The Pelvic and Perineal Fasciae and Their Neural and Vascular Relationships

W. H. ROBERTS, JAMES HABENICHT AND GENE KRISHINGNER Department of Anatomy, Schools of Medicine and Dentistry, Loma Linda University, Loma Linda, California

ABSTRACT This study was based upon a dissection of the pelvic fasciae and associated structures of one hundred and three adult pelves as well as those of three full term fetuses. The perineal fasciae and their neural and vascular relationships were studied in a n additional 55 specimens.

The uterovaginal fascia, as stated by others, is a well-defined structure. One is usually able, on the basis of a fascial cleft, to distinguish readily between the fascial sheath of rectum proper and the deeper layer of subperitoneal fascia, called by some the presacral fascia. The latter is described, including the relationship of the pelvic autonomics thereto. The relationship of the vesical branches of the pelvic plexus and of the venous plexuses to the terminal ureter are also described.

We were able to confirm the presence of a superficial and a deep perineal fascia; the latter forms the inferior boundary of the superficial perineal space proper, as described by others. The relationship of particular nerves (and vessels) to the fascial planes of the perineum follows a definite pattern even when variation from the normal is present.

The dispositions of the pelvic and peri- neal fasciae present many features of prac- tical importance. The present study was undertaken as a means of furthering an understanding of these structures and of clarifying some aspects which have seemed obscure.

Pelvic fasciae By definition, the parietal fascia of the

true pelvis is a part of the general internal investing fascia of the body wall. It con- sists of the fasciae of the piriformis and obturator internus muscles; the superior fascia of the pelvic diaphragm is often in- cluded. The extent of the parietal fascia and its attachments have been well defined by Frazer ('58).

The pelvic subperitoneal fascia, like the parietal fascia, becomes continuous with its abdominal counterpart at the linea ter- minalis. It follows the lateral pelvic wall down to the arcus tendineus fasciae pelvis (continued anteriorly as the puboprostatic or pubovesical ligament) and is then re- flected onto the viscera, forming pathways for supplying nerves and vessels, the "leit- platte" of Pernkopf ('43). Sometimes the visceral fascial investments are spoken of as fascial sheaths, and as such are reflec-

tions of the superior fascia of the pelvic diaphragm and of the urogenital dia- phragm onto the pelvic organs. As stated by Spalteholz ('14) the visceral fascial ele- ments are well defined and are of the nature of a true fascia caudally, but tend to lose their identity cranially where the subperitoneal fascia takes on more of the nature of areolar tissue. The lateral exten- sions, as emphasized by Gaspari and Brizzi ('61), are never free of nerves and vessels. See also Dufour and Mouktar ('63).

The vesical fascia as compared to the vaginal or uterovaginal fascia in the fe- male is, as Shaw ('49) indicates, very thin. Above the vesicourethral junction they may readily be distinguished from one another but below this level they fuse. As suggested by Richardson ('29) the surgical procedure of total hysterectomy is simpli- fied and made less hazardous by develop- ing the vesicovaginal interfascial cleft from above; the uterovaginal fascia, or pubocervical fascia as he calls it, is then incised anteriorly and posteriorly and dis- placed laterally, and along with it the ureter. The veins from the cervix, which traverse the lateral extensions of the fascia and which join the periureteral venous plexus, can then be safely dealt with.

707 ANAT. REC., 149: 707-720.

708 W. H. ROBERTS, JAMES HABENICHT AND GENE KRISHINGNER

The rectovaginal septum, which is in- timately associated with the posterior part of the uterovaginal fascia, as seen in the adult, corresponds to the posterior pro- static fascia or rectovesical septum in the male. The latter, according to Close ('47) should bear Tyrell's name rather than that of Denonvillier since the former was the first to describe it. Laterally, both septa extend out to the arcus tendineus fasciae pelvis. As stated by Uhlenhuth, Wolfe, Smith and Middleton ('48) the plane of cleavage between the rectal fascia and the rectovaginal septum in the female is as well defined as is that between the rectal fascia and the rectovesical septum in the male. Posterolaterally the parametric and para- vaginal tissues in the female are continu- ous with the pararectal tissues as stated by Toldt ('29), as is the prostatic fascia and pararectal tissues in the male, as pointed out by Symington ('14).

