Publications by authors named "Andreas G Reisinger"

8 Publications

  • Page 1 of 1

Effects of anti-resorptive treatment on the material properties of individual canine trabeculae in cyclic tensile tests.

Bone 2021 Sep 1;150:115995. Epub 2021 May 1.

Institute of Lightweight Design and Structural Biomechanics, TU Wien, Gumpendorfer Straße 7, 1060 Vienna, Austria. Electronic address:

Osteoporosis is defined as a decrease of bone mass and strength, as well as an increase in fracture risk. It is conventionally treated with antiresorptive drugs, such as bisphosphonates (BPs) and selective estrogen receptor modulators (SERMs). Although both drug types successfully decrease the risk of bone fractures, their effect on bone mass and strength is different. For instance, BP treatment causes an increase of bone mass, stiffness and strength of whole bones, whereas SERM treatment causes only small (4%) increases of bone mass, but increased bone toughness. Such improved mechanical behavior of whole bones can be potentially related to the bone mass, bone structure or material changes. While bone mass and architecture have already been investigated previously, little is known about the mechanical behavior at the tissue/material level, especially of trabecular bone. As such, the goal of the work presented here was to fill this gap by performing cyclic tensile tests in a wet, close to physiologic environment of individual trabeculae retrieved from the vertebrae of beagle dogs treated with alendronate (a BP), raloxifene (a SERM) or without treatments. Identification of material properties was performed with a previously developed rheological model and of mechanical properties via fitting of envelope curves. Additionally, tissue mineral density (TMD) and microdamage formation were analyzed. Alendronate treatment resulted in a higher trabecular tissue stiffness and strength, associated with higher levels of TMD. In contrast, raloxifene treatment caused a higher trabecular toughness, pre-dominantly in the post-yield region. Microdamage formation during testing was not affected by either anti-resorptive treatment regimens. These findings highlight that the improved mechanical behavior of whole bones after anti-resorptive treatment is at least partly caused by improved material properties, with different mechanisms for alendronate and raloxifene. This study further shows the power of performing a mechanical characterization of trabecular bone at the level of individual trabeculae for better understanding of clinically relevant mechanical behavior of bone.
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http://dx.doi.org/10.1016/j.bone.2021.115995DOI Listing
September 2021

A Review on Recent Advances in the Constitutive Modeling of Bone Tissue.

Curr Osteoporos Rep 2020 Dec 17;18(6):696-704. Epub 2020 Oct 17.

Department of Anatomy und Biomechanics, Karl Landsteiner University of Health Sciences, Krems, Austria.

Purpose Of Review: Image-based finite element analysis (FEA) to predict and understand the biomechanical response has become an essential methodology in musculoskeletal research. An important part of such simulation models is the constitutive material model of which recent advances are summarized in this review.

Recent Findings: The review shows that existing models from other fields were introduced, such as cohesion zone (cortical bone) or phase-field models (trabecular bone). Some progress has been made in describing cortical bone involving physical mechanisms such as microcracks. Problems with validations at different length scales remain a problem. The improvement of recent constitutive models is partially obscured by uncertainties that affect overall predictions, such as image quality and calibration or boundary conditions. Nevertheless, in vivo CT-based FEA simulations based on a sophisticated constitutive behavior are a very valuable tool for clinical-related osteoporosis research.
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http://dx.doi.org/10.1007/s11914-020-00631-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7732794PMC
December 2020

Correction to: A two‑layer elasto‑visco‑plastic rheological model for the material parameter identification of bone tissue.

Biomech Model Mechanobiol 2020 10;19(5):1977

Division Biomechanics, Department of Anatomy and Biomechanics, Karl Landsteiner University of Health Sciences, Krems an der Donau, Austria.

In the original publication of the article.
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http://dx.doi.org/10.1007/s10237-020-01356-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7502445PMC
October 2020

A two-layer elasto-visco-plastic rheological model for the material parameter identification of bone tissue.

