Intraosseous arterial architecture in nontraumatic avascular necrosis of the femoral head. Microangiographic and histologic study.

To determine the vascular architecture of nontraumatic avascular necrosis of the femoral head (ANFH), 38 femoral heads procured from 31 ANFH patients were studied by microangiographic and histologic methods. Microangiography showed that the head was consistently stratified into three zones: the normal vascular, the reparative vascular, and the avascular. Microangiographic abnormalities were closely correlated with the histologic changes in each zone. The extent of the necrotic area proved to depend on the extent and number of involved intraosseous nutrient arteries. Circumscribed necrosis accompanied interruption of the lateral epiphyseal arteries in their intra-capital portion. Extensive necrosis resulted from multiple vascular involvement, which included not only the lateral epiphyseal arteries, but also the superior and inferior metaphyseal arteries. Histologic examination of different levels of the nutrient arteries revealed many intraosseous pathologic vascular changes in apposition to the ischemic episode of the femoral head. Interruption of the blood supply causing ANFH occurs in the intracapital arteries probably because of vascular wall damage, and the extent of necrosis depends on the number of the involved nutrient arteries and their proximity to the intracapital site of origin.