Early Arteriopathy and Postulated Pathogenesis of Osteonecrosis of the Femoral Head

The authors studied 24 core biopsy specimens exhibiting osteonecrosis of the femoral head (ONFH) at the silent stage (i.e., no symptoms or roentgenographic signs but positive scintigrams or positive magnetic resonance images). The histologic findings referring to vascular lesions were compared with those of other tissues: eight capsular tissues and eight superior retinacular vessels obtained from ONFH and 11 femoral heads of osteoarthrosis. All the core biopsy specimens showed trabecular and bone marrow necrosis as well as old and new bone marrow hemorrhages. Vascular lesions were also detected in all core biopsy specimens. Structural damage to arteriolar walls, primarily in the tunica media, consisted of broken-down internal elastic lamina, degeneration of the tunica media, necrosis of smooth muscle cells, and the residue of ruptured blood vessels. This damage was present even in nonnecrotic tissue, indicating the fragility of the intracapital vascular system. Such arteriopathy led to eventual hemorrhagic infarction. Since extracapital blood vessels in osteonecrotic femoral heads showed mild changes and the head of osteoarthrosis showed no vascular changes, the authors conclude that arteriopathy is a specific and primary condition in early ONFH and is implicated in the pathogenesis of ONFH.