Research Papers

Swine Vagina Under Planar Biaxial Loads: An Investigation of Large Deformations and Tears

[+] Author and Article Information
Jeffrey A. McGuire

Department of Biomedical
Engineering and Mechanics,
Virginia Tech,
Blacksburg, VA 24061
e-mail: jeffmcg8@vt.edu

Steven D. Abramowitch

Department of Bioengineering,
University of Pittsburgh,
Pittsburgh, PA 15261
e-mail: sdast9@pitt.edu

Spandan Maiti

Department of Bioengineering,
University of Pittsburgh,
Pittsburgh, PA 15261
e-mail: spm54@pitt.edu

Raffaella De Vita

Department of Biomedical
Engineering and Mechanics,
Virginia Tech,
Blacksburg, VA 24061
e-mail: devita@vt.edu

Manuscript received June 8, 2018; final manuscript received December 3, 2018; published online February 13, 2019. Assoc. Editor: Thao (Vicky) Nguyen.

J Biomech Eng 141(4), 041003 (Feb 13, 2019) (9 pages) Paper No: BIO-18-1270; doi: 10.1115/1.4042437 History: Received June 08, 2018; Revised December 03, 2018

Vaginal tears are very common and can lead to severe complications such as hemorrhaging, fecal incontinence, urinary incontinence, and dyspareunia. Despite the implications of vaginal tears on women's health, there are currently no experimental studies on the tear behavior of vaginal tissue. In this study, planar equi-biaxial tests on square specimens of vaginal tissue, with sides oriented along the longitudinal direction (LD) and circumferential direction (CD), were conducted using swine as animal model. Three groups of specimens were mechanically tested: the NT group (n =9), which had no pre-imposed tear, the longitudinal tear (LT) group (n =9), and the circumferential tear (CT) group (n =9), which had central pre-imposed elliptically shaped tears with major axes oriented in the LD and the CD, respectively. Through video recording during testing, axial strains were measured for the NT group using the digital image correlation (DIC) technique and axial displacements of hook clamps were measured for the NT, LT, and CT groups in the LD and CD. The swine vaginal tissue was found to be highly nonlinear and somewhat anisotropic. Up to normalized axial hook displacements of 1.15, no tears were observed to propagate, suggesting that the vagina has a high resistance to further tearing once a tear has occurred. However, in response to biaxial loading, the size of the tears for the CT group increased significantly more than the size of the tears for the LT group (p =0.003). The microstructural organization of the vagina is likely the culprit for its tear resistance and orientation-dependent tear behavior. Further knowledge on the structure–function relationship of the vagina is needed to guide the development of new methods for preventing the severe complications of tearing.

Copyright © 2019 by ASME
Your Session has timed out. Please sign back in to continue.