Silver ('56) has given rather convincing evidence that the upward migration of the peritoneal excavation between the bladder and protstate (and seminal vesicles) and the rectum, which occurs during the last three months of fetal development can be attributed to the descent of the neck of the bladder. The widely held opinion that the rectovesical septum is a peritoneal deriva- tive originated with Cuneo and Veau (1899). They believed it to be analogous in development to the umbilicoprevesical fascia referred to later. However, as Paitre, Giraud and Dupret ('35) have pointed out, Denonvillier, Farabeuf, and Delbet, also of the French school, believed the septum to be a condensation of the pelvic mesenchyme.

The connective tissues about the uterine vessels are often called the lateral cervical or "cardinal ligaments of Mackenrodt" and those about the middle rectal vessels the lateral ligaments of the rectum, as for in- stance, by Wood and Wilkie ( '33) . On morphological and historical grounds Close ('47) prefers the term neurovascular sheath. It is generally recognized that the supportive function of the vessels and their fascial sheaths is inadequate if the pelvic and urogenital diaphragms, and the vagi- nal fascia, are not intact.

Curtis, Anson, Ashley and Jones '42); Ashley and Anson ('46); and Close ('47),

subdivide the subperitoneal pelvic connec- tive tissues into two layers, a superficial and a deep. Curtis, Anson, Ashley and Jones ('42) speak of the more superficial of the two layers as the true tela subserosa. It contains the superior rectal vessels and associated lymphatics and, laterally, the middle rectal and inferior vesical vessels. Peham and Amreich ('34) mention that a fairly large vaginal branch of the middle rectal artery leaves this layer and enters the "cardinal ligament" from behind. The deeper layer (which Paitre, Giraud and Dupret ('35), and Close ('45), call the presacral fascia) invests the superior hypo- gastric plexus, the right and left hypo- gastric nerves into which the plexus di- vides, and the pelvic splanchnics which join the last-mentioned on their lateral side to form the inferior hypogastric or pelvic plexuses. Gabriel ('37) refers to the deeper layer as the parietal fascia of Waldeyer and speaks of it as a suspensory ligament of the rectum, this suspensory fuction be- ing dependent upon its merging with the fascial sheath of the rectum at the anorec- tal junction.

The autonomic supply to the rectum, of which the parasympathetic is the more important functionally is, as stated by Ash- ley and Anson ('46), given off more or less at right angles to the inferior hypogastric plexus. The vesical branches are usually said to surround the terminal ureter but the present investigation indicates that these are mainly lateral and inferior. The ureter throughout most of its course, as stated by Tobin ('44), lies within the sub- peritoneal fascia. In the peIvis it is at first medial to the uterine artery but eventually passes below it. As Causey ('58) states, the closeness of the relationship of the ureter to the supravaginal cervix is some- what variable, but it always passes an- terior to the anterior vaginal fornix.

Anteriorly the subperitoneal fascia is sometimes subdivided into an umbilico- vesical fascia containing the lateral umbili- cal ligaments and the urachus, and, an umbilicoprevesical fascia, a fibrous layer situated between the former and the trans- versalis fascia, derived as stated by Cuneo and Veau (1899), from obliterated paired peritoneal cul-de-sacs (but which may per- sist) formed as a result of the lateral dis-

PELVIC AND PERINEAL FASCIAE 709

placement of the umbilical arteries during development. Hammond, Yglesias and Davis (’4 1 ) , and Rouviere (’62) have more recently described the relationships of the two fasciae referred to above in some detail.

The fusion fasciae of peritoneal origin described by Toldt (1879) and by Cong- don, Blumberg and Henry (’42) probably do not have a pelvic counterpart. The above-mentioned authors do not describe such nor could we find evidence of it. Some, however, speak of a rectal fusion fascia, to which we will refer below.

Perineal fasciae We were more interested in the fasciae

of the urogenital region than those of the ischiorectal fossa so shall largely confine our remarks to the former. The urogenital diaphragm with its superior and inferior fasciae and its intervening muscles is said by Curtis, Anson and Ashley (’42) to rein- force rather than fill in a defect in the pelvic diaphragm. Early anatomists, as for instance Von Behr (1847), in speaking of the inferior fascia of the urogenital dia- phragm, used the terms perineal ligament (later known as the perineal membrane) and deep perineal fascia synonymously. Colles had described in 1811, as quoted at length by Tobin and Benjamin (’49), a more superficial “strong fascia” bridging the ischiopubic rami and since usually re- ferred to as the superficial perineal fascia. As we shall endeavor to show the “strong fascia” he described no doubt corresponds to the deep perineal fascia as the term is used by Bassett (’61) and others. It cer- tainly would not conform to the mem- branous layer of the superficial with which it is generally equated. Tobin and Benja- min (’49) even doubt that a membranous layer of the superficial fascia can be differ- entiated either on dissection or histologi- cally from the fatty layer and could find no evidence that it attached to the pos- terior border of the urogenital diaphragm. Gallaudet (’31) refers to the deep perineal fascia as the “inferior perineal fascia,” likewise Curtis, Anson and Beaton (’40) and Curtis, Anson and Ashley (’42). The latter, in harmony with the classic con- cept, state that the deep perineal, or “in- ferior perineal fascia” as they call it, is

