This experiment was performed in order to compare the result of fresh patellar osteochondral allotransplantation in rabbits with that of autotransplantation, on which one of the authors had reported previously.
In adult rabbits weighing 2-2.5kg, the right knee was exposed through anteromedial incision and the patella was obtained for graft. All soft tissues attached to the patella were trimmed off. The cortical bone of the patella was also removed from its anterior surface but the subChondral bone, no more than 3mm in its thick-ness, was left.
Thus, a patellar graft, consisting of the articular cartilage and its subchondral bone, was made. This patellar graft was fitted into the artificial osteochondral defect of another rabbit which was made at the medial tibial ccni~le. After the transplantation, along leg plaster cast was applied for 3 weeks to the grafted limb with the knee and ankle in 90 degrees of flexion. The 21 experimental animals were sacrificedt one, two, three, four, six, eight and ten weeks after transplantation. The fates of the grafts were investigated through the roentgenograbhic and histological examinations. The results of this experiment were as follows:
1. The osteocyte in grafted bone remained viable bythe end of 5 weeks after Transplantation. At the end of 6 weeks blood vessels which invaded the grafted subchondral bone. just beneath t´he articular ecartilage were regressed, ´and bone absorption and empty lacunae by osteoclast were rioted. At the end of 8 weeks after transplantation, the grafted bone was replaced completely with new bofle by creeping substitution.
2. The grafted articular cartilage survived till the end of 4 weeks after transplantation. At the end of 6 weeks, decrease in cartilage stain, irregularity of cartilage, disarrangement o~ chondrocytes and fibroblastic invasion from the subchondral bone toward the tide mark were noted. At the end of 8 -weeks, erosion, fibrillation and cloning of superficial cartilage cells were noted and fibroblastic invasion toward the tide mark was more advanced.
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