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Ponnurangam S, O'Connell GD, Chernyshova IV, Wood K, Hung CTH, Somasundaran P. Beneficial effects of cerium oxide nanoparticles in development of chondrocyte-seeded hydrogel constructs and cellular response to interleukin insults. Tissue Eng Part A 2014; 20:2908-19. [PMID: 24762195 PMCID: PMC4229709 DOI: 10.1089/ten.tea.2013.0592] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 04/24/2014] [Indexed: 12/18/2022] Open
Abstract
The harsh inflammatory environment associated with injured and arthritic joints represents a major challenge to articular cartilage repair. In this study, we report the effect of cerium oxide nanoparticles, or nanoceria, in modulating development of engineered cartilage and in combating the deleterious effects of interleukin-1α. Nanoceria was found to be biocompatible with bovine chondrocytes up to a concentration of 1000 μg/mL (60,000 cells/μg of nanoceria), and its presence significantly improved compressive mechanical properties and biochemical composition (i.e., glycosaminoglycans) of engineered cartilage. Raman microspectroscopy revealed that individual chondrocytes with internalized nanoceria have increased concentrations of proline, procollagen, and glycogen as compared with cells without the nanoparticles in their vicinity. The inflammatory response due to physiologically relevant quantities of interluekin-1α (0.5 ng/mL) is partially inhibited by nanoceria. To the best of the authors' knowledge, these results are the first to demonstrate a high potential for nanoceria to improve articular cartilage tissue properties and for their long-term treatment against an inflammatory reaction.
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Kancharala AK, Philen MK. Study of flexible fin and compliant joint stiffness on propulsive performance: theory and experiments. BIOINSPIRATION & BIOMIMETICS 2014; 9:036011. [PMID: 24737004 DOI: 10.1088/1748-3182/9/3/036011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The caudal fin is a major source of thrust generation in fish locomotion. Along with the fin stiffness, the stiffness of the joint connecting the fish body to the tail plays a major role in the generation of thrust. This paper investigates the combined effect of fin and joint flexibility on propulsive performance using theoretical and experimental studies. For this study, fluid-structure interaction of the fin has been modeled using the 2D unsteady panel method coupled with nonlinear Euler-Bernoulli beam theory. The compliant joint has been modeled as a torsional spring at the leading edge of the fin. A comparison of self-propelled speed and efficiency with parameters such as heaving and pitching amplitude, oscillation frequency, flexibility of the fin and the compliant joint is reported. The model also predicts the optimized stiffnesses of the compliant joint and the fin for maximum efficiency. Experiments have been carried out to determine the effect of fin and joint stiffness on propulsive performance. Digital image correlation has been used to measure the deformation of the fins and the measured deformation is coupled with the hydrodynamic model to predict the performance. The predicted theoretical performance behavior closely matches the experimental values.
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Yang W, Sherman VR, Gludovatz B, Mackey M, Zimmermann EA, Chang EH, Schaible E, Qin Z, Buehler MJ, Ritchie RO, Meyers MA. Protective role of Arapaima gigas fish scales: structure and mechanical behavior. Acta Biomater 2014; 10:3599-614. [PMID: 24816264 DOI: 10.1016/j.actbio.2014.04.009] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/12/2014] [Accepted: 04/08/2014] [Indexed: 11/28/2022]
Abstract
The scales of the arapaima (Arapaima gigas), one of the largest freshwater fish in the world, can serve as inspiration for the design of flexible dermal armor. Each scale is composed of two layers: a laminate composite of parallel collagen fibrils and a hard, highly mineralized surface layer. We review the structure of the arapaima scales and examine the functions of the different layers, focusing on the mechanical behavior, including tension and penetration of the scales, with and without the highly mineralized outer layer. We show that the fracture of the mineral and the stretching, rotation and delamination of collagen fibrils dissipate a significant amount of energy prior to catastrophic failure, providing high toughness and resistance to penetration by predator teeth. We show that the arapaima's scale has evolved to minimize damage from penetration by predator teeth through a Bouligand-like arrangement of successive layers, each consisting of parallel collagen fibrils with different orientations. This inhibits crack propagation and restricts damage to an area adjoining the penetration. The flexibility of the lamellae is instrumental to the redistribution of the compressive stresses in the underlying tissue, decreasing the severity of the concentrated load produced by the action of a tooth. The experimental results, combined with small-angle X-ray scattering characterization and molecular dynamics simulations, provide a complete picture of the mechanisms of deformation, delamination and rotation of the lamellae during tensile extension of the scale.
