A Constitutive Model for the Annulus of Human Intervertebral Disc: Implications for Developing a Degeneration Model and Its Influence on Lumbar Spine Functioning

Abstract

The study of the mechanical properties of the annulus fibrosus of the intervertebral discs is significant to the study on the diseases of lumbar intervertebral discs in terms of both theoretical modelling and clinical application value. The annulus fibrosus tissue of the human intervertebral disc (IVD) has a very distinctive structure and behaviour. It consists of a solid porous matrix, saturated with water, which mainly contains proteoglycan and collagen fibres network. In this work a mathematical model for a fibred reinforced material including the osmotic pressure contribution was developed. This behaviour was implemented in a finite element (FE) model and numerical characterization and validation, based on experimental results, were carried out for the normal annulus tissue. The characterization of the model for a degenerated annulus was performed, and this was capable of reproducing the increase of stiffness and the reduction of its nonlinear material response and of its hydrophilic nature. Finally, this model was used to reproduce the degeneration of the L4L5 disc in a complete finite element lumbar spine model proving that a single level degeneration modifies the motion patterns and the loading of the segments above and below the degenerated disc.

Automated finite element meshing of the lumbar spine: Verification and validation with 18 specimen-specific models

“…The bones and endplates were represented by 7470 elements total for each vertebra and were modeled as rigid, similar to several previous studies (Cegoñino et al, 2014;Coombs et al, 2013;Dreischarf et al, 2014;Little et al, 2007;Moramarco et al, 2010;Rao, 2012). Since the bone elements were rigid, their only function in the model was for visualization of the bone surface and confirmation of correct soft tissue attachment.…”

“…These choices improved simulation run times which was important considering the large number of models and simulations completed. While these models are certainly not appropriate for all applications, similar FE models have been published and validated for situations with relatively low loads (Cegoñino et al, 2014;Dreischarf et al, 2014;Little et al, 2007;Moramarco et al, 2010;Rao, 2012). Validation for higher loads, as studied by others (Shirazi-Adl, 2006), or other key variables of interest would likely need to employ more complex modeling methods.…”

An Automated Method for Landmark Identification and Finite-Element Modeling of the Lumbar Spine

“…For this reason, the initial version of the automated method has been designed to create relatively simple and efficient FE models with rigid bones, rigid endplates, and ligaments meshed with 1D structural elements. While these models are certainly not appropriate for all applications, similar FE models have been published and validated for situations with relatively low loads [30][31][32][33][34]. A subject-specific FE model of the lumbar spine was identified and adapted for use as a template FE model for this study [32] (Fig.…”

A comparative study on the mechanical behavior of intervertebral disc using hyperelastic finite element model

“…The study revealed that ALIF had a F. Xie et al / A comparative study on the mechanical behavior of IVD using hyperelastic FEM S179 tendency to aggravate the adjacent upper segmental degeneration, resulting in an adverse biomechanical influence on the upper disc. The AF of the IVD is a complex structure composed of a solid porous matrix, saturated with water [13]. Cegoñino et al [13] developed a constitutive model describing the poromechanical behavior of a porous material with osmotic pressure.…”

“…The AF of the IVD is a complex structure composed of a solid porous matrix, saturated with water [13]. Cegoñino et al [13] developed a constitutive model describing the poromechanical behavior of a porous material with osmotic pressure. FEM was used in their study to analyze the poromechanical behaviors.…”