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Anatomy and Physiology of the Female Perineal Body with Relevance to Obstetrical Injury and Repair

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Anatomy and Physiology of the Female Perineal Body with Relevance to Obstetrical Injury and Repair Clinical Anatomy 15:321–334 (2002) REVIEW Anatomy and Physiology of the Female Perineal Body With Relevance to Obstetrical Injury and Repair 1 2 PATRICK J. WOODMAN * AND DANIEL O. GRANEY 1Department of Obstetrics and Gynecology, Madigan Army Medical Center, Tacoma, Washington 2Department of Biological Structure, University of Washington School of Medicine, Seattle, Washington The female perineal body is a mass of interlocking muscular, fascial, and fibrous components lying between the vagina and anorectum. The perineal body is also an integral attachment point for components of the urinary and fecal continence mechanisms, which are commonly damaged during vaginal childbirth. Repair of injuries to the perineal body caused by spontaneous tears or episiotomy are topics too often neglected in medical education. This review presents the anatomy and physiology of the female perineal body, as well as clinical considerations for pelvic reconstructive surgery. Clin. Anat. 15:321–334, 2002. © 2002 Wiley-Liss, Inc. Key words: perineal body; central tendon; perineum; episiotomy; incontinence; episiorrhaphy INTRODUCTION CLASSIC ANATOMY “I learned how to repair a fourth-degree (episi- MacAlister first named the perineal body in 1889 otomy) long before I learned how to protect the (Oh and Kark, 1973). It marks the embryologic site of perineum…” fusion between the anal tubercles and the pelvic bar, -Quote froma second-year Ob-Gyn resident which separate the cloacal sphincter into anal and urogenital portions. The urorectal septumgrows cau- Ironically, the perineal body is commonly damaged, dally until it reaches the cloacal membrane, dividing but poorly repaired, due in large part to suboptimal the cloaca into two parts: an anterior urogenital sinus knowledge of its anatomy (Sultan et al., 1995). Other and a posterior anorectum(DeLancey, 1989). The factors contributing to poor repair include time pres- urorectal septumbecomesthe perineal body in the sures of a busy clinical schedule, fatigue, inadequate adult. analgesia, or inexperience (Sultan et al., 1995). A poor The perineal body is the central point between the episiorrhaphy can cause pain, dyspareunia (painful urogenital and anal triangles of the perineum. Its intercourse), aerovagina (air trapping within the three-dimensional form has been likened to that of vagina), pelvic organ prolapse froma gaping introitus, the cone of the red pine (Pinus resinosa, Fig. 1) with and fecal or urinary urgency or incontinence. each “petal” representing an interlocking structure, The perineal body is a complex fibromuscular mass into which many structures insert. It is bordered ceph- alad by the rectovaginal septum(Denonvilliers’ fas- The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or reflecting cia), caudad by the perineal skin, anteriorly by the the views of the Department of the Army or the Department of posterior wall of the vagina, posteriorly by the anterior Defense. wall of the anorectum, and laterally by the ischial rami. *Correspondence to: MAJ Patrick J. Woodman, MC, USA, 115 What follows is a description of the formand function Colorado Ct., Southern Pines, NC 28387. of the female perineal body. Terminologia Anatomica E-mail: [email protected] has been used to standardize anatomical nomencla- Received 28 July 2000; Revised 2 August 2000, 7 January 2002 ture (Federative Committee on Anatomical Terminol- Published online in Wiley InterScience (www.interscience.wiley. ogy, 1998). com). DOI 10.1002/ca.10034 © 2002 Wiley-Liss, Inc. 322 Woodman and Graney omy of the external anal sphincter as a triple-loop system of muscle bundles for both males and females. The deep part of the external anal sphincter and a reflection of the levator ani (puborectalis) formthe top loop, and the subcutaneous part of the external anal sphincter forms the bottom loop, both of which attach anteriorly to the perineal body; the superficial part of the external anal sphincter, which forms the middle loop, is tethered posteriorly to the coccyx. Shafik’s work modernized the understanding of the anal con- Fig. 1. The flowering pattern of Pinus resinosa. tinence mechanism. Anteriorly, the perineal body is firmly adhered to the vaginal muscularis submucosa (DeLancey, 1992). such as an insertion site of fascia or a muscle of the perineum. Pelvic musculo-tendinous and fibrous fas- It is suspended anteriorly to the pubic bone by the cial attachments to the perineal body show a similar puborectalis and pubovaginalis. The perineal body is pattern (Fig. 2). also connected anteriorly to the posterior border of the The perineal body is devoid of subcuticular