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research-article

Anisotropic Material Characterization of Human Cervix Tissue based on Indentation

[+] Author and Article Information
Lei Shi

Graduate Research Assistant, Department of Mechanical Engineering, Columbia University, New York, NY, 10027
ls3374@columbia.edu

Wang Yao

Graduate Research Assistant, Department of Mechanical Engineering, Columbia University, New York, NY, 10027
wy2169@columbia.edu

Yu Gan

Graduate Research Assistant, Department of Electrical Engineering, Columbia University, New York, NY, 10027
yg2327@columbia.edu

Lily Zhao

Undergraduate Research Assistant, Department of Mechanical Engineering, Columbia University, New York, NY, 10027
lyz2104@columbia.edu

William Eugene McKee

Undergraduate Research Assistant, Department of Mechanical Engineering, 3 Columbia University, New York, NY, 10027
wem2116@columbia.edu

Joy Vink

Assistant Clinical Professor, Department of Obstetrics and Gynecology, Columbia University, New York, NY, 10032
jyv2101@cumc.columbia.edu

Ronanld Wapner

Vice Chairman for Research, Department of Obstetrics and Gynecology, Columbia University, New York, NY, 10032
rw2191@cumc.columbia.edu

Christine Hendon

Associate Professor, Department of Electrical Engineering, Columbia University, New York, NY, 10027
cpf2115@columbia.edu

Kristin Myers

Associate Professor, Department of Mechanical Engineering, Columbia University, New York, NY, 10027
kmm2233@columbia.edu

1Corresponding author.

ASME doi:10.1115/1.4043977 History: Received March 28, 2019; Revised June 07, 2019

Abstract

The cervix is essential to a healthy pregnancy as it must bear the increasing load caused by the growing fetus. Preterm birth is suspected to be caused by the premature softening and mechanical failure of the cervix. The objective of this paper is to measure the anisotropic mechanical properties of human cervical tissue using indentation and video extensometry. The human cervix is a layered structure, where its thick stromal core contains preferentially aligned collagen fibers embedded in a soft ground substance. The fiber composite nature of the tissue provides resistance to the complex 3-dimensional loading environment of pregnancy. In this work, we detail an indentation mechanical test to obtain the force and deformation response during loading which closely matches in vivo conditions. We postulate a constitutive material model to describe the equilibrium material behavior to ramp-hold indentation, and we use an inverse finite element method based on genetic algorithm optimization to determine best-fit material parameters. We report the material properties of human cervical slices taken at different anatomical locations from women of different obstetric backgrounds. In this cohort of patients, the anterior internal os (the area where the cervix meets the uterus) of the cervix is stiffer than the anterior external os (the area closest to the vagina). The anatomic anterior and posterior quadrants of cervical tissue are more anisotropic than the left and right quadrants. There is no significant difference in material properties between samples of different parities (number of pregnancies reaching viable gestation age).

Copyright (c) 2019 by ASME
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