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Pomwenger W, Entacher K, Resch H, Schuller-Götzburg P. Need for CT-based bone density modelling in finite element analysis of a shoulder arthroplasty revealed through a novel method for result analysis. ACTA ACUST UNITED AC 2014; 59:421-30. [PMID: 24897390 DOI: 10.1515/bmt-2013-0125] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 04/11/2014] [Indexed: 11/15/2022]
Abstract
Treatment of common pathologies of the shoulder complex, such as rheumatoid arthritis and osteoporosis, is usually performed by total shoulder arthroplasty (TSA). Survival of the glenoid component is still a problem in TSA, whereas the humeral component is rarely subject to failure. To set up a finite element analysis (FEA) for simulation of a TSA in order to gain insight into the mechanical behaviour of a glenoid implant, the modelling procedure and the application of boundary conditions are of major importance because the computed result strongly depends upon the accuracy and sense of realism of the model. The goal of this study was to show the influence on glenoid stress distribution of a patient-specific bone density distribution compared with a homogenous bone density distribution for the purpose of generating a valid model in future FEA studies of the shoulder complex. Detailed information on the integration of bone density properties using existing numerical models as well as the applied boundary conditions is provided. A novel approach involving statistical analysis of values derived from an FEA is demonstrated using a cumulative distribution function. The results show well the mechanically superior behaviour of a realistic bone density distribution and therefore emphasise the necessity for patient-specific simulations in biomechanical and medical simulations.
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Dulińska-Molak I, Mao H, Kawazoe N, Chen G. Variation of mechanical property of single-walled carbon nanotubes-treated cells explored by atomic force microscopy. J Biomed Nanotechnol 2014; 10:651-9. [PMID: 24734517 DOI: 10.1166/jbn.2014.1745] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
With a range of biological properties, single-walled carbon nanotubes (SWCNTs) are a promising material for nanobiotechnology. Concerns about their potential effect on human health have led to the interest in understanding the interaction between SWCNTs and cells. There are many reports showing the potential cellular effects of SWCNTs but this issue is quite controversially discussed in the literature. In this study, we used conventional biological evaluation methods and atomic force microscopy (AFM) to compare the effects of SWCNTs on three different cell types: bovine articular chondrocytes, human bone marrow-derived mesenchymal stem cells and HeLa cells. No obvious effects of SWCNTs on cell morphology and viability were observed during 3 days in vitro culture. However, SWCNTs significantly increased the Young's modulus of all the three types of cells. The effect of SWCNTs on Young's modulus was in an increasing order of Hela cells < chondrocytes < mesenchymal stem cells. AFM was shown to be a useful tool for investigation of the effect of nanomaterials on mechanical property of cells.
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81
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Hasan I, Heinemann F, Bourauel C. Biomechanical finite element analysis of self-tapping implants with different dimensions inserted in two bone qualities. BIOMED ENG-BIOMED TE 2014; 59:203-12. [PMID: 24695023 DOI: 10.1515/bmt-2013-0109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 02/03/2014] [Indexed: 11/15/2022]
Abstract
Self-tapping dental implants offer the advantage of shortening the surgical insertion time of the implants and improve primary stability in poor bone quality. Using finite element analysis, a series of self-tapping implants with different diameters and lengths have been analysed with respect to their load transfer to the alveolar bone under axial and 45° loading conditions with a total force of 300 N. The implants were inserted in idealised bone beds with cortical thicknesses of 2 and 3 mm. The implants were considered to have osseointegrated condition. A linear decrease of the maximum stresses and strains in the bone around the implants was observed by increasing the diameter of the implants from 3.7 to 5.5 mm regardless of the length of these implants. Lateral loading of the implants caused a critical increase of the stresses and strains in the bone, in particular with the thin cortical layer of 2 mm. The determined biomechanical characteristics of the self-tapping implants showed their applicability in different bone qualities even with extreme reduced length of 7 mm.
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Hazrati Marangalou J, Eckstein F, Kuhn V, Ito K, Cataldi M, Taddei F, van Rietbergen B. Locally measured microstructural parameters are better associated with vertebral strength than whole bone density. Osteoporos Int 2014; 25:1285-96. [PMID: 24306231 DOI: 10.1007/s00198-013-2591-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 11/25/2013] [Indexed: 01/30/2023]
Abstract
UNLABELLED Whole vertebrae areal and volumetric bone mineral density (BMD) measurements are not ideal predictors of vertebral fractures. We introduce a technique which enables quantification of bone microstructural parameters at precisely defined anatomical locations. Results show that local assessment of bone volume fraction at the optimal location can substantially improve the prediction of vertebral strength. INTRODUCTION Whole vertebrae areal and volumetric BMD measurements are not ideal predictors of vertebral osteoporotic fractures. Recent studies have shown that sampling bone microstructural parameters in smaller regions may permit better predictions. In such studies, however, the sampling location is described only in general anatomical terms. Here, we introduce a technique that enables the quantification of bone volume fraction and microstructural parameters at precisely defined anatomical locations. Specific goals of this study were to investigate at what anatomical location within the vertebrae local bone volume fraction best predicts vertebral-body strength, whether this prediction can be improved by adding microstructural parameters and to explore if this approach could better predict vertebral-body strength than whole bone volume fraction and finite element (FE) analyses. METHODS Eighteen T12 vertebrae were scanned in a micro-computed tomography (CT) system and FE meshes were made using a mesh-morphing tool. For each element, bone microstructural parameters were measured and correlated with vertebral compressive strength as measured experimentally. Whole bone volume fraction and FE-predicted vertebral strength were also compared to the experimental measurements. RESULTS A significant association between local bone volume fraction measured at a specific central region and vertebral-body strength was found that could explain up to 90% of the variation. When including all microstructural parameters in the regression, the predictive value of local measurements could be increased to 98%. Whole bone volume fraction could explain only 64% and FE analyses 76% of the variation in bone strength. CONCLUSIONS A local assessment of volume fraction at the optimal location can substantially improve the prediction of bone strength. Local assessment of other microstructural parameters may further improve this prediction but is not clinically feasible using current technology.
