Mechanical stimuli in prediction of trabecular bone adaptation: numerical comparison

Adaptation is the process, with which bone responds to changes in loading environment and modifies its properties and organisation to meet the mechanical demands. Trabecular bone undergoes significant adaptation when subjected to external forces, accomplished through resorption of old and fractured bone and formation of a new bone material. These processes are assumed to be driven by mechanical stimuli of bone-matrix deformation sensed by bone mechanosensory cells. Although numerous in vivo and in vitro experimental evidence of trabecular bone morphology adaptation was obtained, the exact nature of mechanical stimuli triggering biological responses (i.e., osteoclastic resorption and osteoblastic formation) is still debated. This study aims to compare different mechanical stimuli with regard to their ability to initiate the load-induced adaptation in trabecular bone. For this purpose, a 2D model of two trabeculae, connected at their basement, with bone marrow in the intertrabecular space was developed. The finite-element method was implemented for the model loaded in compression to calculate magnitudes of several candidates of the bone-adaptation stimuli. A user material subroutine was developed to relate a magnitude of each candidate to changes in the shape of trabeculae.