Preparation of On-Axis Cylindrical Trabecular Bone Specimens Using Micro-CT Imaging

2004 ◽  
Vol 126 (1) ◽  
pp. 122-125 ◽  
Author(s):  
Xiang Wang, ◽  
Xiangyi Liu, and ◽  
Glen L. Niebur
Keyword(s):  
Finite Element ◽  
High Resolution ◽  
Coordinate System ◽  
Trabecular Bone ◽  
Cylindrical Specimen ◽  
Longitudinal Axis ◽  
Ct Imaging ◽  
Finite Element Models ◽  
Micro Ct ◽  
Average Deviation

The Orientation of trabecular bone specimens for mechanical testing must be carefully controlled. A method for accurately preparing on-axis cylindrical specimens using high-resolution micro-CT imaging was developed. Sixteen cylindrical specimens were prepared from eight bovine tibiae. High-resolution finite element models were generated from micro-CT images of parallelepipeds and used to determine the principal material coordinate system of each parallelepiped. A cylindrical specimen was then machined with a diamond coring bit. The resulting specimens were scanned again to evaluate the orientation. The average deviation between the principal fabric orientation and the longitudinal axis of the cylindrical specimen was only 4.70±3.11°.

High-resolution finite element models with tissue strength asymmetry accurately predict failure of trabecular bone

2000 ◽  
Vol 33 (12) ◽  
pp. 1575-1583 ◽  
Author(s):  
Glen L Niebur ◽  
Michael J Feldstein ◽  
Jonathan C Yuen ◽  
Tony J Chen ◽  
Tony M Keaveny
Keyword(s):  
Finite Element ◽  
High Resolution ◽  
Trabecular Bone ◽  
Finite Element Models ◽  
Strength Asymmetry

Convergence Behavior of High-Resolution Finite Element Models of Trabecular Bone

1999 ◽  
Vol 121 (6) ◽  
pp. 629-635 ◽  
Author(s):  
G. L. Niebur ◽  
J. C. Yuen ◽  
A. C. Hsia ◽  
T. M. Keaveny
Keyword(s):  
Finite Element ◽  
High Resolution ◽  
Trabecular Bone ◽  
Tissue Level ◽  
Finite Element Models ◽  
Trabecular Thickness ◽  
Convergence Behavior ◽  
Loading Mode ◽  
Element Size ◽  
High Resolution Models

The convergence behavior of finite element models depends on the size of elements used, the element polynomial order, and on the complexity of the applied loads. For high-resolution models of trabecular bone, changes in architecture and density may also be important. The goal of this study was to investigate the influence of these factors on the convergence behavior of high-resolution models of trabecular bone. Two human vertebral and two bovine tibial trabecular bone specimens were modeled at four resolutions ranging from 20 to 80 μm and subjected to both compressive and shear loading. Results indicated that convergence behavior depended on both loading mode (axial versus shear) and volume fraction of the specimen. Compared to the 20 μm resolution, the differences in apparent Young’s modulus at 40 μm resolution were less than 5 percent for all specimens, and for apparent shear modulus were less than 7 percent. By contrast, differences at 80 μm resolution in apparent modulus were up to 41 percent, depending on the specimen tested and loading mode. Overall, differences in apparent properties were always less than 10 percent when the ratio of mean trabecular thickness to element size was greater than four. Use of higher order elements did not improve the results. Tissue level parameters such as maximum principal strain did not converge. Tissue level strains converged when considered relative to a threshold value, but only if the strains were evaluated at Gauss points rather than element centroids. These findings indicate that good convergence can be obtained with this modeling technique, although element size should be chosen based on factors such as loading mode, mean trabecular thickness, and the particular output parameter of interest.

Effects of Thresholding Techniques on μCT-Based Finite Element Models of Trabecular Bone

2006 ◽  
Vol 129 (4) ◽  
pp. 481-486 ◽  
Author(s):  
Chi Hyun Kim ◽  
Henry Zhang ◽  
George Mikhail ◽  
Dietrich von Stechow ◽  
Ralph Müller ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Trabecular Bone ◽  
Volume Fraction ◽  
Ct Images ◽  
Bone Volume ◽  
Finite Element Models ◽  
Micro Ct ◽  
Bone Volume Fraction ◽  
Element Analysis

Microimaging based finite element analysis is widely used to predict the mechanical properties of trabecular bone. The choice of thresholding technique, a necessary step in converting grayscale images to finite element models, can significantly influence the predicted bone volume fraction and mechanical properties. Therefore, we investigated the effects of thresholding techniques on microcomputed tomography (micro-CT) based finite element models of trabecular bone. Three types of thresholding techniques were applied to 16-bit micro-CT images of trabecular bone to create three different models per specimen. Bone volume fractions and apparent moduli were predicted and compared to experimental results. In addition, trabecular tissue mechanical parameters and morphological parameters were compared among different models. Our findings suggest that predictions of apparent mechanical properties and structural properties agree well with experimental measurements regardless of the choice of thresholding methods or the format of micro-CT images.