Ramin, S. , Satin, A. , Stone, J. I. , and Wendel, J. G. , 1992, “ Sexual Assault in Postmenopausal Women,” Obstet. Gynecol., 80(5), pp. 860–864. http://europepmc.org/abstract/MED/1407929 [PubMed]
Sau, A. , Dhar, K. , and Dhall, G. , 1993, “ Nonobstetric Lower Genital Tract Trauma,” Aust. N. Z. J. Obstet. Gynaecol., 33(4), pp. 433–435. [CrossRef] [PubMed]
McLean, I. , Roberts, S. , White, C. , and Paul, S. , 2011, “ Female Genital Injuries Resulting From Consensual and Non-Consensual Vaginal Intercourse,” Forensic Sci. Int., 204(1–3), pp. 27–33. [CrossRef] [PubMed]
Campbell, S. , and Newman, G. , 1971, “ Growth of the Fetal Biparietal Diameter During Normal Pregnancy,” BJOG: An Int. J. Obstet. Gynaecol., 78(6), pp. 513–519. [CrossRef]
Barnhart, K. , Izquierdo, A. , Pretorius, E. , Shera, D. , Shabbout, M. , and Shaunik, A. , 2006, “ Baseline Dimensions of the Human Vagina,” Hum. Reprod., 21(6), pp. 1618–1622. [CrossRef] [PubMed]
Samuelsson, E. , Ladfors, L. , Lindblom, B. , and Hagberg, H. , 2002, “ A Prospective Observational Study on Tears During Vaginal Delivery: Occurrences and Risk Factors,” Acta Obstet. Gynecol. Scand., 81(1), pp. 44–49. [CrossRef] [PubMed]
Hopkins, L. , Caughey, A. , Glidden, D. , and Laros, R. , 2005, “ Racial/Ethnic Differences in Perineal, Vaginal and Cervical Lacerations,” Am. J. Obstet. Gynecol., 193(2), pp. 455–459. [CrossRef] [PubMed]
Andrews, V. , Sultan, A. , Thakar, R. , and Jones, P. , 2006, “ Occult Anal Sphincter Injuries—Myth or Reality?,” BJOG: An Int. J. Obstet. Gynaecol., 113(2), pp. 195–200. [CrossRef]
Gurol-Urganci, I. , Cromwell, D. , Edozien, L. , Mahmood, T. A. , Adams, E. , Richmond, D. , Templeton, A. , and Meulen, J. , 2013, “ Third-and Fourth-Degree Perineal Tears Among Primiparous Women in England Between 2000 and 2012: Time Trends and Risk Factors,” BJOG: An Int. J. Obstet. Gynaecol., 120(12), pp. 1516–1525. [CrossRef]
Martin, J. , Hamilton, B. , Osterman, M. , Driscoll, A. , and Matthews, T. , 2017, “ Births: Final Data for 2015,” Natl. Vital Stat. Rep., 66(1), pp. 1–70.
Riesner, M. , and Polley, L. , 2007, “ Chapter 194—Postpartum Hemorrhage,” Complications in Anesthesia, 2nd ed., J. Atlee , ed., W. Saunders, Philadelphia, PA, pp. 779–781.
Sultan, A. , Kamm, M. , Hudson, C. , Thomas, J. , and Bartram, C. , 1993, “ Anal-Sphincter Disruption During Vaginal Delivery,” New Engl. J. Med., 329(26), pp. 1905–1911. [CrossRef]
Borello-France, D. , Burgio, K. L. , Richter, H. E. , Zyczynski, H. , FitzGerald, M. P. , Whitehead, W. , Fine, P. , Nygaard, I. , Handa, V. L. , Visco, A. G. , and Weber, A. M. , 2006, “ Fecal and Urinary Incontinence in Primiparous Women,” Obstet. Gynecol., 108(4), pp. 863–872. [CrossRef] [PubMed]
Macarthur, A. , and Macarthur, C. , 2004, “ Incidence, Severity, and Determinants of Perineal Pain After Vaginal Delivery: A Prospective Cohort Study,” Am. J. Obstet. Gynecol., 191(4), pp. 1199–1204. [CrossRef] [PubMed]
Williams, A. , Lavender, T. , Richmond, D. , and Tincello, D. , 2005, “ Women's Experiences After a Third-Degree Obstetric Anal Sphincter Tear: A Qualitative Study,” Birth, 32(2), pp. 129–136. [CrossRef] [PubMed]
Williams, A. , Herron-Marx, S. , and Carolyn, H. , 2007, “ The Prevalence of Enduring Postnatal Perineal Morbidity and Its Relationship to Perineal Trauma,” Midwifery, 23(4), pp. 392–403. [CrossRef] [PubMed]
Fernando, R. , and Sultan, A. , 2004, “ Risk Factors and Management of Obstetric Perineal Injury,” Obstet., Gynaecol. Reprod. Med., 14(5), pp. 320–326.
Krstic, R. , 2013, Human Microscopic Anatomy: An Atlas for Students of Medicine and Biology, Springer , Berlin.
Boreham, M. , Wai, C. , Miller, R. , Schaffer, J. , and Word, R. , 2002, “ Morphometric Analysis of Smooth Muscle in the Anterior Vaginal Wall of Women With Pelvic Organ Prolapse,” Am. J. Obstet. Gynecol., 187(1), pp. 56–63. [CrossRef] [PubMed]
