Shlomo Raz1
(1)
Division of Pelvic Medicine and Reconstructive Surgery, UCLA School of Medicine, Los Angeles, CA, USA
Keywords
Pelvic anatomySacrouterine ligamentCardinal ligamentsPelvic fasciaSacrospinous ligamentUrethral supportBladder supportRectal support
Clinicians involved in the care of women should possess a clear conceptual understanding of the anatomy and pathophysiology of pelvic support in order to effectively evaluate and treat disorders of pelvic floor relaxation. This chapter provides a basic review of the anatomy and musculofascial support of major pelvic structures and discusses their importance in clinically significant disorders of pelvic prolapse.
Clinical, urodynamic, radiological, and endoscopic evaluations, as well as operative experience on over 16,000 cases of pelvic reconstruction, have led us to a different understanding of the surgical anatomy and pathophysiology of female stress incontinence and vaginal support. Previously in our work, we recognized the difficulties in the interpretation of anatomic dissections obtained from whole-mount and step sections of the cadaver female pelvis. We found most valuable the use of static and dynamic MR images of the female pelvis and the surgical dissection and exposure of the retropubic and bladder neck area in patients with known pelvic prolapse or stress incontinence, as well as in women with normal control. Our findings support a simplified conceptual understanding of the anatomy of stress incontinence and pelvic support, allowing more rational treatment of these common disorders.
Conceptually, we can divide the vaginal canal into three compartments that have a distinct anatomical structure:
· The anterior compartment, including the urethra, bladder neck, and bladder
· The superior compartment, including the uterus and the cul-de-sac after hysterectomy
· The posterior compartment, including the rectum, the anal canal, the levator plate, the perineum, and the pelvic musculature
These three compartments have strong functional and anatomical interactions. For example, the function and support of the anterior compartment depend on intact posterior and superior compartments. Stress incontinence is in general only one of the manifestations of anterior vaginal wall relaxation, which very often coexists with other anatomical defects. If the superior or posterior compartments are deficient and are not repaired simultaneously with the anterior repair, the posterior and superior defect will be accentuated, and the repair of the anterior vaginal wall may not be long-lasting.
The anatomy of pelvic support comprises a number of elements:
· The bones
· The fascial support
· The muscles
· The nerves
· The vessels
· The pelvic organs
· The urethra
· The bladder
· The uterus–vaginal vault
· The rectum
· The anal canal
· The perineum
1.1 Pelvic Bones and Ligaments
The bony pelvis is the framework from which all pelvic structures ultimately draw support. The pubis and the ischium are the segments of the skeletal structure most important for pelvic support (Fig. 1.1). Some of the ligaments or condensed connective tissue important in pelvic support and function that will be discussed in this chapter include the sacrospinous ligament, the sacrotuberous ligament, the sacrouterine ligaments, the cardinal ligaments, the obturator membrane, the pubocervical fascia, and the prerectal and pararectal fascia (Figs. 1.2 and 1.3).
Fig. 1.1
Osseous structures supporting the pelvic organs include the pubic bone and ischium. The fusion of these two forms the obturator foramen, where the obturator membrane and muscles are inserted
Fig. 1.2
The obturator membrane completely fills the obturator foramen except at its superior lateral aspect, where the obturator vessels and nerves emerge from the pelvis. The sacrospinous ligaments extend from the sacrum to the ischial spine, providing support and a very important landmark in pelvic surgery, which is easily palpated during vaginal surgery. Any procedure should avoid placement of sutures above the ligaments, where the piriformis muscle and lumbosacral nerve plexus are located
Fig. 1.3
Fascial structures important for pelvic support include the sacrouterine–cardinal complex, supporting the uterus and vaginal cuff, and the fascial connective tissue, supporting the pelvic viscera to the levator muscle (arcus tendineus fascia pelvis)
1.1.1 Sacrospinous Ligament
The sacrospinous ligament (SPL) extends from the ischial spine to the medial aspect of the sacrum. It is a strong triangular stricture covered by the coccygeus muscle. It can be considered the tendon of the coccygeus muscle. It is an important reference point for many vaginal procedures because of its distinct consistency and location, allowing the surgeon to guide the placement of sutures or needles in its proximity. Above the sacrospinous ligament is the piriformis muscle and the lumbosacral plexus where the origin of the sciatic nerve is located. The pudendal pedicle enters the sciatic foramen posterior to the lateral margin of the SP ligament under the ischial spine.
