The Composite Of CPC/rhBMP-2 Improving The Fracture Healing Of Osteoporotic Rats: Experimental Studies

Objective: To evaluate the effects of the composite of calcium phosphate cement (CPC) and recombinant human bone morphogenetic protein-2 (rhBMP-2) on the fracture healing of osteoporotic rats.Methods: 70 femal clean rats were divided into two groups: 63 in ovariectomy group were ovariectomized ,7 in sham operation group were sham operated. 10 weeks after operation, dual-energy X-ray absorptiometry confirmed that osteoporotic animals model have been prepared. Fractures were created in the cancellous bone of the distal right femur of 63 osteoporotic rats. All the animals were divided into 3 groups of 21 each randomly: 1) Kirschner wire group: Intramedullary Kirschner wires were made as inner fixation. 2) CPC group: Injectable CPC single was injected into medullar through 9# needle. The fracture parts were holded by hands until CPC harden. 3) CPC-BMP group: treated as CPC group but substituted the composite of CPC/rhBMP-2 for CPC. At 2, 4, 6,8 weeks after treatment, Five animals from each group were killed. The activity of Alkaline phosphatase (ALP) was quantified, the femora were harvested, and the diameter of bone callus were measured. Four of them were prepared for compressive biomechanical testing and one for histological section. At 8 week after treatment, another one femur sample was obtained from each group to observe under scanning election microscope.Results: At the 4 time-points, the diameter of callus, the activity of ALP and the maximum compressive load of femora from CPC-BMP group were higher than those from the other two groups (P<0.05). The femoral maximum loads from CPC group were higher than those from Kirschner wire group at 2nd week (P<0.05). Of CPC-BMP group, active bone formation was observed histological. The fibrous and osseous callus of CPC-BMP group in the site of fracture appeared earlier than the other two groups. The images of the 8th week's SEM and histological section showed that more CPC resorbedin the CPC-BMP group than in the CPC group. Trabecular in the CPC-BMP group, without the view of bone degeneration of osteonecrosis and resorptive lacuna, were stronger than in the other two groups.Conclusion: These studies indicate that: 1) A local injection of CPC/rhBMP-2 accelerates fracture repair in this osteoporotic rat distal femoral fracture model and increases the intensity after bone healing; 2) A local injection of CPC can fix the parts of fracture in an instant; 3) The resorption of CPC is accelerated after Loading rhBMP-2; 4) A local application of CPC/rhBMP-2 can improve the osteoporotic bone quality around it.