Development of Finite Element Analysis for Articular Cartilage considering Electrochemical

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Articular cartilage consists of interstitial fluid, collagen and proteoglycan aggregates which are negatively charged by fixed sulfated glycosaminoglycans. The osmotic pressure due to the negative charges induces swelling and affects the viscoelastic behavior of cartilages. On the other hand, the deformation of the cartilage due to the contact load on the cartilage surface affects in turn the fixed negative charge density to change the eledctrochemical ee in the cartilage. The purpose of this research is to develop finite element analysis approach for such mechanical electrochemical coupling phenomena. In 2002, the triphasic theory describing the mechanical electrochemical phenomena was reformulated to be applicable for the problems with large deformation. The finite element formulation was implemented to a prototype program. In 2003, the nonlinearities of the deformation dependent fixed charge density and permeability of the cartilage were taken in to account in the finite element ana … More lysis and a program was developed with fairly completion. The numerical results show that the dominant factor of viscosity in triphasic structure such as cartilage is the resistance of solid matrix to the interstitial fluid flow. The out flow of interstitial fluid due to the compression induces increase of the fixed charge density and thus increases the stiffness of the cartilage and also the electrical potential and the concentration o ions. Furthermore, the simulation of the cartilage free swelling was carried out to get the results in good agreement with the experimental results. On the other hand, a finite element analysis procedure for contact problems with large sliding was developed by in introducing Gregory patch smoothing algorithm to get off the instability due to the discontinuity of discretized contact surfaces. Finally, the analysis of contact problems for articular cartilage including electrochemical effects becomes possible by experimental measurements of the mechanical electrochemical behaviors of articular cartilages are under development and thus the material constants of the triphasic theory are not revealed in the current stage, the analysis was carried out to get clinical information by treating the cartilage as a single phase of hyperelastic solid which obey the Mooney-Rivlin constitutive relations. Less