Use of a guanidine extract of demineralized bone in the treatment of osteochondral defects of articular cartilage.

In order to evaluate the ability of a guanidine extract of demineralized bone to repair osteochondral defects in articular cartilage, plugs made of this extract were implanted into defects in rabbit knees. The repair tissue was examined macroscopically, histologically, and immunohistochemically at 4, 8, 12, and 30 weeks. Controls (defects that were left empty) showed no cartilage formation. Four weeks after implantation of a guanidine extract plug, histological examination showed a nonhomogeneous metachromatically stained region extending from the surface of the repair tissue down to cancellous bone. This region also was labeled by an anti-type-II collagen antibody, indicating that cartilage-like tissue had been induced. At 8 weeks, the newly formed cartilage in the subchondral and cancellous bone had been partially replaced by bone. At 12 weeks, the thickness of the newly formed cartilage layer had decreased, and most of the newly formed cartilage in the subchondral and cancellous bone had been replaced by bone. In addition, a tidemark was observed. At 30 weeks, the repair tissue was a mixture of cartilage and fibrocartilage, and there was severe degeneration of the cartilage surrounding the repaired defects. These findings indicate that osteochondral defects of articular cartilage can be partially repaired by the implantation of a guanidine extract and that the newly formed cartilage-like tissue is not permanent.