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Irrechukwu ON, Von Thaer S, Frank EH, Lin PC, Reiter DA, Grodzinsky AJ, Spencer RG. Prediction of cartilage compressive modulus using multiexponential analysis of T(2) relaxation data and support vector regression. NMR IN BIOMEDICINE 2014; 27:468-77. [PMID: 24519878 PMCID: PMC4608539 DOI: 10.1002/nbm.3083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 12/04/2013] [Accepted: 01/07/2014] [Indexed: 05/14/2023]
Abstract
Evaluation of mechanical characteristics of cartilage by magnetic resonance imaging would provide a noninvasive measure of tissue quality both for tissue engineering and when monitoring clinical response to therapeutic interventions for cartilage degradation. We use results from multiexponential transverse relaxation analysis to predict equilibrium and dynamic stiffness of control and degraded bovine nasal cartilage, a biochemical model for articular cartilage. Sulfated glycosaminoglycan concentration/wet weight (ww) and equilibrium and dynamic stiffness decreased with degradation from 103.6 ± 37.0 µg/mg ww, 1.71 ± 1.10 MPa and 15.3 ± 6.7 MPa in controls to 8.25 ± 2.4 µg/mg ww, 0.015 ± 0.006 MPa and 0.89 ± 0.25MPa, respectively, in severely degraded explants. Magnetic resonance measurements were performed on cartilage explants at 4 °C in a 9.4 T wide-bore NMR spectrometer using a Carr-Purcell-Meiboom-Gill sequence. Multiexponential T2 analysis revealed four water compartments with T2 values of approximately 0.14, 3, 40 and 150 ms, with corresponding weight fractions of approximately 3, 2, 4 and 91%. Correlations between weight fractions and stiffness based on conventional univariate and multiple linear regressions exhibited a maximum r(2) of 0.65, while those based on support vector regression (SVR) had a maximum r(2) value of 0.90. These results indicate that (i) compartment weight fractions derived from multiexponential analysis reflect cartilage stiffness and (ii) SVR-based multivariate regression exhibits greatly improved accuracy in predicting mechanical properties as compared with conventional regression.
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Ingber DE, Wang N, Stamenović D. Tensegrity, cellular biophysics, and the mechanics of living systems. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2014; 77:046603. [PMID: 24695087 PMCID: PMC4112545 DOI: 10.1088/0034-4885/77/4/046603] [Citation(s) in RCA: 227] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The recent convergence between physics and biology has led many physicists to enter the fields of cell and developmental biology. One of the most exciting areas of interest has been the emerging field of mechanobiology that centers on how cells control their mechanical properties, and how physical forces regulate cellular biochemical responses, a process that is known as mechanotransduction. In this article, we review the central role that tensegrity (tensional integrity) architecture, which depends on tensile prestress for its mechanical stability, plays in biology. We describe how tensional prestress is a critical governor of cell mechanics and function, and how use of tensegrity by cells contributes to mechanotransduction. Theoretical tensegrity models are also described that predict both quantitative and qualitative behaviors of living cells, and these theoretical descriptions are placed in context of other physical models of the cell. In addition, we describe how tensegrity is used at multiple size scales in the hierarchy of life—from individual molecules to whole living organisms—to both stabilize three-dimensional form and to channel forces from the macroscale to the nanoscale, thereby facilitating mechanochemical conversion at the molecular level.
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Head DA, Ikebe E, Nakamasu A, Zhang P, Villaruz LG, Kinoshita S, Ando S, Mizuno D. High-frequency affine mechanics and nonaffine relaxation in a model cytoskeleton. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:042711. [PMID: 24827282 DOI: 10.1103/physreve.89.042711] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Indexed: 06/03/2023]
Abstract
The cytoskeleton is a network of crosslinked, semiflexible filaments, and it has been suggested that it has properties of a glassy state. Here we employ optical-trap-based microrheology to apply forces to a model cytoskeleton and measure the high-bandwidth response at an anterior point. Simulating the highly nonlinear and anisotropic stress-strain propagation assuming affinity, we found that theoretical predictions for the quasistatic response of semiflexible polymers are only realized at high frequencies inaccessible to conventional rheometers. We give a theoretical basis for determining the frequency when both affinity and quasistaticity are valid, and we discuss with experimental evidence that the relaxations at lower frequencies can be characterized by the experimentally obtained nonaffinity parameter.
