| The rapid development of computer technology urges the integration of interdisciplinary technology.With the emergence of the fracture healing simulation as a kind of emerging interdisciplinary technology,the digital simulation of healing process based on biomedical theory has become one of the most significant application of computer simulation technology.Meanwhile,new opportunity can be provided for the development of the subject by means of combining medicine,biomechanics and mechanical engineering.Emerging research direction employs computer technology to predict and simulate movement and restoration law of life entity,so as to provide the basis for the fracture treatment and research about medical equipment.Fracture healing is a kind of repair process,which costs a lot of time.Multi-factors depending on each other in a complex manner have a significant influence on healing.This thesis mainly aimed at mechanics condition and biological factor to develop a dynamic model to simulate complex interactions of mechanical stability,revascularization and tissue differentiation in secondary fracture healing.Unlike previous study models,a three-dimensional finite element model was established to describe fracture callus mechanics based on tetrahedral units.The blood perfusion regarded as a spatio-temporal state variable was included into the model to simulate revascularization process.Combining finite element method and fuzzy logic,the dynamic model described the biological processes of tissue differentiation,including angioenesis,intramembranous ossification,chondrogenesis,cartilage calcification,endochondral ossification,atrophy and so on,all of which depended on local strain state and local blood supply.The callus healing was simulated time-discretely by explicit Euler integration iterative loop over equidistant time steps.Tissue concentrations were updated each time step to obtain the next-time properties of tissues.Secondly,the fracture healing simulation was implemented in the Visual Studio environment.Finally,through the comparison result with the experiment data from the existing literature,the agreement of the simulation results with the sheep experiment verified the simulation program and the model approach.Finally,in order to evaluate how the predicted revascularization depended on the mechanical environment and how the axial stability influenced the fracture healing,this thesis simulated two different healing cases according to two groups of transverse metatarsal osteotomies in sheep.The model predicted slower revascularization and delayed bony bridging for the less stable case,which corresponded well to the experiment observations.In addition,we analyzed the fracture healing under different blood supply condition in order to demostrate the sensitivity to blood.At the same time,based on the extendibility of the simulation program,some reference can be provided for the subsequent improvement of simulation testing platform. |
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