Requirement for total hip arthroplasty: an outcome measure of hip osteoarthritis?

To assess if total hip arthroplasty (THA) is a valid outcome measure of hip osteoarthritis (OA), in respect to clinical and radiological assessments.

A prospective 3 year study of patients who had painful hip OA with an initial radiographic joint space width > or =1 mm at the narrowest point. Dependent variable was THA. Patient data including body mass index, OA structural severity by radiograph, OA symptomatic severity (pain, function), and OA localization were recorded at entry. Pelvic radiographs were obtained before THA, when available, and once yearly during the study.

During the study 106 of 506 patients underwent THA. Risk was estimated (Kaplan-Meier method) to be 8+/-1, 16+/-2, and 23+/-2% after 1, 2, and 3 years, respectively. Factors predisposing to requirement for surgery were: age > or =70 years, female sex, superolateral migration of the femoral head, joint space width <2 mm, Kellgren-Lawrence grade > or =3, pain (visual analog scale) > or =50 mm, and Lequesne index > or =10 with a relative risk of 1.65, 1.71, 1.96, 1.85, 1.89, 1.86, and 2.59, respectively. Mean change in joint space width was 0.22+/-0.50 vs 0.97+/-1.35 mm/year in patients without and with THA, respectively (p<0.0001). Changes in radiological joint space width during the first year were highly predictive of requirement for THA during the 2 following years (risk of 5, 13, 25, and 79% in patients with a radiological joint space width worsening during the first year of 0, < or =25, >25 and < or =50, and >50%, respectively).

These data suggest that THA could be considered as a valid outcome measure in OA. However, further studies should be conducted in other countries with different health care systems to evaluate the inter-country reliability of this measurement.