The healing process of ruptured tendons is problematic due to scar tissue formation and deteriorated material properties. In some cases, it may take nearly a year to complete. Mechanical loading has been shown to positively influence tendon healing; however, the mechanisms remain unclear. Computational mechanobiology methods employed extensively to model bone healing have achieved high fidelity, but not yet been explored to understand tendon regeneration. The general objective of this thesis is to develop computational approaches to enhance the knowledge of the role that mechanical factors play in fibre re-organisation in healing tendons, by proposing an appropriate constitutive formulation, followed by analysing the mechano-adaptation of the models created when regulated by different biophysical stimuli. Curve fitting of an established hyperelastic fibre-reinforced continuum model introduced by Gasser, Ogden and Holzapfel (GOH) against experimental tensile testing data of rat Achilles tendons at four timepoints during the tendon repair was used and achieved excellent fits (0.9903 < R<sup>2</sup> < 0.9986). A parametric sensitivity study using a three-level central composite design, which is a fractional factorial design method, showed that the collagen-fibre-related parameters in the GOH model had almost equal influence on the fitting. The mechano-adaptation of the healing tendons when regulated by axial and principal strain predicted fibre re-organisation comparable to experimental findings, in contrast to models regulated by deviatoric strain. Also, mechano-adaptive models regulated by deviatoric strain were more spatially and temporally sensitive to different boundary conditions - length and loading magnitudes - than those regulated by axial and principal strain. This thesis describes that a hyperelastic fibre-reinforced mechano-adaptive model regulated by axial or principal strain is generally capable of describing the mechanobiological behaviours of healing tendons, and that further experiments should focus on establishing the localised structural and material parameters of collagen fibres and their mechano-adaptive behaviours in the healing tissue.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:730233 |
| Date | January 2016 |
| Creators | Bajuri, Mohd Nazri Bin |
| Contributors | Thompson, Mark S. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ora.ox.ac.uk/objects/uuid:c6daa0b7-4875-4056-b05e-c35097988b72 |
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