Huiskes, HWJ Rik

Müller, R

Rietbergen, B Bert  van

Verhulp, E Eelco

Verhulp, E.

Rietbergen, van, B.

Müller, R.

Huiskes, H.W.J.

NARCIS 

Indirect determination of trabecular bone effective tissue properties using micro-finite element simulations

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 Indirect determination of trabecular bone effective tissueproperties using micro-finite element simulationsCitation for published version (APA):Verhulp, E., Rietbergen, van, B., Müller, R., & Huiskes, H. W. J. (2005). Indirect determination of trabecular boneeffective tissue properties using micro-finite element simulations. Poster session presented at Mate PosterAward 2005 : 10th Annual Poster Contest.Document status and date:Published: 01/01/2005Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 16. Nov. 2023/department of biomedical engineering                            PO Box 513, 5600 MB Eindhoven, The NetherlandsIntroductionOsteoporotic fractures mainly occur at sites with relatively large amounts of trabecular bone. The devastating effects of such fractures can be prevented with accurate predictions of trabecular bone strength. Micro-finite element (µFE) models have been successfully used to study and predict trabecular bone elastic and yield properties. Strength predictions, on the other hand, require the post-yield behavior of trabecular bone tissue.  Due to experimental difficulties this data is not available. The purposes of this study were to (1) indirectly determine the tissue properties using µFE models by iteratively fitting of simulation to experimental results for a trabecular bone specimen and (2) test to what extent the post-yield behavior of other similar specimens can be predicted when using these parameters in µFE analyses.Materials and methodsSeven cylindrical trabecular bone specimens were obtained from bovine tibiae. The samples were compressed in a micro-compression device [1] to create high-resolution CT scans of their original and deformed state. At the same time, the load-displacement curve was measured. The scans of the original structures were converted to µFE models. Following Cezayirlioglu [2], the element were divided into two groups depending on their loading mode (tension or compression) as a result of a linear analysis.A single specimen with median volume fraction (sample 0) was chosen for the fit procedure. First, the properties of the trabecular tissue were based on cortical bone. The yield and post-yield properties were subsequently adjusted in order to get the same apparent load-displacement curve. The resulting properties were used to simulate the compression of the remaining bone samples. The load-displacement curves and local deformations in the scans were used to validate the µFE analyses.ResultsThe results showed that the apparent behavior of the selected trabecular bone specimen could be accurately simulated with the µFE model when the tissue propertiesa)  Specimen level b) Tissue levelFig. 1: µFE-model results before and after the fit procedure compared with the apparent behavior of sample 0 (a), and the accompanying stress-strain relations for the tissue (b).were adjusted (Fig. 1). The resulting properties were similar to those of cortical bone, but ‘compression softening’ had to be introduced to obtain the typical descent in the load-displacement curve seen during compression tests. The fitted tissue behavior for sample 0 was used to simulate the compression experiments of the remain six samples. The results are shown in Fig. 2.Validation on a local level revealed extreme deformations and localized high strains in the µFE meshes (Fig. 3). Cracks were also observed at those locations.Fig. 2: Apparent load-displacement curves of samples 1 – 6. The experimental data is represented with solid lines. The dotted lines are obtained with µFE models that incorporate the tissue properties from the fit procedure.Fig. 3: Rendered CT scans of sample 0 in its initial (A) and deformed (B) state. The deformed µFE mesh (C) is shown for comparison. Local deformations in the CT scans compared well with deformations and high equivalent strain values in the µFE models.ConclusionsThe fit procedure resulted in an accurate reproduction of the measured load-displacement curve of the selected specimen. However, the force-displacement curves of the other specimens predicted from µFE analyses based on the fitted tissue parameters compared less favourable to the experimental data. Natural variations exist in bone tissue properties [3]. It is not clear whether the differences in Fig. 2 are caused by this variations or by other factors, such as experimental artifacts or the formation of cracks, which are not accounted for in the µFE analyses.References:[1] MÜLLER ET AL., Techn Health Care  6:433-444, 1985.[2] CEZAYIRLIOGLU ET AL., J Biomech 18:61-69, 1985.[3] GUO, In: Bone Mechanics Handbook, CRC Press, 2001.Indirect determination of trabecular bone effective tissue properties using micro-finite element simulationsE. Verhulp1, B. van Rietbergen1, R. Müller2 and R. Huiskes11Eindhoven University of Technology, Department of Biomedical Engineering2Swiss Federal Institute of Technology (ETH) and University of Zurich, Institute for Biomedical Engineering

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Indirect determination of trabecular bone effective tissue properties using micro-finite element simulations

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