scholarly journals Micro/Nanostructures and Mechanical Properties of Trabecular Bone in Ovariectomized Rats

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Shidi Hu ◽  
Jin Li ◽  
Lu Liu ◽  
Ruchun Dai ◽  
Zhifeng Sheng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Material Properties ◽  
Volume Fraction ◽  
Structural Characteristics ◽  
Tissue Level ◽  
Ovariectomized Rats ◽  
Mineral Density ◽  
Bone Volume Fraction ◽  
Force Microscopy ◽  
Ovx Rats

Bone mechanical properties encompass both geometric and material factors, while the effects of estrogen deficiency on the material and structural characteristics of bone at micro- to nanoscales are still obscure. We performed a series of combined methodological experiments, including nanoindentation assessment of intrinsic material properties, atomic force microscopy (AFM) characterization of trabecular (Tb) nanostructure, and Tb microarchitecture and 2D BMD. At 15 weeks after surgery, we found significantly less Tb bone mineral density (BMD) at organ (−27%) and at tissue level (−12%), Tb bone volume fraction (−29%), Tb thickness (−14%), and Tb number (−17%) in ovariectomy (OVX) rats than in sham operated (SHAM) rats, while the structure model index (+91%) and Tb separation (+19%) became significantly greater. AFM images showed lower roughness Tb surfaces with loosely packed large nodular structures and less compacted interfibrillar space in OVX than in SHAM. However, no statistically significant changes were in the Tb intrinsic material properties—nanoindentation hardness, elastic modulus, and plastic deformation—nanoindentation depths, and residual areas. Therefore, estrogen deprivation results in a dramatic deterioration in Tb micro/nanoarchitectures, 3D volumetric BMD at both organ and tissue levels, and 2D BMD, but not in the nanomechanical properties of the trabeculae per se.

scholarly journals Structure-Function Relationships of the Vertebral Endplate

2021 ◽  
Author(s):  
Yuanqiao Wu ◽  
Elise Feng-i Morgan ◽  
Johnfredy Loaiza ◽  
Rohin Banerji ◽  
Olivia Rose Blouin
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Yield Stress ◽  
Volume Fraction ◽  
Level Density ◽  
Micro Computed Tomography ◽  
Vertebral Endplate ◽  
Mineral Density ◽  
Bone Volume Fraction ◽  
Apparent Stiffness

Background: Although deformation and fracture of the vertebral endplate have been implicated in spinal conditions such as vertebral fracture and disc degeneration, few biomechanical studies of this structure are available. The goal of this study was to quantify the mechanical behavior of the vertebral endplate. Methods: Eight-five rectangular specimens were dissected from the superior and/or inferior central endplates of human lumbar spine segments L1-L4. Micro-computed tomography (μCT) imaging, four-point-bend testing, and ashing were performed to quantify the apparent elastic modulus and yield stress (modulus and yield stress, respectively, of the porous vertebral endplate), tissue yield stress (yield stress of the tissue of the vertebral endplate, excluding pores), ultimate strain, fracture strain, bone volume fraction (BV/TV), bone mineral density (BMD), and various measures of tissue density and composition (tissue mineral density, ash fraction, and ash density). Regression was used to assess the dependence of mechanical properties on density and composition. Results: Wide variations in elastic and failure properties, and in density and tissue composition, were observed. BMD and BV/TV were good predictors of many of the apparent-level mechanical properties, including modulus, yield stress, and in the case of the inferior vertebral endplate, failure strains. Similar values of the mechanical properties were noted between superior and inferior vertebral endplates. In contrast to the dependence of apparent stiffness and strength on BMD and BV/TV, none of the mechanical properties depended on any of the tissue-level density measurements. Conclusion: The dependence of many of the mechanical properties of the vertebral endplate on BV/TV and BMD suggests possibilities for non-invasive assessment of how this region of the spine behaves during habitual and injurious loading. Further study of the non-mineral components of the endplate tissue is required to understand how the composition of this tissue may influence the overall mechanical behavior of the vertebral endplate.

An Adaptive Structure Topology Optimization Approach Applied to Vertebral Bone Architecture

2018 ◽  
Author(s):  
Anthony A. DiCarlo ◽  
John A. Gallagher
Keyword(s):  
Finite Element ◽  
Topology Optimization ◽  
Material Properties ◽  
Elastic Moduli ◽  
Volume Fraction ◽  
Structural Heterogeneity ◽  
Published Data ◽  
Mineral Density ◽  
Bone Volume Fraction ◽  
Structure Topology

