[The role of mechanical stress on the femoral head in the occurrence of femoral head lesions in spontaneously hypertensive rats].

Using spontaneously hypertensive rats (SHRs), attempts were made to decide whether or not mechanical stress on the femoral head plays a role in the occurrence of the femoral head lesions, namely, avascular necrosis and ossification disturbance. The following measures were taken to reduce mechanical stress: severing of the sciatic nerve, severing of both the sciatic and femoral nerves, and amputation of the hind limb on one side. The frequency of the femoral head lesions was highest in the control group (85%). It was lower in the sciatic nerve severance group, sciatic and femoral nerve severance group, and hind limb amputation group, in that order, showing a direct correlation with the level of mechanical stress. Moreover, histological abnormalities of the growth plate were observed frequently in the outer portion of the femoral head in SHRs with femoral head lesions. These findings indicate that mechanical stress causes an impairment of the femoral head cartilage, resulting in the obstruction of blood vessels leading to the epiphyseal nucleus of the femoral head.