[Avascular necrosis in the femoral head of spontaneously hypertensive rats--correlation between microangiographic and histological findings]. 
The site of interrupted blood flow in the necrotic femoral heads of growing spontaneously hypertensive rats (SHR) and the state of the circulation during the reparative process were investigated by microangiography.  The microangiographic findings of the femoral epiphysis were classified into the following four types: 1) uniform distribution of radiopacity; 2) absence of radiopacity in the medial portion; 3) complete absence of radiopacity; and 4) intercourse of blood vessels between the epiphysis and the metaphysis.  These four types corresponded closely to the degree of the reparative process after necrosis and the retardation of ossification.  The absence of blood vessels indicated the absence of reparative reaction or non-occurrence of ossification.  These findings suggest that necrosis of the femoral head in SHR occurs as a result of interrupted blood flow outside the epiphyseal nucleus.