1.1.2 Sacrotuberous Ligament
The sacrotuberous ligament (STL) is a fan-shaped ligament of the posterior pelvis arising from the posterior sacrum to the ischial tuberosity. It primarily comprises collagen fibers and is strong enough to support the sacrum and prevent it from moving from its position under the body weight. It is a ligament of the sacroiliac joint, which is connected to the sacrum. Though it is not directly involved in pelvic floor relaxation or incontinence, it can lead to pelvic pain in patients with significant trauma of the pelvic structures.
1.1.3 Obturator Membrane
The obturator membrane is a strong, fibrous membrane that spans the obturator foramen. It is perforated superiorly, creating a passage where the obturator vessels and nerves cross to the medial compartment of the thigh. It provides an attachment surface for the internal and external obturator muscles. Obturator sling procedures cross the adductor muscles and the obturator internus and externus muscles. Single-incision slings rely on the placement of anchors through the obturator internus muscle and the obturator membrane.
1.2 Pelvic Musculature
The pelvic bones and fascia (ligaments) make up the scaffolding, but the pelvic and perineal musculature, which attaches to this scaffolding, provides the floor upon which the pelvic organs rest (Fig. 1.4).
Fig. 1.4
Pelvic musculature and its relationship to the ischial spine and the sacrospinous ligament. The piriformis and gluteal muscles are seen in the space above the sacrospinous ligament. The iliococcygeus muscle inserts into the ischial spine and the obturator fascia (arcus tendineus levator ani) while attaching to the coccyx and anococcygeal raphe. The pubococcygeus inserts at the back of the pubis and the anterior arcus tendineus levator ani, extending toward the sacrococcyx. The pubovaginalis and puborectalis are not distinct muscles; rather, they are the medial segments of the pubococcygeus surrounding the vagina and rectum. (a) Three-dimensional MRI reconstruction of the pelvis in a young, nulliparous woman. The levator is inserted at the obturator fascia and the levator hiatus is relatively narrow. (b) A similar reconstruction in a patient with multiple deliveries shows the levator detached from the insertion at the obturator fascia, with widening of the levator hiatus. (c) Axial cut of a T2 MRI image of the pelvis showing the distribution of the pelvic musculature at the level of the trigone. The internal and external obturator are seen and the attachment of the levator musculature to the inner aspect of the obturator internus (arcus tendineus levator ani)
In a superior view of the pelvic floor, several muscular and fascial structures are seen: the piriformis, the internal obturator, the levator (with two main components, iliococcygeus and pubococcygeus), and the coccygeus muscle. The levator ani, comprising the pubococcygeus and iliococcygeus, can be viewed as the major inferior support of the urethra, vagina, and rectum. The medial fibers of the pubococcygeus muscles are also referred as the puborectalis muscle because of its role in the support and function of the anal canal and distal vagina. The levator muscle is a broad, thin sheet extending from the pelvic portion of the pubic bone lateral to the symphysis anteriorly and to the inner surface of the ischial spine posteriorly. Between these points it takes origin by the “arcuate line” of the obturator fascia (arcus tendineus levator ani). From these origins, the fibers extend back medially to unite with the fibers from the opposite side. In the anterior segment, the fibers fail to meet, forming a gap that is completed by the urogenital diaphragm. It is through this U-shaped hiatus that the vagina, rectum, and urethra exit the abdominal cavity. Fibers of the pubococcygeus muscle send a number of muscle fingers into these structures. Around the urethra, they form the extramural skeletal sphincter of the urethra. The fibers fuse posterior, lateral, and anterior to the rectum, forming part of the perineal support and the anal sphincter. The proximal half of the vagina lies horizontally over the levator plate.
Thus, the levator ani holds the intrapelvic organs like a hammock, providing support as well as stabilization during increases in intra-abdominal pressure (Fig. 1.5). Further dissection of this muscle, however, would indicate a more complex anatomy than this simple description suggests. In comparison with other skeletal muscles of the body, the levator has a much greater concentration of connective tissue, and fibers arising anteriorly condense into tough bands that engage in support of the pelvic viscera directly. After multiple deliveries, the relatively narrow levator hiatus opens widely.
Fig. 1.5
Diagram of the pelvic support, depicting the bladder, the obturator muscle and foramen, and the arcus tendineus where the levators are inserting
1.3 Perineal Anatomy
The perineal anatomy adds further support to the pelvic structures (Fig. 1.6). The pubococcygeus muscle is open in the midline creating a hiatus through which the rectum, vagina, and urethra pass. Superficial to the pubococcygeus and iliococcygeus and covering the anterior segment of the levator hiatus is the perineal membrane, which attaches to the inner side of the pubic bone, joins the contralateral side at the central tendon of the perineum, and extends proximal into the posterior vagina for 2–3 cm, where the levator muscles are attached.
