 12 months postsurgery. Although the OMERACT-OARSI criteria were originally designed for use in clinical drug trials, they performed well in classifying patient response 12 months post-THR. Further research is required to understand the determinants of patient outcomes following THR.