Abstract
Aims: To simulate intra-articular fracture healing, this study investigated the regeneration of identical osteochondral gaps within step-offs or on congruous articular surfaces. Methods: Twenty-nine rabbits received either half-millimetre coronal step-offs separated by 0.5X2mm osteochondral gaps (n=16) or identical osteochondral defects alone (n=13) on the medial femoral condyles. After 6, 12 and 24 weeks survival, subchondral bone density about the lesion was measured by pQCT. Cartilage regeneration/degeneration was evaluated with histology and immunostaining for collagen type I and II. Results: Subchondral bone re-establishment was complete in gaps within step-offs by 24 weeks however, showed delayed restoration in defects on congruent surfaces. Repair cartilage quality showed some differences in the two groups producing better results on the low side of step-off group. Increased subchondral bone density associated with moderate cartilage degeneration attributable to high contact stresses was observed at the high sides of stepoffs. Neither bone density changes nor cartilage damage was present around defects on congruent surfaces. Collagen type I content showed decreasing while type II increasing trend in repair cartilage with longer follow-ups in both groups. Conclusions: Osteochondral defects at unloaded surface segments of step-offs displayed different, in certain regards slightly superior repair characteristics than those on congruent surfaces. Minor separation of the two sides of the offsets did not result in severe local degeneration.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
