Geometric and material property study of the human lumbar spine using the finite element method.

In using the finite element method to examine certain aspects of the mechanical behavior of the human lumbar spine, most investigators have made numerous simplifying assumptions regarding the geometric and material data used to build a model of the spine. Since there are no specific rules for choosing geometric and material data for a "normal" human lumbar spine, considerably different types of models have been used by investigators in their finite element studies. In this study, variations in model geometric and material properties are shown to significantly affect the finite element results of an axisymmetric model of the human lumbar spine under axial compression. The Young's moduli of the cancellous bone and intervertebral disc annulus, Poisson's ratios of the cartilaginous end-plate and disc annulus, the width of the disc annulus, the height of the disc, and the ratio of the disc nucleus pressure and axial pressure are recognized as the parametric variables that most significantly affect the finite element solution.