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.

Contribution of Three-Dimensional Trabecular Bone Microstructure of the Proximal Femur to its Mechanical Properties as Assessed by Micro-Finite Element Analysis

2006 ◽  
Vol 321-323 ◽  
pp. 278-281
Author(s):  
Wen Quan Cui ◽  
Ye Yeon Won ◽  
Myong Hyun Baek ◽  
Kwang Kyun Kim
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Trabecular Bone ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Bone Microarchitecture ◽  
Element Model ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
Element Analysis

The purpose of this study was to investigate the contribution of the microstructural properties of trabecular bone in predicting its elastic modulus in the intertrochanteric region. A total of 15 trabecular bone core specimens were obtained from the proximal femurs of patients undergoing total hip arthroplasty. The micro-computed tomography (micro-CT) was used to scan each specimen to obtain micro-morphology. Microstructural parameters were directly calculated using software. Micro-CT images were converted to micro-finite element model using meshing technique, and then micro-finite element analysis (FEA) was performed to assess the mechanical property (Young’s modulus) of trabecular bone. The results showed that the ability to explain this variance of Young’s modulus is improved by combining the structural indices with each other. It suggested that assessment of bone microarchitecture should be added as regards detection of osteoporosis and evaluation of the efficacy of drug treatments for osteoporosis.

Effect of Defect on Elastic/Plastic and Creep Behavior of Bone: A Finite Element Study

2007 ◽  
Author(s):  
A. Ajdari ◽  
P. K. Canavan ◽  
H. Nayeb-Hashemi ◽  
G. Warner
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Trabecular Bone ◽  
Fatigue Loading ◽  
Dimensional Structure ◽  
Plastic Behavior ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Local Bone ◽  
Osteoporotic Vertebral Fractures

Three-dimensional structure of trabecular bone can be modeled by 2D or 3D Voronoi structure. The effect of missing cell walls on the mechanical properties of 2D honeycombs is a first step towards understanding the effect of local bone resorption due to osteoporosis. In patients with osteoporosis, bone mass is lost first by thinning and then by resorption of the trabeculae [1]. Furthermore, creep response is important to analyze in cellular solids when the temperature is high relative to the melting temperature. For trabecular bone, as body temperature (38 °C) is close to the denaturation temperature of collagen (52 °C), trabecular bone creeps [1]. Over the half of the osteoporotic vertebral fractures that occur in the elderly, are the result of the creep and fatigue loading associated with the activities of daily living [2]. The objective of this work is to understand the effect of missing walls and filled cells on elastic-plastic behavior of both regular hexagonal and non-periodic Voronoi structures using finite element analysis. The results show that the missing walls have a significant effect on overall elastic properties of the cellular structure. For both regular hexagonal and Voronoi materials, the yield strength of the structure decreased by more than 60% by introducing 10% missing walls. In contrast, the results indicate that filled cells have much less effect on the mechanical properties of both regular hexagonal and Voronoi materials.

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.

Micro-Computed Tomography to Finite Element Analysis of In Vivo Biodegradable Magnesium-Alloy Screw and Surrounding Bone in Rabbit Femurs

2015 ◽  
Author(s):  
Adrienne F. O. Williams ◽  
Matthew B. A. McCullough
Keyword(s):  
Computed Tomography ◽  
Finite Element ◽  
Mg Alloy ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
Element Analysis ◽  
Animal Modeling ◽  
Finite Element Software ◽  
Over Time

Magnesium (Mg) and its alloys are attractive orthopedic biomaterials because of their degradability and mechanical properties, which are similar to bone’s. Characterizing the mechanical changes and interactions of these promising degradable biomaterials and the host environment (bone) is essential to their success in orthopedic devices. The objective of this study was to develop a protocol to evaluate in vivo biodegradable Mg-alloy screws and surrounding new and cancellous bone in rabbit femurs over time, using high resolution micro-computed tomography (micro-CT) images and the finite element method. Micro-CT was used to visually evaluate bone remodeling and degradation of Mg-alloy screws that were implanted in rabbit femoral condyles for 2, 4, 12, 24, 36 and 52 weeks. Over time, the degradation product around the device and the remainder of the intact core was observed. Scans were segmented into bone, degradation/corrosion products and non-degraded device, then reconstructed into 3D volumes. These volumes were meshed and assigned material properties based on CT data. The meshed volumes were exported to finite element software and analyzed in a virtual environment. Several foundational observations were made about animal modeling of in vivo degrading magnesium devices with a micro-CT to FEA protocol.

