MATURATION-DEPENDENT REPAIR OF UNTREATED OSTEOCHONDRAL DEFECTS IN THERABBIT KNEE-JOINT

Repair of untreated full-thickness cartilage defects in the medial fem oral knee condyle was studied in 17 young, 21 adolescent, and 19 adult rabbits. At 6 weeks, the defect was completely filled by tissue regen eration in all young and adolescent animals, but in only few of the ad ults (p < 0.05). The morphology of all repairs improved from fibrous t issue to hyaline-like cartilage over time (p < 0.05), but at 3 and 6 w eeks, the repair tissue in young and adolescent rabbits was more carti lage-like than in the adults (p < 0.05). In addition, bonding of the r epair tissue to the adjacent cartilage was better in the young and ado lescent than in the adult animals (p < 0.05). At 12 weeks, subchondral bone had formed in some young and adolescent repairs, but in no case in the adults. None of the repairs showed normal cartilage appearance, but formation of hyaline-like cartilage was common at 12 weeks. Irres pective of age or observation time, the repair site showed decreased s tiffness and larger strain values compared to adjacent or control cart ilage (p < 0.001) with no tendency for improvement over time. Younger animals showed a faster filling of the defect and an earlier specializ ation of the repair tissue than adult animals, but the mechanical qual ity of the regenerated tissue remained inferior to normal. (C) 1997 Jo hn Wiley & Sons, Inc.