Abstract
Osteonecrosis of the femoral head is largely due to a blood flow disturbance, but the mechanism of occurrence is not well understood. We observed the vascular morphology of the femoral head in the removed head of osteonecrosis cases; the objective group included 28 osteonecrosis cases, and the control group included six osteoarthritis cases. We observed the vessel's shape of the femoral head sectioned on the coronal plane, and the number and diameter of the vessels in the band region. Although we found an ‘island-shaped elevation’ in the vessel in 15 osteonecrosis cases (53.6%), there was no such elevation in the control group. Necrosis and restoration are very well-known mechanisms of osteonecrosis. Vascular endothelial cells and fibroblastic cells are thought to be shifted to the lumen in the process of restoration, which seems to be a characteristic of osteonecrosis because such structures were not observed in the control group. The total number of vessels in Stage 4 was significantly higher than that in Stages 2 + 3. Unlike a typical inflammatory reaction, the course of the disease is prolonged due to the repetitive necrosis and restoration phases. As a result, the number of vessels increases in Stage 4. Taken together, these two findings (the existence of ‘island-shaped elevation’ in the vessel and the vessel number dominance in Stage 4) are thought to be proof of the repetitive necrosis and the restoration.