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86
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Edwards WB, Schnitzer TJ, Troy KL. Bone mineral and stiffness loss at the distal femur and proximal tibia in acute spinal cord injury. Osteoporos Int 2014; 25:1005-15. [PMID: 24190426 DOI: 10.1007/s00198-013-2557-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 08/21/2013] [Indexed: 11/24/2022]
Abstract
SUMMARY Computed tomography and finite element modeling were used to assess bone mineral and stiffness loss at the knee following acute spinal cord injury (SCI). Marked bone mineral loss was observed from a combination of trabecular and endocortical resorption. Reductions in stiffness were 2-fold greater than reductions in integral bone mineral. INTRODUCTION SCI is associated with a rapid loss of bone mineral and an increased rate of fragility fracture. The large majority of these fractures occur around regions of the knee. Our purpose was to quantify changes to bone mineral, geometry, strength indices, and stiffness at the distal femur and proximal tibia in acute SCI. METHODS Quantitative computed tomography (QCT) and patient-specific finite element analysis were performed on 13 subjects with acute SCI at serial time points separated by a mean of 3.5 months (range 2.6-4.8 months). Changes in bone mineral content (BMC) and volumetric bone mineral density (vBMD) were quantified for integral, trabecular, and cortical bone at epiphyseal, metaphyseal, and diaphyseal regions of the distal femur and proximal tibia. Changes in bone volumes, cross-sectional areas, strength indices and stiffness were also determined. RESULTS Bone mineral loss was similar in magnitude at the distal femur and proximal tibia. Reductions were most pronounced at epiphyseal regions, ranging from 3.0 % to 3.6 % per month for integral BMC (p < 0.001) and from 2.8 % to 3.4 % per month (p < 0.001) for integral vBMC. Trabecular BMC decreased by 3.1-4.4 %/month (p < 0.001) and trabecular vBMD by 2.7-4.7 %/month (p < 0.001). A 3.8-5.4 %/month reduction was observed for cortical BMC (p < 0.001); the reduction in cortical vBMD was noticeably lower (0.6-0.8 %/month; p ≤ 0.01). The cortical bone loss occurred primarily through endosteal resorption, and reductions in strength indices and stiffness were some 2-fold greater than reductions in integral bone mineral. CONCLUSIONS These findings highlight the need for therapeutic interventions targeting both trabecular and endocortical bone mineral preservation in acute SCI.
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Zheng L, Yang J, Hu X, Luo J. Three dimensional finite element analysis of a novel osteointegrated dental implant designed to reduce stress peak of cortical bone. Acta Bioeng Biomech 2014; 16:21-28. [PMID: 25307871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A new type of dental implant was designed as multi-component mainly including inset and abutment between which a gap was introduced to guide the force to transmit from the cancellous bone to cortical bone, with the intention to lower the stress peak at cortical bone. By way of finite element analysis (FEA) associated with advanced computer tomography (CT) and 3D model reconstruction technology to construct precise mandible model, biomechanical aspects of implant were investigated. Compared with traditional implant that created stress dominantly at cortical bone, stress peak at the implant/bone interface in the cervical cortex decreased sharply (about 51%) for the new type of implant. Furthermore, applying varying implant shape and gap dimensions helped to optimize the design of this new implant. Optimization results revealed that: (1) screwed cylindrical implant is superior to tapered, stepped and smooth cylindrical implant in effectively decreasing the stress peak of bone; (2) deepening and widening gap would contribute to the decline of stress peak, but at the cost of break and destruction of the inset; (3) suitable gap size with the depth of 7 mm and width of 0.3 mm would be applicable. This work may provide reference for clinical application of dental implant.
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Veljković DŽ, Ranković VJ, Pantović SB, Rosić MA, Kojić MR. Hyperelastic behavior of porcine aorta segment under extension-inflation tests fitted with various phenomenological models. Acta Bioeng Biomech 2014; 16:37-45. [PMID: 25308095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Most of hyperelastic models for the constitutive modeling of the typical mechanical behaviour of the arterial wall tissue in literature are based on the test data from different animals and arteries. This paper is concerned with the material parameter identification of several phenomenological hyperelastic models by fitting the data from five extension-inflation tests of the porcine aorta segment, carried out in our laboratory. A membrane approximation is used to compute stresses and strains achieved during experiments, with usual assumption of material incompressibility. Three orthotropic two-dimensional strain-energy functions, based on use of the Green-Lagrange strains, are fitted to the test data: the well-known Fung's exponential model; the classical polynomial model with seven constants; and the logarithmic model; and also, two three-dimensional models are employed: polyconvex anisotropic exponential hyperelastic model and the convex isotropic exponential rubber-like hyperelastic constitutive law depending on the first invariant of the right Cauchy-Green deformation tensor. It has been found that isotropic model overestimates values of stresses in axial, and underestimates values of stresses in circumferential direction of artery segment, due to pronounced tissue anisotropy. Also, all two-dimensional models considered give good and similar prediction, while the polyconvex model demonstrates slightly lower performance in the axial direction of artery.
