Acetabular Anatomical Parameters in Patients With Idiopathic Osteonecrosis of the Femoral Head.

Abstract

Osteonecrosis of the femoral head (ONFH) is an increasing worldwide health problem. However, about 30% of the patients are diagnosed with idiopathic ONFH, which means no underlying etiology is identified. We hypothesized that acetabular anatomical abnormalities might be related to idiopathic ONFH. This retrospective, 1:2 matched, case-control study included 101 patients (136 hips) with idiopathic ONFH and 202 control subjects (404 hips) matched for age, gender, and body mass index who had no apparent radiographic hip pathologies. The anteroposterior pelvic X-rays of the patients and control subjects were used to measure the anatomical parameters including the center-edge angle, the sharp angle, the acetabular depth ratio (ADR), and the acetabular head index (AHI). We found that hips with idiopathic osteonecrosis had less acetabular coverage, lower center-edge angle (28.3° vs 32.3°, P < .001), acetabular depth ratio (298.0 vs 306.4, P = .006), and acetabular head index (82.2 vs 85.8, P < .001), and higher sharp angle (39.7° vs 38.0°, P < .001), compared with the control subjects. The incidence of acetabular dysplasia was also higher in the idiopathic ONFH group than the control group. Less acetabular coverage was found in hips with idiopathic osteonecrosis than the control subjects. Less acetabular coverage may be associated with the development of ONFH in East Asian population.