The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Tony M. Keaveny - One of the best experts on this subject based on the ideXlab platform.
-
Computational Modeling of Trabecular Bone Mechanics
Computational Modeling in Biomechanics, 2009Co-Authors: Glen L. Niebur, Tony M. KeavenyAbstract:Computational modeling has become an important tool for understanding Trabecular Bone mechanics. Models provide a means to investigate the individual and combined effects of changes in Trabecular architecture, density, and material properties on overall Trabecular Bone mechanics. In experimental studies, specimen-specific models derived from high-resolution micro-CT scans provide a means to interpret the mechanical testing data at both macroscopic and tissue levels in order to calculate multi-scale material properties. More recently, micro-CT-based finite element modeling has been applied to the detailed investigation of the biomechanical effects of therapeutic treatments, and studies are now using such techniques to address the micro-mechanics of whole-Bone behavior. Advances in computational power and solution algorithms have made Trabecular Bone modeling practical in almost any laboratory. Improvements in imaging technology, the spread of high-speed computing systems, and new computational algorithms will drive continued growth of this technique for the foreseeable future. In addition to its current role as a tool to study basic science and micro-mechanics, this technique may ultimately find clinical usage in diagnosis of disease and assessment of treatments.
-
Damage in Trabecular Bone at small strains.
European journal of morphology, 2005Co-Authors: Elise F. Morgan, Oscar C. Yeh, Tony M. KeavenyAbstract:Evidence that damage decreases Bone quality, increases fracture susceptibility, and serves as a remodeling stimulus motivates further study of what loading magnitudes induce damage in Trabecular Bone. In particular, whether damage occurs at the smaller strains characteristic of habitual, as opposed to traumatic, loading is not known. The overall goal of this study was to characterize damage accumulation in Trabecular Bone at small strains (0.20 - 0.45% strain). A continuum damage mechanics approach was taken whereby damage was quantified by changes in modulus and residual strain. Human vertebral specimens (n = 7) were tested in compression using a multi-cycle load - unload protocol in which the maximum applied strain for each cycle, epsilonmax, was increased incrementally from epsilonmax = 0.20% on the first loading cycle to epsilonmax = 0.45% on the last cycle. Modulus and residual strain were measured for each cycle. Both changes in modulus and residual strains commenced at small strains, beginning as early as 0.24 and 0.20% strain, respectively. Strong correlations between changes in modulus and residual strains were observed (r = 0.51 - 0.98). Fully nonlinear, high-resolution finite element analyses indicated that even at small apparent strains, tissue-level strains were sufficiently high to cause local yielding. These results demonstrate that damage in Trabecular Bone occurs at apparent strains less than half the apparent compressive yield strain reported previously for human vertebral Trabecular Bone. Further, these findings imply that, as a consequence of the highly porous Trabecular structure, tissue yielding can initiate at very low apparent strains and that this local failure has detectable and negative consequences on the apparent mechanical properties of Trabecular Bone.
-
Similarity in the fatigue behavior of Trabecular Bone across site and species.
Journal of biomechanics, 2004Co-Authors: Sean M. Haddock, Oscar C. Yeh, Praveen V. Mummaneni, William S. Rosenberg, Tony M. KeavenyAbstract:Abstract Within the context of improving knowledge of the structure–function relations for Trabecular Bone for cyclic loading, we hypothesized that the S–N curve for cyclic compressive loading of Trabecular Bone, after accounting for differences in monotonic strength behavior, does not depend on either site or species. Thirty-five cores of fresh-frozen elderly human vertebral Trabecular Bone, harvested from nine donors (mean±S.D., age=74±17 years), were biomechanically tested in compression at σ / E 0 values (ratio of applied stress to pre-fatigue elastic modulus) ranging from 0.0026 to 0.0070, and compared against literature data (J. Biomech. Eng. 120 (1998) 647–654) for young bovine tibial Trabecular Bone ( n =37). As reported for the bovine Bone, the number of cycles to failure for the human vertebral Bone was related to σ / E 0 by a power-law relation ( r 2 =0.54, n =35). Quantitative comparison of these data against those reported for the bovine Bone supported our hypothesis. Namely, when the differences in mean monotonic yield strain between the two types of Bone were accounted for, a single S–N curve worked well for the pooled data ( r 2 =0.75, n =72). Since elderly human vertebral and young bovine tibial Trabecular Bone represent two very different types of Trabecular Bone in terms of volume fraction and architecture, these findings suggest that the dominant failure mechanisms in Trabecular Bone for cyclic loading occur at the ultrastructural level.
-
Biomechanics of Trabecular Bone.
