Histologic Analysis of Acetabular and Proximal Femoral Bone in Patients with Osteonecrosis of the Femoral Head

Background: The purpose of this study was to investigate the hypothesis that osteonecrosis of the femoral head may also involve the acetabulum and the proximal part of the femur.

Methods: Twenty-five patients who underwent simultaneous bilateral total hip arthroplasty and thirty-eight patients who had a unilateral total hip arthroplasty for treatment of symptomatic osteonecrosis of the femoral head were included in the study. There were fifty-five men and eight women. The etiology of the osteonecrosis was idiopathic in forty patients (fifty-six hips, 64%), associated with ethanol abuse in eighteen patients (twenty-five hips, 28%), and associated with steroid use in five patients (seven hips, 8%). The mean age of the patients at the time of arthroplasty was 47.1 years. We performed cancellous bone biopsies in the acetabulum, the proximal part of the femur, and the femoral head intraoperatively and then examined the specimens histologically.

Results: Of the eighty-one hips with idiopathic or ethanol-associated osteonecrosis, seventy-six (94%) had normal or stage-1 bone in the acetabulum and the proximal part of the femur according to the system of Arlet and Ficat, and seventy-eight (97%) of the eighty-one had a grade of 0 or 1 according to the system of Humphreys et al. Of the seven hips with steroid-associated osteonecrosis, four had normal or stage-1 bone and a grade of 0 or 1 and three had stage-2 or 3 disease and a grade of 2 or 3. Therefore, the vast majority of hips with idiopathic or ethanol-associated osteonecrosis had normal or nearly normal bone in the acetabulum and the proximal part of the femur. Three of the seven hips with steroid-associated osteonecrosis had abnormal bone in the proximal part of the femur only.

Conclusions: One can expect to find normal or nearly normal cancellous bone in the acetabulum and the proximal part of the femur of patients with either idiopathic or ethanol-associated osteonecrosis of the hip. More extensive osteonecrosis may accompany steroid-associated osteonecrosis of the hip.