FEM of Coupled Chemo-Electro-Mechanical Behavior of Human Intervertebral Disc

This paper describes a fully coupled finite element simulation of the chemo-electro-mechanical effect of the swelling characteristic of a human intervertebral disc. The swelling behavior of human intervertebral disc is strongly influenced by various environmental stimuli such as concentration of the mobile ions, fixed charges on fibrous material, and pH of the surrounding bio-fluid. The swelling behavior can be described by three physical partial differential equations. These equations are-Nernst-Plank for chemical species transport, Poisson’s for the balanced fixed charges inside the vertebral disc, and mechanical field for balanced osmotic pressure and resulting expansion of the disc. The converged solution of the 2D finite element simulation was achieved by full coupling among these equations in moving mesh domain. The effects of several important physical conditions, such as concentration of mobile ions, pH change in surrounding bio-fluid, electrical charge balance, and the expansion/shrinkage of vertebral disc are simulated. The simulation results are discussed in detail.