The pelvis is divided into the greater and lesser pelvis by an oblique plane passing through the sacral promontory, the linea terminalis (arcuate line of the ilium), the pectineal line of the pubis, the pubic crest, and the upper margin of the symphysis pubis. This plane lies at the level of the superior pelvic aperture (pelvic inlet) or pelvic brim. The inferior pelvic aperture or pelvic outlet is irregularly bound by the tip of the coccyx, the symphysis pubis, and the ischial tuberosities. The dimensions of the superior and inferior pelvic apertures have important obstetric implications.
Ligaments Four ligaments—inguinal, Cooper’s, sacrospinous, and sacrotuberous—of the bony pelvis are of special importance to the gynecologic surgeon.
The inguinal ligament is important surgically in the repair of inguinal hernia. The inguinal ligament: 1.
Is formed by the lower border of the aponeurosis of the external oblique muscle folded back upon itself.
2.
Is fused laterally to the iliacus fascia and inferiorly to the fascia lata.
3.
Flattens medially into the lacunar ligament, which forms the medial border of the femoral ring.
Cooper’s ligament is used frequently in bladder suspension procedures. Cooper’s ligament: 1.
Is a strong ridge of fibrous tissue extending along the pectineal line—also known as the pectineal ligament.
2.
Merges laterally with the iliopectineal ligament and medially with the lacunar ligament.
The sacrospinous ligament is often used for vaginal suspension. This ligament offers the advantage of a vaginal surgical route. The sacrospinous ligament: 1.
Extends from the ischial spine to the lateral aspect of the sacrum.
2.
Is separated from the rectovaginal space by the rectal pillars.
3.
Lies anterior to the pudendal nerve and the internal pudendal vessels at its attachment to the ischial spine.
The inferior gluteal artery, with extensive collateral circulation, is found between the sacrospinous and sacrotuberous ligaments and may be injured during sacrospinous suspension (Fig. 5.2) (7). Injury to the inferior gluteal artery, and to the pudendal nerve and internal pudendal vessels, during sacrospinous ligament suspension may be minimized by careful and controlled retraction and suture placement at least two fingerbreadths medial to the ischial spine.
The sacrotuberous ligament is sometimes used as a point of fixation for vaginal vault suspension. The sacrotuberous ligament: 1.
Extends from the ischial tuberosity to the lateral aspect of the sacrum.
2.
Merges medially with the sacrospinous ligament.
3.
Lies posterior to the pudendal nerve and the internal pudendal vessels.
Figure 5.2 Tone drawing of left hemipelvis with sacrospinous ligament reﬂected. a., artery; Inf., inferior; lig., ligament; n., nerve; Sacrosp., sacrospinous; Sacrotub., sacrotuberous. (Redrawn from Thompson JR, Gibbs JS, Genadry R, et al. Anatomy of pelvic arteries adjacent to the sacrospinous ligament: importance of the coccygeal branch of the inferior gluteal artery. Obstet Gynecol 1999;94:973–977, with permission.)
Figure 5.3 The pelvic diaphragm. A: A view into the pelvic ﬂoor that illustrates the muscles of the pelvic diaphragm and their attachments to the bony pelvis. B: A view from outside the pelvic diaphragm illustrating the divisions of the levator ani muscles (superficial plane removed on the right). (continued )