Tissue Level

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The Experts below are selected from a list of 317133 Experts worldwide ranked by ideXlab platform

Cecilia Persson - One of the best experts on this subject based on the ideXlab platform.

Claire L. Brockett - One of the best experts on this subject based on the ideXlab platform.

  • Estimating Tissue-Level properties of porcine talar subchondral bone - dataset
    Co-Authors: Lekha Koria, Marlène Mengoni, Claire L. Brockett

    This dataset contains an excel sheet with the raw data associated with the study "Estimating Tissue-Level properties of porcine talar subchondral bone", as well as the Abaqus input files for both continuum and micro finite element models, the mechanical data in .csv format and the micro-CT image files in .tiff format.

  • Estimating Tissue-Level properties of porcine talar subchondral bone
    Journal of the mechanical behavior of biomedical materials, 2020
    Co-Authors: Lekha Koria, Marlène Mengoni, Claire L. Brockett

    Abstract Tissue-Level properties of bone play an important role when characterising apparent-Level bone biomechanical behaviour and yet little is known about its effect at this hierarchical Level. In combination with trabecular morphological data these properties can be used to predict bone strength, which becomes an invaluable tool for clinicians in patient treatment planning. This study developed specimen-specific micro-finite element (μFE) models using validated continuum-Level models, containing grayscale-derived material properties, to indirectly establish Tissue-Level properties of porcine talar subchondral bone. Specimen-specific continuum finite element (hFE) models of subchondral trabecular bone were setup using μCT data of ten cylindrical specimens extracted from juvenile porcine tali. The models were validated using quasi-static uniaxial compression testing. Validated hFE models were used to calibrate the Tissue modulus of corresponding μFE models by minimising the difference between the μFE and hFE stiffness values. Key trabecular morphological indices (BV/TV, DA, Conn.D, Tb.Th, EF) were evaluated. Good agreement was observed between hFE models and experiment (CCC = 0.66). Calibrated Etiss was 504 ± 37.65 MPa. Average BV/TV and DA for μFE specimens were 0.37 ± 0.05 and 0.68 ± 0.11, respectively. BV/TV (r2 = 0.667) correlated highly with μFE stiffness. The small intra-specimen variation to Tissue-Level properties suggests that variations to apparent-Level stiffness originate from variations to microarchitecture rather than Tissue mechanical properties.

Per Isaksson - One of the best experts on this subject based on the ideXlab platform.

Jeffry S. Nyman - One of the best experts on this subject based on the ideXlab platform.

  • Tissue-Level Mechanical Properties of Bone Contributing to Fracture Risk.
    Current osteoporosis reports, 2016
    Co-Authors: Jeffry S. Nyman, Mathilde Granke, Robert C. Singleton, George M. Pharr

    Tissue-Level mechanical properties characterize mechanical behavior independently of microscopic porosity. Specifically, quasi-static nanoindentation provides measurements of modulus (stiffness) and hardness (resistance to yielding) of Tissue at the length scale of the lamella, while dynamic nanoindentation assesses time-dependent behavior in the form of storage modulus (stiffness), loss modulus (dampening), and loss factor (ratio of the two). While these properties are useful in establishing how a gene, signaling pathway, or disease of interest affects bone Tissue, they generally do not vary with aging after skeletal maturation or with osteoporosis. Heterogeneity in Tissue-Level mechanical properties or in compositional properties may contribute to fracture risk, but a consensus on whether the contribution is negative or positive has not emerged. In vivo indentation of bone Tissue is now possible, and the mechanical resistance to microindentation has the potential for improving fracture risk assessment, though determinants are currently unknown.

  • differential effects between the loss of mmp 2 and mmp 9 on structural and Tissue Level properties of bone
    Journal of Bone and Mineral Research, 2011
    Co-Authors: Jeffry S. Nyman, Conor C Lynch, Daniel S Perrien, Sophie Thiolloy, Elizabeth C Oquinn, Chetan A Patil, G M Pharr, Anita Mahadevanjansen, Gregory R Mundy

