Clinical Review

Pelvic-support defects: a guide to anatomy and physiology

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Due to high postoperative failure rates, the traditional treatment for pelvic-organ prolapse—hysterectomy with anterior and posterior colporrhaphy—is being replaced by procedures that target specific pelvic defects. Thus, a familiarity with pelvic-support mechanisms is crucial to determining corrective measures.


 

References

KEY POINTS
  • The levator complex of muscles and the surrounding connective tissue, vessels, and nerves are often referred to as the pelvic floor.
  • Studies have shown damage to muscle bundles of the levator and nerves of the pelvic floor after childbirth, including atrophic and degenerative muscle changes and slow nerveconduction velocities.
  • To maintain urinary continence, there must either be an intrinsic urethral pressure greater than the pressure in the bladder or occlusion of the urethra when intra-abdominal pressure increases.

Childbirth, chronic coughing, heavy lifting, or just inherent connective-tissue weakness and aging—each of these can cause pathophysiologic changes in the muscular and fascial structures of the pelvic floor, possibly leading to pelvic-support defects and, over time, pelvic-floor dysfunction. Patients with this condition may experience discomfort, urinary or fecal incontinence, or organ prolapse.

Traditionally, hysterectomy with anterior and posterior colporrhaphy has been the standard treatment for pelvic-organ prolapse. But due to this procedure’s high postoperative failure rate,1-3 a new approach is beginning to emerge. Lately, clinicians in the field of pelvicfloor dysfunction have begun advocating specialized evaluation techniques—among them, site-specific physical examinations, urodynamic testing, anal manometry, and anal sphincter ultrasound—to identify and measure anatomic and physiologic pelvic-support defects. Once the physician has determined the specific cause of the patient’s dysfunction, he or she can then direct treatment toward that defect.4 Therefore, when site-specific examination uncovers a paravaginal defect, for example, or ultrasound demonstrates anal sphincter disruption, a repair can be planned that will include correcting those problems.

Recently, pelvic reconstructive surgeons have focused on developing procedures that restore normal anatomy. Unfortunately, this goal is not achieved in most reparative pelvic operations. Instead, the most common operations reduce vaginal volume, create resistance to prolapse, or suspend an organ from a stable anatomic site—thereby repairing the defect by creating a compensatory defect, rather than by recreating a normal pelvic anatomy.

Beyond identifying patients with pelvicfloor dysfunction, the clinician’s job is to ascertain the defects causing the problem5 and determine appropriate diagnostic and therapeutic techniques. A familiarity with the anatomy of the pelvis is, of course, vital to this process. In this article, I detail the anatomic and physiologic support mechanisms of the female pelvis, along with various conditions leading to pelvic-organ prolapse.

Anatomic support mechanisms

Since malpositioning of the pelvic organs is the main contributor to uterine or vaginal prolapse, special attention must be paid to the positioning and support of the urethra, bladder, vagina, uterus, and perineum. These organs are held in place by an interactive network of bones, connective tissues, muscles, vessels, and adventitial sheaths, all of which create normal pelvic-organ support.

The bony pelvis. This structure serves as the anchoring site for the dense connective tissue or fascial coverings of the pelvic musculature. The anterior connective tissue attachments, inserting along the pubic bone, consist of the pubo-urethral ligaments and endopelvic fascia. Laterally, the dense connective-tissue covering of the obturator muscle attaches to the inferior pubic ramus from behind the symphysis pubis along the linea terminalis and, posteriorly, to the ischial spines. Posteriorly, the lateral margins of the sacrum serve as the attachment for the cardinal-uterosacral ligament complex.5

The muscles of the pelvic floor. The bony structures fuse to the pelvic organs through a contiguous network of connective tissue that surrounds the obturator and levator muscles. The obturator muscle is in contact with the lateral pelvic wall. The bowl-shaped levator muscle is joined to the obturator muscle at the arcus tendineus fascia—or “white line” the pelvis and consists of 3 parts: iliococcygeus, pubococcygeus, and puborectalis. Within the levator muscle sit the urethra, bladder base, vaginal tube, and anorectum. The levator complex of muscles and the surrounding connective tissue, vessels, and nerves are often referred to as the pelvic floor (FIGURE 1).2,5

Connective tissue of the pelvis. These organs are surrounded by what has traditionally been called endopelvic fascia (FIGURE 2). For more than 50 years, experts have debated whether this tissue is truly fascia.6-8 Histologically, it is largely smooth muscle, elastin, and collagen. More recently, it was suggested this be called fibromuscular connective tissue.5 It serves as a surrounding connective tissue, anchoring the pelvic organs to the muscles, and the muscles to the bony pelvis. Through these tissues traverse the nerves and blood vessels that add support to the tissue and keep it vital.6-8 The urethra, vagina, and anus open onto the vulva and perineum by passing through a breach in the levator muscle collectively called the genital hiatus.

A unifying theory of the anatomic vaginal support. According to DeLancey, the normal anatomic position of the distal vagina in the standing female is a vertical ascent of 1 to 3 cm.9 From the midvagina to the vaginal apex, the axis of the vagina is more horizontal, forming an approximately 120° angle.

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