Synthetical Evaluation Of Composite Material Of Bone Morphogenetic Protein, Decalcified Bone Matrix And Bone Cement

OBJECTIVE It is common to be met in orthopedic clinic that the bone defects caused by bone tumors which have no ideal methods to repair at present However the clinical results that arrest people's attention have been got by the surgical treatment for bone tumors with microwave-induced hyperthermia and the allograft decalcified bone matrix (DBM) combined with bone cement (BC) had been used to try repairing the bone defects caused by microwave-induced hyperthermia in recent years. In order to further improve the bone formation inductive activity, we try to mix the bovine bone morphogenetic protein (bBMP) with this composite material and this experiment was designed to determine the biological procedure of the composite material of DBM, BC and bBMP when it was implanted in the canine femoral defect caused by microwave-induced hyperthermia. The aim of the present experiment is to prepare and evaluate the composite material of bovine bone morphogenetic protein (bBMP), decalcified bone matrix (DBM) and bone cement (BC) for the clinical use and the batch process.METHODS The allograft canine DBM which diameter was less than 2.0mm was prepared and sterilized to use. The bBMP was extracted from the fresh cortex of the four limbs of the young ox and its bone formation inductive activity was determined. First mix the bBMP and DBM together with the proportion of 1:25 with adsorption and directly, then add BC with different weight proportion and finally the composite material was examined by biomechanics, scan electron microscope, determinations of bone formation inductive activity and biocompatibility. The canine femoral defect model was caused by microwave-induced hyperthermia and the composite material was implanted into the canine right femoral defect and the left one was filled up with BC only as a contrast. The canine femurs were examined by X-ray, 99mTc-MDP bone scintigraphy, biomechanics, histology, flurescence labeling of terramycin and India ink staining.RESULTS The bBMP had strong bone formation inductive activity. At the third day when it was buried in the muscles of the behind legs of the mouse, there were a large number of6mesenchymal cells around the bBMP and at the seventh day the mesenchymal cells were differentiated into the chondrocytes. At the fourteenth day the cartilage was formed and at the twenty-first day and the twenty-eighth day the new bone was formed. Though the bone inductive activity of the composite material was weaker and the amount of the new bone which it inducted to form was less than that of bBMP, it had very strong bone inductive activity. There was no affect for the bone formation inductive activity of the composite material when the bBMP was combined with DBM with different method. However the direct method was the most convenient. When the composite material was implanted into the abdominal cavity of the mouse, no animal died in the acute toxicity test and the body weight, red blood cells, white blood cells and hemoglobin of the mouse were not affected in the subacute test. The composite material did not affect the function of hemolysis and coagulation. The determinative results of biomechanics was that the biomechanical intensity of the composite material decreased when the proportion of DBM was from 0% to 75%. However the composite material had enough intensity to bear a load when the proportion of DBM was 50% and 60%. Under the scan electron microscope, there were irregular gaps in the composite material and most of them with the diameter was less than 100 u m and the porosity was less than 20% when the proportion of DBM was 40%. So it was unfavorable for the new bone to form and the new blood vessels to reconstruct. However there were many irregular gaps with diameter of 200 u m to 800 u m in the composite material with the proportion of DBM was 50% and 60% and the porosity was 32% to 55%. There were more irregular gaps with diameter of 200 u m to 800 u m in the composite material with the proportion of DBM was 75% and the porosity was more than 60%. However the DBM...