within the superficial perineal space, which is thought of as being bounded iii- feriorly by the membranous layer of the superficial perineal fascia. The term “external perineal fascia” is used by Gow (’60) who describes i t as attaching to the posterior border of the urogenital &;a- phragm, to the margins of the ischiopubic rami, and as being continuous at the base of the urogenital diaphragm with the sulb- diaphragmatic or “extra-pelvic’’ part of the obturator internus fascia, and anteriorly with the deep fascia of the penis. He coin- siders it to be the true boundary of the superficial perineal space with which we would agree.

We were able to demonstrate to our own satisfaction that, as noted by Bassett (’61), the perineal branch of the posterior fe- moral cutaneous nerve, in its perineal course, runs in the fascial cleft between the membranous layer of the superficial fascia and the deep perineal fascia. The perineal branches of the internal pudein- dal artery and the pudendal nerve aice given off in the anterior part of the pudein- dal canal. The nerve in turn gives off cutaneous or posterior scrotal (labial branches which, after leaving the canad, continue forward for about 2.5 cm in a tunnel in the deep perineal fascia, finally piercing it to join the perineal branch of the posterior femoral cutaneous in the fascial cleft. Both eventually pierce the membraneous layer of the superficial peri- neal fascia to supply the skin of the scro- tum. They never actually enter the super- ficial perineal space. The membranous layer of the superficial fascia, if it is a distinct entity, and we feel that it is, is more readily demonstrable in lean su’b- jects. We have noted in previous studies on the popliteal fascia and the fascial sheath about the popliteal vessels that too much reliance cannot be placed upon histological findings when it comes to dif- ferentiating fasciae; the latter opinion is also held by Shaw (’49).

As Tobin and Benjamin (’49) state the posterior scrotal branches of the perineal nerve and the accompanying vessels have been variously described as running deep to, superficial to, or within the superficial perineal fascia. Why this might be so has been indicated above; further there are

710 W. H . ROBERTS, JAMES HABENICHT AND GENE KRISHINGNER

many variations in the nerve supply to the perineum, some of which have been alluded to briefly by Schafer and Syming- ton (’09), such as a perforating branch of the perineal nerve. While experimentally injected media may extravasate widely and not be contained by a so-called mem- branous layer of the superficial fascia, as demonstrated by the first-mentioned authors, the clinical studies of Wesson ( ’53 ) indicate that a well defined deep perineal fascia is capable of limiting to the perineum abscesses or hemorrhages deep to it, whereas similar collections in the cleft between superficial and deep peri- neal fasciae are able to extend up onto the abdomen. This is in harmony with Colles’ original description. Again this apparent discrepancy can be resolved if one thinks of the deep perineal fascia as being sepa- rate and distinct from the membranous layer of the superficial fascia. It would seem more appropriate if Colles’ name were associated with the deep perineal fascia rather than with the membranous layer.

The communication between the fascial clefts of the perineal and the lower ab- dominal regions has been called recently the “abdomino-scrota1 opening”; the term “perineo-abdominal communication” would seem to be more correcct, if such a term has any merit in describing this potential area of communication, since, while it con- nects with a similar cleft in the scrotum, the perineo-abdominal communication is the more direct.

MATERIALS AND METHODS

The pelvic fasciae were studied in 14 females and six males as well as in three full term fetuses (one male and two fe- males); the distribution of the pelvic blood vessels was studied bilaterally in an additional 57 males and 26 females (only a brief reference will be made to this part of the study). The fasciae of the peri- neum proper andvtheir neural and vascular relationships were studied bilaterally in 55 specimens (25 males and 30 females).

The pelvic fasciae were first of all ex- amined with the pelvis intact, then either with the pelvis sectioned in the mid-sagit- tal plane, or from the lateral aspect after removing pubis and ischium excepting the

ischial spine. In studying the fasciae of the urogenital region and their neurovas- cular relationships it was found helpful to trace forward the supplying nerves and vessels from the gluteal region and from the ischiorectal fossa.