Fig. 1.6
(a) Superior view of the pelvis to show the pelvic musculature to include the piriformis, the coccygeus, the iliococcygeus, and pubococcygeus muscles. Through the genital hiatus the urethra, the bladder (A) and the rectum (B) cross the pelvic floor. The iliococcygeus inserts in a condensation of the internal obturator (arcus tendineus levator ani). (b) Diagram of the pelvic musculature depicting the levator hiatus, where the urethra, the vagina (A), and the rectum (B) are traversing from the pelvis. Extensions of the levator surround the organs as they cross the levator hiatus. Posterior to the rectum is the anococcygeal raphe. Between the rectum and vagina, the rectovaginal raphe provides the first line of support to the perineum and central tendon. Some fibers surround the urethral hiatus. (c) Diagram of an inferior view of the pelvic floor including the transverse perineum, the anal canal, the perineal membrane (inferior fascia of the urogenital diaphragm), the levator and the central tendon of the perineum
A line drawn between the ischial tuberosities divides the perineum into anterior urogenital and posterior anal triangles. The urogenital triangle in the female is divided in half longitudinally by the clitoris, urethra, and vaginal vestibule. The ischiocavernosus muscles cover the two clitoral crura as they attach to the ischia of the pubis. The bulbocavernosus muscles run on each side of the vestibule beneath the labia, between the clitoris anteriorly and the perineal body posteriorly. There are also two paired, superficial transverse perinei muscles, which run on each side of the perineal body to the ischial tuberosities laterally.
In the center of the anal triangle of the perineum is the anal canal. The muscle fibers of the superficial anal sphincter enclose the anus as they run between the anococcygeal ligament and the perineal body. The deep anal sphincter fibers completely encircle the anal canal and fuse superiorly with inferomedial fibers of the levator ani (pubococcygeus/puborectalis).
1.4 Support of Pelvic Organs
The vagina, bladder, urethra, and rectum are covered by connective tissue that supports the organs to the lateral pelvic wall musculature and fascia (arcus tendineus fascia pelvis) (Figs. 1.7, 1.8, and 1.9).
Fig. 1.7
Diagrammatic superior view of the pelvic organs, supporting fascia, and the spaces in between, including the presacral, rectovaginal, vesicovaginal, and retropubic spaces
Fig. 1.8
Sagittal view of the pelvic organs depicting the retropubic, vesicovaginal, rectovaginal, and retrorectal spaces. It is in these spaces that the connective tissue supporting the pelvic organs to the lateral pelvic wall (levator) is present
Fig. 1.9
Conceptual diagram of pelvic organ support. The connective tissues present in the retropubic space (endopelvic fascia), vesicovaginal space (pubocervical fascia), and prerectal space (prerectal fascia) surround the pelvic organs. They fuse laterally to insert into the levator fascia (arcus tendineus fascia pelvis)
At the level of the urethra and the bladder, the pelvic connective tissue splits into a vaginal side (periurethral and perivesical fascia) and an abdominal side (endopelvic fascia) providing lateral support to the urethra, bladder neck, and the bladder, to the arcus tendineus fascia pelvis. The vaginal side of this connective tissue covering the urethra and bladder is called the pubocervical fascia, extending from the pubic bone to the arcus tendineus fascia pelvis laterally to the cervix and its supporting structures.
Similarly, the rectum is enclosed by connective tissue that attaches to the lateral pelvic wall. The prerectal and pararectal fasciae are only parts of this connective tissue; they are not defined ligaments.
Because surgical procedures are done in specific areas of the vaginal wall, depending on the anatomical location, we can define areas of specialization of the supporting connective tissue. As mentioned, these structures are not tendons or fascia, and they are not separate structures but rather are in continuity with the other areas of support. The separation into specific areas is artificial but helps in the understanding of the surgical anatomy, the exposure, and the use of these structures to reconstruct pelvic defects.
At the level of the bladder, the vaginal side of the pubocervical fascia is called perivesical fascia. It covers the anterior bladder wall and joins laterally to the posteriorly located endopelvic fascia to form the vesicopelvic ligament responsible for bladder support. At the level of the cervix and uterus, two areas of strong connective tissue anchor the cervix to the lateral pelvic wall (cardinal or lateral ligaments), and the sacrouterine ligaments anchor it to the sacrum and fascia of the coccygeus and levator fascia.
Again, we feel that all these ligaments are not distinct anatomical structures but are only part of the concentration of connective tissue responsible for pelvic organ support.
