Fracfional Necrosis of the Femoral Head Epiphysis

It is generally accepted that the initial changes in ischaemic necrosis of the femoral head include death of both trabeculae and of intertrabecular bone marrow and blood vessels. The direct cause ofthis necrosis is vascular occlusion or disruption (Trueta and Harrison 1953; Trueta 1957). Repair of dead cancellous bone is considered to be heralded by vascular ingrowth from the surrounding living tissue. Appositional new bone is laid down against the dead trabeculae (Phemister 1930; Catto 1965; Rosingh et al. 1969) and this is followed by remodelling (Kenzora et al. 1978). The process is identical to the revasculansation of free autogenous bone grafts. Temporary ischaemia of the epiphysis of the femoral head, caused by raised intra-articularpressure or an extreme position of the joint, may also result in damage and repair which follows the same sequence of events unless circulation is restored quickly (Woodhouse 1964; Tachdjian and Grana 1968; Henard 1971 ; Calvert et al. 1984). In contrast, partial occlusion of the circulation to bone and bone marrow in the rabbit has been shown to