A model for the compressible, viscoelastic behavior of human amnion addressing tissue variability through a single parameter

Mauri, Arabella; Ehret, Alexander E.; Focatiis, Davide S.A. De; Mazza, Edoardo

doi:10.1007/s10237-015-0739-0

Cited by 21 publications

(15 citation statements)

References 71 publications

(92 reference statements)

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“…. ., N. The fibres are assumed to be embedded in a compressible matrix and the overall strain energy in terms of the left Cauchy-Green tensor b, its determinant J 2 ¼ det b and l f i reads C ¼ m 0 (e qg 2 1)/(2q), with [33,38] Hs, where s is the Cauchy stress tensor, H is the AM thickness in the initial state and l 3 is the stretch in the membrane normal direction [23]. Computations were performed in Abaqus with a user subroutine for the material model, using three-and four-node elements in plane stress state (CPS3, CPS4), and the results were analysed in consideration of a reference tension corresponding to the one applied in the experimental procedure.…”

Section: Hybrid Continuum -Discrete Modelmentioning

confidence: 99%

On the defect tolerance of fetal membranes

et al. 2019

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A series of mechanical experiments were performed to quantify the strength and fracture toughness of human amnion and chorion. The experiments were complemented with computational investigations using a ‘hybrid’ model that includes an explicit representation of the collagen fibre network of amnion. Despite its much smaller thickness, amnion is shown to be stiffer, stronger and tougher than chorion, and thus to determine the mechanical response of fetal membranes, with respect to both, deformation and fracture behaviour. Data from uniaxial tension and fracture tests were used to inform and validate the computational model, which was then applied to rationalize measurements of the tear resistance of tissue samples containing crack-like defects. Experiments and computations show that the strength of amnion is not significantly reduced by defects smaller than 1 mm, but the crack size induced by perforations for amniocentesis and fetal membrane suturing during fetal surgery might be larger than this value. In line with previous experimental observations, the computational model predicts a very narrow near field at the crack tip of amnion, due to localized fibre alignment and collagen compaction. This mechanism shields the tissue from the defect and strongly reduces the interaction of multiple adjacent cracks. These findings were confirmed through corresponding experiments, showing that no interaction is expected for multiple sutures for an inter-suture distance larger than 1 mm and 3 mm for amnion and chorion, respectively. The experimental procedures and numerical models applied in the present study might be used to optimize needle and/or staple dimensions and inter-suture distance, and thus to reduce the risk of iatrogenic preterm premature rupture of the membranes from amniocentesis, fetoscopic and open prenatal surgery.

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Section: Hybrid Continuum -Discrete Modelmentioning

confidence: 99%

On the defect tolerance of fetal membranes

et al. 2019

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“…For the fluid phase (which in this work is considered as Newtonian and, due the quasi-static nature of the mechanical analysis, incompressible) a softer and nearly incompressible solid ( ν = 0.499) with a bulk modulus of 2 GPa was considered [27]. For simplicity, small strains were considered in the histology-based modelling.…”

Section: Methodsmentioning

confidence: 99%

Histology-based homogenization analysis of soft tissue: application to prostate cancer

Palacio-Torralba

Good

McNeill

et al. 2017

J. R. Soc. Interface.

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It is well known that the changes in tissue microstructure associated with certain pathophysiological conditions can influence its mechanical properties. Quantitatively relating the tissue microstructure to the macroscopic mechanical properties could lead to significant improvements in clinical diagnosis, especially when the mechanical properties of the tissue are used as diagnostic indices such as in digital rectal examination and elastography. In this study, a novel method of imposing periodic boundary conditions in non-periodic finite-element meshes is presented. This method is used to develop quantitative relationships between tissue microstructure and its apparent mechanical properties for benign and malignant tissue at various length scales. Finally, the inter-patient variation in the tissue properties is also investigated. Results show significant changes in the statistical distribution of the mechanical properties at different length scales. More importantly the loss of the normal differentiation of glandular structure of cancerous tissue has been demonstrated to lead to changes in mechanical properties and anisotropy. The proposed methodology is not limited to a particular tissue or material and the example used could help better understand how changes in the tissue microstructure caused by pathological conditions influence the mechanical properties, ultimately leading to more sensitive and accurate diagnostic technologies.

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“…The tension relaxation was hence attributed to the outflow of water for short time-scales and creep of the fibres for longer ones. The former, intrinsically bi-phasic behaviour was represented by a volumetric viscoelastic model, where the collagen network is represented by means of a discrete set of N representative fibre families, distributed uniformly in the membrane plane and with a small off-plane inclination (details in [1]). Neglecting fibre creep, the Helmholtz free energy density Ψ = µ 0 /(2q)[e qg − 1] [3] of the material is specified by, cf.…”

Section: A Compressible Viscoelastic Model Of the Amnionmentioning

confidence: 99%

“…The remaining term g 1 is associated with the small elastic volume change J e of the interstitial fluid within the material, which is treated as an internal state variable with evolution equation, cf. [1] …”

Section: A Compressible Viscoelastic Model Of the Amnionmentioning

confidence: 99%