Desired properties of disc in numerical models and its influence on biomechanical behavior of lumbar spine

In this paper, nonlinear finite element modeling has been presented to conduct a parametric study of disc properties on biomechanical behavior of lumbar spine. This model includes vertebra (cancellous bone and cortical bone), disc (nucleus, annulus fibrosus, and collagen fibers), end plates, and ligaments. Medical image processing software package of Mimics (Materialise Inc., Leuven, Belgium) has been used in the current study to create a more realistic geometrical model of lumber spine. HyperMesh software (Altair, Troy, MI, USA) has then been employed to provide a better meshing of different parts of lumbar spine. Following applying loads and boundary conditions to the model, finite element analysis has been conducted in ABAQUS (ABAQUS Inc., Providence, RI, USA). Experimental tests available in literature indicate that lumbar spine shows a nonlinear mechanical behavior; hence, to consider this nonlinear behavior in this work, ligaments and annulus fibers have been modeled as nonlinear springs. The obtained results of the current study, which include intradiscal pressure and intervertebral rotation, have been compared with previous experimental as well as numerical data. The results of this work show that increasing of hyperelastic material constants of disc leads to decreasing of disc intervertebral rotation for each case study considered.