Trabecular Remodeling Simulation of a Vertebral Body with a Fixation Screw Using Voxel Finite Element Models

A three-dimensional simulation of trabecular surface remodeling was performed to investigate the basic effects of a fixation screw on the trabecular structural changes in a vertebral body. Voxel-based finite elements were used to construct computational models of the bone and screw for an entire vertebral body with the screw and for the bone-screw interface. The remodeling simulation for the entire vertebral body showed that the implantation of the fixation screw caused changes in the mechanical environment in the cancellous bone, leading to trabecular structural changes at the cancellous level. The effect of the screw on trabecular orientation was greater in the regions above and below the screw than on that in front of the screw. In the case of the bone-screw interface, the trabecular structural changes depended on the load applied to the screw. It was suggested that bone resorption predicted in the pull-out loading case would be a candidate cause of loosening of the screw. The results indicate that the effects of the implanted screw on the trabecular structural changes would be more important for longer-term fixation.