Combining local bone morphometry and micro-finite elements analysis to investigate localization phenomena in trabecular bone

Abstract

Consulta en la Biblioteca ETSI Industriales (7986)

[EN] The strength of our bone results from a complex combination of different quantities like shape, mass, architecture and material properties. The role of the inner trabecular architecture is crucial in osteoporotic individuals which have, together with a decreased bone mass, a strong deterioration of the trabecular network. The impairment at the trabecular level could lead to a local increase of stresses and strains and the regions subjected to these localizations could be ¿weak points¿ in the structure since they could initiate and/or propagate bone failure. Employing image guided failure assessment (IGFA), an experiment technique which combines mechanical testing with ¿CT measurements, trabecular failure has indeed been observed to be local and to start from individual elements. The main goal of the proposed research project is to investigate the possible link between geometrically weak elements and localization phenomena in real trabecular networks. For this purpose ¿CT images of human bone samples will be analyzed with local morphology in order to distinguish between rod-like or plate-like trabeculae and to extract geometrical parameters like trabecular thickness, trabecular length, trabecular orientation and trabecular volume on an individual base. After the morphological characterization, the same voxel-based dataset will be converted into elements and the internal distributions of stresses and strains will be computed with the finite element method implemented in a home made code (ParFE). A preliminary study is needed to asses the influence of the finite-element resolution on local mechanical quantities computed at the trabecular level (e.g., mean stress, mean strain or mean strain energy absorbed in single trabecula). The results of this kind of analysis will be plots where a geometrical quantity (e.g., trabecular thickness, slenderness ratio, trabecular volume) is plotted on the x-axis while a mechanical quantity (e.g., maximum strain, strain energy density) is plotted on the y-axis. This kind of plots should help to answer the following questions: ¿ Which type of correlation exists between geometrical and mechanical aspect at a structural level of single trabeculae? ¿ Are there different correlations for healthy or osteoporotic architectures? ¿ Which geometrical quantities (e.g., trabecular thickness, slenderness ratio, etc.) have more influence on the local mechanical behaviour? ¿ How are mechanical quantities like stresses or strain locally redistributed in the neighbourhood of trabeculae which are geometrically weak?