Influence of β-calcium phosphate on repair of large bone defects using nested composite bone graft of allogeneic bone and vascular autograft bone

Abstract

Objective To study the influence of β-calcium phosphate on the repair of large bone defects using nested composite bone graft of allogeneic bone and vascular autograft bone. Methods Sixteen New Zealand rabbits of 6 months old were randomly divided into 2 equal groups (n=8). Models of 15 mm large bone defect were created on the middle and upper shaft of the right tibia in all the rabbits. The defects were repaired using nested composite bone graft of allogeneic bone and vascular autograft bone. The gap between the allogeneic bone and the autograft bone in the composite bone graft was filled with β-calcium phos-phate in the experimental group but not filled in the control group. X-ray examination was conducted to observe fracture healing on the right postoperative day and 8 and 12 weeks after operation; examination of bone mineral density in the bone defect area was conducted at 1, 8 and 12 weeks after operation; histological observation of samples was made at 8 and 12 weeks after operation. The 2 groups were compared regarding the effect of β-calcium phosphate on the repair of bone defects. Results All the animals survived till the observation time and their wounds healed well without any infection. X-ray showed better bone union in the experimental group than in the control group at 8 and 12 months after operation. In the experimental group, the bone mineral density at one week(0.171±0.016 g/cm2) increased significantly at 8 weeks(0.293±0.014 g/cm2) but decreased significantly at 12 weeks (0.274±0.014 g/cm2) (P< 0.05); in the control group, the bone mineral density at one week (0.154±0.011 g/cm2) increased significantly at 8 weeks(0.211±0.008 g/cm2) and increased significantly still higher at 12 weeks (0.235±0.010 g/cm2) (P< 0.05). At 8 and 12 weeks, the bone mineral density in the control group was significantly lower than in the experimental group(P< 0.05). Histological detection showed that massive new bone formed in the composite bone graft in the experimental group at 8 and 12 weeks after operation while little new bone formed in the bone defect area and there was a distinct gap between the allogeneic bone and the autograft bone in the control group. Conclusion As filling of β-calcium phosphate particles can accelerate formation of new bone callus to promote healing of long bone defects, it makes up for the shortcoming of conventional nested composite bone graft of allogeneic bone and vascular autograft bone. Key words: Transplantation, autologous; Reconstructive surgical procedures; Animal experimentation; β-calcium phosphate; Large bone defects