FINDINGS

Pelvic fasciae and relation of neural and vascular structures thereto

In respect to the pelvic fasciae we were mainly interested in the subperitoneal and visceral fascial elements so shall confine our remarks to these. The pelvic sub- peritoneal fascia, as related to the pelvic wall posteriorly, as others have shown, has superficial and deep components, sep- arated by a potential fascial cleft. The superficial and deep componuents merge with one another, and also with the su- perior fascia of the pelvic diaphragm, at the anorectal junction (fig. 1). The super- ficial or more anterior layer forms the fas- cia1 sheath of the rectum; it encloses the rectum and the pararectal fat in which are embedded the superior rectal vessels, the middle rectal vessels (when present), and the accompanying lymphatics and autonomic nerves (fig. 2).

The deeper layer of the subperitoneal fascia posteriorly and inferiorly forms a continuous hammock-like sheet from one side of the pelvis to the other, extending out to the arcus tendineus fasciae pelvis on either side. This deeper layer lends sup- port to the superior hypogastric plexus and right and left hypogastric nerves, and, in- feriorly, to the inferior hypogastric or pel- vic plexus. The branches from the in- ferior hypogastric plexus to the rectum form a distinct bundle; it is about 1 cm in length, and is given off from the plexus about 6 ern above the anus, or at approxi- mately the level of the ischial spine. The more important of the vesical branches pass immediately lateral to, and slightly below, the terminal ureter (fig. 3) . The long somatic branches of S 3 and 4 which supply the levator ani muscle run in the superior fascia of the pelvic diaphragm.

The ureter, while it for the most part lies within the subperitoneal fascia, is, near its termination, invested by postero- lateral extensions of the vesical fascia. A large vein from the cervix pierces the

PELVIC AND PERINEAL FASCIAE 71 1

A.;l;aca communis d e x b a , Venn cava ,, A.iLaca externa , .

,/’ H y m e n ‘ r! Sep tum rec to- va male I’aasc uterova+nale <.

Fig. 1 This sagittal section of a female pelvis (right side) shows the following fascial compo- nents : the umbilicoprevesical fascia (indicated by an asterisk), the uterovaginal fascia, the fascial sheath of rectum proper, and finally that part of the subperitoneal fascia continued down into ithe pelvis, and constituting the only parietal fascia over the mid-sacrum often spoken of as the “pre- sacral fascia.” (The uterus was cut a little to the left of the midline.)

uterovaginal fascia to join, usually, the inferior vesical veins which pass back- ward, between the vesical and uterovaginal fascial layers, in close vicinity to the ureter. In other specimens one or more veins from the cervix were found to pierce both the uterovaginal fascia and the vesi- cal fascial investment of the ureter to pass below the ureter and to enter the internal iliac vein direct, It is in dealing with the veins in this region that the surgeon may damage the ureter after having safely ligated the uterine artery and its accom-

panying vein. Above this level, in the male, the inferior vesical plexus of veins receives tributaries arising in and arou:nd the seminal vesicles.

The uterovaginal fascia is a substantial structure. When incised over the cervix it can be readily displaced laterally. It forms a sheath for the upper vagina as well as the cervix and has lateral exten- sions which carry it out to the arcus tendineus fasciae pelvis. It is pierced, as indicated above, by veins which pass lat- erally from the cervix uteri.

712 W. H. ROBERTS, JAMES HABENICHT AND GENE KRISHINGNER

Fig. 2 The left side of the pelvis shown in figure 1. The inferior hypogastric plexus is shown in relation to the deeper layer of the subperitoneal fascia. The relation of the ureter to the uterine artery is also indicated.

The middle rectal artery when present may pass either through or above the pel- vic splanchnics. Its vaginal branch (or branches) is usually small but such a branch may be almost as large as the uterine artery, as seen in two specimens studied. That the relationship of such a vaginal branch to the so-called “transverse cervical ligament of Mackenrodt” is not constant, is indicated by the fact that while it did enter it in one, in the other specimen where the middle rectal artery came off the internal pudendal, both it and its vagi- nal branch passed along the lateral pelvic wall for a considerable distance before supplying the organs for which they were destined, the vaginal branch passing onto

the vagina well below the level where the uterine artery passed into the meso- metrium.

