Intact articular cartilage cryopreservation. In vivo evaluation

By varying the parameters that determine the cryopreservation process (freezing rate, storage temperature, cryoprotective agents, storage time), various protocols have been designed for preservation of osteochondral allografts of rabbit femoral condyles. The grafts were implanted orthotopically for three months. After harvesting, the results were evaluated by optical microscopy, histochemistry, and electron microscopy (scanning and transmission). A quantitative study and statistical analysis was performed using a gradation scale of chondral degeneration. Synovial reaction was higher in the fresh allograft than in the cryopreservation groups. Glycerol yielded better results than DMSO as a cryoprotective agent. No cryopreservation protocols produced the results equal to the control groups of either fresh auto- or allografts. Optimal preservation was achieved with either the group with hypothermic storage at 4 degrees for no more than 48 hours or the group with slow freezing to -80 degrees and preparative exposure to 15% glycerol at 4 degrees for 60 minutes. No statistically significant differences were found in these two groups.