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Skacel P, Bursa J. Comparison of constitutive models of arterial layers with distributed collagen fibre orientations. Acta Bioeng Biomech 2014; 16:47-58. [PMID: 25308192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Several constitutive models have been proposed for description of mechanical behaviour of soft tissues containing collagen fibres. The model with aligned fibres is modified in this paper to take the dispersion of fibre orientations into account through angular integration and it is compared with the model that is defined through generalized structure tensor. The paper is focused on the effect of fibre dispersion on the resulting stress-strain behaviour predicted by both models analyzed. Analytical calculations are used for the comparison of the mechanical behaviour under a specific biaxial tension mode. The two models have been implemented into commercial finite element code ANSYS via user subroutines and used for numerical simulation resulting in a non-homogeneous stress field. The effects of the fibre dispersion predicted by both models being compared differ significantly, e.g., the resulting stress difference between both models is lower than 10% only in the case of extremely small dispersion of collagen fibres orientation (κ< (0.01 to 0.03)). These results are consistent with those of other related literature. The applicability of the model defined through the generalized structure tensor is discussed.
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Trajkovski A, Omerovic S, Krasna S, Prebil I. Loading rate effect on mechanical properties of cervical spine ligaments. Acta Bioeng Biomech 2014; 16:13-20. [PMID: 25307779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Mechanical properties of cervical spine ligaments are of great importance for an accurate finite element model when analyzing the injury mechanism. However, there is still little experimental data in literature regarding fresh human cervical spine ligaments under physiological conditions. The focus of the present study is placed on three cervical spine ligaments that stabilize the spine and protect the spinal cord: the anterior longitudinal ligament, the posterior longitudinal ligament and the ligamentum flavum. The ligaments were tested within 24-48 hours after death, under two different loading rates. An increase trend in failure load, failure stress, stiffness and modulus was observed, but proved not to be significant for all ligament types. The loading rate had the highest impact on failure forces for all three ligaments (a 39.1% average increase was found). The observed increase trend, compared to the existing increase trends reported in literature, indicates the importance of carefully applying the existing experimental data, especially when creating scaling factors. A better understanding of the loading rate effect on ligaments properties would enable better case-specific human modelling.
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Mori T, Ishii S, Greendale GA, Cauley JA, Sternfeld B, Crandall CJ, Han W, Karlamangla AS. Physical activity as determinant of femoral neck strength relative to load in adult women: findings from the hip strength across the menopause transition study. Osteoporos Int 2014; 25:265-72. [PMID: 23812598 PMCID: PMC3877714 DOI: 10.1007/s00198-013-2429-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 05/14/2013] [Indexed: 11/28/2022]
Abstract
UNLABELLED Our objective was to examine associations of physical activity in different life domains with peak femoral neck strength relative to load in adult women. Greater physical activity in each of the domains of sport, active living, home, and work was associated with higher peak femoral neck strength relative to load. INTRODUCTION Our objective was to examine the associations of physical activity in different life domains with peak femoral neck strength relative to load in adult women. Composite indices of femoral neck strength integrate body size with femoral neck size and bone mineral density to gauge bone strength relative to load during a fall, and are inversely associated with incident fracture risk. METHODS Participants were 1,919 pre- and early perimenopausal women from the Study of Women's Health Across the Nation. Composite indices of femoral neck strength relative to load in three failure modes (compression, bending, and impact) were created from hip dual-energy X-ray absorption scans and body size. Usual physical activity within the past year was assessed with the Kaiser Physical Activity Survey in four domains: sport, home, active living, and work. We used multiple linear regression to examine the associations. RESULTS Greater physical activity in each of the four domains was independently associated with higher composite indices, adjusted for age, menopausal transition stage, race/ethnicity, Study of Women's Health Across the Nation study site, smoking status, smoking pack-years, alcohol consumption level, current use of supplementary calcium, current use of supplementary vitamin D, current use of bone-adverse medications, prior use of any sex steroid hormone pills or patch, prior use of depo-provera injections, history of hyperthyroidism, history of previous adult fracture, and employment status: standardized effect sizes ranged from 0.04 (p < 0.05) to 0.20 (p < 0.0001). CONCLUSIONS Physical activity in each domain examined was associated with higher peak femoral neck strength relative to load in pre- and early perimenopausal women.
