| ObjectiveTo obtain an ideal bone graft , the study prepared an Combined bone graft made from a- calcium sulphate hemihydrate (α-CSH) and β- tricalcium phosphate(β-TCP),at the same time the study explored : (1) The method of preparing the Combined bone graft. (2) The physical and chemical characteristics of the Combined bone graft. (3) The degradational characteristics of the Combined bone graft. (4) The bone formation ability of the Combined bone graft.Methods1. The a-CSH is made from calcium sulphate dihydrate(CSD)under the special temperature and pressure; ?TCP is made from cancellous bone in the femur of healthy cattle by sintered two times under high temperature after defats and decells; The suspl is prepared by putting the powder of a-CSH into dehydrated alcohol, and put the same mass ?TCP bead of diameter 0.85-2mm into the suspl ,vibration and stoving at the heating oven of 37癈,after stoving the Combined bone graft was gotten; all the materials were Confirmered by Scanning electron microscope (SEM)and X-ray diffraction (XRD).2. Testing the setting time, setting strength and porosity in vitro after setting of the Combined bone graft according to proper ratio of solid and liquid, and testing the change of composition after setting with XRD, and observing the change of section after setting with SEM.3. Prerared combined bone graft into circular cylinder of 12mm high and 8mm dimeter ,put the cylinder into PBS solution of PH7.4 ,observing the change of the PH of the solution, strength and ratio of degradation of the cylinder. Specimens were implanted in rabbit muscle to evaluate the ratio of degradation , the change of strength and the reaction of tissue around the materials at 4, 8, 12weeks after implanting.4. Bilateral distal femoral bone defects of rabbits (10x5mm)were made which was 4mm distance from the articular facet of distal femoral. The defects were filledwith α—CSH,β-TCP or combined bone graft and the blank was not filled any materials . Specimens of distal femoral were retrieved at 4, 8 and 12 weeks after operation. Ability of bone formation about the materials were observed .Results1. β-TCP was made from cancellous bone in the femur of cattle under special conditions , which contained the spatial structure of normal cancellous bone. α-CSH was made from CSD under special temperature and pressure ,which is more pure and regulation in crystal form, α-CSH and β-TCP can be maded into combined artificial bone2. Combined bone graft can srlf-set in situ, the initial setting time is 4.6 ± 1.3min,and the final setting time is 13.1 ± 2.9min at the ratio of solid to liquid 1g:0.2ml; the initial strength of the Combined bone graft after setting is 8.95 ± 1.43Mpa, after setting the CSH transformed into CSD, and the section was covered by the cryetal of CSD.3. The PH of the combined bone graft kept declining to about 5.6, which is between the PH of α-CSH (about 5.2)and β-TCP(about 7.4) . The ratio of degradation of the combined bone graft is 42.2% after 4weeks , 61.3% after 8 weeks, and 70.5% after 12weeks in vitro. The strength of the combined bone graft is 2.51±0.81 Mpa after 4 weeks , and 0 after 8 and 12 weeks in vitro. The ratio of degradation of the combined bone graft is 51.5% after 4weeks , 68.5% after 8 weeks, and 78.8% after 12weeks in vivo.The strength of the combined bone graft is 3.43 ± 0.97Mpa after 4 weeks, and 1.30 ± 0.3Mpa after 8 weeks, and 0.87 ± 0.16Mpa after 12 weeks. There is no inflammatory reaction in the tissues around the materials during degradation.4. Evaluation o f the bone formation of the combined bone graft: X-ray and molybdenum target shows the bone infiltration was obvious in combined bone graft both in the center and edge of the materials, only little bone infiltration can be seen in the edge ofα-CSH, β-TCP and the blank, the center of α-CSH became vacant zone because of the faster speed of degredation.Pathology section shows new bone grows in the edge and center of the combined bone graft, butthe new bone grows only in the edge of α-CSH and β-TCP. Statistics shows the amount of new bone of combined bone graft is more than α-CSH , β-TCPand the blank. More fluorescence materials were observed in combined bone graft showed the new bone formation was active and bone rebuilding was faster than α-CSH , β-TCPand the blank .Conclusion1. Combined bone graft can be prepared by α-CSH and β-TCP using dehydrated alcohol as a media, there is not same report in the world at present.2.The combined bone graft has good performance of self-setting in situ , the Strength of setting is near to cancellous bone which can meet the need of repairing the defect in the location of non-weight loading.3. The experiment shows that the ratio of degradation of combined bone graft is between the α-CSH and β-TCP, the requirement ratio of degredation can be get by adjusting the rate of the two materials.4. The bone formation of combined bone graft is evident in the defect,the ability of bone formation is better than α-CSH and β-TCP.
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