Electronic Theses and Dissertations

Identifier

1268

Author

Jie Gao

Date

2014

Date of Award

12-1-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Engineering

Concentration

Mechanical Engineering

Committee Chair

Esra Roan

Committee Member

John Williams

Committee Member

Hsiang H Lin

Committee Member

Gladius Lewis

Abstract

It is generally accepted that mechanical loading of the growth plate influences bone growth and development. Previous computational studies of growth plate mechanics have been carried out at the tissue level and have focused on the beginning stage of development before and after the formation of the secondary center of ossification. This has led to the formulation of mechanoregulatory bone growth theories in terms of tissue level hydrostatic stresses and tensile strains. However, growth continues until the growth plate is a thin undulating structure sandwiched between bone layers. Within this structure, it is the chondrocytes, organized and arranged in columnar (tube) structures known as chondrons that are responsible for bone growth through proliferation and differentiation. However, the mechanical environment of the chondrocytes inside these chondrons is not known adn it is unclear how the mechanistic theories developed at the tissue level might apply at the cellular level. Therefore, the overall ain of this study was to develop a new multiscale computational approach to predict the state of stress and strain in chondrocytes when the growth plate is under moderate compression. This work is devided into three parts. In Part 1, the compressive elastic modulus of the growth plate cartilage was extracted by simulating previous exprements using finite element methods. Triaxial, nonuniform states of stress and strain were found within the 3D structure of the thin growth plate layer at the tissue level. In Part 2, the incorporation of cellular level detail in a multiscale model led to the discovery that the strain patterns along the length of the chondrons are reversed in peripheral regions of the growth plate in comparison with central locations, which has ramifications for the interpretation of experimental observations made at peripheral regions of a specimen. Finally, in Part 3, when cellular strain and hydrostatic stress were considered simultaneously, the model predicted a gradient in cell stress and strain along the length of the chondrons that is consistent with mechanoregulatory bone growth theories. This is the first study to show the relevance and validity of bone growth theories at the cellular level.

Comments

Data is provided by the student.

Library Comment

dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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