The Simulation Of Remodeling And Cross-Section Growth Of Diaphysis

Bone metabolism is a complex process which controls bone growth and modeling during development, and bone remodeling after maturation. Mechanical factors involve in the whole process. To make the bone structure to adapt to changing mechanical environment, the interaction between bone resorption and bone formation adjusts the bone shape, size and organic composition. Abnormal conversion between bone resorption and formation can cause bone disease such as osteoporosis, bone deformity and so on. In order to have a better understanding and provide a theoretical basis for preventing and treating diseases, finite element technique has been widely applied. So research on simulation of bone remodeling and the process of cross-section growth has important academic significance and technical value.This paper carries out numerical simulation of bone remodeling of Wistar rat femur based on bone adaptive remodeling theory, integrated into the physiological regulation of bone growth. According to the relationship between load subject to on the femur and time, we simulate the change in the cross-section diameter of diaphysis during growth. Proximal femur is scanned by Micro-CT to obtain image data. The image data is processed to construct a uniform surface mesh model, and then the model is imported into the finite element software ANSYS to create FEM. The approximately real material property which is obtained using the relation between CT value and bone density is assigned into each element of FEM. Bone remodeling algorithm is performed by writing a program using APDL language. To get close to physiological mechanism of bone, interaction between bone cells and cells is considered into algorithm, apparent density of proximal femur can be obtained after iterative calculation. In addition, assuming the initial cross-section of diaphysis, the finite element analysis is performed to obtained stimulus of each element in cross-section, and then new shape of cross-section can be calculated according to the relation between stimulus and rate of bone remodeling. Repeating above process, the growth process of cross-section of diaphysis can be simulated.Some parameters such as bone remodeling coefficient, the reference value of stimulus and so on are researched in this paper. It is shown that results are consistent with actual physical structure after setting appropriate parameters above. The load is delivered from the femur head to cortical bone, bone which is dense on the surface of diaphysis represents cortical bone; bone marrow cavity appears in the middle region of diaphysis where bone density gets close to zero. For bone initial geometries, the periosteal and endosteal diameters are set, the results show that the periosteal and endosteal diameters can increased significantly after simulation, it is presented that periosteum expands outward and endosteal resorbs after expansion.