Fracture analysis of a cortical bone sample from a tibia of a 70 years-old human male donor is conducted computationally using an extended finite element method. The cortical bone microstructure is represented by several osteons arranged based on bone microscopy image. The accuracy of results is examined by comparing a linear elastic fracture mechanics approach with a cohesive segment approach and varying the finite element model mesh density, element type, damage evolution, and boundary conditions. Microstructural features of cortical bone are assumed to be linear elastic and isotropic. We find that the accuracy of results is influenced by the finite element model mesh density, simulation increment size, element type, and the fracture approach type. Using a relatively fine mesh or small simulation increment size gives inaccurate results compared to using an optimized mesh density and simulation increment size. Also, mechanical properties of cortical bone phases influence the crack propagation path and speed.