Bone is a highly adaptive biological structure. Following Wolff’s law, bone realigns and grows to adapt to its mechanical environment. This leads to structural heterogeneity of trabecular bone and orthotropic symmetry of the elastic properties. Determining the bone alignment and material properties for living patients is difficult and involves implantation of force and displacement sensors on the bone to determine the compliance and stiffness properties. Micro-computed tomography along with finite element modeling have been limited to the vertebrae of donor cadavers to evaluate trabecular architecture, material properties, and density. Here, an adaptive structure topology optimization algorithm is presented and used to predict trabecular architecture. The algorithm predicts the optimal structure by minimizing the global compliance. The lumbar 1 (L1) vertebra is used as an example. Loads common to L1 vertebrae are applied and bone volume fraction measurements that can be taken easily from living patients through bone mineral density scans are used as the only inputs. The mathematical model is an adaptation of “99 Line Topology Optimization Code Written in Matlab” developed by Sigmund (2001). Bone is locally assumed to be isotropic with an elastic modulus of 13 GPa and the Poisson ratio of 0.3 applied to each element. The resulting structural heterogeneity results in global orthotropic relations. The model uses bone volume fraction and the loading orientation as inputs and gives the corresponding ideal bone structure geometry as an output. The trabecular structure can be predicted solely from the results of a bone mineral density scan. Finite element analysis of the optimized structure is then conducted and the global material properties are determined. While this model is for two-dimensional examples representing planes within the vertebral bone, it is extended to three-dimensional modeling to develop the cortical bone geometry and define the total volume. Matlab is then used to run the topology optimization simulation. The ideal structure is defined by optimizing for a prescribed displacement field of the system following the implementation of a gradient descent optimization method. The results are compared to published values from a combined experimental and numerical procedure. The procedure on sectioned vertebrae reported average ratios between elastic moduli of E1/E2 = 5.2, E1/E3 = 8.8, and E2/E3 = 1.4. Results between the models and the previously published data yield similar transversely isotropic symmetry in the elastic moduli of trabecular bone. However, the elastic moduli ratios are not quite in agreement. Improving the accuracy of the boundary conditions and loading of the finite element model may improve the correlation between the optimization models and published data.

scholarly journals Compressive axial mechanical properties of rat bone as functions of bone volume fraction, apparent density and micro-ct based mineral density

2010 ◽  
Vol 43 (5) ◽  
pp. 953-960 ◽  
Author(s):  
Esther Cory ◽  
Ara Nazarian ◽  
Vahid Entezari ◽  
Vartan Vartanians ◽  
Ralph Müller ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Apparent Density ◽  
Volume Fraction ◽  
Bone Volume ◽  
Micro Ct ◽  
Mineral Density ◽  
Bone Volume Fraction ◽  
Rat Bone

scholarly journals Raloxifene inhibits the overexpression of TGF-β1 in cartilage and regulates the metabolism of subchondral bone in rats with osteoporotic osteoarthritis

2020 ◽  
Author(s):  
Shao-Hua Ping ◽  
Fa-Ming Tian ◽  
Hao Liu ◽  
Qi Sun ◽  
Li-Tao Shao ◽  
...  
Keyword(s):  
Subchondral Bone ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Volume Fraction ◽  
Clinical Indication ◽  
Tartrate Resistant Acid Phosphatase ◽  
Mineral Density ◽  
Bone Volume Fraction ◽  
Ovx Rats ◽  
Tgf Β1

Overexpression of transforming growth factor-beta 1 (TGF-β1) and subchondral bone remodelling play key roles in osteoarthritis (OA). Raloxifene (RAL) reduces the serum level of TGF-β1 in postmenopausal women. However, the effect of RAL on TGF-β1 expression in articular cartilage is still unclear. Therefore, we aimed to investigate the protective effect of RAL on osteoporotic osteoarthritis via affecting TGF-β1 expression in cartilage and the metabolism of subchondral bone. Osteoporotic osteoarthritis was induced by a combination of anterior cruciate transection (ACLT) and ovariectomy (OVX). Rats were divided into five groups (n = 12): The sham group, the ACLT group, the OVX group, the ACLT + OVX group, and the RAL group (ACLT + OVX + RAL, 6.25 mg/kg/day for 12 weeks). Assessment was performed by histomorphology, microcomputed tomography (micro-CT) scan, immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining. We found that severe cartilage degeneration was shown in the ACLT + OVX group. The histomorphological scores, the levels of TGF-β1, and its related catabolic enzymes and osteoclasts numbers in the ACLT + OVX group were higher than those in other groups (p < 0.05). Furthermore, structure model index (SMI) and trabecular spacing (Tb.Sp) were decreased (p < 0.05), while bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular number (Tb.N) were increased by RAL compared with the ACLT + OVX group (p < 0.05). Our findings demonstrated that RAL in clinical doses retards the development of osteoporotic osteoarthritis by inhibiting the overexpression of TGF-β1 in cartilage and regulating the metabolism of subchondral bone. These results provide support for RAL in the expansion of clinical indication for prevention and treatment in postmenopausal osteoarthritis.