1.4.1 Urethral Support
1.4.1.1 Pubourethral Ligaments or Fascia
The urethra is supported mainly by two bands of connective tissue: the pubourethral ligaments, connecting the urethra to the inferior rami of the pubic bone, and the urethropelvic fascia, connecting the proximal urethra to the lateral pelvic wall (arcus tendineus fascia pelvis).
The pubourethral ligaments are the best described and can be found connecting the inner surface of the pubic bone with the midurethra (Fig. 1.10a). They are homologous to the puboprostatic ligaments in men. They are the only connection of the urethra to the pubic bone (Fig. 1.10b). They help to support and stabilize the urethra and anterior vaginal wall to the inferior aspect of the pubic bone. Weakness in these ligaments permits posterior and inferior displacement of the urethra but does not contribute significant support to the bladder neck (Fig. 1.10c). Just distal to these ligaments, the extramural skeletal muscle fibers are located.
As described above, the pubourethral ligaments divide the urethra into three areas: a proximal third, including the bladder neck and intra-abdominal urethra; the midurethra, including the pubourethral ligament and the extramural skeletal musculature; and the distal third, which is only a conduit for the urine, without function with regard to continence. The proximal third of the urethra is responsible for passive continence; the midurethra is responsible for passive and active continence and acts as an important defense mechanism against sudden increases in abdominal pressures when the proximal urethra is incompetent. This is the thickest part of the urethra and corresponds to the area of highest concentration of skeletal musculature and the area of highest urethral pressure.
How are these ligaments or fascia seen in surgery? When entering the retropubic space during vaginal surgery, we create a window by detaching the urethropelvic ligament from the arcus tendineus fascia pelvis of the levator muscle (Fig. 1.10d). Inserting a finger into the retropubic space at the same spot and pointing the finger in an anterior direction, we can feel the pubourethral ligaments as they attach to the inferior rami of the pubic bone. Another view of the pubourethral ligaments can be seen during the suprameatal approach to the urethra for bladder neck closure or urethrolysis (Fig. 1.10e, f). Dynamic MRI can also demonstrate the function of the ligaments as the urethra rotates with strain, with the point of fixation on the inferior ramus of the pubic bone. In patients with pelvic floor relaxation, the attachment of the urethra to the inferior pubic bone is weakened, increasing the distance from the pubic bone to the urethra and therefore facilitating the downward and inferior rotation of the urethra. This anatomical change may affect the compensatory mechanism of the urethra during changes in abdominal pressure.
Fig. 1.10
(a) Cadaveric dissection. After penetration of the urethropelvic fascia, the retropubic space is exposed, revealing the arcus tendineus, the detached urethropelvic fascia, and the pubourethral fascia. (b) Sagittal midline pelvic MRI showing the attachments of the urethra to the inferior rami of the pubis. The pubourethral fascia is the only attachment of the urethra to the pubic bone. (c) Sagittal midline pelvic MRI during straining in a patient with stress incontinence and mild cystocele. The urethra shows downward rotation and separation from the inferior ramus of the pubic bone. (d) After entering the retropubic space and detaching the urethropelvic fascia from the arcus tendineus, just superior and medial is where the pubourethral fascia can be found, which supports the midurethra to the inferior ramus of the pubic bone. (e) Suprameatal incision exposing the anterior distal urethra. The retropubic space will be entered to detach the pubourethral fascia. (f) The retropubic space was entered anterior to the urethra, detaching the pubourethral fascia from the inferior ramus of the pubic bone
1.4.1.2 The Urethropelvic Fascia
The urethropelvic fascia is a name that we use to describe another “specialized” group of fibers of functional significance to stress incontinence, which support the urethra and bladder neck to the lateral pelvic wall (arcus tendineus fascia pelvis). This fascia is not a separate structure but rather an area of the condensed connective tissue around the pelvic viscera in charge of urethral support. The endopelvic fascia covers the abdominal side of the pelvic viscera, including the bladder neck and urethra; on the vaginal side, the urethra is covered by the periurethral fascia. The periurethral fascia is simply the area of the pubocervical fascia covering the urethra. Both the endopelvic and periurethral fasciae are fused laterally to support the proximal urethra to the arcus tendineus fascia pelvis of the levator muscle. MRI studies and surgical dissections help to clarify the anatomy of this structure. Using a vaginal coil to expand the vaginal canal and increase resolution, we can appreciate that the sphincteric unit is surrounded by the periurethral and endopelvic fasciae attaching lateral to the levator muscle (Fig. 1.11a, b). During stress incontinence surgery, we incise the lateral vaginal wall and enter the retropubic space by detaching the urethropelvic fascia from the arcus tendineus. Again, it is important to appreciate that the pubourethral and urethropelvic ligaments are not separate structures but merely an area of continuous connective tissue supporting the pelvic viscera and joined to the levator musculature.
