The impact of bone morphogenetic protein-2 (BMP-2), Vascular Endothelial Growth Factor (VEGF) and basic Fibroblast Growth Factor (b-FGF) on the osteointegration, the degradation and biomechanical properties of a synthetic bone substitute

Introduction: It was the purpose of this investigation to test the osteointegrative capacity and the degradation rate of a neutralized glass ceramic within an animal model after loading with different growth factors. Materials and Methods: The glass ceramic GB9N was implanted in the medial tibial head of mature merino sheep (n = 48) after being loaded with either Bone Morphogenetic Protein-2 (BMP-2, 100 mug/100 mul), Vascular Endothelial Growth Factor (VEGF, 100 mug/100 mul), basic Fibroblast Growth Factor (b-FGF, 60 mug/100 mul) or unloaded. At 4 weeks (n=24) and 9 months (n=24) after operation histomorphological, histomorphometrical and biomechanical investigations were performed. Results: The amount of newly formed bone was different within the study groups after 4 weeks. BMP-2 induced a significant increase in bone formation and a significant decrease of residual substitute. b-FGF and VEGF induced no such effects in comparison to the controls. Biomechanical investigations could only demonstrate slight increases of the maximal fracture load in the BMP-2 group after 4 weeks in comparison to the others. At 9 months after operation no differences concerning newly formed bone could be found in the study groups comparing to the controls. Only the amount of residual substitute was still significantly lower in the BMP-2 group. Biomechanical data could demonstrate maximal fracture loads of all study samples achieving the level of the controls. Conclusion: This investigation has demonstrated that by combining synthetic bone substitutes with growth factors certain parameters of the bone remodelling process can intitially be influenced in a positive way.