Radiological study of the sandwich method in cervical anterior fusion using autologous vertebral bone grafts

Autologous bone grafts from cervical vertebral bodies (Williams-Isu method) are used for anterior fusion of the cervical spine. When adequate amounts of bone cannot be harvested from the vertebral body, hydroxyapatite (a ceramic) is placed between the bone grafts (the sandwich method). We conducted a radiological study to examine the efficacy of the sandwich method by comparing the alignment of the whole spine and the fused segment between patients who had received a sandwich graft (n=20) and a control group (n=20). Although there was no difference between the two groups with respect to the alignment of the whole spine, the alignment and height of the fused segment was significantly better in the patients in the sandwich graft group. In both groups the position of the anterior edge of the graft and the loss in the angle of the fused segment were significantly correlated (p<0.05). We found that the sandwich method not only reinforced the graft, but also yielded better results with respect to the angle and height of the fused segment.