Abnormalities of the blood vessels feeding the femoral head liable to osteonecrosis in spontaneously hypertensive rats

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In order to elucidate the cause of osteonecrosis of the femoral head in spontaneously hypertensive rats (SHRs), which resembles the osteonecrosis of Perthes'disease, we investigated the development of the blood vessels forming the epiphyseal nucleus of the rat femoral heads, and the abnormalities of the blood vessels feeding the femoral heads of SHRs. The vascular casts of the proximal femur were observed using both an optical and a scanning electron microscopy (SEM). In the growing rats at the age of 5 weeks, the lateral epiphyseal vessela (LEVs) budded out from the arch of the blood vessels on the femoral neck. During the period of 9-15 weeks after birth, when osteonecrosis of the femoral heads in SHRs occurred frequently, LEVs, which were the main feeding vessels, entered from the lateral of the femoral heads. Anastomosing branches of LEVs between the epiphysis and the femoral neck were scarce even in the femoral heads showing normal ossification. It seemed that the development of LEVs did not proceed normally in this period. Furthermore, remarkable segmental stenosis and the obstruction of LEVs were often recognized near the lateral of the femoral heads.These results suggested that LEVs in growing SHRs have the vascular structure that could cause an interruption of the blood supply to the femoral heads.