In this study, serial changes in mechanical strengths of allogenic bone grafts were evaluated 2, 4, 6 and 12 weeks after grafting.
Experimental subjects were two kinds of inbred rats with different M.H.C. Femoral diaphyses of Fischer 344 rats were treated with (1) freezing at-80°C, (2) lyophilizing, (3)-defatting or (4) decalcifying. Fresh femoral diaphyses were used as controls. These treated bones were grafted into subcutaneous spaces of Brown-Norway rats and Fischer 344 rats. Fischer 344 rats were used in fresh isogenic grafts cases.
The mechanical strengths of bones treated under various methods were measured by bending test using a strength-test machine with a microcomputer.
Results:
1. In bending tests, the maximum load values of treated bones were low compared with that of fresh bones. The load values of decalcified bones were unmeasurable.
2. After grafting, the bending strengths of fresh allogenic bones were extremely low, that of bones frozen at -80°C or lyophilized bones were reduced a little and that of defatted bones were not reduced. On and after 4 weeks following grafting, the load values of decalcified bones were measurable. The bending strengths of fresh isogenic bones were low compared with that of fresh allogenic bones, but after 4 weeks following grafting strengths were slightly high.
3. The above results suggest that defatted bones are recommended for bone grafting when mechanical strength is required.