Biomech Model Mechanobiol 2020 Dec 6;19(6):2149-2162. Epub 2020 May 6.

Division Biomechanics, Department of Anatomy and Biomechanics, Karl Landsteiner University of Health Sciences, Krems an der Donau, Austria.

The ability to measure bone tissue material properties plays a major role in diagnosis of diseases and material modeling. Bone's response to loading is complex and shows a viscous contribution to stiffness, yield and failure. It is also ductile and damaging and exhibits plastic hardening until failure. When performing mechanical tests on bone tissue, these constitutive effects are difficult to quantify, as only their combination is visible in resulting stress-strain data. In this study, a methodology for the identification of stiffness, damping, yield stress and hardening coefficients of bone from a single cyclic tensile test is proposed. The method is based on a two-layer elasto-visco-plastic rheological model that is capable of reproducing the specimens' pre- and postyield response. The model's structure enables for capturing the viscously induced increase in stiffness, yield, and ultimate stress and for a direct computation of the loss tangent. Material parameters are obtained in an inverse approach by optimizing the model response to fit the experimental data. The proposed approach is demonstrated by identifying material properties of individual bone trabeculae that were tested under wet conditions. The mechanical tests were conducted according to an already published methodology for tensile experiments on single trabeculae. As a result, long-term and instantaneous Young's moduli were obtained, which were on average 3.64 GPa and 5.61 GPa, respectively. The found yield stress of 16.89 MPa was lower than previous studies suggest, while the loss tangent of 0.04 is in good agreement. In general, the two-layer model was able to reproduce the cyclic mechanical test data of single trabeculae with an root-mean-square error of 2.91 ± 1.77 MPa. The results show that inverse rheological modeling can be of great advantage when multiple constitutive contributions shall be quantified based on a single mechanical measurement.
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http://dx.doi.org/10.1007/s10237-020-01329-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7603462PMC
December 2020

Computational and experimental methodology for site-matched investigations of the influence of mineral mass fraction and collagen orientation on the axial indentation modulus of lamellar bone.

J Mech Behav Biomed Mater 2013 Dec 29;28:195-205. Epub 2013 Jul 29.

Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gusshausstrasse 27-29, A-1040 Vienna, Austria; Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands. Electronic address:

Relationships between mineralization, collagen orientation and indentation modulus were investigated in bone structural units from the mid-shaft of human femora using a site-matched design. Mineral mass fraction, collagen fibril angle and indentation moduli were measured in registered anatomical sites using backscattered electron imaging, polarized light microscopy and nano-indentation, respectively. Theoretical indentation moduli were calculated with a homogenization model from the quantified mineral densities and mean collagen fibril orientations. The average indentation moduli predicted based on local mineralization and collagen fibers arrangement were not significantly different from the average measured experimentally with nanoindentation (p=0.9). Surprisingly, no substantial correlation of the measured indentation moduli with tissue mineralization and/or collagen fiber arrangement was found. Nano-porosity, micro-damage, collagen cross-links, non-collagenous proteins or other parameters affect the indentation measurements. Additional testing/simulation methods need to be considered to properly understand the variability of indentation moduli, beyond the mineralization and collagen arrangement in bone structural units.
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http://dx.doi.org/10.1016/j.jmbbm.2013.07.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3843116PMC
December 2013

Principal stiffness orientation and degree of anisotropy of human osteons based on nanoindentation in three distinct planes.

J Mech Behav Biomed Mater 2011 Nov 22;4(8):2113-27. Epub 2011 Jul 22.

Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gusshausstrasse 27-29, A-1040 Vienna, Austria.