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Migacz K, Chłopek J, Morawska-Chochół A, Ambroziak M. Gradient composite materials for artificial intervertebral discs. Acta Bioeng Biomech 2014; 16:3-12. [PMID: 25306938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Composites with the gradient of Young's modulus constitute a new group of biomimetic materials which affect the proper distribution of stresses between the implant and the bone. The aim of this article was to examine the mechanical properties of gradient materials based on carbon fibre-polysulfone composite, and to compare them to the properties of a natural intervertebral disc. Gradient properties were provided by different orientation or volume fraction of carbon fibres in particular layers of composites. The results obtained during in vitro tests displayed a good durability of the gradient materials put under long-term static load. However, the configuration based on a change in the volume fraction of the fibres seems more advantageous than the one based on a change of the fibres' orientation. The materials under study were designed to replace the intervertebral disc. The effect of Young's modulus of the material layers on the stress distribution between the tissue and the implant was analyzed and the biomimetic character of the gradient composites was stated. Unlike gradient materials, the pure polysulfone and the non-gradient composite resulted in the stress concentration in the region of nucleus pulposus, which is highly disadvantageous and does not occur in the stress distribution of natural intervertebral discs.
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Hussein AI, Jackman TM, Morgan SR, Barest GD, Morgan EF. The intravertebral distribution of bone density: correspondence to intervertebral disc health and implications for vertebral strength. Osteoporos Int 2013; 24:3021-30. [PMID: 23863990 PMCID: PMC4465501 DOI: 10.1007/s00198-013-2417-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 05/20/2013] [Indexed: 10/26/2022]
Abstract
UNLABELLED This study's goal was to determine associations among the intravertebral heterogeneity in bone density, bone strength, and intervertebral disc (IVD) health. Results indicated that predictions of vertebral strength can benefit from considering the magnitude of the density heterogeneity and the congruence between the spatial distribution of density and IVD health. INTRODUCTION This study aims to determine associations among the intravertebral heterogeneity in bone density, bone strength, and IVD health METHODS Regional measurements of bone density were performed throughout 30 L1 vertebral bodies using micro-computed tomography (μCT) and quantitative computed tomography (QCT). The magnitude of the intravertebral heterogeneity in density was defined as the interquartile range and quartile coefficient of variation in regional densities. The spatial distribution of density was quantified using ratios of regional densities representing different anatomical zones (e.g., anterior to posterior regional densities). Cluster analysis was used to identify groups of vertebrae with similar spatial distributions of density. Vertebral strength was measured in compression. IVD health was assessed using two scoring systems. RESULTS QCT- and μCT-based measures of the magnitude of the intravertebral heterogeneity in density were strongly correlated with each other (p < 0.005). Accounting for the interquartile range in regional densities improved predictions of vertebral strength as compared to predictions based only on mean density (R (2) = 0.59 vs. 0.43; F-test p-value = 0.018). Specifically, after adjustment for mean density, vertebral bodies with greater heterogeneity in density exhibited higher strength. No single spatial distribution of density was associated with high vertebral strength. Analyses of IVD scores suggested that the health of the adjacent IVDs may modulate the effect of a particular spatial distribution of density on vertebral strength. CONCLUSIONS Noninvasive measurements of the intravertebral distribution of bone density, in conjunction with assessments of IVD health, can aid in predictions of bone strength and in elucidating biomechanical mechanisms of vertebral fracture.
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Wojcinski S, Brandhorst K, Sadigh G, Hillemanns P, Degenhardt F. Acoustic radiation force impulse imaging with virtual touch tissue quantification: measurements of normal breast tissue and dependence on the degree of pre-compression. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:2226-2232. [PMID: 24035624 DOI: 10.1016/j.ultrasmedbio.2013.06.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 06/24/2013] [Accepted: 06/29/2013] [Indexed: 06/02/2023]
Abstract
Acoustic radiation force impulse imaging (ARFI) with Virtual Touch tissue quantification (VTTQ) enables the determination of shear wave velocity in meters per second (m/s). We investigated shear wave velocity in normal breast tissue and analyzed the influence of the degree of pre-compression on the measurements. In repeated measurements and with normal pre-compression, the mean shear wave velocity in breast parenchyma was significantly higher than that in breast adipose tissue (3.33 ± 1.18 m/s vs. 2.90 ± 1.10 m/s; p < 0.001; 712 measurements in 89 patients). Furthermore, we found a significant positive correlation between degree of pre-compression and velocity measurements. Shear wave velocities with low, moderate and high pre-compression were 1.89, 3.18 and 4.39 m/s in parenchyma, compared with 1.46, 2.55 and 3.64 m/s in adipose tissue, respectively (p < 0.001; 360 measurements in 60 patients). VTTQ of breast tissue is a feasible method with high accuracy; however, the degree of pre-compression applied may significantly influence the measurements.