Annual review of biomedical engineering, 2001Co-Authors: Tony M. Keaveny, Glen L. Niebur, Elise F. Morgan, Oscar C. YehAbstract:Trabecular Bone is a complex material with substantial heterogeneity. Its elastic and strength properties vary widely across anatomic sites, and with aging and disease. Although these properties depend very much on density, the role of architecture and tissue material properties remain uncertain. It is interesting that the strains at which the Bone fails are almost independent of density. Current work addresses the underlying structure-function relations for such behavior, as well as more complex mechanical behavior, such as multiaxial loading, time-dependent failure, and damage accumulation. A unique tool for studying such behavior is the microstructural class of finite element models, particularly the "high-resolution" models. It is expected that with continued progress in this field, substantial insight will be gained into such important problems as osteoporosis, Bone fracture, Bone remodeling, and design/analysis of Bone-implant systems. This article reviews the state of the art in Trabecular Bone biomechanics, focusing on the mechanical aspects, and attempts to identify important areas of current and future research.
-
Uniaxial yield strains for bovine Trabecular Bone are isotropic and asymmetric.
Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 1999Co-Authors: Wesley C. Chang, Tennille M. Christensen, Tania P. Pinilla, Tony M. KeavenyAbstract:Although evidence suggests that yield strains for Trabecular Bone are isotropic, i.e., independent of loading direction, decisive support for this hypothesis has remained elusive. To explicitly test whether yield strains for Trabecular Bone are isotropic, compressive and tensile yield strains of 51 specimens of bovine tibial Trabecular Bone (0.41 +/- 0.08 g/cm3 [mean apparent density +/- SD]) were measured without end artifacts in on-axis (along the principal Trabecular orientation) and off-axis (30-40 degrees oblique to on-axis) orientations. Yield strains for the on-axis and off-axis orientations were similar in tension (0.80 +/- 0.03% compared with 0.85 +/- 0.04%, p = 0.21) and compression (0.97 +/- 0.05% compared with 0.96 +/- 0.07%, p > 0.99); as expected, modulus and strength depended on loading direction. When considered with an ancillary experiment on bovine tibial Trabecular Bone that showed yield strains to be similar between on-axis and 90 degrees off-axis Bone, these results firmly establish the isotropy of uniaxial yield strains for bovine tibial Trabecular Bone. This Bone is of high density and has a strong, plate-type, anisotropic architecture. Therefore, yield strains for uniaxial loading are expected to be isotropic, or nearly so, for other types of dense Trabecular Bone, although further work is required to confirm this and to establish this behavior for Bone of lower density.
Karine Briot - One of the best experts on this subject based on the ideXlab platform.
-
Trabecular Bone Score: Where are we now?
Joint bone spine, 2015Co-Authors: Valérie Bousson, Catherine Bergot, Bruno Sutter, Thierry Thomas, Sauveur Bendavid, Claude-laurent Benhamou, Hubert Blain, Michel Brazier, Véronique Breuil, Karine BriotAbstract:The Trabecular Bone Score is a rather new index obtained at the lumbar spine at the same time as a real Bone mineral density. It was developed to reflect Bone microarchitecture. It was proposed to be easily used in everyday practice as a surrogate of Bone strength. Our aim was to review 1. technical points such as correlations between Trabecular Bone Score and Bone microarchitectural parameters, Trabecular Bone Score and Bone strength, the effects of dual-energy X-ray absorptiometry image spatial resolution, age, macroarchitecture, body mass index, and osteoarthritis, on Trabecular Bone Score, and 2. evidences to use Trabecular Bone Score for separating individuals with fragility fractures from controls, predicting fragility fractures, and for longitudinally monitoring changes related to treatments. Correlations between Trabecular Bone Score and Bone microarchitectural parameters vary widely across Bone sites, microarchitectural parameters, and study designs. In vivo, the Trabecular Bone Score explains little of the variance in Trabecular microarchitectural parameters. We emphasize that it is a texture parameter. The Trabecular Bone Score is reduced in patients with fragility fracture. Several retrospective and prospective studies have shown its discriminative ability regarding the fracture risk. When combining the areal Bone mineral Density and Trabecular Bone Score, the Trabecular Bone Score remains a predictor of fracture but not the areal Bone Mineral Density. However in prospective studies, the best predictor of fracture remains hip areal Bone mineral density. Due to the lack of evidence, we recommend not to use Trabecular Bone Score for following patients treated by anti-osteoporotic drugs.
Valérie Bousson - One of the best experts on this subject based on the ideXlab platform.
-
Trabecular Bone Score: Where are we now?