Haversian systems or 'osteons' are cylindrical structures, formed by bone lamellae, that make up the major part of human cortical bone. Despite their discovery centuries ago in 1691 by Clopton Havers, their mechanical properties are still poorly understood. The objective of this study is a detailed identification of the anisotropic elastic properties of the secondary osteon in the lamella plane. Additionally, the principal material orientation with respect to the osteon is assessed. Therefore a new nanoindentation method was developed which allows the measurement of indentation data in three distinct planes on a single osteon. All investigated osteons appeared to be anisotropic with a preferred stiffness alignment along the axial direction with a small average helical winding around the osteon axis. The mean degree of anisotropy was 1.75±0.36 and the mean helix angle was 10.3°±0.8°. These findings oppose two well established views of compact bone microstructure: first, the generally clear axial stiffness orientation contradicts a regular 'twisted plywood' collagen fibril orientation pattern in lamellar bone that would lead to a more isotropic behavior. Second, the class of transverse osteons were not observed from the mechanical point of view.
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http://dx.doi.org/10.1016/j.jmbbm.2011.07.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268337PMC
November 2011

Elastic anisotropy of bone lamellae as a function of fibril orientation pattern.

Biomech Model Mechanobiol 2011 Feb 27;10(1):67-77. Epub 2010 Apr 27.

Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gusshausstrasse 27-29, Vienna, Austria.

In this study, the homogenized anisotropic elastic properties of single bone lamellae are computed using a finite element unit cell method. The resulting stiffness tensor is utilized to calculate indentation moduli for multiple indentation directions in the lamella plane which are then related to nanoindentation experiments. The model accounts for different fibril orientation patterns in the lamellae--the twisted and orthogonal plywood pattern, a 5-sublayer pattern and an X-ray diffraction-based pattern. Three-dimensional sectional views of each pattern facilitate the comparison to transmission electron (TEM) images of real lamella cuts. The model results indicate, that the 5-sublayer- and the X-ray diffraction-based patterns cause the lamellae to have a stiffness maximum between 0° and 45° to the osteon axis. Their in-plane stiffness characteristics are qualitatively matching the experimental findings that report a higher stiffness in the osteon axis than in the circumferential direction. In contrast, lamellae owning the orthogonal or twisted plywood fibril orientation patterns have no preferred stiffness alignment. This work shows that the variety of fibril orientation patterns leads to qualitative and quantitative differences in the lamella elastic mechanical behavior. The study is a step toward a deeper understanding of the structure-mechanical function relationship of bone lamellae.
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http://dx.doi.org/10.1007/s10237-010-0218-6DOI Listing
February 2011

Sensitivity analysis and parametric study of elastic properties of an unidirectional mineralized bone fibril-array using mean field methods.

Biomech Model Mechanobiol 2010 Oct 5;9(5):499-510. Epub 2010 Feb 5.

Vienna University of Technology, Institute of Lightweight Design and Structural Biomechanics, Austria.

The key parameters determining the elastic properties of an unidirectional mineralized bone fibril-array decomposed in two further hierarchical levels are investigated using mean field methods. Modeling of the elastic properties of mineralized micro- and nanostructures requires accurate information about the underlying topology and the constituents' material properties. These input data are still afflicted by great uncertainties and their influence on computed elastic constants of a bone fibril-array remains unclear. In this work, mean field methods are applied to model mineralized fibrils, the extra-fibrillar matrix and the resulting fibril-array. The isotropic or transverse isotropic elastic constants of these constituents are computed as a function of degree of mineralization, mineral distribution between fibrils and extra-fibrillar matrix, collagen stiffness and fibril volume fraction. The linear sensitivity of the elastic constants was assessed at a default set of the above parameters. The strain ratios between the constituents as well as the axial and transverse indentation moduli of the fibril-array were calculated for comparison with experiments. Results indicate that the degree of mineralization and the collagen stiffness dominate fibril-array elasticity. Interestingly, the stiffness of the extra-fibrillar matrix has a strong influence on transverse and shear moduli of the fibril-array. The axial strain of the intra-fibrillar mineral platelets is 30-90% of the applied fibril strain, depending on mineralization and collagen stiffness. The fibril-to-fibril-array strain ratio is essentially ~1. This study provides an improved insight in the parameters, which govern the fibril-array stiffness of mineralized tissues such as bone.
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http://dx.doi.org/10.1007/s10237-010-0190-1DOI Listing
October 2010