Are the uterosacral ligaments detached in young women with pelvic floor symptoms after birth?

Sir,

Are the uterosacral ligaments really “detached” from the uterus in women with pelvic floor symptoms after first vaginal birth as Krcmar and colleagues suggest in their article, “Multilevel musculo-fascial defect magnetic resonance study of female pelvic floor: retrospective case control study in women with pelvic floor dysfunction after the first vaginal delivery?”¹ In this overall excellent article, the authors say that the “uterosacral ligament detachment” is more common among symptomatic women.

We suggest that use of the term “detached” is misleading because it indicates that a structure is no longer connected between two points. This does not represent what the authors found. In defining what they mean in this research, the study uses the term “attached” when “both origin/insertion points should be simultaneously visible at least in one axial section” and “detached” when this definition was not met. This issue is important because of the mechanical implications of the term “detached.” It is also at odds with surgeons' experience in the operating room, where they routinely can palpate the uterosacral ligaments during vaginal hysterectomy for prolapse.

There are several reasons other than detachment why the ligaments may not be seen all the way from their origin to insertion in a single slice. First, if the ligaments are at an oblique angle to the scan plane, they might not be seen all the way from origin to insertion in one slide. Our studies show that the uterosacral ligaments in women with prolapse are at a different angle than normal women² and an angled ligament may not be seen in a single slice. Second, in our first MRI description of the ligaments³ and subsequent work,^{4, 5} it became evident to us that changes in surrounding structures or partial volume averaging may obscure these very thin tissues.

The authors did show that these structures had different appearances in the two groups, and we do not dispute that—only the implications of the term “detached” are at issue. We think it would be better to refer to the observations by saying that the uterosacral ligaments were “not visible” in a single slice rather than saying they were “detached.” This would be consistent with surgical and MRI findings. Acknowledging that the reason for the difference in visibility between the groups is not established might stimulate further analysis to explain this difference. For example, tipping the plane at which the MRI slices are viewed can be done easily in 3D Slicer with the “Reformat” feature and would allow the changed angle hypothesis to be easily tested. In addition, partial volume averaging or distortion of surrounding tissues (such as a full rectum) that obscured their visibility could be considered.

Again, we would like to congratulate the authors on their detailed observations and look forward to continued progress in understanding the nature of visible abnormalities in imaging.

This work is supported by the National Institutes of Health grant #RC2 DK122379.