Abstract
An individual trabecula in a cancellous bone is a porous material consisting of a lamellar bone matrix and interstitial fluid in a lacuno-canalicular porosity. The flow of interstitial fluid created by the application of mechanical load to a bone is considered to stimulate osteocytes for regulating bone remodeling, as well as enhance the transport of signaling molecules. The purpose of this study is to investigate, based on poroelastic theory, the flow-induced stimuli given to the osteocytes embedded in an individual lamellar trabecula. A single trabecula was modeled as a two-dimensional poroelastic slab composed of multiple layers subjected to cyclic uniaxial and bending loading. To consider the spatial variations in material properties due to lamellar structure of the trabecula, each layer was assumed to have a different value of permeability. By analytically solving the diffusion equation obtained from poroelasticity, we developed a solution for the interstitial fluid pressure in the lacuno-canalicular porosity within the single trabecula. Based on the solution obtained, we demonstrated the distribution of seepage velocity across the trabecula and qualitatively assessed the mechanical stimuli given to the osteocytes. The results suggested that osteocytes close to the trabecular surfaces are normally exposed to larger flow stimuli than those located around the center of the trabecula, regardless of the loading conditions and the spatial variations in permeability. On the other hand, osteocytes around the center of the trabecula, particularly with relatively large inner permeability, are stimulated by the fluid flow when the bending load is more dominant than the uniaxial load. Our theoretical approach might provide a better understanding of the effect of the spatial variations in bone material properties on the flow-mediated cellular mechanotransduction and signal transport for bone remodeling.