Takano, C. C. , Gira, M. J. , Sartori, M. G. , Castro, R. A. , Arruda, R. M. , Simo, M. J. , Baracat, E. C. , and de Lima, G. R. , 2002, “ Analysis of Collagen in Parametrium and Vaginal Apex of Women With and Without Uterine Prolapse,” Int. Urogynecol. J., 13(6), pp. 342–345. [CrossRef]
Ulrich, D. , Edwards, S. , Su, K. , White, J. , Ramshaw, J. , Jenkin, G. , Deprest, J. , Rosamilia, A. , Werkmeister, J. , and Gargett, C. , 2014, “ Influence of Reproductive Status on Tissue Composition and Biomechanical Properties of Ovine Vagina,” PLoS One, 9(4), p. e93172. [CrossRef] [PubMed]
Ulrich, D. , Edwards, S. , Letouzey, V. , Su, K. , White, J. , Rosamilia, A. , Gargett, C. , and Werkmeister, J. , 2014, “ Regional Variation in Tissue Composition and Biomechanical Properties of Postmenopausal Ovine and Human Vagina,” PLoS One, 9(8), p. e104972. [CrossRef] [PubMed]
Rynkevic, R. , Martins, P. , Hympanova, L. , Almeida, H. , Fernandes, A. , and Deprest, J. , 2017, “ Biomechanical and Morphological Properties of the Multiparous Ovine Vagina and Effect of Subsequent Pregnancy,” J. Mech., 57, pp. 94–102.
Badiou, W. , Granier, G. , Bousquet, P. , Monrozies, X. , Mares, P. , and de Tayrac, R. , 2008, “ Comparative Histological Analysis of Anterior Vaginal Wall in Women With Pelvic Organ Prolapse or Control Subjects—A Pilot Study,” Int. Urogynecol. J., 19(5), pp. 723–729. [CrossRef]
Kerkhof, M. , Ruiz-Zapata, A. , Bril, H. , Bleeker, M. , Belien, J. , Stoop, R. , and Helder, M. , 2014, “ Changes in Tissue Composition of the Vaginal Wall of Premenopausal Women With Prolapse,” Am. J. Obstet. Gynecol., 210(2), p. 168. [CrossRef] [PubMed]
Sridharan, I. , Ma, Y. , Kim, T. , Kobak, W. , Rotmensch, J. , and Wang, R. , 2012, “ Structural and Mechanical Profiles of Native Collagen Fibers in Vaginal Wall Connective Tissues,” Biomaterials, 33(5), pp. 1520–1527. [CrossRef] [PubMed]
Baah-Dwomoh, A. , McGuire, J. , Tan, T. , and De Vita, R. , 2016, “ Mechanical Properties of Female Reproductive Organs and Supporting Connective Tissues: A Review of the Current State of Knowledge,” ASME Appl. Mech. Rev., 68(6), p. 060801. [CrossRef]
Robison, K. , Conway, C. , Desrosiers, L. , Knoepp, L. , and Miller, K. , 2017, “ Biaxial Mechanical Assessment of the Murine Vaginal Wall Using Extension–Inflation Testing,” ASME J. Biomech. Eng., 139(10), p. 104504. [CrossRef]
Oyen-Tiesma, M. , and Cook, R. , 2001, “ Technique for Estimating Fracture Resistance of Cultured Neocartilage,” J. Mater. Sci.: Mater. Med., 12(4), pp. 327–332. [CrossRef] [PubMed]
Stok, K. , and Oloyede, A. , 2003, “ A Qualitative Analysis of Crack Propagation in Articular Cartilage at Varying Rates of Tensile Loading,” Connect. Tissue Res., 44(2), pp. 109–120. [CrossRef] [PubMed]
Fessel, G. , Wernli, J. , Li, Y. , Gerber, C. , and Snedeker, J. , 2012, “ Exogenous Collagen Cross-Linking Recovers Tendon Functional Integrity in an Experimental Model of Partial Tear,” J. Orthop. Res., 30(6), pp. 973–981. [CrossRef] [PubMed]
Taylor, D. , O'Mara, N. , Ryan, E. , Takaza, M. , and Simms, C. , 2012, “ The Fracture Toughness of Soft Tissues,” J. Mech. Behav. Biomed. Mater., 6, pp. 139–147. [CrossRef] [PubMed]
Yang, W. , Sherman, V. , Gludovatz, B. , Schaible, E. , Stewart, P. , Ritchie, R. , and Meyers, M. , 2015, “ On the Tear Resistance of Skin,” Nat. Commun., 6, p. 6649. [CrossRef] [PubMed]
Ehret, A. , Bircher, K. , Stracuzzi, A. , Marina, V. , Zündel, M. , and Mazza, E. , 2017, “ Inverse Poroelasticity as a Fundamental Mechanism in Biomechanics and Mechanobiology,” Nat. Commun., 8(1), p. 1002. [CrossRef] [PubMed]
Bal, H. , and Getty, R. , 1972, “ Vaginal Histology of the Domestic Pig: Histomorphology From Birth to 8 Years With Some Clinical Aspects,” J. Reprod. Fertil., 28(1), pp. 1–7. [CrossRef] [PubMed]
