Articular cartilage is a tough and resilient tissue lining the ends of articulating bones. It provides a smooth surface for joint locomotion as well as transmitting the force between bones. The main components of articular cartilage are collagen (20% w/w), proteoglycans (10% w/w) and water (70% w/w). The interactions between these three give the tissue its special characteristics. Water as a molecule is often forgotten when considering the mechanical properties of articular cartilage. This thesis aims to increase our knowledge of the role of water molecules in the load bearing mechanisms of the tissue. It will also investigate the material properties of cartilage as hydrogel. Different rates of loading (impact and slow compression) were used on partially dehydrated articular cartilage (bovine and human). The impact was also recorded using high-speed video cameras. Values of modulus of elasticity, Poisson's ratio, energetic coefficient of restitution were measured together with viscoelastic spectra, by Fourier transformation, and Dynamic Mechanical Analysis. Differential scanning calorimetry (DSC) was also performed on bovine and human articular cartilage, as well as transmission electron microscopy where different freeze substitution solvents were used. The stiffness of the tissue increased and the energetic coefficient of restitution decreased with decreasing water content. Cartilage explants had a smaller volume at the point of full strain than at the start of the impact and this volume loss was associated with the level of hydration of the tissue. Poisson's ratio was not associated with the water content of the tissue. The DSC showed that the water existed in the tissue in different environments, as the exothermic traces showed melting patterns with multiple peaks. Transmission electron micrographs revealed an area surrounding the collagen molecules that could be associated water. These results indicate that water might exist in a structured way in the tissue, and that it is important for the mechanical capabilities of the tissue.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:693281 |
| Date | January 2016 |
| Creators | Cederlund, Anna Angelica |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230580 |
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