Long-term survival of regenerated cartilage on a large joint surface.

The one-year survival of regenerated cartilage on a large articular surface is presented using the McDowell in vivo model. The model provides a mechanically shielded environment in which regenerated cartilage can be protected from intra-articular stresses while normal joint motion is maintained. New tissue was allowed to grow from bleeding subchondral bone for 12 weeks at which time the original mechanical environment was reintroduced. Our study showed that neo-cartilage would grow to cover the entire joint surface of a patella and could survive for one year. Histologic observations indicated a maturing hyaline-like tissue. Biomechanical analyses showed that the regenerated cartilage became stiffer and less permeable within the time of this study. Biochemical evaluations demonstrated stable properties out to the longest time point. Control specimens, which were not shielded from stress, showed insignificant amounts of new tissue growing on the patellar surfaces.