Surgical Anatomy for the Reconstructive Surgeon

Image 1.1

Prolapse identified on the dependent examination (Photo Elise J.B. De)

Prolapse staging on physical examination has been reported according to a few staging systems. The most common in clinical practice is the Baden-Walker Halfway system (Fig. 1.1) [1]. The Baden Walker system consists of four grades reported with respect to the compartment in question: Grade 0 (no prolapse), Grade 1 (halfway to the hymenal remnant), Grade 2 (at the hymen), Grade 3 (halfway past the hymen) and Grade 4 (maximum descent). More recently, the Pelvic Organ Prolapse Quantification system (POP-Q) was described to provide a more objective and reproducible staging system (Fig. 1.2) [2]. This system allows for more consistent reporting in research. The POP-Q measures six points relative to the hymen during maximal Valsalva maneuver (Aa, Ba, C, D, Ap, Bp) as well as total vaginal length (TVL), perineal body (PB), and the genital hiatus (GH) which are measured supine at rest. The stage reports the most severe portion of prolapse. All points above the hymen are negative, the hymen is zero, and those beyond the hymen are positive. For Stage 1, the most distal aspect of the prolapse is more than 1 cm above the hymen (<−1). Stage II, the most distal point is within 1 cm of the hymen (−1 to 1). Stage III is more than 1 cm beyond the hymen (> + 1) and Stage IV involves complete eversion.

Fig. 1.1

Visual comparison of systems used to quantify pelvic organ prolapse (POP) (Image 1 in: Theofrastous and Swift [1])

Fig. 1.2

Pelvic organ prolapse quantification system (Figure 1 in: Bump et al. [2])

An enterocele can be visible or palpable but often it is not confidently identified until the surgical procedure (Image 1.2). Some clinicians employ magnetic resonance imaging (MRI) to aid in the assessment of prolapse, particularly enterocele. Dynamic MRI with straining effort does not show the apical and posterior compartment defects as well as magnetic resonance defecography. Preoperative MRI is not the practice of the authors. Confounders that will impact surgical planning include ulceration (Image 1.3a). Severe ulceration can put the untreated patient at risk for bowel evisceration if neglected (Image 1.3b). A foreshortened vagina will limit the vaginal reconstructive options (Image 1.4). It is also important to recognize rectal mucosal prolapse, which the patient can mistake as a vaginal bulge when reporting her intake history (Image 1.5).

Image 1.2

Enterocele visible on exam (Photo Elise J.B. De)

Image 1.3

(a, b) Ulceration and, in the worst case scenario, evisceration (Courtesy of O. Lenaine Westney, M.D. and Brian Murray, M.D.)

Image 1.4

Foreshortened vagina (Courtesy O. Lenaine Westney MD)

Image 1.5

Rectal mucosal prolapse (Courtesy Elise J.B. De, M.D.)

Supports

Supports within the pelvis include bones, muscles, and viscerofascial layers. The “fascias” are in fact condensations of areolar tissue, and the “ligaments” condensations of fibrous tissue, collagen, muscle and nerves.

Bony Pelvic Anatomy

The anatomy of the pelvis starts with the bony pelvis. Important structures relevant to pelvic reconstruction include the pubic symphysis, obturator foramen, sacral promontory, ischiopubic rami and the ischial spines (Image 1.6). Special attention should be given to the relationship of the obturator vessels and nerves to the obturator foramen, the pudendal nerves and vessels to the ischial spine, the sacral nerve roots to the piriformis muscle and the internal iliac vessels, and the anterior longitudinal ligament to the sacral promontory.

Image 1.6

Anatomy of the bony pelvis (Courtesy Alexandra Rehfuss, M.D.)

Muscles of the Pelvic Floor

The superficial muscular layer of the female perineum includes the ischiocavernosus muscle, the superficial transverse perineal muscle, the external anal sphincter and the bulbocavernosus muscle (Image 1.7) [3]. The convergence of the superficial transverse perineal muscle, external anal sphincter and bulbocavernosus muscle forms the base of the perineal body, which is a cone-shaped structure the apex of which continues with the rectovaginal fascia.

Image 1.7

Muscles in the superficial perineal pouch in women (Fig. 5.71 in Drake et al. [12])

The next deepest muscular layer of the pelvic floor includes the deep transverse muscle of the pelvis, the urethrovaginal sphincter, the compressor urethrae muscles and the external urethral sphincter (Image 1.8) [4–7].

Image 1.8

(a) Muscles of deep perineal pouch in women (Image 259 in Drake et al. [4]). (b) Nerves of the perineum in women (perineal membrane removed on left side to expose deep perineal pouch; inferior view) (Image 267 in Drake et al. [5])

The deepest muscular layer of the female pelvic floor is the pelvic diaphragm. It forms a support layer among the pubis, coccyx, and arcus tendineus levator ani to provide support to the urethra, vagina and rectum. The pelvic diaphragm is made up of (1) the coccygeus muscle and (2) the levator ani: the puborectalis, pubococcygeus or pubovisceral and iliococcygeus muscles (Image 1.9) [8].

