AbstractLoad-induced fluid flow in lacunae – canalicular porosity in bone, induced by the mechanical loading, has been reported to play an essential role in bone metabolism, mechanotransduction, and bone adaptation. The applied load causes the fluid inside the lacunae – canalicular porosity to flow, which generates shear stresses on the osteocytes. The energy of the moving fluid that gets dissipated can be considered a stimulus for bone adaptation&nbsp;[1].This study aims to provide an insight into why bone formation is more pronounced at endocortical surface relative to the periosteal surface under the application of load, as suggested by Birkhold et al.&nbsp;[2]. We present a finite element model of a poroelastic cylinder subject to different loading conditions – axial loading, cantilever loading, three-point bending, and four-point bending. This simplified geometric model is used as the ideal representation of cortical bone. Using soil element (C3D8RP – Continuous 3 Dimensional 8 noded reduced integration pore pressure hexahedral element) type, a coupled pore fluid diffusion and stress analysis are performed in ABAQUS. The periosteal surface of the bone is impermeable in nature, and the endosteal surface is permeable. Therefore to simulate these conditions, zero pressure boundary condition ) on the inner surface and zero velocity boundary condition, i.e., zero flow boundary condition on the outer surface are applied, where ‘r’ is a vector in the radial direction. In all the cases, sinusoidal loads are used at a frequency of 2Hz for 1 second such that it would be able to generate a strain of &nbsp;&gt;1500 µe. The Fluid velocity and pressure estimated by the above analysis are used to calculate the dissipation energy. The osteocytes, the most abundant cells present in the bone, form a cellular network through their processes in the lacunae – canalicular porosity. These cells can transmit signals from one place to another through this network. The weighted average of the dissipation energy in the zone of influence includes the non-local behavior of osteocytes.Here, we showed that despite lower mechanical stresses at the endocortical surface relative to a periosteal surface, the dissipation energy is higher at the endocortical surface due to its permeable nature, which makes endocortical surface more responsive during bone apposition than the periosteal surface.&nbsp;&nbsp;Key Words: Endocortical Surface, Periosteal Surface, Load – induced fluid flow.&nbsp;References[1] N. C. Kumar, I. Jasiuk and J. Dantzig, "Dissipation Energy as a stimulus for Cortical Bone Adaptation," Journal of Mechanics of Materials and Structures, vol. 6, no. 1-4, pp. 303-319, 2011.[2] A. I. Birkhold, H. Razi1, G. N. Duda, R. Weinkamer, S. Checa and B. M. Willie, "The Periosteal Bone Surface is Less Mechano-Responsive than the Endocortical," Scientific Reports, pp. 1-11, 2006.

Investigating the Difference in Cortical Bone Adaptation at Endocortical and Periosteal Surfaces by Fluid Flow Analysis

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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