Osteonecrosis and ossification disturbance of the femoral head in spontaneously hypertensive rats.

The usefulness of spontaneously hypertensive rats (SHR) as a model animal for Perthes disease was evaluated because bone necrosis and ossification disturbance are frequently found in SHR. Twenty femoral heads from twenty-week-old male SHR were compared with twenty femoral heads from each control strain, Wistar Kyoto rat, Wistar rat and Donryu rat, in radiological and histological studies. SHR radiographs revealed flattening of the femoral head, radiolucent area and absence of trabeculae in the ossific nucleus as well as shortening and broadening of the neck. In the histological study of epiphysis in SHR, bone necrosis and various stages of its repair process and ossification disturbance represented the main findings. Incidence of these abnormal findings were significantly higher than in the control groups. Clarification of the causes of bone necrosis and ossification disturbance in SHR will provide a key to the understanding of the pathogenesis in Perthes disease.