Osteonecrosis of the femoral head of growing, spontaneously hypertensive rats.

The femoral head lesions of male spontaneously hypertensive rats (SHRs), which occur naturally and resemble Perthes' disease in man, were investigated radiographically and histologically. In the early phase of growth in SHRs, i.e., a period of 6 to 15 weeks after birth, the femur was shorter than that of control rats, and ossification in the epiphysis of the femoral head was considerably retarded. Osteonecrosis of the femoral head of SHRs appeared at the age of 9 weeks, and occurred in eight out of 12 femoral heads at 15 weeks. We suggest that osteonecrosis in the femoral head of SHRs is due to an abnormality of the cartilage in the epiphysis and metaphyseal growth plate and subsequent enchondral ossification.