105 Biphasic Continumm Analysis on Viscoelastic Behavior of Intervertebral Disc

Abstract

A human intervertebral disc is composed of nucleus pulposus of a gel-liked material and annulus fibrosus of an anisotropic fiber reinforced material, which shows nonlinear visoelasotic behavior. In order to simulate the time-dependent behavior, this paper presents a finite element analysis using the biphasic theory proposed by Mow V.C et al. Nucleus pulposus is modeled as biphasic material composed of a solid matrix phase and an interstitial fluid phase. The intrinsic mechanical properties of each phase as well as the mechanical interaction between these two phase afford the tissue its interesting rheological behavior. The solid matrix is intrinsically incompressible, linearly elastic and nondissipative while the interstitial fluid is intrinsically incompressible and nondissipative. Further, it was assumed that the only dissipation comes from the frictional drag of relative motion between the phase. Therefore, the creep behavior under constant loading and the stress relaxation behavior under constant deformation could be simulated using this model.