A microangiographic study of idiopathic osteonecrosis of the femoral head.

Microangiography was performed on 31 femoral heads with idiopathic osteonecrosis to investigate the pathogenesis of this disease from the aspect of circulation disturbance. Microangiography showed the following: (1) the interruption of the superior retinacular arteries in the extraosseous area; (2) the presence of numerous newly formed vessels of varying diameter arising from the stumps of the interrupted superior retinacular arteries; (3) compensatory hypertrophy and large-area invasion of the inferior retinacular arteries and the ligamentum teres arteries, both of which medially enter the affected head; and (4) the blockage of revascularization, which occurred along the area of subchondral fracture and collapse at the weight-bearing region. These findings strongly suggest that revascularization is aborted by the subchondral fracture and collapse caused by weight bearing. It was assumed that interference with revascularization occurred repeatedly in the repair process of affected heads due to the influence of subchondral fracture and collapse caused by weight bearing.