Abstract: To observe the metabolism changes in the course of repair and avascular necrosis of the femoral head, the experiment was carried out on 26 adult dogs,6 of them were used as control. Avascular necrosis of the left femoral head was induced by freezing method with liquid nitrogen, and the right half being used as self-control. The 20 dogs were divided into four groups, 5 dogs in each which was sacrificed in 15、60、120 and 180 days after operation respectively. All the femoral heads were examined by biochemical methods. The cross-link and non-cross-link collagen contents, aminohexose contents of each cancellous bone and cartilage' bone of fresh femoral-heads，bone tissue collagenase activity and calcium contents were detected. The collagen contents of cancellous bone, including cross-link and non-cross-link which had no significant change in 15 day, reduced in 60 day group and further reduced in 120 or 180 day groups,Activity of tissue collagenase of cancellous bone reduced in 15 day after experimental necrosis （P＜0.01）， but significant increased in 60 day group （P＜0.01），and in 120 or 180 day groups （P＜0.05）. The calcium level had a same change as in the cancellous bone. The results suggested that the collagen and collagenase may play an important role in the course of avascular necrosis and repair of femoral head.

Key words: Avascular necrosis, Femoral head, Collagen,Collagenase, Dog