UNS: Collaborative Research: Impact of Pregnancy on the Mechanics of Vaginal Tissue

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Pelvic floor disorders (PFDs) encompass a number of medical conditions including stress urinary and fecal incontinence, and pelvic organ prolapse. Although not often discussed, these conditions are extremely common, with more than 50% of parous women having some degree of a PFD during their lifetime and 11% of women requiring surgery. These disorders severely alter the quality of life of women often leading to isolation and depression. To someone not entirely familiar with internal female pelvic anatomy, it may appear that the vagina is no more important than the rectum or urethra in the development of these disorders. However, the vagina is the primary support structure for the urethra, bladder, uterus, and rectum. The vagina is, in turn, supported by a combination of muscle and connective tissues. A direct insult to the vagina and/or its supportive muscles and tissues compromises the function of other pelvic organs. Thus, it should come as no surprise that excessive stretching and tearing of the vagina during labor and vaginal delivery are predisposing factors for the development of PFDs. It is still unclear, however, which of the structural and mechanical alterations that occur in vaginal tissue during pregnancy predispose women to the development of PFDs. This collaborative project aims to characterize, for the first time, the mechanisms of stretch induced damage and tear propagation in virgin and pregnant rat vaginal tissue. A comprehensive set of ring tests will be conducted to determine the functional role of the tissue?s constituents (collagen, elastin, and smooth muscle cells) on both the active and passive mechanics of the vagina. Planar biaxial tests will be performed to study the tear propagation process. The results of these tests will guide the development of a new constitutive model that will capture the active and passive mechanical response of the vaginal tissue, including stretch-induced damage. The constitutive model will be implemented into a finite element code especially developed to simulate damage and tear propagation of vaginal tissue. For validation, three-dimensional in-vivo experimental data, which are collected by conducting inflation tests that simulate a birth injury within a state-of-the-art 7T micro-MRI, will be utilized.