Neocartilage after artificial cartilage repair in the rabbit: histology and proteoglycan fragments in joint fluid.

Repair of full-thickness cartilage defects of the rabbit medial femoral condyle with artificial plugs and periosteal grafts was followed for 1 year. The morphological characteristics of the neocartilage after repair and the concentration of proteoglycan fragments in the joint fluid (CPFF) were evaluated. The CPFF showed only a weak correlation to the histological score of the neocartilage. Normal cartilage and subchondral bone did not develop with any of the repair alternatives. With a Dacron plug, neocartilage formation appeared earlier than with natural repair and was better than with periosteal grafting. Increased CPFFs were found in all specimens with repair at 3 months, probably reflecting the remaining effect of surgery. At 6 months, the CPFFs had normalized to control values. At 1 year, the CPFFs were again similar to those at the 3-month evaluation. This was paralleled by a degeneration of the neocartilage. We conclude that Dacron plugs could serve as a scaffold for neocartilage formation. The CPFF reflected surgical trauma and late degeneration of neocartilage but did not indicate minor differences in quality between cartilage repair techniques, probably because of the limited size of the grafted defect.