Experimental Study on the Osteosynthetic Properities of Sterilized Allografts


Abstract


Serious problems associated with frozen allografts include infection developing after implantation and difficulty in obtaining them in Japan because of religious and social factors. If the osteosynthetic properties of sterilized allografts, such as autoclaved allografts (135 , 10 min) and ethylene oxide gas sterilized allografts (EOG allografts), are similar to those of frozen allografts (-80 ), such allografts would overcome the problem mentioned above. The purpose of this study is to compare the osteosynthetic properties of sterilized allografts with those of frozen allografts in animal experiments. The allografts were obtained from the 10 mm femoral diaphysis of Wistar rats and treated with one of the above-mentioned sterilization conditions. The immunological response was checked by the skin graft assay. Each allograft was implanted into a 10 mm femoral diaphyseal defect made in an SD rat. In other sterilized allograft implanted groups, the reconstructions were supplemented with autolysed antigen-extracted allogeneic bone (AAA bone). The reconstructions were investigated with respect to incorporation by radiography, histology and microangiography at 2, 4, 8, 12, 16, 24 weeks after reconstruction. In the skin graft assay, the antigen level of the sterilized allografts was similar to that of the frozen allografts, but was not completely extracted. Bony union was achieved at 8 weeks after reconstruction of the frozen allografts and at 12 weeks after reconstruction of the sterilized allografts radiographically. New appositional bone was present at the border of the grafted bone at 8 weeks after transplantation of the frozen allografts. On the other hand, no appositional bone was present at the border of the sterilized allograft at 12 weeks after transplantation. These findings suggest that frozen allografts, but not sterilized allografts, have an osteoinductive property which is largely destroyed by the sterilization methods. The blood vessel density of the sterilized allografts was lower than that of the frozen allografts. The reason for this difference is that sterilized allografts have only osteoconduction. But new bone formation after the invasion of new vessels occurred in the sterilized allografts by osteoconduction. Supplemented with AAA bone, each type of allograft exhibited abundant new bone formation and invasion of new vessels compared to the nonsupplemented allografts. As the union of the sterilized allografts was satisfactory at the host-graft junction by osteoconduction, it is concluded that these allografts can be used for the reconstruction of large skeletal defects. And the addition of osteoinductive material can improve the incorporation of the sterilized allograft.

JOURNAL OF THE JUZEN MEDICAL SOCIETY 101, 802-816i1992j


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