Ex-vivo measurement of the biaxial properties of rat vagina: Some preliminary results

Pelvic floor disorders (PFDs) concern a wide range of disorders that occur when one of the organs of the reproductive system loses its functionality. To date, PFDs affect nearly 30 million women in the U.S. and the symptoms usually associated with these disorders include urinary and fecal incontinence, pain, psychological and emotional distress. While the exact etiology of PFDs is unknown, mechanical alterations to pelvic organs, supportive ligaments, fasciae, and muscles due to pregnancy, age, and weight gain contribute to the development of these disorders. There is an unmet clinical need to characterize the mechanical properties of the female reproductive organs and supporting tissues. One PFD is related to the decrease in the mechanical integrity of the vagina, which can cause the pelvic organs to descend into the vagina, a condition known as pelvic organ prolapse. Within this context, the aim of this work was to devise a biaxial testing system for assessing passive properties of rat vagina. While many studies characterized the uniaxial mechanical properties of vaginal tissues, biaxial mechanical properties are almost unexplored. Nonetheless, the nonlinear and anisotropic nature of vaginal tissue has already been shown in a few preliminary studies. In this study, the development of a testing system is presented. The system is tested using rubber specimens since the mechanical properties of rubber are well known. Finally, some preliminary data were collected using specimens from rat vagina. The results showed that the “toe region” of the tissue computed along the longitudinal axis is more extended than the counterpart measured along the circumferential axis, confirming the capability of the proposed system to properly measure the mechanical properties of vagina along the two main axes simultaneously.