Objective: The uterosacral ligaments (USL) are important anatomical structures in the female pelvis. They extend from the caudal part of the uterus and the cervix, running laterally around the rectum, and fan out to connect with the endopelvic fascia at the sacrum and the fascia of the pelvic floor muscles. It is hypothesized that the microstructure and mechanical properties of the USL change with age and in cases of pelvic floor dysfunction due to tensile forces. This may contribute to the development of pelvic organ prolapse (POP). The aim of this study was to analyze histological and microstructural differences in various regions of the USL. Additionally, we aimed to investigate whether the "deep layer" mentioned in some studies - a deeply running part of the USL extending toward the pelvic floor muscles - can be identified macroscopically and histologically. Methods: A comprehensive literature review on the current research regarding the function and structure of the USL and their possible association with POP was performed. The USL of 23 female cadavers (13 unembalmed, 10 embalmed) were first examined macroscopically in situ. Subsequently, the right USL of the unembalmed specimen were excised and histologically analyzed using Hematoxylin-Eosin, Sirius Red, Masson-Goldner-Trichrome, and Resorcin-Fuchsin staining. In the fixed specimens, a complete in situ dissection was performed, followed by the extraction and histological examination of the right USL (also using Hematoxylin-Eosin, Sirius Red, Masson-Goldner trichrome and Resorcin-Fuchsin staining). Results: Our study demonstrated regional heterogeneity within the USL: The cervical region was particularly firm and broad, whereas the USL became less dense and fanned out in the sacral region. Additionally, an asymmetry in length was observed, with the left USL being shorter than the right in all examined specimens. Microscopic examination using various staining techniques enabled a detailed analysis of the composition of the USL, revealing regional differences in the orientation of collagen fibers as well as in the distribution of smooth muscle, connective tissue, and fat tissue. Although statistical significance could not be established due to the small sample size, a distributional difference in smooth muscle showed up to a fivefold higher proportion of smooth muscle in the young group compared to the aged group. Clear visual differences were also observed between individual body donors, which is likely attributable to high interindividual variability. Conclusion: The observed interindividual variability in the expression of the different components and the varying proportion of smooth muscle across age groups are particularly relevant in the clinical field of urogynecology. The expanded knowledge of the regional structure and indications of age-related changes in the USL provide additional information for the further development and optimization of surgical procedures for the correction of POP.
Regional histological and microstructural variation within the uterosacral ligament in context of pelvic floor disfunction
Milcher, M. (Author). 2025
Student thesis: Diploma thesis