Joint bone spine, 2015Co-Authors: Valérie Bousson, Catherine Bergot, Bruno Sutter, Thierry Thomas, Sauveur Bendavid, Claude-laurent Benhamou, Hubert Blain, Michel Brazier, Véronique Breuil, Karine BriotAbstract:The Trabecular Bone Score is a rather new index obtained at the lumbar spine at the same time as a real Bone mineral density. It was developed to reflect Bone microarchitecture. It was proposed to be easily used in everyday practice as a surrogate of Bone strength. Our aim was to review 1. technical points such as correlations between Trabecular Bone Score and Bone microarchitectural parameters, Trabecular Bone Score and Bone strength, the effects of dual-energy X-ray absorptiometry image spatial resolution, age, macroarchitecture, body mass index, and osteoarthritis, on Trabecular Bone Score, and 2. evidences to use Trabecular Bone Score for separating individuals with fragility fractures from controls, predicting fragility fractures, and for longitudinally monitoring changes related to treatments. Correlations between Trabecular Bone Score and Bone microarchitectural parameters vary widely across Bone sites, microarchitectural parameters, and study designs. In vivo, the Trabecular Bone Score explains little of the variance in Trabecular microarchitectural parameters. We emphasize that it is a texture parameter. The Trabecular Bone Score is reduced in patients with fragility fracture. Several retrospective and prospective studies have shown its discriminative ability regarding the fracture risk. When combining the areal Bone mineral Density and Trabecular Bone Score, the Trabecular Bone Score remains a predictor of fracture but not the areal Bone Mineral Density. However in prospective studies, the best predictor of fracture remains hip areal Bone mineral density. Due to the lack of evidence, we recommend not to use Trabecular Bone Score for following patients treated by anti-osteoporotic drugs.
Erich Schneider - One of the best experts on this subject based on the ideXlab platform.
-
Structure and function of vertebral Trabecular Bone.
Spine, 1997Co-Authors: Theo H. Smit, A Odgaard, Erich SchneiderAbstract:Study design A combined morphologic and finite-element study on vertebral Trabecular Bone. Objective To relate the form and function of vertebral Trabecular Bone, in an attempt to better understand the mechanical function of a lumbar vertebra. Summary of background data The architecture of Bone is closely related to its mechanical function (Wolff's Law). In the human spine, vertebrae are subjected to a large variety of loads. Yet, these Bones show a typical architecture, which means that they carry typical loads. Methods Five Trabecular Bone cubes from specific sites of a lumbar vertebra were 3D-reconstructed for computerized analysis. The architecture of the specimens was quantified by the Bone volume fraction and a measure of anisotropy, the mean Bone length. A finite element model was used to calculate internal stresses within a homogeneous vertebral body under basic loads. For each load case, Bone volume fraction of the specimens was compared with the equivalent von Mises stress, and mean Bone length was compared with the principal stress directions. Results Bone volume fraction poorly related to the von Mises stress in the physiologic load case of axial compression. However, high Bone volume fractions exist at locations where multiple load situations occur (e.g., near the pedicles and endplates). Remarkably, these sites also show finer architectures. Comparison of mean Bone length with principal stresses revealed that the vertebral Trabecular Bone architecture particularly, but not entirely, corresponds to the stress field under axial compression. The horizontal struts near the end-plates were found to be due to the function of the healthy intervertebral disc, and facetal joint loads introduce stress components that relate well with the Bone structures near the pedicle bases. Conclusions The Trabecular Bone architecture and the vertical orientation of the facet joints suggest that walking may be the main activity that determines the lumbar vertebral Bone architecture.
S.t.s. Al-hassani - One of the best experts on this subject based on the ideXlab platform.
-
A morphological model of vertebral Trabecular Bone.
Journal of biomechanics, 2002Co-Authors: H.s. Kim, S.t.s. Al-hassaniAbstract:In their micro-structures, typical natural cellular materials such as vertebral Trabecular Bone have a network of doubly tapered struts, thickening near the strut joints. However, past analytical models for vertebral Trabecular Bone do not take account of the effect of strut taper on the mechanical properties. This paper presents an analytical cell model comprised of doubly tapered struts to predict the global mechanical properties of vertebral Trabecular Bone. The predicted results for male, female, and both sexes fit the experimental data well. By considering several strut taper geometries, it is shown that the horizontal Young's modulus and the horizontal uniaxial collapse stress are, in some cases, approximately 1.8- and 2.2-fold higher, respectively, than those of the uniform strut model. This finding illustrates the importance of increased Trabecular thickening near the strut joints (i) for improving the accuracy of calculating the mechanical properties and (ii) for the effective treatment of aged Bone using drug therapy. It also highlights the need to combine Trabecular architecture measurements with information about the morphology near the strut joints.