Gruber, D. , Warner, W. , Lombardini, E. , Zahn, C. , and Buller, J. , 2011, “ Anatomical and Histological Examination of the Porcine Vagina and Supportive Structures: In Search of an Ideal Model for Pelvic Floor Disorder Evaluation and Management,” Female Pelvic Med. Reconstr. Surg., 17(3), pp. 110–114. [CrossRef] [PubMed]
Sutton, M. , Orteu, J. , and Schreier, H. , 2009, Image Correlation for Shape, Motion and Deformation Measurements, Springer, New York.
Lionello, G. , Sirieix, C. , and Baleani, M. , 2014, “ An Effective Procedure to Create a Speckle Pattern on Biological Soft Tissue for Digital Image Correlation Measurements,” J. Mech. Behav. Biomed. Mater., 39, pp. 1–8. [CrossRef] [PubMed]
Rubod, C. , Boukerrou, M. , Brieu, M. , Dubois, P. , and Cosson, M. , 2007, “ Biomechanical Properties of Vaginal Tissue—Part 1: New Experimental Protocol,” J. Urol., 178(1), pp. 320–325. [CrossRef] [PubMed]
Rubod, C. , Boukerrou, M. , Brieu, M. , Jean-Charles, C. , Dubois, P. , and Cosson, M. , 2008, “ Biomechanical Properties of Vaginal Tissue: Preliminary Results,” Int. Urogynecol. J., 19(6), pp. 811–816. [CrossRef]
Koh, C. , Strange, D. , Tonsomboon, K. , and Oyen, M. , 2013, “ Failure Mechanisms in Fibrous Scaffolds,” Acta Biomater., 9(7), pp. 7326–7334. [CrossRef] [PubMed]
Waldman, S. , and Lee, J. , 2002, “ Boundary Conditions During Biaxial Testing of Planar Connective Tissues—Part 1: Dynamic Behavior,” J. Mater. Sci.: Mater. Med., 13(10), pp. 933–938. [CrossRef] [PubMed]
Waldman, S. , Sacks, M. , and Lee, J. , 2002, “ Boundary Conditions During Biaxial Testing of Planar Connective Tissues—Part II: Fiber Orientation,” J. Mater. Sci. Lett., 21(15), pp. 1215–1221. [CrossRef]
Sun, W. , Sacks, M. , and Scott, M. , 2005, “ Effects of Boundary Conditions on the Estimation of the Planar Biaxial Mechanical Properties of Soft Tissues,” ASME J. Biomech. Eng., 127(4), pp. 709–715. [CrossRef]
Eilaghi, A. , Flanagan, J. , Brodland, G. , and Ethier, C. , 2009, “ Strain Uniformity in Biaxial Specimens Is Highly Sensitive to Attachment Details,” ASME J. Biomech. Eng., 131(9), p. 091003. [CrossRef]
Jacobs, N. , Cortes, D. , Vresilovic, E. , and Elliott, D. , 2013, “ Biaxial Tension of Fibrous Tissue: Using Finite Element Methods to Address Experimental Challenges Arising From Boundary Conditions and Anisotropy,” ASME J. Biomech. Eng., 135(2), p. 021004. [CrossRef]
Zhao, X. , Berwick, Z. , Krieger, J. , Chen, H. , Chambers, S. , and Kassab, G. , 2014, “ Novel Design of Cruciform Specimens for Planar Biaxial Testing of Soft Materials,” Exp. Mech., 54(3), pp. 343–356. [CrossRef]
Nolan, D. , and McGarry, J. , 2016, “ On the Correct Interpretation of Measured Force and Calculation of Material Stress in Biaxial Tests,” J. Mech. Behav. Biomed. Mater., 53, pp. 187–199. [CrossRef] [PubMed]
Cioffi, J. , Swain, J. , and Arundell, F. , 2010, “ The Decision to Suture After Childbirth: Cues, Related Factors, Knowledge and Experience Used by Midwives,” Midwifery, 26(2), pp. 246–255. [CrossRef] [PubMed]
Metcalfe, A. , Tohill, S. , Williams, A. , Haldon, V. , Brown, L. , and Henry, L. , 2002, “ A Pragmatic Tool for the Measurement of Perineal Tears,” B. J. Midwifery, 10(7), pp. 412–417. [CrossRef]
Edozien, L. , Gurol-Urganci, I. , Cromwell, D. , Adams, E. , Richmond, D. , Mahmood, T. , and Meulen, J. , 2014, “ Impact of Third-and Fourth-degree Perineal Tears at First Birth on Subsequent Pregnancy Outcomes: A Cohort Study,” BJOG: An Int. J. Obstet. Gynaecol., 121(13), pp. 1695–1703. [CrossRef]
Shek, K. , Green, K. , Hall, J. , Guzman-Rojas, R. , and Dietz, H. , 2016, “ Perineal and Vaginal Tears Are Clinical Markers for Occult Levator Ani Trauma: A Retrospective Observational Study,” Ultrasound Obstet. Gynecol., 47(2), pp. 224–227. [CrossRef] [PubMed]


