The effect of subchondral bone defect in femoral head on structure and metabolism of article cartilage

OBJECTIVE: To investigate the changes of structure and metabolism of the cartilage of femoral head overlying the bone defect in animal model and analyse the possible effect of the necrotic area of the femoral head on the cartilage overlying there. METHODS: 18 adult hybrid dogs was applied for bone defect model of femoral head. Of the femoral heads, the left was applied for bone defect model, the right for shame-operation. 5, 5, and 8 animals were sacrificed respectively 4, 12 and 24 weeks after operation and the femoral heads were received for examinations. The X-rays films were taken just before the animals were sacrificed. After the cartilage specimens were decalcified, dehydrated and embedded, sections 6, u thick were made. They were stained with hematoxylin-eosin, sirius-red and toilude blue. The biochemical assay were performed. RESULTS: 12 and 24 weeks after operation of bone defect, cartilage histology and biochemistry demonstrated the signs of articular cartilage pathological changes. The arrangement of chondrocytes were disorder. The number of chondrocytes decreased. The cartilage surface lost its smoothness, and these kinds of changes were more severe in the area next to the bone defect. Fibrosis and vasi formation were found. Tidemark had the changes of discontinuation and veil. Glycosaminoglycans decreased. CONCLUSION: The bone defect, whose damaged structure strength and decreased blood supply is similar, had effect on the structure and metabolism of the articular cartilage near the bone defect, and suggest osteonecrosis at the stage of pro-collapse may affect the cartilage overlying it.