The dissection of the vaginal wall from the urethra is avascular, and no distinct plane or space is encountered. Rather, the vagina and urethra are lightly fused so that the vaginal wall conforms to the shape of this periurethral fascia and follows its anatomy. In the normal female, the vaginal wall ascends laterally and superiorly and attaches very loosely to the urethropelvic fascia at its anchor to the lateral pelvic floor, thereby giving the characteristic “H” shape of the vaginal lumen in cross-sectional imaging (periurethral sulcus).
During vaginal surgery for incontinence, we often enter the retropubic space by dissection over the periurethral fascia by perforating the attachment of the ligaments (endopelvic and periurethral) to the lateral pelvic wall. With a finger in the retropubic space, we can anchor and feel the strength of the attachments and use this structure in the surgical correction of stress incontinence (Fig. 1.11c, d).
The urethropelvic fascia is the only structure connecting the urethra to the levator muscle. In the young, it provides a strong and elastic support connecting the bladder neck and urethra to the lateral pelvic wall. Contraction of the levator or obturator muscles will increase the tensile forces of the urethropelvic ligaments, improving seal and continence. Weakness of the levator plate and/or the urethropelvic fascia (owing to detachment or elongation of the urethropelvic ligaments) will facilitate urethral and bladder neck hypermobility, reducing the functional efficiency of the proximal urethra (Fig. 1.11e).
Fig. 1.11
(a) T2 MRI image of the urethra. Using a vaginal coil, the vaginal distension allows us to see the urethra supported like two wings laterally to the levator muscle. The levator inserts on a condensation of the obturator muscle. ATFP, arcus tendineus fascia pelvis; ATLA, arcus tendineus levator ani. (b) Diagram of the urethropelvic fascia, composed of a vaginal side (periurethral fascia) and an abdominal side (endopelvic fascia), both fusing laterally to support the urethra to the levator fascia (ATFP). (c) During stress incontinence surgery, dissection over the periurethral fascia allows detachment of the urethropelvic fascia from the arcus tendineus fascia pelvis. (d) With a finger in the retropubic space, the urethropelvic ligament is palpated and elevated. (e) Lateral cystogram in a patient with stress incontinence. During straining, the urethra is moved away from its normal close proximity to the inferior rami of the symphysis into a low position, owing to weakness of the pubourethral and urethropelvic fascia. Most patients with this anatomic defect do not lose urine unless there is an intrinsic sphincter defect
1.4.2 Bladder Support: The Vesicopelvic Fascia or Ligaments
Bladder support is very similar and only a continuation of the urethral support. “Vesicopelvic ligaments” is a name that we use to describe the trapezoid structure responsible for connecting the bladder to the lateral pelvic wall (Fig. 1.12a). It is not a separate structure but rather another specialization of the levator fascia responsible for bladder support. The endopelvic fascia covers the abdominal side of the bladder, and the perivesical fascia covers the vaginal side. Both fuse laterally to support the bladder to the arcus tendineus fascia pelvis (Fig. 1.12b).
Fig. 1.12
(a) Diagram of the anterior vaginal wall after a vertical incision is made. The pubocervical fascia extends from the pubic bone to the cervix. The area of fascia around the urethra is called periurethral, and the area around the bladder is called perivesical fascia. (b) Diagram depicting the open anterior vaginal wall. The envelope of connective tissue around the urethra attaches to the levator fascia via the urethropelvic fascia (combination of periurethral and endopelvic). The envelope of connective tissue around the bladder attaches to the lateral pelvic wall via the vesicopelvic fascia (combination of perivesical and endopelvic). (c) Surgical dissection around the perivesical fascia during a cystocele repair shows the lateral attachments of the bladder to the lateral pelvic wall (arcus tendineus fascia pelvis). (d) After a lateral incision of the anterior vaginal wall, the perivesical fascia was entered, detaching the bladder from the arcus tendineus. The margins of the vesicopelvic fascia (a combination of perivesical and endopelvic) are palpated and retracted. (e) Most patients with significant anterior vaginal wall prolapse present with a combination of urethral hypermobility, central and lateral defects, and vault prolapse. Successful repair of this condition requires support of the vaginal cuff and urethral support as well as the repair of the lateral and central defects
During vaginal surgery, if a vertical incision is made in the anterior vaginal wall from the urethra to the cervix, the fascia from the pubic bone to the cervix (commonly known as the pubocervical fascia) is exposed. The segment of pubocervical fascia covering the bladder area is called the perivesical fascia. Surgical dissection around the perivesical fascia toward the lateral pelvic wall reveals the attachment of the bladder to the levator fascia (arcus tendineus). By entering this attachment, we enter the paravesical space. The margins of the vesicopelvic fascia can be seen as they are detached from the arcus tendineus, retracted, or used in surgical repair of bladder prolapse (Fig. 1.12c, d).
