Computational Modelling of the Mechanics of Trabecular Bone and Marrow Using Fluid Structure Interaction Techniques

Abstract

Bone marrow found within the porous structure of trabecular bone provides a specialized environment for numerous cell types, including mesenchymal stem cells (MSCs). Studies have sought to characterize the mechanical environment imposed on MSCs, however, a particular challenge is that marrow displays the characteristics of a fluid, while surrounded by bone that is subject to deformation, and previous experimental and computational studies have been unable to fully capture the resulting complex mechanical environment. The objective of this study was to develop a fluid structure interaction (FSI) model of trabecular bone and marrow to predict the mechanical environment of MSCs in vivo and to examine how this environment changes during osteoporosis. An idealized repeating unit was used to compare FSI techniques to a computational fluid dynamics only approach. These techniques were used to determine the effect of lower bone mass and different marrow viscosities, representative of osteoporosis, on the shear stress generated within bone marrow. Results report that shear stresses generated within bone marrow under physiological loading conditions are within the range known to stimulate a mechanobiological response in MSCs in vitro. Additionally, lower bone mass leads to an increase in the shear stress generated within the marrow, while a decrease in bone marrow viscosity reduces this generated shear stress.

A simple rocker‐induced mechanical stimulus upregulates mineralization by human osteoprogenitor cells in fibrous scaffolds

“…A more even distribution of mineral may be obtained by turning the scaffold over during rocking or by adapting the culture system such that the scaffold is suspended in flowing fluid. One would need a computational model of fluid flow through a porous medium to calculate what the shear stress is on the walls of the electrospun fibres, such as those used for other types of porous scaffolds (Birmingham, Grogan, Niebur, Mcnamara, & McHugh, 2013; Marin & Lacroix, 2015). …”

Multiscale fluid–structure interaction modelling to determine the mechanical stimulation of bone cells in a tissue engineered scaffold

“…In recent studies, advanced two-way fluid structure interaction (FSI) methods have been applied to model the complex interaction between soft cells and tissues and extracellular fluid flow (Birmingham et al 2013;Vaughan et al 2013, Verbruggen et al 2013). This approach allows deformable structures and resulting fluid flow fields to be predicted.…”

Mechanical Stimulation of Bone Marrow In Situ Induces Bone Formation in Trabecular Explants

“…To avoid artefacts at the external artificial fluid layer in the model, the shear stress in the marrow was analysed in a sub region (2.85 X 2.85 X 3.3 mm 3 ) at the peak point of shear stress in a cycle. Shear stress was calculated using the reported shear rate based on the second invariant of the rate of strain tensor and multiplying this by the viscosity 4,21 . Media flow was assumed to have a negligible effect on the generation of shear stress in the bone explants due to the high viscosity of marrow compared to media and so was not included in the models.…”

“…Computational and numerical models have been used to predict shear stress generated within trabecular bone marrow due to LMHF vibration and compression 4,14,19 . An analytical continuum level mixture theory 19 predicted shear stresses (~0.5 Pa) in trabecular bone during cyclic low amplitude strains.…”