A mechano-regulation model of fracture repair in vertebral bodies.

In this study a multi-scale mechano-regulation model was developed in order to investigate the mechanobiology of trabecular fracture healing in vertebral bodies. A macro-scale finite element model of the spinal segment L3-L4-L5, including a mild wedge fracture in the body of the L4 vertebra, was used to determine the boundary conditions acting on a micro-scale finite element model simulating a portion of fractured trabecular bone. The micro-scale model, in turn, was utilized to predict the local patterns of tissue differentiation within the fracture gap and then how the equivalent mechanical properties of the macro-scale model change with time. The patterns of tissue differentiation predicted by the model appeared consistent with those observed in vivo. Bone formation occurred primarily through endochondral ossification. New woven bone was predicted to occupy the majority of the space within the fracture site approximately 7-8 weeks after the fracture event. Remodeling of cancellous bone architecture was then predicted, with complete new trabeculae forming due to bridging of the microcallus between the remnant trabeculae.