Idiopathic chondrolysis of the hip: an ultrastructural study of the articular cartilage of the femoral head.

Core biopsies obtained from the articular cartilage of the femoral head of a 16-year-old girl with idiopathic chondrolysis of the hip were subjected to an ultrastructural study. Zone I was missing and zone II was the most superficial layer present in the articular cartilage of our patient. Collagen fibrils were thinner than normal and more uniform in diameter, and proteoglycans were normally distributed among them. Degenerating chondrocytes were found, as well as debris of dead cells, but many chondrocytes were still vital and engaged in active synthesis. Most of the chronic degenerative changes observed in ultrastructural studies on osteoarthritis were not observed in this case of idiopathic chondrolysis which seems to be, on the basis of our findings, a pathological process which develops and runs its course very quickly.