Vincent Di Marino1 and Hubert Lepidi1
(1)
UER Médecine, Aix-Marseille Université, Marseille, France
Abstract
This ligament is a fibro-elastic and fatty formation, which connects the bulbo-clitoral organ to the pubic symphysis and to the infra-umbilical linea alba. In spite of its volume and size, few authors have actually studied this formation and most of the authors, who have written about the clitoris, have simply pointed out the existence of this formation or provided erroneous representations, such as a minuscule symphysis fibrous attachment. It is Poirier and Charpy, in 1901, who provided the first anatomical description of this ligament.
This ligament is a fibro-elastic and fatty formation, which connects the bulbo-clitoral organ to the pubic symphysis and to the infra-umbilical linea alba. In spite of its volume and size, few authors have actually studied this formation and most of the authors, who have written about the clitoris, have simply pointed out the existence of this formation or provided erroneous representations, such as a minuscule symphysis fibrous attachment. It is Poirier and Charpy, in 1901, who provided the first anatomical description of this ligament.
At first sight, the shape of the ligament is that of a quadrangular pyramid, with a clitoral base and a prepubic and sagittally flattened top. The ligament insertions at the level of the clitoris protrude ahead of the elbow and overflow onto the descending part of the body and may even reach the glans. These insertions are present on the corporeal albuginea and spread to overflow over the lateral sides of the latter. Certain fibres of the ligament meet on the inferior surface of the clitoral body to form a sort of hammock. Other fibres extend laterally on either side of the clitoral body and are lost in the derma of the labia majora (Fig. 12.1). Some fibres also reach the medial part of the bulbospongiosus muscle. The ligament extends with the fibrous tissue of the retro-crural fascia and is connected, with the latter, to the pre-symphysis fibrous coating, at the level of the crura and of the ascending portion of clitoral body. From this clitoral base, the ligament pyramid can be described as follows (Fig. 12.1):
Fig. 12.1
Four pictures of a prepubic dissection to demonstrate the position of suspensory and fundiform ligaments. (a, c) Right lateral view and anterior view showing the suspensory ligament in place. (b, d) Left lateral views showing the suspensory ligament partially detached. b bulb, cr crus, fl fundiform ligament, h hood, i-p r ischio-pubic ramus, p pubis, sl suspensory ligament, superficial portion, sl′ suspensory ligament, deep portion. The White asterisk shows ligamentary fibres extending in the derma of labia majora. The Black asterisk shows ligamentary fibres reaching the medial part of the bulbo-spongiosus muscle. The white arrow shows the neuro-vascular bundle (bulbar vessels and bulbar nerve).
· Two large triangular lateral surfaces, whose base measures on average 2.3 cm and extends from the retro-crural fascia to the junction between the body and the glans clitoridis.
· A ventral surface corresponding to the thickness of the ligament (3–4 mm), which becomes wider at the level of its clitoral attachment (around 1 cm large).
· A dorsal surface extending without any boundary line with the retro-crural fascia. When this fascia is absent or not very developed, its base measures around 8 mm but when in contact with the pubic symphysis, the ligament insertion spreads out as a triangular surface.
· A superior end, which gradually becomes tapered and loses itself on the linea alba, above the pubic insertions of the latter.
The ligament has an overall length of 8–9 cm.
Such as already described by Poirier and Charpy, it is possible to distinguish two parts of the suspensory ligament of the clitoris:
· A deep part, attached to the angle of the clitoris and the back of the first centimetres of the body. This part is attached to the retro-crural fascia, on the caudal half of the anterior surface of the pubic symphysis, and its fibres mix with those of the pre-symphysis fibrous coating (Fig. 5.3).1
· A superficial part,2 covering the preceding part, attached to the descending portion of the body of the clitoris, passing in front of the symphysis, then spreading out and ending laterally at the level of mons pubis (mons veneris) in the fibrous parts of the subcutaneous fascia of Camper and, for its median part, over the last caudal centimetres of the infra-umbilical linea alba (Fig. 12.1).
