Mechanical Properties Evaluation And Application Analysis Of Heterotopic Osteogenic Material Based On BMP-2 Microspheres

Bone defects are a major threat to human health.At present,surgery is the main method to deal with bone defects,and this requires bone defect repair materials.Bone defects are primarily treated with artificial bone grafts and bone grafts,and both materials have disadvantages.Heterotopic bone provides advantages that other materials do not provide in the treatment of bone defects.MPEG-PCL microspheres loaded with bone morphogenetic protein-2(BMP-2/MPEG-PCL-MS)are an emerging means of culturing heterotopic bone.However,the effect of such microspheres on the quality of heterotopic bone osteogenesis has rarely been studied.The performance of heterotopic bone as a bone repair material has also rarely been reported.To explore the effect of microspheres on heterotopic bone osteogenesis and the performance of heterotopic bone on bone repair,this paper evaluates the effects of microspheres and the performance of heterotopic bone through mechanical properties,material properties,and finite element(FE)simulation.The results of the study could provide a basis for evaluating the performance of ectopic osteogenesis as bone repair materials.In this paper,material properties of ectopic osteogenesis were obtained by scanning ectopic osteogenesis by Micro-CT in the microsphere group and the control group,that could reflect the quality of osteogenesis and the mechanical properties of ectopic osteogenesis to a certain extent.The mechanical properties of the two types of ectopic bone formation were studied,and the compressive strength of the ectopic bone formation was compared with the in-situ bone femoral.The possibility of ectopic bone formation as a bone repair material was explored from a mechanical point of view.The hardness and modulus of elasticity of the bones were investigated by nanoindentation experiments,and the hardness and modulus of elasticity of the ectopic bone are important factors affecting the effect of bone repair.The results showed that the BMP-2-loaded microspheres had a great improvement in the quality of ectopic osteogenesis,and the quality of ectopic osteogenesis and mechanical properties of the microspheres group were significantly better than those of the control group,showing the potential of more excellent bone repair materials.This paper establishes an ectopic osteogenic finite element model(FEM)based on Micro-CT scan data.Comparing the ectopic osteogenic FEM simulation data with the pressure test data,this paper explores the factors that affect the simulation accuracy of the FEM,such as material property assignment,mesh delineation,and force area,etc.And this paper also explores a line of FEM simulation technology that could balance the simulation accuracy and computational speed.The results show that there is no much difference in calculation accuracy of the FEM between using Ansys to mesh and set material property assignments based on the homogenization method and using Mimics to mesh and set material properties based on Hu values.The former has higher accuracy in the solution with fewer errors.In the simulation of the revised finite element stress surface with 3D printing technology,the FEM which uses Ansys to mesh and set the material could attribute assignment based on the homogenization method,that has higher accuracy and smaller error fluctuations,and it is also more capable for providing scientific and reasonable finite element analysis data.For the analysis of the mechanical properties of ectopic osteogenesis as a bone defect repair material,a FEM of the mouse in situ femur and a corresponding FEM of the bone defect were established.After completing the validation of the model reliability,the mechanical performance of ectopic osteogenesis as a cancellous bone defect repair material was compared with that of in situ femur.At the same time,models of bone defects in different parts were established,and the applicability of heterotopic osteogenesis as a bone repair material was studied.The results show that the established FEM of the mouse femur has excellent reliability,and the heterotopic bone is more effective as a repair material for the cancellous bone of the femur in different bone repair modes.The four-week BMP-2 microspheres were the least effective as a repair material for cortical bone defects,the four-week BMP-2 microspheres performed slightly better than the eight-week BMP-2 solution group in different modes of bone repair,and the eight-week BMP-2 microspheres were the most stable in several modes of bone repair,and the deformation was significantly less than the other groups,providing direct evidence that the eight-week BMP-2 microspheres can be used as a repair material for femoral defects,and it could be judged that the eight-week BMP-2 microspheres have the potential of a bone repair material.This topic provides strong theoretical and data support for the further development of heterotopic bone as a bone repair material,and it has made useful attempts to explore the medical-industrial combination research and application path for bone repair.