Steroid-induced Early Changes in the Femoral Head and Hip Joint in Rats

Abstract

Purpose: To determine if the early changes to the articular cartilage and synovium of the hip joint in relation to steroid-induced osteonecrosis of the femoral head is either as a preceding factor or as a secondary consequence in the pathomechanism. Materials and Methods: Thirty-two Sprague Dawley rats were divided into two groups, 16 receiving a steroid injection and 16 as a control group. Tissue samples of the hip joint were taken from 4 rats from each group every 4 weeks over a 16 week period. The specimens were investigated for the early changes to the articular cartilage, subchondral bone of the femoral head and the synovium after H & E staining and toluidine blue stain. Five histological criteria were applied to determine the cartilage status. Results: Histologically, there was a gradual increase in chondrocyte cloning in the steroid injection group. In addition, synovial hypertrophy and the enlargement of fatty cysts with the loss of hematopoietic cells were observed. Conclusion: Synovial hypertrophy and some evidences of articular cartilage degeneration associated with steroid-induced early femoral head osteonecrosis appears to be the result of a direct inflammatory reaction to the steroid injection. This suggests that early presentation of the pathologic lesion in the hip joint might occur without definitive radiological evidence of femoral head osteonecrosis.