Quantitative analysis of uterosacral ligament origin and insertion points by magnetic resonance imaging

Abstract

Objective: To estimate the percentage of healthy women in whom the uterosacral ligaments are identifiable on standard magnetic resonance imaging (MRI) scans and to determine origin points from the genital tract and insertion points on the pelvic sidewall.

Methods: Eighty-two asymptomatic women (mean +/- standard deviation age 53 +/- 12 years; mean parity 2.5, range 0-7) volunteered for this study. They were eligible if the most dependent vaginal wall point lay at least 1 cm above the hymenal ring remnant during a Valsalva maneuver. Axial proton density MRI of the entire pelvis was analyzed at 5-mm intervals. All results were referenced to the ischial spine. We determined the visibility of the uterosacral ligaments and located their origins from the genital tract and their insertion points on the pelvic sidewall.

Results: Uterosacral ligaments were visible in 61 (87%) of 70 analyzable scans. They extended over a mean craniocaudal distance of 21 +/- 8 mm (range 10-50). Three regions of origin were found: cervix alone, cervix and vagina in the same section, and vagina alone. Thirty-three percent, 63%, and 4% of 254 identified origin points were from these three areas, respectively. Of 259 uterosacral insertion points, 82% overlaid the sacrospinous ligament/coccygeus muscle complex, 7% the sacrum, and 11% the piriformis muscle, the sciatic foramen, or the ischial spine. Although uterosacral ligament morphology was similar bilaterally, its craniocaudal extent was greater on the right side.

Conclusion: In healthy women, the uterosacral ligament origin and insertion points exhibited greater anatomic variation than their name would imply.

Figure 1

Axial scan at the level of the cervix. This image demonstrates the uterosacral ligament origins and insertions, and the measuring strategy. The origin of the uterosacral ligaments from the cervix (white arrowheads) and their insertions (black arrowheads) on the pelvic sidewall are seen. The location of the insertion point (b) on a line (ac) between the body midline and the ischium (I) was measured as described in Materials and Methods. The location of the bladder (B), cervix (C), rectum (R), coccyx (X), and coccygeus muscle (CM) are shown. © 2004 DeLancey. Umek. Uterosacral Ligament Anatomy on MRI. Obstet Gynecol 2004.

Figure 2

Examples of common uterosacral origins and insertions. Points of origins (white arrowheads) are the cervix (C) in panel a, cervix/vagina (C, V) in panels b and c, and vagina (V) in panel d. Points of insertion (black arrowheads) are the sacrum in panel a, the coccygeus muscle in panel b, the piriformis muscle in panel c, and the ischial spine (IS) in panel d. R = rectum. © 2004 DeLancey. Umek. Uterosacral Ligament Anatomy on MRI. Obstet Gynecol 2004.

Figure 3

Variation in uterosacral ligament anatomy in 2 healthy women. Top row (a–d) shows images of a 57- year-old woman, bottom row (e–h) shows images of a 58-year-old woman. Numbers in the right lower corner indicate in millimeters the distance of the picture plane relative to the ischial spine. White arrowheads point to origins from the genital tract, and black arrowheads point to insertions on the pelvic sidewall. Uterosacral origins are from the cervix in panels a and e, from cervix and vagina in panels b–d and f–h. Uterosacral insertions are on the coccygeus muscle/sacrospinous ligament complex in panels a–c and f–h, near the ischial spine in panel d, and on the sacrum in panel e. Note that the uterosacral ligaments of the woman on the top row (panel c) are thicker than those of the woman on the bottom row (panel g). © 2004 DeLancey. Umek. Uterosacral Ligament Anatomy on MRI. Obstet Gynecol 2004.