Experimental Study On Membrane Technique For Repairing Bone Defects By Implanting True Bone Ceramic Combined With Vascular Endothelial Growth Factor

Objective To study the repair effect of vascular endothelial growth factor (VEGF) on bone defect and the effects on angiogenesis and bone regeneration of VEGF combined with true bone ceramic (TBC) by membrane technique. And further we explored bone healing mechanisms and reciprocity of membrane guided bone regeneration (MGBR) and osteoinduction. In addition we investigated why VEGF-TBC composite material by expanded poly tetrafluorethylene (e-PTFE) membrane can repair the bone defect successfully. At last we discussed the potential application of this material at clinic.Methods The whole quantity of experimental animals was fifty-two New Zealand rabbits. They were divided into two groups randomly. Each group had two subgroups. We build the animal model of 10mm bone defect where was in the middle of rabbits radius. The first group: to implant TBC combined with VEGF by e-PTFE in right radius (A subgroup), to implant TBC combined with VEGF in left radius (B subgroup), the second group: to implant TBC with e-PTFE membrane in right radius (C subgroup), to implant only TBC in left radius (D subgroup). Ten New Zealand rabbits in each group underwent X-ray investigation randomly, the bone healing rates of osteosynthesis sites were observed and bone density of the implant postoperatively at the 2^nd, 4^th, 6^th, 8th and 12^th week were measured. At the same time, four rabbits in each group were killed and the histology of bone specimen were studied. The results ofall groups were contrasted with each other. Results1. Observation of X-ray graphicsthe A subgroup had apparently osteogenic manifestation at the 4^th week and formed mass bony callus at the 6^th week after operation, all the bone defects got clinical cured at the 8^th week. the B and C subgroups had osteogenic manifestation at the 4th week and formed mass bony callus from the 6^th week to the 8^th week after operation, the bone healing rate of the implant postoperatively was 80% at the 8^th week. All the bone defects got clinical cured at the 12^th week after operation. the D subgroup had only unconspicuously osteogenic manifestation at the 4^th week after operation. the healing rate of the bone defects was 50% at the 8^th week and was 80% at the 12^th week after operation.2. Meterage of bone densitythe bone density of the A, B, C and D subgroups in bone defect area had no obvious difference, but was all lower than the bone density of rabbit normal radius at the 2^nd week after operation. the bone density of the A subgroup was getting higher and higher at the 4^th, the 6^th week. At the 8^th week, it was similar to the bone density of the rabbit normal radius. the bone density of the B and C subgroups in bone defect area was begin to increase at the 4^th week, and persistently increased from the 6^th to the 8^th week. At the 12^th week, it was similar to the bone density of the rabbit normal radius. the bone density of the D subgroup in bone defect area was begin to increase at the 4^th week, and was getting higher and higher from the 6^th week to the 12^th week, but was all lower than others.3. Observation of histologythe A subgroup had active osteogenicity at the 2^nd week, and then began to form mass bony callus and Haversian system in the 4^th6th week after operation. At the 8^th week, there appeared a lot of mature bony callus and signs of clinical cure. the B and C subgroups had signs of osteogenicity at the4th week, and the bony callus began to increase from the 6th to the 8th week. At the 12th week, there appeared mature bony callus and Haversian system. The D subgroup had signs of osteogenicity at the 4th week, bony callus gradually increased from the 6th to the 8th week, and at the 12th week bony callus and Haversian system appeared at middle level. Conclusion1. VEGF can cut down the time of bone defect repair through improving angiogenesis, bone tissue regeneration, and through increasing vascular endothelial cell (VEC), osteoblast and chondroblast proliferation.2. e-PTFE membrane can bring to success of bone regeneration through preventing fibroblast connective tissue from invading the bone defect area, guiding the potential osteogenic cell and osteoinduction factor concentrated under membrane and avoiding nonunion occurrence.3. True bone ceramic (TBC) has the three-dimensional net structure, the high biodegradability, excellent property of osteoacusis and super biocom -patibility, so it can be using as frame material for repairing bone defect.4. VEGF-TBC combined with e-PTFE membrane has more osteogenic ability and it can repair bone defect excellently. It has a good potential application prospect at clinic as a kind of bone tissue-engineering vehicle.