fracture mechanics analysis of fourth lumbar vertebra in method of finite element analysis

Objective: in this paper, finite element model of the l4 vertebra subjected to combination of compression and flexion loading in isotropic and anisotropic cases is investigated. methods: in both cases, the vertebra is considered homogeneous. also, the body of vertebra is divided to cancellous and cortical sections in anisotropic model, but the process is assumed isotropic such as isotropic model. the maximum von mises stress on the fourth lumbar vertebrae is obtained. also, the stress intensity factor is analyzed with placing a small crack on the critical region of the model from view point of fracture mechanics. furthermore, the required force for the fracture of fourth lumbar vertebrae is obtained through increasing the applied force for assumed model. results: the results show that the highest stress value and its position is 7.237mpa in the upper pedicle region for anisotropic property of vertebrae. at the end of this article, stress intensity factors in different aspect ratios of crack for anisotropic vertebrae under combination of flexion and compression loading are plotted.