Ex Vivo Uniaxial Tensile Properties of Rat Uterosacral Ligaments.

This manuscript presents new experimental methods for testing the ex vivo tensile properties of the uterosacral ligaments (USLs) in rats. The USL specimens ([Formula: see text]) were carefully dissected to preserve their anatomical attachments, and they were loaded along their main in vivo loading direction (MD) using a custom-built uniaxial tensile testing device. During loading, strain maps in both the MD and the perpendicular direction (PD) were collected using the digital image correlation technique. The mean (± S.E.M.) maximum load and displacement at the maximum load were [Formula: see text] N and [Formula: see text] mm, respectively. The USLs were found to be highly heterogeneous structures, with some specimens experiencing strains in the MD that were lower than [Formula: see text] and others reaching strains that were up to [Formula: see text] in the intermediate region. At 0.5 kPa stress, a value reached by all the specimens, the mean strain in the MD was [Formula: see text] while at 5 kPa stress, a value achieved only by 9 out of the 21 specimens, the mean strain increased to [Formula: see text]. Under uniaxial loading, the specimens also elongated in the PD, with strains that were one order of magnitude lower than the strains in the MD; at the 0.5 kPa stress, the mean strain in the PD was recorded to be [Formula: see text] and, at the 5 kPa stress, the strain in the PD was [Formula: see text]. The directions of maximum principal strains remained almost unchanged with the increase in stress, indicating that little microstructural re-organization occurred due to uniaxial loading. This study serves as a springboard for future investigations on the supportive function of the USLs in the rat model by offering guidelines on testing methods that capture their complex mechanical behavior.

In-plane and out-of-plane deformations of gilt utero-sacral ligaments.

The uterosacral ligaments (USLs) are supportive structures of the uterus and apical vagina. The mechanical function of these ligaments within the pelvic floor is crucial not only in normal physiological conditions but also in reconstructive surgeries for pelvic organ prolapse. Discrepancies in their anatomical and histological description exist in the literature, but such discrepancies are likely due to large variations of these structures. This makes mechanical testing very challenging, requiring the development of advanced methods for characterizing their mechanical properties. This study proposes the use of planar biaxial testing, digital image correlation (DIC), and optical coherence tomography (OCT) to quantify the deformations of the USLs, both in-plane and out-of-plane. Using the gilts as an animal model, the USLs were found to deform significantly less in their main direction (MD) of in vivo loading than in the direction perpendicular to it (PD) at increasing equibiaxial stresses. Under constant equibiaxial loading, the USLs deform over time equally, at comparable rates in both the MD and PD. The thickness of the USLs decreases as the equibiaxial loading increases but, under constant equibiaxial loading, the thickness increases in some specimens and decreases in others. These findings could contribute to the design of new mesh materials that augment the support function of USLs as well as noninvasive diagnostic tools for evaluating the integrity of the USLs.

Mechanics of Uterosacral Ligaments: Current Knowledge, Existing Gaps, and Future Directions.

The uterosacral ligaments (USLs) are important anatomical structures that support the uterus and apical vagina within the pelvis. As these structures are over-stretched, become weak, and exhibit laxity, pelvic floor disorders such as pelvic organ prolapse occur. Although several surgical procedures to treat pelvic floor disorders are directed toward the USLs, there is still a lot that is unknown about their function. This manuscript presents a review of the current knowledge on the mechanical properties of the USLs. The anatomy, microstructure, and clinical significance of the USLs are first reviewed. Then, the results of published experimental studies on the in vivo and ex vivo, uniaxial and biaxial tensile tests are compiled. Based on the existing findings, research gaps are identified and future research directions are discussed. The purpose of this exhaustive review is to help new researchers navigate scientific literature on the mechanical properties of the USLs. The use of these structures remains very popular in reconstructive surgeries that restore and augment the support of pelvic organs, especially as synthetic surgical mesh implants continue to be highly controversial.

Contractile Properties of Vaginal Tissue.

The vagina is an important organ of the female reproductive system that has been largely understudied in the field of biomechanics. In recent years, some research has been conducted to evaluate the mechanical properties of the vagina, but much has focused on characterizing the passive mechanical properties. Because vaginal contractions play a central role in sexual function, childbirth, and development and treatment of pelvic floor disorders, the active mechanical properties of the vagina must be also quantified. This review surveys and summarizes published experimental studies on the active properties of the vagina including the differences in such properties determined by anatomic regions and orientations, neural pathways, life events such as pregnancy and menopause, pelvic floor disorders such as prolapse, and surgical mesh treatment. Conflicting experimental findings are presented, illustrating the need for further research on the active properties of the vagina. However, consensus currently exists regarding the negative impact of surgical mesh on vaginal contractility. This review also identifies knowledge gaps and future research opportunities, thus proving a firm foundation for novice and experienced researchers in this emerging area of biomechanics and encouraging more activity on women's sexual and reproductive health research.