Abstract

BackgroundFinite element analysis results will show significant differences if the model used is performed under various material properties, geometries, loading modes or other conditions. This study adopted an FE model, taking into account the possible asymmetry inherently existing in the spine with respect to the sagittal plane, with a more geometrically realistic outline to analyze and compare the biomechanical behaviour of the lumbar spine with regard to the facet force and intradiscal pressure, which are associated with low back pain symptoms and other spinal disorders. Dealing carefully with the contact surfaces of the facet joints at various levels of the lumbar spine can potentially help us further ascertain physiological behaviour concerning the frictional effects of facet joints under separate loadings or the responses to the compressive loads in the discs.MethodsA lumbar spine model was constructed from processes including smoothing the bony outline of each scan image, stacking the boundary lines into a smooth surface model, and subsequent further processing in order to conform with the purpose of effective finite element analysis performance. For simplicity, most spinal components were modelled as isotropic and linear materials with the exception of spinal ligaments (bilinear). The contact behaviour of the facet joints and changes of the intradiscal pressure with different postures were analyzed.ResultsThe results revealed that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger loadings. In axial rotation, the facet joint forces were relatively larger in the contralateral facet joints than in the ipsilateral ones at the same level. Although the effect of the preloads on facet joint forces was not apparent, intradiscal pressure did increase with preload, and its magnitude increased more markedly in flexion than in extension and axial rotation.ConclusionsDisc pressures showed a significant increase with preload and changed more noticeably in flexion than in extension or in axial rotation. Compared with the applied preloads, the postures played a more important role, especially in axial rotation; the facet joint forces were increased in the contralateral facet joints as compared to the ipsilateral ones at the same level of the lumbar spine.

Highlights

  • Finite element analysis results will show significant differences if the model used is performed under various material properties, geometries, loading modes or other conditions

  • The present study developed an finite element (FE) model of the lumbar spine with a realistic geometric shape, in the posterior bony parts of the spine, to simulate the lumbar spine subjected to several loading conditions and approached the above mentioned claim, in order to investigate to what extent the real geometry of the lumbar spine is affected by asymmetry

  • The numerical results were principally concerned with facet joint forces at various levels of the lumbar spine and the intradiscal pressures in the discs under different preloads

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Summary

Introduction

Finite element analysis results will show significant differences if the model used is performed under various material properties, geometries, loading modes or other conditions. The lumbar spine is a part of the human body that is frequently activated during daily life This leads to a high incidence of disc problems, such as herniated disc, sciatica, and low back pain. Such disorders may arise from the wide range of motion in the lumbar spine, In a real human spine, the geometry is different at each spinal level, such as the curvature of the facet joint, the dimensions of the vertebrae, and the height of the vertebral discs. Elucidating how the posture or loading mode influences the biomechanical behaviour at such levels is of interest to researchers

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