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Nonlinear finite element analysis of anular lesions in the L4/5 intervertebral disc

Little, J. Paige, Adam, Clayton J., Evans, John H., Pettet, Graeme J., & Pearcy, Mark J. (2007) Nonlinear finite element analysis of anular lesions in the L4/5 intervertebral disc. Journal of Biomechanics, 40(12), pp. 2744-2751.

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Abstract

Degenerate intervertebral discs exhibit both material and structural changes. Structural defects (lesions) develop in the anulus fibrosus with age. While degeneration has been simulated in numerous previous studies, the effects of structural lesions on disc mechanics are not well known. In this study, a finite element model (FEM) of the L4/5 intervertebral disc was developed in order to study the effects of anular lesions and loss of hydrostatic pressure in the nucleus pulposus on the disc mechanics. Models were developed to simulate both healthy and degenerate discs. Degeneration was simulated with either rim, radial or circumferential anular lesions and by equating nucleus pressure to zero. The anulus fibrosus ground substance was represented as a nonlinear incompressible material using a second-order polynomial, hyperelastic strain energy equation. Hyperelastic material parameters were derived from experimentation on sheep discs. Endplates were assumed to be rigid, and annulus lamellae were assumed to be vertical in the unloaded state. Loading conditions corresponding to physiological ranges of rotational motion were applied to the models and peak rotation moments compared between models. Loss of nucleus pulposus pressure had a much greater effect on the disc mechanics than the presence of anular lesions. This indicated that the development of anular lesions alone (prior to degeneration of the nucleus) has minimal effect on disc mechanics, but that disc stiffness is significantly reduced by the loss of hydrostatic pressure in the nucleus. With the degeneration of the nucleus, the outer innervated anulus or surrounding osseo-ligamentous anatomy may therefore experience increased strains.

Impact and interest:

22 citations in Scopus
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18 citations in Web of Science®

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ID Code: 7449
Item Type: Journal Article
Additional Information: For more information, please refer to the journal's website (see link) or contact the author. Author contact details: j2.little@qut.edu.au
Keywords: intervertebral disc, degeneration, anular lesions, finite element, hyperelastic
DOI: 10.1016/j.jbiomech.2007.01.007
ISSN: 0021-9290
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > BIOMEDICAL ENGINEERING (090300) > Biomechanical Engineering (090302)
Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > BIOMEDICAL ENGINEERING (090300)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2007 Elsevier
Deposited On: 09 May 2007
Last Modified: 29 Feb 2012 23:34

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