Cranial versus iliac onlay bone grafts in the facial skeleton: a macroscopic and histomorphometric study

We compared autologous bicortical ilial and cranial bone grafts onlaid to the facial skeleton in 60 adult New Zealand rabbits to evaluate the initial phase of incorporation of these grafts. The animals were distributed in two equal groups in which either cranial or iliac grafts were harvested and fixated, devoid of their periosteum, in direct contact with the nasal bone with micro screws. Each of these two groups were then subdivided into three groups, which corresponded to the three times the animals were killed: 18 days, 30 days, and 60 days. The grafts were measured in their linear dimensions and weighed before fixation and after harvesting when the animals were killed. Undecalcified histological sections were prepared, and histomorphometric parameters of bone formation (bone volume, osteoid volume, surface thickness, and osteoblastic surface) and resorption (osteoclastic surface and eroded surface) were measured. The results confirmed those of previous studies in that cortical grafts maintained their volumes to a greater extent than their cancellous counterparts indicating that the remodeling process may be uncoupled in the transplanted iliac grafts. It is postulated that the significant decrease in mechanical stimulus that the cancellous grafts undergo determines this imbalance in the remodeling activity, which results in greater bone resorption than formation and thus decreased volume.