The Conduction Of Poroelastic Mechanical Signals From Osteon To Osteocyte Scale

The human body is usually in a complex stress environment.When the mechanical signal of external load is transmitted to the microscopic scale of bone tissue,the liquid in bone tissue flows and permeates to its microscopic structure level(osteon-lacuna-canaliculi system),and further produces a series of physical effects that stimulate cellular response and make reactions such as osteoclasts and osteoblast,which in turn cause tissue structural changes,ultimately allowing bone to adapt to the external mechanical environment with optimal structure.This is the mechanism of load signal transmission and bone remodeling in vivo,but the scientific quantification pathway of this mechanism is not very clear,especially the mechanical and biological mechanisms under the involvement of osteocytes are not very clear.Based on poroelastic theory,this paper constructs a cross-scale conduction model of fluid flow stimulation signals in bone tissue for studying the fine-microscopic conduction mechanism of internal fluid stimulation signals,and further explores the microscopic structure of bone tissue under the macroscopic load "feel" to the size of the mechanical signal.In this paper,a two-dimensional osteon-osteocyte system section model(including microscopic structures such as lacuna,osteocyte and canaliculi),a three-dimensional osteon-osteocyte system model(including homogenized lacuna and osteocyte),three-dimensional lacuna-canaliculi model and two-dimensional real osteocyte model are established based on poroelastic theory.The results show that the same functional unit at different locations can experience the same magnitude of external load stimulation.Osteocyte processes have the strongest ability to "feel" mechanical signals compared to osteocyte bodies,lacunae and canaliculi.It can be said that processes are the optimal "mechanical receptors" at the microscopic scale of bone tissue.At the microscopic scale,ellipse osteocyte have stronger force transmission ability than circle osteocyte.The horizontally aligned osteocytes are more sensitive to mechanical stimulation than vertical osteocytes.As osteocytes elastic modulus increases,the mechanical signals transmitted to the surface of osteocytes gradually increase.However,changes in the permeability of osteocytes and bone matrix do not affect stress and strain around osteocytes,and only have a significant effect on pressure gradient on osteocyte surface.Compared to an idealized model,a real cell model can more reasonably explain the phenomenon of sudden changes in pore pressure and flow velocity in a region.The stress and strain felt by osteocytes are synchronous with the load,but the pore pressure and flow velocity inside osteocytes have a significant hysteresis effect,which may explain the phenomenon that flow potential behind loading in the force and electric effect of bone.