Modeling of human intervertebral disc annulus fibrosus with complex multi-fiber networks
Type de document
Études primaires
Année de publication
2021
Langue
Anglais
Titre de la revue
Acta Biomaterialia
Première page
208
Dernière page
221
Résumé
Collagen fibers within the annulus fibrosus (AF) lamellae are unidirectionally aligned with alternating orientations between adjacent layers. AF constitutive models often combine two adjacent lamellae into a single equivalent layer containing two fiber networks with a crisscross pattern. Additionally, AF models overlook the inter‐lamellar matrix (ILM) as well as elastic fiber networks in between lamellae. We developed a nonhomogenous micromechanical model as well as two coarser homogenous hyperelastic and microplane models of the human AF, and compared their performances against measurements (tissue level uniaxial and biaxial tests as well as whole disc experiments) and seven published hyperelastic models. The micromechanical model had a realistic non-homogenous distribution of collagen fiber networks within each lamella and elastic fiber network in the ILM. For small matrix linear moduli (<0.2 MPa), the ILM showed substantial anisotropy (>10%) due to the elastic fiber network. However, at moduli >0.2 MPa, the effects of the elastic fiber network on differences in stress-strain responses at different directions disappeared (<10%). Variations in sample geometry and boundary conditions (due to uncertainty) markedly affected stress-strain responses of the tissue in uniaxial and biaxial tests (up to 16 times). In tissue level tests, therefore, simulations should represent testing conditions (e.g., boundary conditions, specimen geometry, preloads) as closely as possible. Stress/strain fields estimated from the single equivalent layer approach (conventional method) yielded different results from those predicted by the anatomically more accurate apparoach (i.e., layerwise). In addition, in a disc under a compressive force (symmetric loading), asymmetric stress-strain distributions were computed when using a layerwise simulation. Although all developed and selected published AF models predicted gross compression-displacement responses of the whole disc within the range of measured data, some showed excessively stiff or compliant responses under tissue-level uniaxial/biaxial tests. This study emphasizes, when constructing and validating constitutive models of AF, the importance of the proper simulation of individual lamellae as distinct layers, and testing parameters (sample geometric dimensions/loading/boundary conditions). © 2021 Acta Materialia Inc.
Mots-clés
Colonne vertébrale, Spinal column, Mécanique humaine, Body mechanics
Numéro de projet IRSST
2014-0009
Citation recommandée
Ghezelbash, F., Eskandari, A. H., Shirazi-Adl, A., Kazempour, M., Tavakoli, J., Baghani, M. et Costi, J. J. (2021). Modeling of human intervertebral disc annulus fibrosus with complex multi-fiber networks. Acta Biomaterialia, 123, 208-221. https://doi.org/10.1016/j.actbio.2020.12.062