Grahic Jump Location
Fig. 1

Diagram of the vaginal tract within the swine displaying the three regions and two cross sections from which samples were taken for histological analysis. Blue squares represent specimens stained with MT stain and magenta squares represent specimens stained with VVG stain.

Grahic Jump Location
Fig. 2

Schematic of the specimen in the (a) undeformed configuration and (b) deformed configuration. HLD, HCD, hLD, and hCD represent the distances between hooks in the LD and CD as indicated by the subscripts. 2A and 2a represent the lengths of the major axis of the tear, 2B and 2b represent the lengths of the minor axis of the tear, and A and a represent the areas of the elliptically shaped tear.

Grahic Jump Location
Fig. 3

Histology of full thickness vaginal cross section: (a) MT-stained slide and (b) VVG-stained slide. (c) Percent content of smooth muscle, collagen, and elastin reported as mean ± standard deviation (n =12).

Grahic Jump Location
Fig. 4

Stress–strain data in the LD (solid lines) and CD (dashed lines) for specimens in the NT group (n =9)

Grahic Jump Location
Fig. 5

Mean (± standard deviation) stress–strain data in the LD (solid lines and circles) and CD (dashed lines and triangles) for specimens in the NT group (n =9)

Grahic Jump Location
Fig. 6

Axial Lagrangian strain maps in the (a) LD and (b) CD of a single specimen at four values of NHD

Grahic Jump Location
Fig. 7

Stress versus NHD data in the LD (solid lines) and CD (dashed lines) of specimens in the LT group (n =9)

Grahic Jump Location
Fig. 8

Stress versus NHD data in the LD (solid lines) and CD (dashed lines) of specimens in the CT group (n =9)

Grahic Jump Location
Fig. 9

Mean (± standard deviation) stress data in the LD (solid colored bars with solid lines) and CD (patterned color bars with dashed lines) of the NT (n =9), LT (n =9), and CT (n =9) groups at three levels of NHD. Significant differences in stress were found between the LD and CD for the NT group at all three levels of NHD.

Grahic Jump Location
Fig. 10

(a) Normalized length, a/A, versus NHD data in the LD (solid lines and circles) and normalized length, b/B, versus NHD data in the CD (dashed lines and triangles) for the LT group (n =9). (b) Normalized length, a/A, versus NHD data in the CD (dashed lines and triangles) and normalized length, b/B, versus NHD data in the LD (solid lines and circles) for the CT group (n =9). Mean (±standard deviation) data are also reported (black symbols).

Grahic Jump Location
Fig. 11

Normalized changes in the areas, a/A, versus the average of the NHD data in the LD and CD for the LT and CT groups. Mean (± standard deviation) data are also reported (black symbols).



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In