Study Of Theory And Method For Numerical Simulation Of Bone Remodeling In Weightlessness

Bone is an evolving tissue that is active throughout the whole life. Bone changes its shape and mechanical properties as a response to the mechanical environment. This adaptive behavior is known as adaptive bone remodeling and consists of deposition and resorption of bone material, causing internal density and modulus changes in bone microstructure. During space flight, there’s a reduced load on astronauts’ bones due to weightlessness. This lessened load can shift the bone resorption/growth balance toward more resorption, resulting in bone loss. These changes of bone tissue in long-duration space fight would affect astronauts’ health and impair their physical and mental efficiency. The bone mass and structure changes could be predicted by means of mathematical models. Establishing a numerical model and quantitatively analyzing the bone remodeling process has significant technical and academic value.A mathematical model of bone remodeling was established base on mechanostat theory and the simulation of remodeling model was realized by the second exploiting programming of finite element software ANSYS. Firstly, 2D and 3D finite element models of proximal femur were constructed based on CT images and bone remodeling model was verified. Then bone density changes in 45d-6° head-down bed rest experiment were simulated and the results were compared with measurement data of bed rest experiment. Lastly, bone remodeling process in weightlessness during space fight and bone recovery process after the gravity of ground retrieves was simulated. The time dependence of bone remodeling rate and the bone loss under different load conditions were also studied.The simulation results proved that the mathematical model and simulation program could accurately predict bone remodeling process. The predictions of the model using equivalent stress as the mechanical stimuli were most consistent with the CT image. All the simulation results of bone remodeling in bed rest experiment and in weightlessness environment were well matched with the measurement data and available published data. The predicted changing trend of bone density would be more agree with the actual case by regulating the remodeling rate. The accurate prediction of bone remodeling process would provide a theoretical basis for developing measures to counteract bone loss.