Image 1.9

Pelvic diaphragm. The pelvic diaphragm is made up of (1) the coccygeus muscle and (2) the levator ani: the puborectalis (added to original image), pubococcygeus (or pubovisceral) and iliococcygeus muscles. Additional structures to note: arcus tendineus fascia pelvis, arcus tendineus levator ani, obturator internus muscle, piriformis muscle, ischial spine, obturator canal (not to be confused with Alcock’s) (Figure 2.2 in Walters and Karram [8])

The coccygeus (also termed the ischiococcygeus) muscle attaches medially to the lateral margins of the coccyx and the levator plate and laterally to the ischial spine (Image 1.9) [8]. The puborectalis muscles arise from the posterior pubic symphysis/rami and form a sling around the vagina, rectum, and the apex of the perineal body, determining the pelvic hiatus. The pubococcygeus (or pubovisceralis) muscles originate from the posterior aspect of the pubic bones and form four groups of fibers: the pubovaginal muscle, urethral hammock (pubourethral and urethropelvic) ligaments; the puboperineal muscle that inserts on the apex of the perineal body; the puboanalis muscle that inserts in between the internal and external anal sphincters; and the pubococcygeus fibers that form the levator plate. The iliococcygeus muscle arises from the arcus tendineus levator ani and inserts on the coccyx posteriorly as well as the levator plate. The boundaries of the pubrectalis, pubococcygeus and iliococcygeus muscles are difficult to delineate but all work to provide pelvic floor support. These four muscles fuse in the midline to form the levator plate, which attaches posteriorly to the coccyx.

The muscles of the pelvic sidewalls are the piriformis and obturator internus (Images 1.8b and 1.9). The obturator internus, which essentially lies over the obturator foramen, arises from the obturator membrane, ischium, and rim of the pubis. It passes through the lesser sciatic foramen and inserts on the greater trochanter. Its anteromedial fascia forms the arcus tendineus fascia pelvis (the lateral attachment of the pubocervical fascia) and the arcus tendineus levator ani – this being the origin of the iliococcygeus muscle. In the pelvis, the posteromedial surface of the obturator internus forms the lateral wall of the ischioanal fossa and forms the sheath that surrounds the internal pudendal nerve and vessels (Alcock’s canal). The piriformis is located dorsal and lateral to the coccygeus muscle. The piriformis arises from the anterior surface of the sacrum and from the gluteal surface of the ilium near the posterior inferior iliac spine. It passes out of the pelvis through the greater sciatic foramen and inserts on the greater trochanter. In the pelvis, the anterior surface of the piriformis is in contact with the rectum, sacral nerve plexus and branches of the internal iliac vessels.

Viscerofascial Layers and Ligaments

The endopelvic fascia is formed by fibrous and elastic tissue, collagen, and proteoglycans, in association with muscles and nerves and is responsible for the suspension of all pelvic viscerae, receiving different names according to its morphofunctional characteristics: the cardinal-uterosacral complex, the pubocervical fascia, the rectovaginal fascia and the urethropelvic ligament. The arcus tendineus fascia pelvis (ATFP), (Images 1.9 [8], 1.10 [9] and 1.15 [14]) runs from the pubic symphysis to the ischial spine and represents the insertion of the pubocervical fascia on the obturator internus muscle fascia. It supports the bladder and vagina laterally, forming the anterolateral vaginal sulcus. Detachment of the bladder from this support is seen in a lateral cystocele, appreciable by palpation of the descending sulcus during Valsalva on exam. It is important to note the position of the ischial spine in relation to the ATFP. The ATFP is used by some as an anchoring stitch for the Kelly-Kennedy plication, it provides the lateral support in a vaginal paravaginal repair, and is also the site of graft attachment in many non-native tissue repairs. See below regarding the three levels of support characterized by DeLancey. The ATFP is considered “Level II”.

Image 1.10

Endopelvic fascia and connective tissue supports (Figure 2 in DeLancey [9])

The commonly called uterosacral and cardinal ligaments are ligament-like structures formed by a condensation of the hypogastric fascia that suspends the pericervical ring and/or upper part of the vagina (paracolpium). Based on an anatomical magnetic resonance imaging study of 20 patients, the fibers of the portion of this fascial condensation that is called the cardinal ligament are positioned in a cranial to caudal direction and originate at the pelvic sidewall at the upper margin of the greater sciatic foramen in the majority of cases (Image 1.11) [10]. The uterosacral ligament (USL) fibers are oriented in a ventral to dorsal direction, arise from the anterior sacral aspect at the level of the greater sciatic foramen medial to the sacral foramina, and contain fibrous tissue and smooth muscle (Image 1.12) [11]. Together, these are called the cardinal-uterosacral ligament complex and, when dissected, they are revealed as more of a condensation or fold than an actual structure. Nevertheless, when placed on traction there is usually a substantial structure to palpate, visualize and suture (see below regarding avoidance of nerve injury).

