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Relative roles of cortical and trabecular thinning in reducing osteoporotic vertebral body stiffness: A modeling study

McDonald, Katrina A., Little, J. Paige, Pearcy, Mark J., & Adam, Clayton J. (2009) Relative roles of cortical and trabecular thinning in reducing osteoporotic vertebral body stiffness: A modeling study. In Goh, James C. & Lim, CT (Eds.) 13th International Conference on Biomedical Engineering (ICBME), 3-6 December, 2008, Singapore.

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Abstract

While the effects of reduced bone density on osteoporotic vertebral strength are well known, the relative roles of cortical shell and trabecular architecture thinning in determining vertebral stiffness and strength are less clear. These are important parameters in investigating the changing biome-chanics of the ageing spine, and in assessing the effect of stiff-ening procedures such as vertebroplasty on neighbouring spinal segments. This work presents the development of a microstructural computer model of the osteoporotic lumbar vertebral body, allowing detailed prediction of the effects of bone micro-architecture on vertebral stiffness and strength.
Microstructural finite element models of an L3 human ver-tebral body were created. The cortex geometry was repre-sented with shell elements and the trabecular network with a lattice of beam elements. Trabecular architecture was varied according to age. Each beam network model was validated against experimental data. Models were generated to represent vertebral bodies of age <50 years, age 50-75y and age >75y respectively. For all models, an initial cortical shell thickness of 0.5mm was used, followed by reductions in the age >75y models to 0.35mm and 0.2mm to represent cortical thinning in late stage osteoporosis. Loads were applied to simulate in vitro biomechanical testing, compressing the vertebra by 20% of its height. Predicted vertebral stiffness and strength reduced with pro-gressive age changes in microarchitecture, demonstrating a 44% reduction in stiffness and a 43% reduction in strength, between the age <50 and age >75 models. Reducing cortical thickness in the age >75 models demonstrated a substantial reduction in stiffness and strength, resulting in a 48% reduc-tion in stiffness and a 62% reduction in strength between the 0.5mm and 0.2mm cortical thickness models. Cortical thinning in late stage osteoporosis may therefore play an even greater role in reducing vertebral stiffness and strength than earlier reductions due to trabecular thinning.

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ID Code: 17340
Item Type: Conference Paper
Keywords: Vertebra mechanics, FE modeling, trabecular architecture, osteoporosis, cortical shell
DOI: 10.1007/978-3-540-92841-6_436
ISBN: 9783540928416
ISSN: 16800737
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > BIOMEDICAL ENGINEERING (090300) > Biomechanical Engineering (090302)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Current > Institutes > Institute of Health and Biomedical Innovation
Past > Schools > School of Engineering Systems
Copyright Owner: Copyright 2009 Springer
Copyright Statement: The original publication is available at www.springerlink.com
Deposited On: 26 Jun 2009 11:13
Last Modified: 29 Feb 2012 23:57

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