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95
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Dutta D, Lee KW, Allen RA, Wang Y, Brigham JC, Kim K. Non-invasive assessment of elastic modulus of arterial constructs during cell culture using ultrasound elasticity imaging. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:2103-2115. [PMID: 23932282 PMCID: PMC3786060 DOI: 10.1016/j.ultrasmedbio.2013.04.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2013] [Revised: 04/25/2013] [Accepted: 04/28/2013] [Indexed: 05/30/2023]
Abstract
Mechanical strength is a key design factor in tissue engineering of arteries. Most existing techniques assess the mechanical property of arterial constructs destructively, leading to sacrifice of a large number of animals. We propose an ultrasound-based non-invasive technique for the assessment of the mechanical strength of engineered arterial constructs. Tubular scaffolds made from a biodegradable elastomer and seeded with vascular fibroblasts and smooth muscle cells were cultured in a pulsatile-flow bioreactor. Scaffold distension was computed from ultrasound radiofrequency signals of the pulsating scaffold via 2-D phase-sensitive speckle tracking. Young's modulus was then calculated by solving the inverse problem from the distension and the recorded pulse pressure. The stiffness thus computed from ultrasound correlated well with direct mechanical testing results. As the scaffolds matured in culture, ultrasound measurements indicated an increase in Young's modulus, and histology confirmed the growth of cells and collagen fibrils in the constructs. The results indicate that ultrasound elastography can be used to assess and monitor non-invasively the mechanical properties of arterial constructs.
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Jefferies S, Lööf J, Pameijer CH, Boston D, Galbraith C, Hermansson L. Physical properties and comparative strength of a bioactive luting cement. COMPENDIUM OF CONTINUING EDUCATION IN DENTISTRY (JAMESBURG, N.J. : 1995) 2013; 34 Spec No 8:8-14. [PMID: 24568170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
UNLABELLED New dental cement formulations require testing to determine physical and mechanical laboratory properties. OBJECTIVES To test an experimental calcium aluminate/glass-ionomer cement, Ceramir C and B (CC and B), regarding compressive strength (CS), film thickness (FT), net setting time (ST) and Vickers hardness. An additional test to evaluate potential dimensional change/expansion properties of this cement was also conducted. METHODS AND MATERIALS CS was measured according to a slightly modified ISO 9917:2003 for the CC and B specimens. The samples were not clamped while being exposed to relative humidity of great than 90 percent at 37 degrees C for 10 minutes before being stored in phosphate-buffered saline at 37 degrees C. For the CS, four groups were tested: Group 1-CC and B; Group 2-RelyX Luting Cement; Group 3-Fuji Plus; and Group 4-RelyX Unicem. Samples from all groups were stored for 24 hours before testing. Only CCandB was tested for ST and FT according to ISO 9917:2003. The FT was tested 2 minutes after mixing. Vickers hardness was evaluated using the CSM Microhardness Indentation Tester using zinc phosphate cement as a comparison material. Expansion testing included evaluating potential cracks in feldspathic porcelain jacket crowns (PJCs). RESULTS The mean and standard deviation after 24 hours were expressed in MPa: Group 1 equals 160 plus or equal to 27; Group 2 equals 96 plus or equal to 10; Group 3 equals 138 plus or equal to 15; Group 4 equals 157 plus or equal to 10. A single-factor ANOVA demonstrated statistically significant differences between the groups (P less than 0.001). Pair-wise statistical comparison demonstrated a statistically significant difference between Groups 1 and 2. No statistically significant differences were found between other groups. The FT was 16.8 plus or equal to 0.9 and the ST was 4.8 plus or equal to 0.1 min. Vickers hardness for Ceramir C and B was 68.3 plus or equal to 17.2 and was statistically significantly higher (P less than 0.05) than Fleck's Zinc Phosphate cement at Vickers hardness of 51.4 plus or equal to 10. There was no evidence of cracks due to radial expansion in PJCs by the Ceramir C and B cement. CONCLUSION All luting cements tested demonstrated compressive strengths well in excess of the ISO requirement for water-based cements of no less than 50 MPa. Ceramir C and B showed significantly higher CS than RelyX Luting Cement after 24 hours, but was not significantly higher than either Fuji Plus or RelyX Unicem. The ST and FT values of CC and B conform to and are within the boundaries of the requirements of the standard. Surface hardness was statistically higher than and comparable to zinc phosphate cement. There was no evidence of potentially clinically significant and deleterious expansion behavior by this cement. All cements tested demonstrated acceptable strength properties. Within the limits of this study, Ceramir C and B is deemed to possess physical properties suitable for a dental luting cement.
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Hambli R. Micro-CT finite element model and experimental validation of trabecular bone damage and fracture. Bone 2013; 56:363-74. [PMID: 23850483 DOI: 10.1016/j.bone.2013.06.028] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 06/11/2013] [Accepted: 06/30/2013] [Indexed: 11/15/2022]
Abstract
Most micro-CT finite element modeling of human trabecular bone has focused on linear and non-linear analysis to evaluate bone failure properties. However, prediction of the apparent failure properties of trabecular bone specimens under compressive load, including the damage initiation and its progressive propagation until complete bone failure into consideration, is still lacking. In the present work, an isotropic micro-CT FE model at bone tissue level coupled to a damage law was developed in order to simulate the failure of human trabecular bone specimens under quasi-static compressive load and predict the apparent stress and strain. The element deletion technique was applied in order to simulate the progressive fracturing process of bone tissue. To prevent mesh-dependence that generally affects the damage propagation rate, regularization technique was applied in the current work. The model was validated with experimental results performed on twenty-three human trabecular specimens. In addition, a sensitivity analysis was performed to investigate the impact of the model factors' sensitivities on the predicted ultimate stress and strain of the trabecular specimens. It was found that the predicted failure properties agreed very well with the experimental ones.