The Modified Super-Ellipsoid Yield Criterion for Human Trabecular Bone

2004 ◽  
Vol 126 (6) ◽  
pp. 677-684 ◽  
Author(s):  
Harun H. Bayraktar ◽  
Atul Gupta ◽  
Ron Y. Kwon ◽  
Panayiotis Papadopoulos ◽  
Tony M. Keaveny
Keyword(s):  
Finite Element ◽  
High Resolution ◽  
Trabecular Bone ◽  
Yield Surface ◽  
Shear Loading ◽  
Finite Element Models ◽  
Normal Strain ◽  
Multiaxial Loading ◽  
Yield Behavior ◽  
Strain Space

Despite the importance of multiaxial failure of trabecular bone in many biomechanical applications, to date no complete multiaxial failure criterion for human trabecular bone has been developed. By using experimentally validated nonlinear high-resolution, micro-mechanical finite-element models as a surrogate for multiaxial loading experiments, we determined the three-dimensional normal strain yield surface and all combinations of the two-dimensional normal-shear strain yield envelope. High-resolution finite-element models of three human femoral neck trabecular bone specimens obtained through micro-computed tomography were used. In total, 889 multiaxial-loading cases were analyzed, requiring over 41,000 CPU hours on parallel supercomputers. Our results indicated that the multiaxial yield behavior of trabecular bone in strain space was homogeneous across the specimens and nearly isotropic. Analysis of stress-strain curves along each axis in the 3-D normal strain space indicated uncoupled yield behavior, whereas substantial coupling was seen for normal-shear loading. A modified super-ellipsoid surface with only four parameters fit the normal strain yield data very well with an arithmetic error±SD less than −0.04±5.1%. Furthermore, the principal strains associated with normal-shear loading showed excellent agreement with the yield surface obtained for normal strain loading (arithmetic error±SD<2.5±6.5%). We conclude that the four-parameter “Modified Super-Ellipsoid” yield surface presented here describes the multiaxial failure behavior of human femoral neck trabecular bone very well.

scholarly journals Spatial Correlations of Trabecular Bone Microdamage with Local Stresses and Strains Using Rigid Image Registration

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Srinidhi Nagaraja ◽  
Oskar Skrinjar ◽  
Robert E. Guldberg
Keyword(s):  
Finite Element ◽  
Image Registration ◽  
Trabecular Bone ◽  
Tissue Level ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
Element Analysis ◽  
Registration Algorithm ◽  
Local Bone ◽  
Local Stresses

Although microdamage is known to accumulate in trabecular bone with overloading and aging, the tissue-level stresses and strains associated with local bone failure are not well known. Local correlation of microdamage with microstructural stresses and strains requires methods to accurately register histological sections with micro-computed tomography (micro-CT) based finite element models. In addition, the resolution of correlation (i.e., grid size) selected for analysis may affect the observed results. Therefore, an automated, repeatable, and accurate image registration algorithm was developed to determine the range of local stresses and strains associated with microdamage initiation. Using a two-dimensional rigid registration algorithm, bone structures from histology and micro-CT imaging were aligned. Once aligned, microdamaged regions were spatially correlated with local stresses and strains obtained from micro-CT based finite element analysis. Using this more sophisticated registration technique, we were able to analyze the effects of varying spatial grid resolution on local stresses and strains initiating microdamage. The results indicated that grid refinement to the individual pixel level (pixel-by-pixel method) more precisely defined the range of microdamage initiation compared to manually selected individual damaged and undamaged trabeculae. Using the pixel-by-pixel method, we confirmed that trabecular bone from younger cows sustained higher local strains prior to microdamage initiation compared to older bone.

Micro-CT-Based Large Scale Linear Finite Element Models Predict the Strength of Human Thoracic and Lumbar Vertebral Bodies

2007 ◽  
Author(s):  
Yener N. Yeni ◽  
Do-Gyoon Kim ◽  
Roger R. Zauel ◽  
Evan M. Johnson ◽  
Dianna D. Cody
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Quantitative Computed Tomography ◽  
Finite Element Models ◽  
Micro Ct ◽  
Linear Finite Element ◽  
Vertebral Strength ◽  
Local Properties ◽  
Vertebral Bodies ◽  
Architectural Detail

Vertebral fractures are among the most common and debilitating fractures. Structural organization of cancellous and cortical bone in a vertebra and their local properties are important factors that determine the strength of a vertebra. Linear finite element models utilizing Quantitative Computed Tomography (QCT) images have proven useful for predicting vertebral strength and are potentially useful in predicting risk of fracture in a clinical setting [1]. However, the amount of architectural detail in these models is not sufficient for studying trabecular stress and strains, and their relationship with the microscopic structure, which is important for understanding the mechanisms behind vertebral fragility.

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