Trauma of delivery, hysterectomy, aging of the tissues, hormonal deficiency, and pelvic floor relaxation may produce three types of abnormalities of bladder support: a central defect, a lateral (paravaginal) defect, and a transverse–proximal defect (Fig. 1.12e). A combination of the three types is common. In central defects, the bladder is herniated in the midline, through the attenuated perivesical fascia, but the lateral support of the bladder is preserved (Fig. 1.13a, b). In patients with lateral defects, the attachment of the bladder to the lateral pelvic wall is defective, resulting in a sliding displacement of the bladder wall (Fig. 1.13c). With transverse defects, the pubocervical fascia is separated from its attachment to the cervix, producing a proximal descent of the bladder. The etiology of cystocele is complex and can include factors like levator musculature damage, denervation, elongation, or detachment of the fascial structures from their lateral anchors to the lateral pelvic wall. The presence of significant lateral and transverse cystocele is intimately related to vaginal vault support, and the outcome of surgery for significant cystocele depends to a great extent on the outcome of vaginal vault support.
Fig. 1.13
(a) Diagram of the trapezoid supporting the anterior vaginal wall, associated distally to the urethral support, laterally to the arcus tendineus fascia pelvis, and posteriorly to the same supporting structures of the uterus and vaginal cuff (cardinal–sacrouterine complex). (b) Diagram depicting a central defect cystocele. The lateral support is present, but weakness of the perivesical fascia allows the bladder to prolapse centrally. (c) Diagram depicting a lateral defect cystocele, in which the lateral support of the bladder to the arcus tendineus is elongated or detached. (d) The anterior vaginal wall support is a trapezoid with the lateral walls at the arcus tendineus fascia pelvis, the distal support is similar to the urethra, and the proximal support is the same as the ureters and the vault (sacrouterine–cardinal complex). (e) In a lateral defect, the lateral attachment of the anterior vaginal wall is sliding downward owing to detached or elongated vesicopelvic fascia. (f) In a central defect, the lateral attachment is maintained, while the bladder is prolapsed through a central defect of the pubocervical fascia
Static and dynamic MRI and cystourethrogram have helped to define better the anatomy of anterior vaginal wall prolapse. As will be discussed later, the most common abnormality is a combination in which the lateral and central supports of the bladder are damaged, together with hypermobility of the urethra and bladder neck. The frequency of this combination has a great impact on the surgical correction of cystocele. We believe that if surgery is performed, most patients should have repair of all the anterior vaginal wall defects (unless contraindicated). Merely repairing the central defect without repairing the urethral defect and the lateral bladder defect can result in a significant rate of cystocele recurrence and the continuation or appearance of de novo stress incontinence. Abdominal surgeries such as Burch colposuspension or paravaginal suspension can correct only the lateral defect, and they are not indicated in the repair of cystocele with a significant central defect. Sacrocolpopexy can effectively repair vault prolapse and reduce the cystocele, but it will not correct urethral hypermobility or a significant central defect.
1.4.3 Uterine and Vaginal Vault Support
The sacrouterine ligaments provide the most important support to the uterus and the vaginal cuff (see Fig. 1.3). The ligaments anchor the cervix to the anterolateral margins of the sacrum and pelvic fascia. They are strong in young women, but with aging, menopause, and multiple deliveries, they may become detached, attenuated, and elongated, leading to uterine or vault prolapse. The ligaments are important in vaginal reconstructive surgery, as vault suspension procedures are aimed to substitute for the attenuated ligaments. The total length of the ligaments is approximately 12 cm, with a distal attachment to the posterior lateral cervix and proximal vagina for a distance of 2–3 cm, where the ligaments fuse with the cardinal ligaments to form the cardinal–sacrouterine complex. The ligament curves around the rectum toward the sacrum, attaching at the S3 level with extensions toward S2. The superior anchor point is wide from the sacral foramina medially to the sacroiliac joint extending to the fascia of the coccygeus and sacrospinous ligaments.