scholarly journals An evaluation using micro-CT data of the stress formed in the crown and periodontal tissues from the use of Peek post and Peek crown: A 3D finite element analysis study

2018 ◽  
Vol 8 (3) ◽  
pp. 144-150 ◽  
Author(s):  
Samet Tekin ◽  
Özkan Adıgüzel ◽  
Suzan Cangül
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Computer Program ◽  
Cortical Bone ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
Incisor Tooth ◽  
Element Analysis ◽  
Periodontal Tissues ◽  
Dental Post

Aim: Metal-supported ceramics as crown material and glass fibre posts as dental post materials are in frequent current use. In recent years, it has been claimed that stress-based biomechanical problems in dentistry can be resolved with the benefit of the low elasticity modulus of polyetheretherketone (PEEK) material. The aim of this study was to use finite element analysis (FEA) to compare the stresses formed by forces applied after the use of PEEK material as dental post and crown material as an alternative to glassfibre posts and metal-supported ceramic crowns. Material and Method: The stress analysis metthod used in this study was FEA. First, micro-computed tomography (micro-CT) images were obtained of a maxillary central incisor tooth and the data of the post materials scanned with a 3-dimensional (3D) laser scanner were uploaded to a computer program. 3D models were obtained with designs made in the computer program of all the materials. The modelling of a maxillary central tooth was completed using 2 different post materials (glassfibre and PEEK) and 2 different crown materials (metal ceramic and PEEK) and 4 groups were formed for analysis. By applying force of 100N at 135˚ from the absolute central point of the palatinal surface of the tooth, the stress values and distribution occurring in the 3D peiodontal models were compared.   Results: The use of PEEK post reduced the stresses occurring on the periodontal ligament (PDL) and the cortical bone, and caused no significant change in the stresses on the crown. The use of PEEK crown reduced the stresses occurring on the crown and increased the stresses occurring on the PDL and cortical bone. Conclusion: With further in vitro and clinical studies of PEEK material, it can be considered that within a short time PEEK post and PEEK crown could be in routine use in dentistry.

High-Risk Tissue Distribution in the Human Proximal Femur Under Sideways Fall Loading

2012 ◽  
Author(s):  
Shashank Nawathe ◽  
Alissa Romens ◽  
Mary L. Bouxsein ◽  
Tony M. Keaveny
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Trabecular Bone ◽  
Proximal Femur ◽  
Structural Integrity ◽  
Load Transfer ◽  
Biomechanical Testing ◽  
Micro Ct ◽  
Element Analysis ◽  
Femoral Strength

Despite the central role of femoral strength in the etiology of osteoporotic hip fractures [1], the associated micromechanical basis of femoral strength remains poorly understood. Cadaver studies [2] using biomechanical testing have established that both the cortical and trabecular bone contribute to the structural integrity of the proximal femur but these studies did not address mechanisms. Addressing mechanisms, theoretical and finite element continuum analyses have assessed cortical-trabecular load sharing and have described stress and strain distributions throughout the proximal femur [1,3]. However, the regions of the bone at highest risk of initial failure remain unclear, in part because the continuum nature and low spatial resolution of these previous analyses render them incapbable of capturing load transfer associated with the microstructure of the trabecular bone and the sometimes thin cortex. Overcoming this limitation, micro-CT-based finite element analysis has recently been applied to the entire proximal femur [4], but so far only two femurs have been analyzed and thus reported trends are difficult to generalize. To extend this recent work and provide further insight into the microstructural basis of femoral strength, we applied micro-CT based finite element analysis to investigate femoral micro-mechanics in a cohort of elderly human proximal femurs.

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