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

Objective. To assess if total hip arthroplasty (THA) is a valid outcome mea sure of hip osteoarthritis (OA), in respect to clinical and radiological as sessments. Methods. A prospective 3 year study of patients who had painful hip OA with an initial radiographic joint space width greater than or equal to 1 mm at the narrowest point. Dependent variable was THA. Patient data including bo dy mass index, OA structural severity by radiograph, OA symptomatic severit y (pain, function), and OA localization were recorded at entry. Pelvic radi ographs were obtained before THA, when available, and once yearly during th e study. Results. During the study 106 of 506 patients underwent THA. Risk was estim ated (Kaplan-Meier method) to be 8 +/- 1, 16 +/- 2, and 23 +/- 2% after 1, 2, and 3 years, respectively. Factors predisposing to requirement for surge ry were: age greater than or equal to 70 years, female sex, superolateral m igration of the femoral head, joint space width < 2 mm, Kellgren-Lawrence g rade 2 3, pain (visual analog scale) greater than or equal to 50 mm, and Le quesne index greater than or equal to 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 spac e 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 wi dth during the first year were highly predictive of requirement for THA dur ing the 2 following years (risk of 5, 13, 25, and 79% in patients with a ra diological joint space width worsening during the first year of 0, less tha n or equal to 25, > 25 and less than or equal to 50, and > 50%, respectivel y). Conclusion, These data suggest that THA could be considered as a valid outc ome measure in OA. However, further studies should be conducted in other co untries with different health care systems to evaluate the inter-country re liability of this measurement.