In this study, a fully automated workflow is presented for the biomechanical simulation of bone-implant systems using the example of a fractured tibia. The workflow is based on routinely acquired tomographic data and consists of an automatic segmentation and material assignment, followed by a mesh generation step and, finally, a mechanical simulation using the finite element method (FEM). Because of the high computational costs of the FEM simulations, an adaptive mesh refinement scheme was developed that limits the highest resolution to materials that can take large amounts of mechanical stress. The scheme was analyzed and it was shown that it has no relevant impact on the simulation precision. Thus, a fully automatic, reliable and computationally feasible method to simulate mechanical properties of bone-implant systems was presented, which can be used for numerous applications, ranging from the design of patient-specific implants to surgery preparation and post-surgery implant verification.