The cardinal ligaments, also called Mackenrodt’s ligaments, are thick, triangular concentrations of pelvic fascia containing the uterine arteries, which originate from the pelvic fascia in the region of the greater sciatic foramina. They insert into the lateral aspects of a ring of fascia encircling the uterine cervix and isthmus, and into the adjacent vaginal wall as well, providing major uterine and apical vaginal support. The cardinal ligaments fuse posteriorly with the sacrouterine ligaments and insert into the posterolateral aspect of the pericervical fascial ring and lateral vaginal fornices (Fig. 1.14). Further uterine support is provided by the broad ligaments, which are more superiorly located and covered by anterior and posterior folds of the peritoneum; they attach the lateral walls of the uterine body to the pelvic sidewall. They contain the fallopian tubes, the round and ovarian ligaments, and the uterine and ovarian vessels.
Fig. 1.14
(a) During vaginal hysterectomy, a curved clamp is inserted to isolate the sacrouterine–cardinal complex. (b) The cardinal–sacrouterine complex has been transected and separated from the uterus. A clamp is holding the ligaments
1.4.4 Support of the Posterior Vaginal Wall and Rectum
A complex fascial and muscular arrangement provides support to the posterior vagina and rectum, as connective tissue covers the anterior rectal wall (prerectal fascia) and the posterior rectal wall (anterior sacral fascia); they are fused laterally to attach to the levator muscle (arcus tendineus fascia pelvis).
When a woman with normal support is in the erect position, the posterior vaginal wall has a curvature (banana shape) with two distinct portions: proximal and distal. The proximal vagina forms a posterior angle of approximately 110° with the vertical line (Fig. 1.15a, b). The point of angulation indicates the point where the vagina crosses the pelvic floor musculature (pubococcygeus–puborectalis) (Fig. 1.15c). The proximal third of the vagina is in a horizontal plane resting over this levator plate. The distal vagina is in a more straight-up position, forming a 45° angle with the vertical line. This angle reflects the degree of support of the levators and the urogenital diaphragm pulling forward the distal vagina. Restoration of this anatomy is important in posterior vaginal wall reconstruction.
In patients with pelvic floor relaxation, the normal anatomy of the posterior vagina is lost. The levator plate descends (becoming convex instead of horizontal) (Fig. 1.16b), the levator hiatus enlarges, and the normal distal vaginal angulation of 110° disappears. The distal half of the vagina is no longer 45° from the vertical. The vagina is now rotated downward and posteriorly and is no longer in a high, supported horizontal position. Herniation of the rectum (rectocele) may ensue. MRI again can help in understanding the anatomical changes observed in patients with pelvic floor relaxation.
In patients with damage to the vaginal outlet (the perineal or urogenital diaphragm), the introitus is wider, and the distance between the urethra and posterior fourchette is increased (see Fig. 1.15). Different degrees of perineal tear may be seen, from minimal tears with only a small separation of the perineum to a severe degree in which the perineal structures have disappeared and the posterior vaginal wall reaches the anterior rectal wall.
Fig. 1.15
(a) Diagram of pelvic organ support. The distal third of the vagina is at a 45° angle to the vertical line, even as the proximal vagina is in an almost horizontal plane (110° with the vertical line). The angulation or levator notch is the point of insertion of the pubococcygeus and puborectalis muscles, which pull the vaginal canal and rectum toward the pubic bone. (b) Three-dimensional MRI reconstruction of the vagina showing the elevation of the distal third at the point of insertion of the puborectalis. (c) Sagittal MRI of a patient without prolapse showing the urethra, the bladder, the anal canal, and the indentation (levator notch) where the puborectalis (part of the pubococcygeus) is inserted. During voluntary or reflect contraction, the levator pulls the vagina and rectum anteriorly toward the pubic bone. During voluntary relaxation, the distance increases and the levator descends. The distance between the inferior rami of the symphysis and the levator notch defines the size of the levator hiatus, usually 5–6 cm. (d) Three-dimensional reconstruction of the levator plate showing a wide levator hiatus in a patient with multiple deliveries and significant pelvic floor relaxation. (e) Sagittal MRI of a patient with posterior vaginal prolapse. The vaginal axis and the levator muscle are more vertical, the rectum protrudes from the vaginal canal, and there is disappearance of the levator notch. The distance between the anal canal and the inferior rami of the pubic bone is increased, confirming the widening of the levator hiatus
Fig. 1.16
