A multi-scale finite element model for the analysis of human vertebral columns : from osteocytes to vertebrae

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A multi-scale finite element model for the analysis of human vertebral columns : from osteocytes to vertebrae

 

Author: Kong, Jackson
Title: A multi-scale finite element model for the analysis of human vertebral columns : from osteocytes to vertebrae
Degree: M.Sc.
Year: 2014
Subject: Spine.
Spine -- Imaging.
Hong Kong Polytechnic University -- Dissertations
Department: Interdisciplinary Division of Biomedical Engineering
Pages: viii, 73 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2673254
URI: http://theses.lib.polyu.edu.hk/handle/200/7338
Abstract: Various computational models have been developed in the past that aimed to complement experimental approaches for better understanding the complex physiology of bone. In regard to the human spine, finite element models for the vertebra at organ level, and micro-CT based finite element models for trabecular bones have evolved since early nineties. Despite extensive developments in the past two decades, a hierarchical, computational model of the human spine that couples the aforesaid models with models down to cellular level is not available in the open literature, to the best knowledge of the author. Such a model, which can be used as a computational microscopy tool, enables researchers to visualize how physiological loads transfer across different scales of bones in vivo. As such, this project attempts to develop a pilot, multi-scale, finite element model, starting from the lumber vertebra at macro scale, through the vertebral trabecular bones, down to the osteocyte lacunae at micro scale. To this end, finite element models at three disparate scales were first constructed using Abaqus: 1) at macro scale (organ level), models for the lumber vertebrae, previously developed by other researchers, were modified and adopted in this study; 2) at meso scale (trabecular tissue level), micro-CT based finite element models were generated for the trabecular bones; and 3) at micro scale (cellular level), finite element models of an idealized, elliptical lacuna, with different orientations, embedded in pericellular and extracellular materials were established. By applying the theory of homogenization, the said models were coupled to form a hierarchical, multi-scale finite element model. In this model, effective material properties was obtained from the finer scale model, through the process of homogenization, and fed directly into the next higher scale whilst the stress/strain distribution subsequently computed from the higher scale model is transferred, through the process of localization, to that of the finer scale. Results of principal stresses, strains and von Mises stresses distributions at respective scale were computed for various load cases imposed on the macro-scale model. Subsequent comparisons of these distributions reveal how stresses and strains are amplified or attenuated at each scale, thus providing an insight of the in vivo mechanical environment that would be sensed by the osteocyte under physiological conditions.

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