The mechanical behavior of cells in the annulus fibrosus: a finite element analysis [article]

Leonard Pianalto, University Of Calgary, University Of Calgary, Neil A. Duncan
2005
Graduate Studies Legacy Theses 2001 The mechanical behavior of cells in the annulus fibrosus: a finite element analysis Pianalto, Leonard Pianalto, L. (2001). The mechanical behavior of cells in the annulus fibrosus: a finite element analysis (Unpublished master's thesis). ABSTRACT Intervertebral disc degeneration is a prevalent problem and is a key factor directly or indirectly related to low back pain. The mechanical environment of the cells in a degenerated disc is substantially altered, and
more » ... likely influences the metabolic behavior of the cells. A more detailed and quantitative description of the stress-strain environment in and around the cells would be valuable to better understand the process by which the cells sense and react to the mechanical stimulus. Recent studies have greatly contributed to the pool of material property data describing the extracellular matrix and the intervertebral disc cells. And with the advent of laser scanning confocal microscopy, the ability to validate the in situ deformation of cells under externally applied loads is now possible. Therefore, the objective of this study has been to develop a finite element model of cells in the intervertebral disc, and to investigate the in situ mechanical environment of the cells under physiologic loading. Several three-dimensional finite element models were developed: 1) a lumbar motion segment model including two adjacent vertebrae, ligaments, and the intervertebral disc; 2) a tissue model to duplicate specimens used in bi-axial tests to validate material property formulations and model predictions; and 3) a micro model with sufficient flexibility to model various cell shapes including spheroids, ovoids, and more general shapes from reconstructed microscope images. Selected elements in the larger scale models were used to "drive" the micro models. Material properties of the disc were based on a fibre reinforced poro-hyperelastic material model. The cells were modeled as linear elastic. The motion segment model was used to simulate a known dangerous movement consisting of combined axial compression, lateral bending, twisting and forward flexion. Elements in the posterolateral and anterior regions of the disc were then used to drive micro models of ovoid and spherical cells in the outer and inner annulus respectively. Significant differences in cell volume changes and deformation were observed between 1.
doi:10.11575/prism/11217 fatcat:5jr3ucsagnb2tggey2qjrhe7z4