Image 1.11

MR reconstruction: the “Cardinal Ligament” fibers are positioned in a cranial to caudal direction and the “Uterosacral Ligament” fibers are positioned in a ventral to dorsal direction (Figure 2a and b in Ramanah et al. [10])

Image 1.12

(a) Photo: Transparent arrow indicates the uterosacral ligament complex (Photo Courtesy Peter Cole, M.D.) (b) MRI of uterosacral ligament insertion: The origin of the uterosacral ligaments from the cervix (white arrowheads) and their insertions (black arrowheads) on the pelvic sidewall. The location of the insertion point (b) on a line (ac) between the body midline and the ischium (I). The location of the bladder (B), cervix (C), rectum (R), coccyx (X), and coccygeus muscle (CM) are shown (Image 1 in Umek et al. [11])

The sacrospinous ligament connects the ischial spine and the sacrum (Image 1.13) [12]. The internal pudendal artery and nerve run posterior to the sacrospinous ligament, close to the spine, and the nerve to the levator ani muscle runs anterior to its medial third (Image 1.14) [13].

Image 1.13

Sacrospinous ligament and relationship to pudendal nerve (Figure 5.15 in Drake et al. [12])

Image 1.14

Nerve of the levator ani (Figure 4 in Barber et al. [13])

In 1992, DeLancey described three levels of support created by the endopelvic fascia and connective tissue (Image 1.10). Level I support (apical-uterus and post-hysterectomy vaginal apex) includes the cardinal-uterosacral complex. Loss of level I support results in apical prolapse. Level II support consists of the pubocervical fascia and its attachment to the ATFP and the rectovaginal fascia and its attachment to the iliococcygeus muscle. Loss of level II support can result in anterior wall prolapse, which can be due to a transverse detachment (detachment of the pubocervical fascia from the pericervical ring), a lateral defect (detachment from the ATFP), or a central defect. Disruption of the rectovaginal fascia is also a level II loss of support and will result in a proximal (fascial detachment from the pericervical ring) or distal (detachment for the perineal body apex) rectocele. Level III support (distal urethra and distal vagina) includes the perineal membrane and perineal body. Loss of level III support results in urethral hypermobility and perineal body disruption [7].

DeLancey theory on stress urinary incontinence is depicted in a lateral drawing expanding on these relationships (Image 1.15) [14]. In this drawing, one can appreciate the importance of the ATFP providing lateral support to the vagina and urethra. The support of the urethra is contiguous with the anterior vaginal wall and is bridged by the endopelvic fascia fusing into the ATFP. The detrusor fibers tunnel laterally into the bladder neck providing constant tone. The circumferential striated sphincter fibers of the external urethral sphincter provide compression primarily in the middle third of the urethra. Stress urinary incontinence will result from poor urethral coaptation, compression or support. Pliability can be reduced by radiation, pelvic surgery or poor estrogenization. Tone can be impacted by hypermobility, pelvic surgery, radiation and neurologic conditions. The surgical approach will only address the anatomic factors. The anatomic lateral supports are seen in vivo in the MR image and the photo (Image 1.16a), in which one can appreciate the continuity of support of the urethra with the anterior vaginal wall (Image 1.15 and 1.16c).

Image 1.15

Relationship of urethra to lateral supports (Figure 1 in Ashton-Miller and DeLancey [14])

Image 1.16

(a) Distal defect of anterior support involving the urethra and proximal lateral vaginal support (Courtesy Philippe Zimmern, M.D.) MR Image showing the lateral attachments of the urethra (normal support). (Courtesy Shlomo Raz M.D.) (b) Lateral view of normal anterior vaginal wall support with bladder support extending back to the level of the ischial spines. Note normal midline and lateral support (Figure 54-1A in Karram [15]) (c) Lateral view of a midline defect. Note the bulging of the bladder into the midportion of the vagina with maintenance of lateral support. Thus the anterior vaginal fornix is maintained on each side (Figure 54-1C in Karram [15]). (d) Lateral view of bilateral paravaginal defects. Note the complete detachment of the white line from its normal attachment, resulting in complete loss of the anterolateral supports of the anterior segment. Figure 54-1E in Karram [15]) (e) Lateral view of a transverse defect. Note that the bladder prolapse is between the normal upward attachment and the cervix or vaginal apex, usually resulting in what is termed a high cystocele (Figure 54-1G in Karram [15]). (f) Note that the bladder descends around the normal upper attachment of the fascia or the muscular lining of the vagina (Figure 54-1H in Karram [15])

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