In one specimen the iliococcygeus was absent but well-defined pubococcygeus and coccygeus muscles were present. An apo- neurosis replaced the first-mentioned. It, along with the fasciae of the pelvic dia- phragm, and the ischiorectd fat, appar- ently prevented any tendency to perineal herniation.

Perineal fasciae and retation of neural and vascular structures thereto

When it is remembered that the sensory nerves in general run in the deep fascia until they approach their destination, it

PELVIC AND PERINEAL FASCIAE 71.3

(s epkum rectovesicale) - 1

Fig. 3 This figure shows the relationship of the vesical branches of the pelvic plexus to the terminal ureter. Note that the nerve fasciculi are mainly posterolateral and inferior. The ureter has been pulled aside.

becomes less difficult to define the deep perineal fascia. Admittedly, in some cases, particularly the obese, the latter may be no firmer in texture than the superficial perineal fascia (of Colles). In others, how- ever, even in the elderly, it is a very sub- stantial layer. The perineal branch (or branches) of the posterior femoral cutane- ous nerve always has a more superficial course than the posterior scrotal (labial) branches of the perineal nerve and the associated vessels. The former, usually a single trunk with a large lateral and a small medial branch, having pierced the deep fascia, the fascia lata in this case,

enters the perineal region by piercing the membranous layer of the superficial peri- neal fascia and then continues forward in the fascia1 cleft between the superficial and deep perineal fasciae. The posterior scrotal (labial) nerves and vessels pass be- tween two laminae of, or traverse a tunnel in, the deep perineal fascia (fig. 4). They give off fine branches, usually, which may either pierce the deep perineal fascia or take an indirect course and swing around the posterior border of the urogenital clia- phragm; in either case they usually com- municate with the perineal branch of the posterior femoral cutaneous within the f'as-

714 W. H. ROBERTS, JAMES HABENICHT AND GENE KRISHINGNER

cia1 cleft. The posterior scrotal (labial) nerves may tunnel the deep fascia only a relatively short distance before entering the fascial cleft. Variations in the nerve supply to the perineum, as indicated be- low, are common, but the relation of spe- cific branches to the fascial layers is re- markably constant.

Instances where an aberrant posterior scrotal (labial) nerve was present

In seven of the 55 specimens examined, a large superficial or posterior scrotal (labial) branch of the perineal nerve was found to communicate with and form a significant part of the perineal branch of the posterior femoral cutaneous. In three of them it entirely replaced it. The condi-

tion was unilateral unless otherwise indi- cated.

In the first specimen (no. 27) the peri- neal branch of the posterior femoral cutaneous was large but was nevertheless joined by a fairly large communicating branch from the perineal nerve which passed around the posterior border of the urogenital diaphragm to enter the fascial cleft. The communicating branch left the perineal nerve quite far back in the ischio- rectal fossa but distal to the inferior rectal nerve.

In the second, third and fourth speci- mens (no. 33, 38 and 55) a superficial branch of the perineal nerve which entered the fascial cleft, as did the one described above, had largely replaced the perineal

v i \ \ ’. Fascia perinei super- 1, Fascia Perinei D y o f . f;c;& (Colles) ’ \ J . J Vv., n. labialis post.

Fig. 4 This is a dissection of the female perineum showing the fascial cleft between the super- ficial and deep perineal fasciae, traversed by the perineal branch of the posterior femoral cutaneous nerve; the posterior labial vessels and nerves tunnel the deep perineal fascia. Also shown is the superficial perineal space proper and its contents. The space is bounded below by the deep perineal fascia and above by the inferior fascia of the urogenital diaphragm.

PELVIC AND PERINEAL FASCIAE 71.5

branch of the posterior femoral cutaneous, the latter being very small (fig. 5 ) .

In the fifth specimen (no. 39) a super- ficial branch of the perineal nerve entirely replaced the perineal branch of the pos- terior femoral cutaneous. It again left the pudendal canal fairly far back in the ischiorectal fossa but distal to the inferior rectal nerve. On the opposite side a per- forating cutaneous branch of the pudendal replaced the perineal branch of the pos- terior femoral cutaneous - this is referred to again below.

In the sixth specimen (no. 48) the peri- neal branch of the posterior femoral cuta- neous, which received a communicating branch arising from a perforating cutane- ous branch of the pudendal, supplied only the skin about the anus and the perineum, a superficial branch of' the perineal supply- ing the scrotum; the latter swung around the posterior border of the urogenital diaphragm rather than entering within, and piercing, the deep perineal fascia, as

is customary for the posterior scrot.al branches of the perineal.

