| The primary objective of this thesis is to develop an experimental/theoretical strategy to nondestructively determine both the mechanical properties and biochemical compositions of articular cartilage by using indentation test. To facilitate such objective, triphasic mixture theory was employed to model this charged-hydrated-soft biological tissue, and the formulations of the theory were successfully simplified at three distinct levels. A general correspondence principle was established between pure elastic material and triphasic medium at final steady state in a tensorial formulation. This makes the employment of triphasic analysis as straightforward as using an elastic model. The equations of motion governing this trinary mixture were further linearized and transformed by using regular perturbation method and defining two potential functions, and finally simplified to four succinct partial differential equations. In order to investigate the mechano-electrochemical behaviors of cartilage under dynamic loading, the simplified governing equations were successfully transferred into frequency domain. Mathematically, the cost to obtain the cartilage response at a specific frequency is only a single matrix inversion.; Based on the theoretical progress, an innovative algorithm was developed which can simultaneously determine the intrinsic mechanical properties and fixed charge density (FCD) of cartilage by using the experimental data from a single indentation test. The study in this thesis showed that the calculated FCD values match perfectly with those from biochemical assay. Since both mechanical properties of cartilage solid matrix and FCD are sensitive indexes for initial OA tissue, such technique is believed to have great clinical values in the detection of early stage OA and the examination of OA etiology.; Finally, in the light of the full series triphasic solutions developed in this thesis, the comprehensive mechano-electrochemical responses of cartilage, such as solid matrix deformation, fluid pressurization, osmotic pressure, FCD and ion concentration distribution, water and ion fluxes, and electric potential or electric current, were examined for typical in situ configurations, representing an initial effort towards the understanding of mechano-transduction of chondrocytes in articular cartilage. |
