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Étude biomécanique de la dégénérescence du disque intervertébral à l'aide d'un modèle éléments finis poroélastique.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Chagnon, Amélie |
| Copyright Year | 2009 |
| Abstract | RESUME Les disques intervertebraux conferent flexibilite et mobilite a la colonne vertebrale, et sont responsables d'amortir et de transmettre les chargements tout le long du rachis. Avec l'âge et les facteurs environnementaux, l'usure et la degenerescence des disques peuvent survenir et affecter considerablement leurs fonctions principales. La degenerescence est generalement accompagnee de douleurs, principalement dans la region lombaire, celle etant la plus sollicitee mecaniquement. L'etude de cette pathologie a ete entreprise par plusieurs experimentations sur des rachis cadaveriques, afin de mieux comprendre les effets de la degenerescence sur la mobilite discale. En complement a ces etudes, des modeles elements finis ont ete developpes afin de representer le comportement biphasique des disques, essentiel a la representation de la degenerescence discale, mais peu de modeles ont ete reellement exploites pour etudier la pathologie elle-meme. Le present projet visait a developper et valider un modele poroelastique, par elements finis, du disque intervertebral, puis a exploiter ce modele pour identifier les parametres biomecaniques discaux ayant une influence significative sur les comportements biomecaniques des disques sains et degeneres. Le premier objectif du projet etait de developper et de valider un modele par elements finis poroelastique et parametrique du disque intervertebral lombaire integrant une representation generique des differentes structures du disque, des plateaux cartilagineux et des corps vertebraux. La geometrie simplifiee a ete generee a partir de courbes parametriques et de mesures experimentales tirees de la litterature. La hauteur discale et les proprietes poroelastiques des disques sains (grade I de la classification de Thompson) et degeneres (grades III et IV) ont ete tires de la litterature. La validation a ensuite ete realisee pour les modeles des disques de grades I, III et IV a l'aide de courbes experimentales de fluage en compression extraites de la litterature. De plus, les amplitudes de mobilite ont ete comparees pour des sollicitations en inflexion laterale, flexion et extension, par rapport a celles issues d'experimentations in vitro presentees dans la litterature. Les profils de pression interstitielle, de contrainte effective et de contrainte totale ont ete compares entre les differents niveaux de degenerescence du disque, et l'apport des differents chargements a ete calcule afin d'identifier la phase (solide ou fluide) qui regit le comportement discal, sous l'application de chargement en compression, inflexion laterale, flexion et extension. Pour ce faire, une contrainte de 0,35 MPa a ete appliquee pour le chargement en compression, et -ABSTRACT The intervertebral discs impact the flexibility and mobility of the spine and play an important role in transmitting loads through the spine. Disc wear and degeneration occur as a result of age and environmental factors while these changes affect the main function of the disc. The degeneration is generally associated with low back pain, mainly in the lumbar region, where the spine carries heavy loads. Experimental studies were realized on cadaveric functional units to investigate this pathology and to understand its effect on spinal mobility. As a complement, poroelastic finite element (FE) models have been developed and used to represent the biphasic behaviour of the disc. The inclusion of this poroelasticity is essential in the representation of the degeneration process. However, to date such models were not really used to study the degenerative pathology by itself. The purpose of this project was to develop and validate a poroelastic parametric FE model of the intervetebral disc and then identify the significant biomechanical parameters affecting the healthy and degenerated disc behaviour. The first objective of this project was to develop and validate a poroelastic parametric FE model, which integrates a generic representation of the disc structure, endplates and vertebral bodies. The simplified geometry was generated using published parametric equations and data found in the literature. Disc height and poroelastic properties of both healthy (Thomson grade I) and degenerated (Thompson grades III and IV) discs were also taken from published data. FE models were validated using published experiments exploring creep. Ranges of motion (ROM) in lateral bending, flexion and extension were compared with those from published in vitro experiments. Pore pressure (PP), effective stress (SE) and total stress (ST) profiles were analyzed as a function of time following the application of load along discal region profiles for each disc grade. The relative contribution of SE and PP was then analyzed as function of time and in the mid-sagittal region. To do so, a compressive stress of 0,35 MPa was applied for every loading case and a moment of 5Nm was added. Simulations of grades I, III and IV disc models using the compressive stress alone agreed well with available published experimental creep data. However, ranges of motion obtained from bending moments were lower than published experimental values. As compared with healthy disc models, stress profiles were mainly concentrated in the annulus region for degenerated disc models (principally in the compressed zone). The PP was dissipated as consolidation occurs, at a higher rate for highly degenerated discs (GR.IV). Then, as the fluid was expulsed, the solid matrix took up extra stresses. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://publications.polymtl.ca/219/1/2009_AmelieChagnon.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