    Matrix metalloproteinases (MMPs) are capable of processing certain components of bone Tissue, including type 1 collagen, a determinant of the biomechanical properties of bone Tissue, and they are expressed by osteoclasts and osteoblasts. Therefore, we posit that MMP activity can affect the ability of bone to resist fracture. To explore this possibility, we determined the architectural, compositional, and biomechanical properties of bones from wild-type (WT), Mmp2−/−, and Mmp9−/− female mice at 16 weeks of age. MMP-2 and MMP-9 have similar substrates but are expressed primarily by osteoblasts and osteoclasts, respectively. Analysis of the trabecular compartment of the tibia metaphysis by micro–computed tomography (µCT) revealed that these MMPs influence trabecular architecture, not volume. Interestingly, the loss of MMP-9 improved the connectivity density of the trabeculae, whereas the loss of MMP-2 reduced this parameter. Similar differential effects in architecture were observed in the L5 vertebra, but bone volume fraction was lower for both Mmp2−/− and Mmp9−/− mice than for WT mice. The mineralization density and mineral-to-collagen ratio, as determined by µCT and Raman microspectroscopy, were lower in the Mmp2−/− bones than in WT control bones. Whole-bone strength, as determined by three-point bending or compression testing, and Tissue-Level modulus and hardness, as determined by nanoindentation, were less for Mmp2−/− than for WT bones. In contrast, the Mmp9−/− femurs were less tough with lower postyield deflection (more brittle) than the WT femurs. Taken together, this information reveals that MMPs play a complex role in maintaining bone integrity, with the cell type that expresses the MMP likely being a contributing factor to how the enzyme affects bone quality. © 2011 American Society for Bone and Mineral Research.

Frédéric Juillard - One of the best experts on this subject based on the ideXlab platform.

  • theoretical bounds for the influence of Tissue Level ductility on the apparent Level strength of human trabecular bone
    Journal of Biomechanics, 2013
    Co-Authors: Shashank Nawathe, Frédéric Juillard, Tony M. Keaveny

    The role of Tissue-Level post-yield behavior on the apparent-Level strength of trabecular bone is a potentially important aspect of bone quality. To gain insight into this issue, we compared the apparent-Level strength of trabecular bone for the hypothetical cases of fully brittle versus fully ductile failure behavior of the trabecular Tissue. Twenty human cadaver trabecular bone specimens (5 mm cube; BV/TV=6-36%) were scanned with micro-CT to create 3D finite element models (22-micron element size). For each model, apparent-Level strength was computed assuming either fully brittle (fracture with no Tissue ductility) or fully ductile (yield with no Tissue fracture) Tissue-Level behaviors. We found that the apparent-Level ultimate strength for the brittle behavior was only about half the value of the apparent-Level 0.2%-offset yield strength for the ductile behavior, and the ratio of these brittle to ductile strengths was almost constant (mean +/- SD=0.56 +/- 0.02; n=20; R-2=0.99 between the two measures). As a result of this small variation, although the ratio of brittle to ductile strengths was positively correlated with the bone volume fraction (R-2=0.44, p=0.01) and structure model index (SMI, R-2=0.58, p < 0.01), these effects were small. Mechanistically, the fully ductile behavior resulted in a much higher apparent-Level strength because in this case about 16-fold more Tissue was required to fail than for the fully brittle behavior; also, there was more tensile- than compressive-mode of failure at the Tissue Level for the fully brittle behavior. We conclude that, in theory, the apparent-Level strength behavior of human trabecular bone can vary appreciably depending on whether the Tissue fails in a fully ductile versus fully brittle manner, and this effect is largely constant despite appreciable variations in bone volume fraction and microarchitecture. (C) 2013 Elsevier Ltd. All rights reserved.

  • Effects of TissueLevel Ductility on Trabecular Bone Strength
    Co-Authors: Frédéric Juillard

    Osteoporosis is one of the most common skeletal diseases that lead to an accelerated bone loss due to an imbalance in bone turnover. This low bone mass and degraded bone microarchitecture cause a reduction in mechanical properties and an associated increase in fracture risk. If individual trabeculae become more brittle with aging, disease, or drug treatment, how does that influence the strength of the overall trabecular bone? This multi-scale issue, which relates energy absorption or Tissue ductility at one scale to load-carrying capacity or strength at a higher scale, is particularly relevant in osteoporosis applications since it is well known that aging and drug treatments can influence Tissue-Level ductility. However, the link between Tissue ductility and apparent-Level strength for trabecular bone is poorly understood and thus is it not currently possible to infer how known changes in Tissue ductility translate into the higher scale and more clinically relevant changes in trabecular strength. To provide insight into this issue, our goal in this study was to determine how trabecular strength is altered when the Tissue is changed from perfectly brittle to perfectly ductile – the two extremes of possible Tissue-Level ductility. The results show that overall trabecular strength can vary two-fold if the Tissue is entirely brittle compared to entirely ductile. The comparison with the experimental data suggests that at low bone volume fraction, real variations in Tissue ductility could be important since the real behavior is situated between the ductile and brittle behaviors. If so, this implies that future studies assessing the structural consequence of changes in Tissue-Level ductility need to consider the bone volume fraction. Our analyses are unique since they are the first to account for the complex 3D geometric detail of real trabecular microarchitecture and this study is the first to mechanistically link Tissue-Level ductility, a potentially important aspect of Tissue material behavior, to the apparent-Level strength, which is relevant clinically.