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Research Papers

About Puncture Testing Applied for Mechanical Characterization of Fetal Membranes

[+] Author and Article Information
Wilfried Bürzle

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
Institute for Mechanical Systems,
Tannenstrasse 3, CLA H 23.2,
Zurich 8092, Switzerland
e-mail: buerzle@imes.mavt.ethz.ch

Edoardo Mazza

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
Institute for Mechanical Systems,
Leonhardstrasse 21, LEE N 210,
Zurich 8092, Switzerland
e-mail: mazza@imes.mavt.ethz.ch

John J. Moore

Division of Neonatology,
Case Western Reserve
University School of Medicine,
2500 MetroHealth Drive,
Cleveland, OH 44109
e-mail: Jmoore@metrohealth.org

1Corresponding author.

Manuscript received April 10, 2014; final manuscript received August 8, 2014; accepted manuscript posted August 29, 2014; published online September 17, 2014. Assoc. Editor: David Corr.

J Biomech Eng 136(11), 111009 (Sep 17, 2014) (8 pages) Paper No: BIO-14-1158; doi: 10.1115/1.4028446 History: Received April 10, 2014; Revised August 08, 2014; Accepted August 29, 2014

Puncture testing has been applied in several studies for the mechanical characterization of human fetal membrane (FM) tissue, and significant knowledge has been gained from these investigations. When comparing results of mechanical testing (puncture, inflation, and uniaxial tension), we have observed discrepancies in the rupture sequence of FM tissue and significant differences in the deformation behavior. This study was undertaken to clarify these discrepancies. Puncture experiments on FM samples were performed to reproduce previous findings, and numerical simulations were carried out to rationalize particular aspects of membrane failure. The results demonstrate that both rupture sequence and resistance to deformation depend on the samples' fixation. Soft fixation leads to slippage in the clamping, which reduces mechanical loading of the amnion layer and results in chorion rupturing first. Conversely, the stiffer, stronger, and less extensible amnion layer fails first if tight fixation is used. The results provide a novel insight into the interpretation of ex vivo testing as well as in vivo membrane rupture.

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References

Figures

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Fig. 1

Illustration of the puncture test setup (a) and sample fixation (b). The sample fixation was designed to be similar to the one used in Refs. [7] and [8].

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Fig. 2

Schematic drawing of the deflected membrane sample with indication of geometrical quantities (a) as well as illustration of the axial equilibrium of forces (b). The reference configuration obtained by the use of a force threshold is characterized by the initial apex displacement U0.

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Fig. 3

Illustration of the finite element model used for the two numerical simulations performed, i.e., case 1 simulates tight sample fixation at the outer boundary, and case 2 allows for sample sliding within the clamping assuming a friction coefficient μ

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Fig. 4

Sample specific force–displacement curves for the five membranes tested and illustration of the determination of maximum force and displacement. Data are reported up to the first decrease in force.

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Fig. 5

Comparison of the simulation results with the averaged experimental data. Simulation results were obtained for two cases, i.e., case 1, assuming tight sample fixation at the outer extremity, and case 2, allowing for sample slippage inside the clamping

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Fig. 6

Illustration of the stretch distribution across the nominal sample thickness in the center of the sample. Distributions are shown for the two simulations performed, in short: case 1, assuming tight sample fixation, and case 2, allowing for sample slippage.

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Fig. 7

Comparison of the averaged experimental force–displacement curves obtained with the long sample fixation (LC) and the short sample fixation (SC) as well as the corresponding model prediction for the SC

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