In the seventh specimen (no. 53) a superficial perineal branch of the perined nerve again took the place of the perineal branch of the posterior femoral cutaneous. This branch was given off deep to the sacrotuberous ligament and took an inde- pendent course in the lateral wall of the ischiorectal fossa below and parallel to the pudendal canal and the structures in it, i.e., medial to the ischial tuberosity. It swung around the posterior border of the urogenital diaphragm to enter the fascia1 cleft. One of the posterior scrotal branches of the perineal nerve left the perineal far- ther back than usual but still entered the deep perineal fascia.

Instances where an aberrant branch of the pudendal nerve supplied

the perineum In one specimen (no. 31) referred to

again below, the pudendal, near its origin,

1

buperkicial perineal fascia of Colles

Fig. 5 Male perineum. The superficial perineal fascia has been reflected. On the left side is seen the perineal branch of the posterior femoral cutaneous nerve in the cleft between the superficial and deep perineal fasciae. On the right is a slight variant in that a posterior scrotal nerve takes a more superficial course than usual and joins a small perineal branch of the posterior femoral cutaneous. Normally the posterior scrotal nerves and vessels tunnel the deep perineal fascia for some distance before piercing it.

w. H. ROBERTS, JAMES HABENICHT AND GENE KRISHINGNER 716

gave a communicating branch to the peri- neal branch of the posterior femoral cutaneous which had been given off from the posterior femoral cutaneous high up in the pelvis. The latter took an otherwise normal course in that it passed lateral to the sacrotuberous ligament and to the ischial tuberosity and eventually, entered the fascial cleft. In another specimen (no. 48), also referred to gain below, the pudendal nerve gave off a perineal branch which entirely replaced the perineal branch of the posterior femoral cutaneous. The course and distribution of this aberrant perineal branch was similar to the perineal branch of the posterior femoral cutaneous mentioned above.

Instances where the perforating cutaneous nerve entered into the nerue

supply of the perineum A perforating cutaneous, arising from

the pudendal nerve in each instance, was found to largely or entirely replace the perineal branch of the posterior femoral cutaneous in an additional six of the 55 specimens. This condition was unilateral in five instances and bilateral in the sixth. In a seventh specimen a perforating cutaneous, formed by the junction of a branch from the posterior femoral cutane- ous and from the pudendal, pierced the deep part of the sacrotuberous ligament from lateral to medial, joined the perineal nerve and was distributed with it. The term perforating cutaneous is being used in the broad sense to include any nerve that pierces the sacrotuberous ligament.

In the first specimen (no. 31) the per- forating cutaneous gave a large communi- cating branch to the posterior femoral cutaneous as well as to its perineal branch which, in this case, was very small. The latter thus reinforced was distributed nor- mally. On the opposite side the perineal branch of the posterior femoral cutaneous, given off near the origin of the latter, re- ceived a communicating branch from the pudendal nerve, also given off near its origin, i.e., high in the pelvis, there being a Y-shaped connection between the two. The perineal branch of the posterior fe- moral cutaneous was otherwise normal in its course and distribution.

In the second specimen (no. 37) the perforating cutaneous was found to be almost identical, in respect to its com- munications and in its distribution, with the aberrant perineal branch of the pos- terior femoral cutaneous on the second side of specimen no. 31. It arose from the pudendal and the posterior femoral cutaneous high in the pelvis, passed lateral to the ischial tuberosity and was distrib- uted in much the same way as a perineal branch of the posterior femoral cutaneous. Unlike the other it pierced the sacrotuber- ous ligament rather than passing lateral to i t . The nerve supply to the perineum on the opposite side was entirely typical.

In the third specimen (no. 28) a large perforating cutaneous nerve, after having pierced the sacrotuberous ligament, passed medial to the most prominent part of the ischial tuberosity rather than lateral to it, as in the case of the first two specimens. It pursued an independent course to the perineum, where, after piercing the super- ficial perineal fascia, it entered the fascial cleft. The perineal branch of the posterior femoral cutaneous in this instance was very small. The nerve distribution on the opposite side was normal : a lateral branch of the perineal branch of the posterior femoral cutaneous supplied the lower or posterior part of the labium majus; a medial branch entered the fascial cleft to supply the labium more anteriorly (more commonly these two branches show the reversed distribution).

