Porous polymer implants for repair of full-thickness defects of articular cartilage: an experimental study in rabbit and dog.

Full-thickness defects of articular cartilage were repaired by implantation of porous polymer implants in rabbits and dogs. The quality of the repair tissue was determined by collagen typing with antibodies. Implants with varying pore sizes and chemical composition were used. The effect of loading and motion was determined by inserting implants higher than, level with and lower than the surrounding cartilage. It appeared that healing took place by formation of fibrocartilaginous repair tissue containing both type I and type II collagen. Hyaline cartilage was observed in a minority of the rabbits used but not in the dog. Fibrocartilage formation in the dog was simulated by implantation of a porous polymer. Chemical composition of the polymer did not alter the results, neither did loading of the implant. It is concluded that the formation of fibrocartilaginous repair cartilage is stimulated by implantation of a porous polymer. This tissue seemed to function adequately in the dog but did show signs of degeneration in the rabbit.