fatty perineal membrane (Wilson, 1967). Laterally, the per- tissue. Upon removal of the fatty tissue in the adjacent ineal body is firmly attached to the ischiopubic rami urogenital and anal triangles, however, the superficial by the superficial transverse perineal muscles. Along perineal space can be explored. The bulbospongiosus its upper lateral borders, the perineal body is attached muscles, located lateral and deep to the introitus and to the pubococcygeus, pubovaginalis, and puborectalis labia majora, respectively, insert into the inferior limit portions of the levator ani muscle group. of the perineal body with the superficial transverse Posterior and superiorly, the perineal body commu- perineal muscles and the subcutaneous portion of the nicates with the longitudinal fibrous sheath of the external anal sphincter. The deep part of the perineal internal anal sphincter, which starts to curve anteriorly body occupies the upper half of the space anterior to toward the posterior wall of the vagina at the level of the anal canal. the anorectal junction (Oh and Kark, 1973). Oh and Kark (1972) suggested that the external The pudendal nerve supplies most of the innerva- anal sphincter forms a single muscle bundle in the tion to the perineal body. It is formed from the ventral female, unlike the male that appears to form distinct rami of S2–4 spinal nerves inferomedial to the sciatic portions. Shafik (1975, 1976a,b) described the anat- nerve, descends between the coccygeus and piriformis Fig. 2. Female perineal body (shaded area). Note the cut-aways of the pubococcygeus, bulbospon- giosus, and superficial transverse perinei muscles. Illustration by Mr. Tom Pierce. Female Perineal Body 323 muscles, and leaves the pelvis through the greater nal lymph nodes, and internal iliac lymph nodes, in sciatic foramen. It then crosses the posterior surface of order of importance (Netter, 1989). the ischial spine and enters the perineumthrough the lesser sciatic foramen to travel along the lateral wall of MODERN ANATOMY the ischioanal fossa within the pudendal (Alcock’s) canal (Benson, 1989). The inferior rectal nerve usually The classic description of the urogenital diaphragm branches off as the pudendal nerve wraps around the includes the deep transverse perineal muscles, encap- ischial spine and subsequently supplies the external sulated within layers of the superior and inferior fas- anal sphincter, which is involved in maintaining fecal ciae of the urogenital diaphragm(Netter, 1989). Oel- continence, and provides sensory innervation to the rich (1983) contended that he could not identify the anal canal below the pectinate line. At the level of the “urogenital diaphragmof Henle” as a distinct anatom- joined superior fascia of the pelvic diaphragmand the ical entity. He conducted an extensive review of the endopelvic fascia, the pudendal nerve divides again literature, performed gross and histological sections on into the dorsal nerve of the clitoris and the perineal 43 fetal pelves and 43 adult pelves at various stages of nerve. The perineal nerve supplies the perineal body development (66 mm crown-rump length fetuses to and the labia. Other branches of the perineal nerve 30-year-old adults) and concluded that teachings supply the external urethral sphincter muscle, which about the existence of the urogenital diaphragmwere is involved in maintaining urinary continence. The unfounded, notwithstanding their promulgation anal canal above the pectinate line is innervated by throughout the anatomical and medical literature for the uterovaginal portion of the inferior hypogastric most of the 20th century. All of the following contrib- plexus and the pelvic splanchnic nerves. Because of ute to the confusion: difficulty of dissection in the its proximity to the anal canal and its close association area, few and small skeletal muscle fibers, the replace- with the internal anal sphincter, small autonomic ment of skeletal muscle fibers by collagen bundles nerve branches to the perineal body are possible with age, the large amount of surrounding smooth (Moore, 1992). Perineal branches of the posterior fem- muscle, and an extensive connective tissue investment. oral cutaneous nerve may also provide innervation. Oelrich’s (1983) major contribution was to describe Arterial supply to the perineal body comes primar- the external urethral sphincter as encircling the mid- ily fromthe internal pudendal artery, one of the dle third of the length of the urethra (Fig. 3). More branches of the anterior trunk of the internal iliac caudally the compressor urethrae and the urethrovag- artery. The internal pudendal artery accompanies the inal sphincter pass anterior to the urethra. The com- pudendal nerve through the pudendal canal and di- pressor urethrae originates fromthe ischiopubic ramus vides into the inferior rectal and perineal arteries
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