Segmental bone grafting. Comparison of different types of graft in dogs.

We have compared the biological behaviour of eight types of segmental tibial grafts in dogs under different immunological conditions: autografts, allografts, allografts with short-term immunosuppression (4 weeks), and allografts with longterm suppression (20 weeks). Some grafts were revascularised by microsurgical anastomosis, others were not. The long-term immunosuppressed allografts are most similar to autografts in terms of perfusion pattern and graft-host interface healing. The difference between long-term immunosuppressed allografts and allografts which were not immunosuppressed was highly significant (P less than 0.01). The viability of long-term immunosuppressed allografts, as measured by fluorochrome-labelled osteons, did not reach the level of the autografts, but still differed significantly from the allografts which were not immunosuppressed. Immunosuppression, therefore, improves the survival and the quality of the graft, more so for long-term immunosuppressed grafts, and also in revascularised grafts.