The incorporation of different sorts of cancellous bone graft and the reaction of the host bone. A histomorphometric study in sheep

We performed a morphological and histomorphometric analysis of the use of either autografts, or of frozen or freeze-dried cancellous bone allografts in sheep. A cancellous bone defect was created in the lateral portion of the distal epiphysis of the left femur. Four groups of six animals were monitored for 3 months. In the first group, the cavity was filled with autograft, in the second with frozen allograft and in the third with freeze-dried allograft. In the last group, the cavity was not filled and served as control. A study of the host bone showed that the mean trabecular width of the peripheral osteoid was greatest in the control group, while the number of osteoblasts and osteoclasts was significantly lower in the freeze-dried allograft group. However, the different bone grafts that were used to fill the cavity showed a greater trabecular width and area in the autografts. Among the frozen allografts, these measurements were also greater than in the freeze-dried allograft group. The 'erosion surface' of the freeze-dried allograft group was also found to be three times greater, and there were a larger number of osteoclasts and osteoclastic nuclei. We concluded that the 'lyophilised' allografts were re-absorbed rapidly and that there were no major morphological differences between the frozen allografts and the autograft groups.