In the fourth specimen (no. 39) the perineal branch of the posterior femoral cutaneous was absent on both sides. The perforating cutaneous took its place on one side; a superficial branch of the peri- neal nerve communicated with it in the fascial cleft, as so often happens. On the opposite side the perineal branch of the Posterior femoral cutaneous was replaced by a superficial or posterior scrota1 branch of the perineal nerve, one of the three such instances referred to above.

In the fifth specimen (no. 5 8 ) , the perineal branch of the posterior femoral cutaneous was absent on both sides. On one side the perforating cutaneous, which replaced it, took a medial course in rela- tion to the tuberosity of the ischium. On the opposite side a perineal branch of the

PELVIC AND PERINEAL FASCIAE 71 7

pudendal, given off near its origin, and which passed just lateral to the sacro- tuberous ligament, and lateral to the prominent part of the ischial tuberosity, replaced it.

In the sixth specimen (no. 43) , the perforating cutaneous nerve, present bi- laterally, in each instance pierced the lat- eral edge of the sacrotuberous ligament and joined the perineal branch of the pos- terior femoral cutaneous near the ischial tuberosity, its fibers being distributed with this nerve. On the one side the perineal branch of the posterior femoral cutaneous, thus reinforced, supplied the skin posterior to the anus, the skin about the anus, and the perineum, but was not distributed to the scrotum, the scrotal branch being re- placed by a superficial branch of the peri- neal nerve (another one of the three such referred to above). On the opposite side the perineal branch of the posterior fe- moral cutaneous, after receiving the per- forating cutaneous, was distributed in the ordinary manner.

In the seventh specimen (no. 51) the perforating cutaneous was formed on each side by junction of communicating branches from the posterior femoral cuta- neous and the pudendal nerve. In this respect it was similar to specimens nos. 31 and 37 in having this Y-shaped con- figuration. After having pierced the deep part of the sacrotuberous ligament it joined the perineal branch of the pudendal nerve and was distributed with it in the usual manner.

In other specimens the perforating cuta- neous nerve, present unilaterally or bilat- erally (as in no. 18) supplied the skin of the lower gluteal and posterior anal regions. In one specimen (no. 50) the perforating cutaneous was a dorsal ramus of S 3.

The perforating cutaneous therefore was found to supply in some cases the lower gluteal region and posterior anal region, in others both these areas as well as the perineum. In still others it was found to be distributed in whole or in part to the scrotum or labia, communicating with or taking the place of the perineal branch of the posterior femoral cutaneous. And in one specimen the perforating cuta- neous joined the perineal nerve and was distributed with it. Schafer and Syming-

ton ('09) speak of the inferior hemor- rhoidal (rectal) nerve as often piercing the great or the small sacrosciatic (sacro- tuberous or sacrospinous) ligament on its way to the perineum. They state also that the lateral superificial perineal nerve (the more lateral of the principal superficial or posterior scrotal branches of the perineal nerve) may likewise pierce the great sacro- sciatic (sacrotuberous) ligament. We did not encounter any example of the first. The last-mentioned probably correspond to those instances which we have dle- scribed where the perforating cutaneous supplied the perineum. These variations are not too surprising since the lowest root of the posterior femoral cutaneous nerve from the third sacral, is said by Brash ('51) to be associated with either the origin of the perforating cutaneous or of the pudendal nerve. They occur with about equal frequency in male the femabe.

The perineal branch of S 4 was seen occasionally in our dissections (in speci- men no. 53 it was unusually large) and appeared to be distributed in the manner usually described. After piercing the coc- cygeus i t enters the ischiorectal fossa, pass- ing on the medial side of the sacrospinous ligament rather than lateral to it. as does the pudendal nerve. It supplies the sphincter ani externus and adjacent peri- neum.

Within the superficial perineal space proper, as indicated in figure 2 are to be found : the bulb, the paired bulbospo~i- giosus muscles, the crura and the ischilo- cavernosus muscles, the superficial trans- verse perineal muscles (not shown) and the branches of the perineal nerve and of the internal pudendal artery supplying the previously mentioned structures. The pos- terior scrotal nerves and vessels which lie within the deep perineal fascia, and the perineal branch of the posterior femoral cutaneous which lies in the fascia1 cleft would not, in the strict sense, be within the superficial perineal space if the deep perineal fascia is to be considered its inferior boundary.