(a) Exposure of the posterior vaginal wall in a patient with a large rectocele and widening of the levator hiatus. (b) Diagram depicting the anatomy of pelvic floor relaxation. The levator plate descends, losing its horizontal axis, and the levator hiatus widens. (c) The perineal membrane joins in the midline at the perineum and extends several centimeters inside the vaginal canal. The levators (pubococcygeus) attach to the perineal membrane. (d) Damage to the perineal membrane widens the perineum and the distal vagina. Approximation of the perineal membrane to the midline will narrow the levator hiatus and correct in great part the perineal defect. (e) The perineal membrane covers the puborectalis, pubococcygeus, and iliococcygeus muscles. It inserts in the inferior rami of the ischiopubic arch, joining the contralateral side in the central tendon of the perineum, leaving a hiatus for the vaginal canal. The ischiocavernosus muscles cover the crura of the clitoris, and the bulbocavernosus muscles cover the fibro-fatty issue of the labia. The transverse perineum inserts laterally in the ischial tuberosity and medially joins the bulbocavernosus muscle and external anal sphincter to form the central tendon of the perineum
As is the case with anterior vaginal wall defects, combined defects of posterior vaginal support at both the level of the pelvic floor and the perineum often occur, particularly in cases of severe prolapse. Three defects are generally present: weakness of the prerectal fascia covering the rectovaginal septum, widening of the levator hiatus and perineal membrane, and laxity of the perineal musculature. To provide normal introital size and improved posterior vaginal support, corrective surgery of the posterior vaginal wall should address all the defects: correction of the rectocele by reinforcement of the attenuated prerectal and pararectal fasciae, repair of the defect of the levator muscles by reapproximation of the widened perineal membrane, restoration of the horizontal supporting plate for the proximal vagina, and repair of the fascia and musculature of the perineum, when defective.
1.5 Innervation and Vascular Supply to the Pelvis
Figures 1.17, 1.18, and 1.19 show diagrams of the vascular supply and innervation of the pelvis and perineum, providing greater understanding of the anatomy of the pelvis.
Fig. 1.17
(a) The internal iliac artery provides vascular supply to the pelvic organs, particularly from its anterior branch. The pudendal and inferior gluteal arteries run posterior to the sacrospinous ligaments. The other branches are the umbilical, superior vesical, uterine, inferior vesical, vaginal, and middle rectal arteries. (b) From the internal iliac artery, the vaginal and uterine arteries provide blood supply to the vagina and uterus through multiple small arterial branches. They anastomose to the ovarian artery, a branch from the anterior aorta
Fig. 1.18
(a) The hypogastric sympathetic plexus descends around the aorta and major pelvic vessels, joining the visceral branches of the sacral root (S2, S3, S4) to form the pelvic plexus lateral to the uterus and rectum. The pelvic plexus provides visceral (sympathetic and parasympathetic) innervation to the bladder, vagina, uterus, and rectum. (b) The sacral plexus originates from the sacral roots S2, S3, and S4, with anterior branches providing somatic and sensory fibers to the skin and muscular structures of the pelvis. Visceral branches of the sacral roots join the sympathetic hypogastric (T9–L1) forming the pelvic plexus. (c) From the sacral plexus, the pudendal nerve provides visceral and somatic innervation to most of the pelvic muscles and viscera (Adapted from Online Atlas: Visible Body). The femoral cutaneous nerve emerges behind the sciatic notch to provide genital branches to the posterior perineum and inferior labia. The ilioinguinal nerve provides innervation to the suprapubic area and superior labia. The genital branch of the genitofemoral nerve provides innervation to the labial area. The pudendal nerve provides somatic (motor and sensory) innervation to the pelvic musculature and skin structures of the perineum
Fig. 1.19
Diagram of the perineum showing the approximate areas of sensory innervation originating from the different pelvic nerves
Suggested Reading
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Hsu Y, DeLancey JO. Functional anatomy and pathophysiology of pelvic organ prolapse. In: Raz S, Rodriguez L, editors. Female urology. 3rd ed. Philadelphia: Saunders-Elsevier Publishers; 2008. p. 542–5.CrossRef
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Netter F. Reproductive system, Ciba collection of medical illustrations, vol. 2. Summit: Ciba-Geigy Corp., Medical Education Division; 1965.
Ramanah R, Berger MB, Parratte BM, DeLancey JO. Anatomy and histology of apical support: a literature review concerning cardinal and uterosacral ligaments. Int Urogynecol J. 2012;23(11):1483–94.CrossRefPubMedPubMedCentral
Visible body. 3D human anatomy. Argosy Publishing; 2014. http://visiblebody.com