Caractérisation expérimentale et modélisation par éléments finis poroélastique d'un disque intervertébral lombaire porcin en compression axiale

Abstract

Spinal fusion instrumentations are commonly used to straighten the deformed or unstable spine. However, proximal junctional kyphosis or fractures occur after surgery due to the high stiffness of the implants leading to premature degeneration of the vertebrae and intervertebral discs. Several studies have investigated the choice of spinal fusion instrumentation components to decrease these complications, but none have done so by considering their impact over time. The objective of this project is to develop a poroelastic finite element model of a swine intervertebral disc to evaluate the impact of vertebral fusion instrumentation. The use of poroelastic allows taking into account the evolution over time of deformations, stresses and fluid exchanges in the intervertebral discs. The intervertebral discs behavior includes creep and stress relaxation. Since intervertebral discs stress relaxation behavior was not documented in the literature, axial compression tests were carried out on 11 healthy porcine functional units to characterize this behavior. From these experiments, maximum stress, Young's modulus at equilibrium and generalized Maxwell rheological parameters were identified. The samples’ dimensions were used to define the finite elements model’s geometry while the stress relaxation results were used to calibrate the model. The intervertebral dis model’s creep response was then compared with data published by Nikkhoo et al. (2013a). The results suggest that the material laws in ABAQUS software adequately represent the creep behavior, but they are not adapted to reproduce the stress relaxation behavior of intervertebral discs. Comprehensive poroelastic laws will need to be implemented to study the impact of vertebral fusion instrumentation on the intervertebral discs.

Date	25 Oct 2017
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Yvan Petit (Supervisor) & Éric Wagnac (Co-supervisor)