Role of pin protrusion in the etiology of chondrolysis: a surgical model with radiographic, histologic, and biochemical analysis.

We studied a model of pin protrusion in rabbit hips to determine if chondrolysis is produced. Enzymatic degradation of the articular cartilage remote from the pin site and mechanical destruction of the acetabulum occurred. Loss of proteoglycans in the articular cartilage averaged approximately 30%, and matched the increase in neutral protease activity. This presumably accounts for the loss of height that occurs in chondrolysis, but throughout the study, the joint space did not narrow; instead, it increased. This suggests that some other factor is needed to produce chondrolysis, such as a slip or an immune response.