Histological Degeneration of the Acetabular Cartilage in Osteonecrosis of the Femoral Head
T Sakai¹, K Ohzono¹, SB Lee¹, N Sugano², T Nishii², H Miki², M Takao², T Koyama², D Morimoto¹, H Yoshikawa^2
1Department of Orthopaedic Surgery, Osaka National Hospital, and ²Department of Orthopaedic Surgery, Osaka University Medical School, Osaka, Japan

Purpose: In order to investigate the relationship between the degeneration of the acetabular cartilage and the radiological staging of osteonecrosis of the femoral head, the following study was performed.

Patients and Methods: Acetabular cartilage with subchondral bone was taken from the superior dome from 34 hips of 30 patients undergoing total hip arthroplasty due to osteonecrosis of the femoral head. The specimens were stained with hematoxylin-eosin and safranin-O, and were evaluated as to thinning of the cartilage, fibrillation, cleft, and proliferation of the chondrocytes. There were 18 females and 12 males with average age of 49 years. We used the radiological staging system proposed by the working group of the Specific Disease Investigation Committee under the auspices of the Japanese Ministry of Health, Labor and Welfare. There were eight hips in stage IIIA (collapse of the femoral head is less than 3 mm), 19 hips in stage IIIB (collapse is 3 mm or greater), and seven stage IV hips.

Results: All 34 specimens showed histological abnormality. In eight stage IIIA hips, six hips were mild and two were moderate degeneration. In 19 stage IIIB hips, five hips were mild, six were moderate, and eight had severe arthrosis. Seven stage IV hips had severe arthrosis.

Discussion and Conclusion: Although the radiographs cannot demonstrate early degeneration of cartilage and degenerative changes are present in stage III hips, histological degenerative changes in stage IIIB hips are more severe than those in stage IIIA hips. These findings should be kept in mind in treating the patients with osteonecrosis of the femoral head.