Nonlinear Gross Response Analysis of a Lumbar Motion Segment in Combined Sagittal Loadings

[+] Author and Article Information
A. Shirazi-Adl, G. Drouin

Department of Mechanical Engineering, Ecole Polytechnique de Montréal, Montreal, Quebec, Canada H3C 3A7

J Biomech Eng 110(3), 216-222 (Aug 01, 1988) (7 pages) doi:10.1115/1.3108434 History: Received September 22, 1986; Revised June 01, 1988; Online June 12, 2009


A 3-D nonlinear mathematical model is used to analyze the mechanical response of a lumbar L2–3 motion segment including the posterior elements when subjected to combined sagittal plane loads. The loadings consist of axial compression force, anterior and posterior shear forces, and flexion and extension moments. The facet articulation is modelled as a general moving contact problem and the ligaments as a collection of uniaxial elements. The disk nucleus is considered as an inviscid fluid and the annulus as a composite of collagenous fibers embedded in a matrix of ground substance. The presence of axial compression force reduces the segmental stiffness in flexion whereas a reverse trend is predicted in extension. In the presence of axial compression with and without sagittal shear force, flexion considerably increases the intradiscal pressure while extension reduces it. In other words, under an identical compression force, disk pressure is predicted to be noticeably larger in flexion than in extension. The segmental mechanical response in extension loadings is markedly influenced by the changes in the relative geometry of the articular surfaces at the lower regions. Finally, the deformation of the bony structures plays a significant role in the segmental mechanics under relatively large loads.

Copyright © 1988 by ASME
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