Construction And Validation Of A Hybrid Lumbar Spine Model For The Fast Evaluation Of Intradiscal Pressure And Mobility

Abstract

A novel hybrid model of the lumbar spine, allowing<br> fast static and dynamic simulations of the disc pressure<br> and the spine mobility, is introduced in this work. Our<br> contribution is to combine rigid bodies, deformable finite<br> elements, articular constraints, and springs into a unique model<br> of the spine. Each vertebra is represented by a rigid body<br> controlling a surface mesh to model contacts on the facet<br> joints and the spinous process. The discs are modeled using<br> a heterogeneous tetrahedral finite element model. The facet<br> joints are represented as elastic joints with six degrees of<br> freedom, while the ligaments are modeled using non-linear<br> one-dimensional elastic elements. The challenge we tackle<br> is to make these different models efficiently interact while<br> respecting the principles of Anatomy and Mechanics.<br> The mobility, the intradiscal pressure, the facet joint force and<br> the instantaneous center of rotation of the lumbar spine are<br> validated against the experimental and theoretical results of<br> the literature on flexion, extension, lateral bending as well as<br> axial rotation.<br> Our hybrid model greatly simplifies the modeling task and<br> dramatically accelerates the simulation of pressure within the<br> discs, as well as the evaluation of the range of motion and the<br> instantaneous centers of rotation, without penalizing precision.<br> These results suggest that for some types of biomechanical<br> simulations, simplified models allow far easier modeling and<br> faster simulations compared to usual full-FEM approaches<br> without any loss of accuracy.