Development and validation of a finite element model of human intervertebral disc in multiaxial loading including the contributions of cartilage endplate and residual strains in the annulus fibrosus
Date
2018
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Publisher
University of Delaware
Abstract
The intervertebral disc is a fibrocartilaginous tissue which provides flexibility and load support in the spine. The disc is composed of three substructures: a central and gelatinous nucleus pulposus surrounded by the fibrous lamellae of the annulus fibrosus and enclosed superiorly and inferiorly by the cartilage endplates. The structure and biochemical composition of these three constituents give rise to the non-linear, anisotropic, viscoelastic, and biphasic mechanical behaviors of the disc. Improving the ability to quantify disc biomechanics is essential to understanding the processes of aging and degeneration. Specifically, developing and validating computational modeling techniques to evaluate the relationships between disc degeneration and disc mechanics can inform on disc structure-function relationships, which will improve the accuracy of diagnoses, and aid in design of therapeutic interventions. ☐ Finite element models are valuable tools for quantifying the complex mechanics of the disc, however their formulation and validation are complicated by disc geometry, the complex constitutive models required for mechanics of the disc sub-structures, and technical requirements for multiaxial experimental testing. Historically finite element models have therefore been limited in their model development and validation. Our lab recently developed and validated a finite element model of the disc for compressive loading, however this model was not validated in multiaxial loading. ☐ The overall objective of this dissertation was to further develop and validate a finite element model of the disc by incorporating residual stresses and validating the model against experimental multiaxial mechanical data. To achieve this objective, the mechanical properties and anatomy of the cartilage endplate were added to a finite element model of the human disc, a multiaxial experimental dataset was generated, and a novel multigenerational constitutive modeling approach was used to add residual stresses to the model. The outcome of this thesis is a finite element model with predictive capabilities in multiaxial loading.