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Zdunek A, Kurenda A. Determination of the elastic properties of tomato fruit cells with an atomic force microscope. SENSORS (BASEL, SWITZERLAND) 2013; 13:12175-91. [PMID: 24030683 PMCID: PMC3821342 DOI: 10.3390/s130912175] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/23/2013] [Accepted: 09/05/2013] [Indexed: 01/11/2023]
Abstract
Since the mechanical properties of single cells together with the intercellular adhesive properties determine the macro-mechanical properties of plants, a method for evaluation of the cell elastic properties is needed to help explanation of the behavior of fruits and vegetables in handling and food processing. For this purpose, indentation of tomato mesocarp cells with an atomic force microscope was used. The Young's modulus of a cell using the Hertz and Sneddon models, and stiffness were calculated from force-indentation curves. Use of two probes of distinct radius of curvature (20 nm and 10,000 nm) showed that the measured elastic properties were significantly affected by tip geometry. The Young's modulus was about 100 kPa ± 35 kPa and 20 kPa ± 14 kPa for the sharper tip and a bead tip, respectively. Moreover, large variability regarding elastic properties (>100%) among cells sampled from the same region in the fruit was observed. We showed that AFM provides the possibility of combining nano-mechanical properties with topography imaging, which could be very useful for the study of structure-related properties of fruits and vegetables at the cellular and sub-cellular scale.
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Ishii S, Cauley JA, Greendale GA, Crandall CJ, Huang MH, Danielson ME, Karlamangla AS. Trajectories of femoral neck strength in relation to the final menstrual period in a multi-ethnic cohort. Osteoporos Int 2013; 24:2471-81. [PMID: 23436075 PMCID: PMC3880423 DOI: 10.1007/s00198-013-2293-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 01/11/2013] [Indexed: 12/19/2022]
Abstract
UNLABELLED The purpose of this study was to describe the evolution of femoral neck strength relative to load across the menopause transition. It declined significantly over the 10 years bracketing the final menstrual period, and the rate of decline was modified by body mass index, race/ethnicity, and smoking status. INTRODUCTION Composite indices of femoral neck strength, which integrate dual energy X-ray absorptiometry (DXA)-derived bone mineral density and bone size with body size, are inversely associated with hip fracture risk. Our objective was to describe longitudinal trajectories of the strength indices across the menopausal transition. METHODS Data came from the Study of Women's Health Across the Nation; participants were pre- or early peri-menopausal, ages 42-53 at baseline, and were followed up for 9.1 ± 1.8 years. Composite indices of femoral neck strength in different failure modes (compression, bending, and impact) were created in 921 women who had three or more hip DXA scans and had definable final menstrual period (FMP) dates. We used mixed effects models to fit piecewise linear growth curves to the baseline-normalized strength indices as a function of time to/after the FMP. RESULTS Compression and impact strength indices did not decline until 1 year prior to the FMP, and declined rapidly thereafter, with some slowing of decline 1 year after the FMP. Bending strength index increased slightly until 2 years prior to the FMP, then plateaued, and began to decline at the FMP. Mean decline in strength indices over 10 years was 6.9 % (compression), 2.5 % (bending), and 6.8 % (impact). Women with higher body mass index had larger declines in two of the three indices. Other major modifiers of rates of decline were race/ethnicity and smoking status. CONCLUSIONS Femoral neck strength relative to load declines significantly during the menopausal transition, with declines commencing 1 to 2 years prior to the FMP.
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Bar-On B, Wagner HD. The emergence of an unusual stiffness profile in hierarchical biological tissues. Acta Biomater 2013; 9:8099-109. [PMID: 23669625 DOI: 10.1016/j.actbio.2013.04.052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 04/14/2013] [Accepted: 04/16/2013] [Indexed: 11/20/2022]
Abstract
Biological tissues usually exhibit complex multiscale structural architectures. In many of these, and particularly in mineralized tissues, the basic building block is a staggered array-a composite material made of soft matrix and stiff reinforcing elements. Here we study the stiffness of non-overlapping staggered arrays, a case that has not previously been considered in the literature, and introduce closed-form analytical expressions for its Young's modulus. These expressions are then used to estimate the stiffness of natural staggered biocomposites such as low-mineralized collagen fibril and mineralized tendon. We then consider a two-scale composite scheme for evaluating the modulus of a specific hierarchical structure, the compact bone tissue, which is made of mineralized collagen fibrils with weakly overlapping staggered architecture. It is found that small variations in the staggered structure induce significant differences in the macroscopic stiffness, and, in particular, provide a possible explanation for the as yet unexplained stiffening effects observed in medium-mineralized tissues.
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