scholarly journals Combination treatment with pioglitazone and fenofibrate attenuates pioglitazone-mediated acceleration of bone loss in ovariectomized rats

2011 ◽  
Vol 212 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Rana Samadfam ◽  
Malaika Awori ◽  
Agnes Bénardeau ◽  
Frieder Bauss ◽  
Elena Sebokova ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Mass ◽  
Trabecular Bone ◽  
Bone Mineral ◽  
Combination Treatment ◽  
Mass Gain ◽  
Ovariectomized Rats ◽  
Concomitant Treatment ◽  
Mineral Density ◽  
Ovx Rats

Peroxisome proliferator-activated receptor (PPAR) γ agonists, such as pioglitazone (Pio), improve glycemia and lipid profile but are associated with bone loss and fracture risk. Data regarding bone effects of PPARα agonists (including fenofibrate (Feno)) are limited, although animal studies suggest that Feno may increase bone mass. This study investigated the effects of a 13-week oral combination treatment with Pio (10 mg/kg per day)+Feno (25 mg/kg per day) on body composition and bone mass parameters compared with Pio or Feno alone in adult ovariectomized (OVX) rats, with a 4-week bone depletion period, followed by a 6-week treatment-free period. Treatment of OVX rats with Pio+Feno resulted in ∼50% lower fat mass gain compared with Pio treatment alone. Combination treatment with Pio+Feno partially prevented Pio-induced loss of bone mineral content (∼45%) and bone mineral density (BMD; ∼60%) at the lumbar spine. Similar effects of treatments were observed at the femur, most notably at sites rich in trabecular bone. At the proximal tibial metaphysis, concomitant treatment with Pio+Feno prevented Pio exacerbation of ovariectomy-induced loss of trabecular bone, resulting in BMD values in the Pio+Feno group comparable to OVX controls. Discontinuation of Pio or Feno treatment of OVX rats was associated with partial reversal of effects on bone loss or bone mass gain, respectively, while values in the Pio+Feno group remained comparable to OVX controls. These data suggest that concurrent/dual agonism of PPARγ and PPARα may reduce the negative effects of PPARγ agonism on bone mass.

scholarly journals Jumping exercise preserves bone mineral density and mechanical properties in osteopenic ovariectomized rats even following established osteopenia

2017 ◽  
Vol 28 (4) ◽  
pp. 1461-1471 ◽  
Author(s):  
R . Okubo ◽  
L. S. Sanada ◽  
V. A. Castania ◽  
M. J. Q. Louzada ◽  
F. J. A. de Paula ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Mineral Density ◽  
Bone Mineral ◽  
Ovariectomized Rats ◽  
Mineral Density ◽  
Jumping Exercise

Directional Tortuosity as a Predictor of Modulus Damage for Vertebral Cancellous Bone

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
David P. Fyhrie ◽  
Roger Zauel
Keyword(s):  
Mechanical Properties ◽  
Cancellous Bone ◽  
Volume Fraction ◽  
Compressive Strain ◽  
Effective Modulus ◽  
Hard Tissue ◽  
Bone Volume Fraction ◽  
Tissue Microstructure ◽  
Induced Changes ◽  
Effective Mechanical Properties

There are many methods used to estimate the undamaged effective (apparent) moduli of cancellous bone as a function of bone volume fraction (BV/TV), mean intercept length (MIL), and other image based average microstructural measures. The MIL and BV/TV are both only functions of the cancellous microstructure and, therefore, cannot directly account for damage induced changes in the intrinsic trabecular hard tissue mechanical properties. Using a nonlinear finite element (FE) approximation for the degradation of effective modulus as a function of applied effective compressive strain, we demonstrate that a measurement of the directional tortuosity of undamaged trabecular hard tissue strongly predicts directional effective modulus (r2 > 0.90) and directional effective modulus degradation (r2 > 0.65). This novel measure of cancellous bone directional tortuosity has the potential for development into an anisotropic approach for calculating effective mechanical properties as a function of trabecular level material damage applicable to understanding how tissue microstructure and intrinsic hard tissue moduli interact to determine cancellous bone quality.

scholarly journals Effects of the Peroxisome Proliferator-Activated Receptor (PPAR)-δ Agonist GW501516 on Bone and Muscle in Ovariectomized Rats

Endocrinology ◽  
2014 ◽  
Vol 155 (6) ◽  
pp. 2178-2189 ◽  
Author(s):  
M. P. Mosti ◽  
A. K. Stunes ◽  
M. Ericsson ◽  
H. Pullisaar ◽  
J. E. Reseland ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Bone Loss ◽  
Ovariectomized Rats ◽  
Whole Body ◽  
Control Group ◽  
High Dose ◽  
Peroxisome Proliferator ◽  
Mineral Density ◽  
Muscle Morphology ◽  
Ovx Rats