DISCUSSION

The two more important components of the visceral or subperitoneal pelvic fas- cia are probably the uterovaginal and the

718 W. H. ROBERTS, JAMES HABENICHT AND GENE KRISHINGNER

presacral fasciae. The uterovaginal fascia, which forms the fascial sheath of the upper vagina and cervix is traversed by cervical veins passing to the periureteral venous plexus. Both fasciae are traversed by branches of the pelvic splanchnics and accompanying vessels, including lym- phatics which pass to the internal iliac and sacral lymph nodes. While the pre- sacral fascia is in direct contact with the sacrum, elsewhere it is not the parietal layer, the piriformis and obturator inter- nus fasciae and the superior fascia of the pelvic diaphragm assuming that role, it being separated by fascial clefts from these and from the component of the sub- peritoneal fascia which enters into the formation of the fascial sheath of the rectum.

The term “presacral fascia” as applied to the posterior part of the deeper layer of the subperitoneal fascia, and as used by Paitre, Giraud and Dupret (’35) and by Close (’47), seems as descriptive as any. The latter speaks of this layer, because of its inferior attachments, as being a part of the visceral pelvic fascia, whereas others speak of it as a part of the parietal pelvic fascia. Since the presacral fascia is first parietal and then becomes visceral, both terms are correct, as in turn could be said of the superior fascia of the pelvic diaphragm.

The rectum is more or less of a midline structure and, as one would expect, no evidence was found of a retrorectal fu- sion fascia in terms of a fusion of two apposed layers, a parietal and a mesen- teric. We prefer not to think of the fused fascial sheath of rectum and the presacral fascia as a fusion fascia in the usually accepted sense.

If one considers the deep perineal fascia as being the inferior boundary of the superficial perineal space, then to be con- sistent one has to exclude the perineal branch of the posterior femoral cutaneous nerve as a contained structure since it runs in the cleft between superficial and deep perineal fasciae, and also the Dosterior scrotal nerves and vessels since they tra- verse a tunnel in the deep facia. This relationship being quite constant is an aid in identifying the fascial lavers in this region. What we have called the deep

perineal fascia is undoubtedly the struc- ture represented in many atlases as the superficial perineal fascia.

The variations in the cutaneous nerve supply to the perineal region have no doubt contributed to some of the discrepancies in the literature concerning the relationship of the posterior scrotal (labial) nerves and vessels to the superficial perineal fascia. One reads a good deal about tropism in relation to the course of certain nerves. Is there such a thing as tropism in reverse? In other words if certain fibers enter an area do they exclude others? Or, are varia- tions in nerve supply simply an aberrant course of fibers destined for a certain area?

CONCLUSIONS

The deeper layer of the subperitoneal fascia, sometimes spoken of as the pre- sacral fascia, and continuous above with the subperitoneal fascia of the abdomen, forms a hammock-like sheet from one side of the pelvis to the other, extending lat- erally to the arcus tendineus fasciae pelvis on either side. Embedded in i t are the superior hypogastric plexus and right and left hypogastric nerves and the inferior hypogastric (pelvic) plexuses. A fascial sheath of the rectum derived from the more superficial layer of the subperitoneal fascia, and enclosing the superior and middle rectal vessels and associated lym- phatics and autonomic nerves, may be differentiated from the deeper layer or “presacral fascia.” Similarly the Dresacral fascia may be differentiated from the superior fascia of the pelvic diaphragm or epimysium of the coccygeus and levator ani muscles.

The relationship of the veins of the cervix uteri to the uterovaginal fascia and of both these and the pelvic splanchnics to the terminal ureter has been indicated. An unusually large vaginal artery arising from the middle rectal was noted in two cases. Its origin and course, as indicated, is variable.

The differentiation of the membranous layer of the superficial perineal fascia (of Colles) and the deep perineal fascia is made less difficult if it is borne in mind that there is a remarkably constant rela- tionship of nerves and vessels to them. Variations in the nerve supply to the peri-

PELVIC AND PERINEAL FASCIAE 71.9

neal region such as have been described, are fairly common but in their distribution tend to follow a very definite pattern in relation to the fascial planes. It seems probable that the “strong fascia” to which Colles referred in his original description is related more particularly to the deep perineal fascia rather than the membran- ous layer of the superficial fascia with which his name is usually associated.

ACKNOWLEDGMENTS

Many helpful suggestions have been received from colleagues in the Depart- ment of Anatomy, in particular Drs. Charles Harrison, Daniel Mitchell and Howard Smith. The encouragement of Dr. Harold Shryock. Chairman of the Depart- ment of Anatomy, and the work of Mrs. Lucille Innes, the artist, and other mem- bers of the staff of the Audiovisual De- partment has also been much appreciated.

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