Estrogen deficiency promotes bone loss and skeletal muscle dysfunction. Peroxisome proliferator-activated receptors (PPARs) have 3 subtypes (α, δ, and γ). PPARγ agonists induce bone loss, whereas PPARα agonists increase bone mass. Although PPARδ agonists are known to influence skeletal muscle metabolism, the skeletal effects are unsettled. This study investigated the musculoskeletal effects of the PPARδ agonist GW501516 in ovariectomized (OVX) rats. Female Sprague Dawley rats, 12 weeks of age, were allocated to a sham-operated group and 3 OVX groups; high-dose GW501516 (OVX-GW5), low-dose GW501516 (OVX-GW1), and a control group (OVX-CTR), respectively (n = 12 per group). Animals received GW501516 or vehicle (methylcellulose) daily for 4 months by gavage. Bone mineral density (BMD) was assessed by dual x-ray absorptiometry at the femur, spine, and whole body. Bone microarchitecture at the proximal tibia was assessed by microcomputed tomography, and dynamic histomorphometry was performed. Quadriceps muscle morphology and the relative expression of mitochondrial proteins were analyzed. Bone metabolism markers and metabolic markers were measured in plasma. After 4 months, the OVX-GW5 group displayed lower femoral BMD than OVX-CTR. Trabecular separation was higher in the GW-treated groups, compared with OVX-CTR. The OVX-GW5 group also exhibited lower cortical area fraction and a higher structure model index than OVX-CTR. These effects coincided with impaired bone formation in both GW groups. The OVX-GW5 group displayed elevated triglyceride levels and reduced adiponectin levels, whereas no effects on muscle morphology or mitochondrial gene expression appeared. In summary, the PPARδ agonist GW501516 negatively affected bone properties in OVX rats, whereas no effects were detected in skeletal muscle.

Misalignment Error in Cancellous Bone Apparent Elastic Modulus Depends on Bone Volume Fraction and Degree of Anisotropy

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Matthew B. L. Bennison ◽  
A. Keith Pilkey ◽  
W. Brent Lievers
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Cancellous Bone ◽  
Volume Fraction ◽  
Experimental Studies ◽  
Bone Volume ◽  
Bone Volume Fraction ◽  
Skeletal Site ◽  
Degree Of Anisotropy ◽  
Misalignment Error

Abstract Cancellous bone is an anisotropic structure with architectural and mechanical properties that vary due to both skeletal site and disease state. This anisotropy means that, in order to accurately and consistently measure the mechanical properties of cancellous bone, experiments should be performed along the primary mechanical axis (PMA), that is, the orientation in which the mechanical properties are at their maximum value. Unfortunately, some degree of misalignment will always be present, and the magnitude of the resulting error is expected to be architecture dependent. The goal of this work is to quantify the dependence of the misalignment error, expressed in terms of change in apparent elastic modulus (ΔE), on both the bone volume fraction (BV/TV) and the degree of anisotropy (DA). Finite element method (FEM) models of bovine cancellous bone from five different skeletal sites were created at 5 deg and 20 deg from the PMA determined for each region. An additional set of models was created using image dilation/erosion steps in order to control for BV/TV and better isolate the effect of DA. Misalignment error was found to increase with increasing DA and decreasing BV/TV. At 5 deg misaligned from the PMA, error is relatively low (&lt;5%) in all cases but increases to 8–24% error at 20 deg. These results suggest that great care is needed to avoid introducing misalignment error into experimental studies, particularly when studying regions with high anisotropy and/or low bone volume fraction, such as vertebral or osteoporotic bone.

scholarly journals Comparative finite-element analysis: a single computational modelling method can estimate the mechanical properties of porcine and human vertebrae

2014 ◽  
Vol 11 (95) ◽  
pp. 20140186 ◽  
Author(s):  
K. Robson Brown ◽  
S. Tarsuslugil ◽  
V. N. Wijayathunga ◽  
R. K. Wilcox
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Model Development ◽  
Computational Modelling ◽  
Bone Volume Fraction ◽  
Element Analysis ◽  
Modelling Method ◽  
Modelling Techniques ◽  
Musculoskeletal Systems ◽  
Development And Validation

Significant advances in the functional analysis of musculoskeletal systems require the development of modelling techniques with improved focus, accuracy and validity. This need is particularly visible in the fields, such as palaeontology, where unobservable parameters may lie at the heart of the most interesting research questions, and where models and simulations may provide some of the most innovative solutions. Here, we report on the development of a computational modelling method to generate estimates of the mechanical properties of vertebral bone across two living species, using elderly human and juvenile porcine specimens as cases with very different levels of bone volume fraction and mineralization. This study is presented in two parts; part I presents the computational model development and validation, and part II the virtual loading regime and results. This work paves the way for the future estimation of mechanical properties in fossil mammalian bone.

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