It is interesting to observe that this superficial part is significantly long and especially that it has, such as already observed by M.A. Rees et al., a multiplanar configuration (such as the entire bulbo-clitoral organ). The attachments to the mons pubis are made according to a frontal plane (that of the abdominal wall) but then, imperceptibly, the fibres of this superficial part are arranged on a sagittal plane to join the clitoris (Figs. 12.1 and 12.2). It should also be noted that the attachments to the mons pubis are very spread out (8 cm on average). As regards the length of the superficial part, from the mons pubis up to the clitoris, it is difficult to give a figure because, in more than half of the cases, we could observe a median cranial extension of this superficial part in the form of a thin 1-cm wide fibrous cord, of variable length, in front of the infra-umbilical linea alba, in the direction of the umbilicus, which it sometimes reaches. However, in most cases, this fibrous condensation becomes thinner and then merges with the white line. It is this formation, which has previously been described by authors as the fundiform ligament of the clitoris (Fig. 12.1). Lastly, it should be noted that the superficial and deep parts of the division are quite often visible on the median sagittal MRI sections of the abdominal wall (Fig. 12.2).
Fig. 12.2
Aspects of the suspensory ligament of clitoris. (a) NMR median sagittal section of the pelvis showing the clitoris and his suspensory ligament (red arrow). (b) Dorsal view of the suspensory ligament on a pelvic dissection. an angle of clitoral body, bl bladder, bo clitoral body, cr crus clitoridis, fl fundiform ligament, n dorsal nerve of clitoris, p pubic symphysis, R rectum, r-cr f retro-crural fascia, rec abd rectus abdominis muscle, sl suspensory ligament, u urethra, va vagina (white curved arrow showing vaginal cavity)
The structure of the ligament explains its solidity: It consists of resistant collagen packs, with which are mixed numerous elastic fibres and fatty tissue (Fig. 12.3). The microscopic examination is particularly interesting because it shows an accordion-shaped fold of the collagen bundles. This configuration obviously forms a lengthening reserve for a ligament, which must allow clitoral mobility, even of small amplitude. At its base, the collagen bundles extend with the corporeal albuginea bundles and the cavernous septum bundles. Numerous neurovascular components, following the dorsolateral parts of the clitoral body, cross through this base (Fig. 12.3): the 2 arteries and the 2 dorsal nerves of the clitoris, or the median dorsal part, such as the main large dorsal vein of the clitoris, always with 2 or 3 satellite veins.3 However, while the veins cross directly through the fibrous framework, which maintains them open, the nerves pass through small islands of fatty tissue, thus providing them with a certain amount of freedom. The arteries, as for them, remain surrounded by a protective fibrous sheath. The collagen packs become denser and exchange their fibres with those of the prepubic fibrous coating at the top of the ligament, i.e. in the tapered part. It should also be noted that extremely developed venous networks cross through the ligament longitudinally. These networks establish anastomoses between the clitoral veins and the median veins of the anterior abdominal wall (which form an additional drainage pathway for clitoral venous blood).
Fig. 12.3
Histological aspects of the suspensory ligament of clitoris. (a) Photomicrograph of a frontal section of the base of suspensory ligament (sl) (magenta arrow): standard staining by HEAS. a artery, Nnerve, V principal dorsal vein, v accessory dorsal veins, bo clitoral body. (b) Photomicrograph of a frontal section of the base of suspensory ligament (mauve arrow): PS100 staining. (c) Nerves through the suspensory ligament within islands of adipose tissue. (d) Curious kinks in collagen fibres of ligament. (e) Staining by orcein, highlightening the elastic fibres (black coloured). (f) A great Pacinian corpuscle in the sl, among the collagen fibres
The question of the role played by the suspensory ligament is of primary importance: Why such a large ligament for such a small organ? The answers are determined from anatomical observation:
· The first role is a support role for the clitoris which is obvious when observing the “ligament hammock” arranged not only under the elbow (or angle) but also under the entire descending portion of the clitoris. This support is static during the quiescent phase. It becomes active during intercourse and “contributes to the stability of the clitoris” (M.A. Rees et al.), thus preventing the clitoris from hindering the penis’ back-and-forth movements. Abdominal musculatures are involved in this active role (via the insertion of the superficial bundle of the ligament on the linea alba). Musculature of erectile bodies, via fibres of the ischiocavernosus and bulbospongiosus muscles, which mix with the collagen bundles of the suspensory ligament, is also involved.
· The second role is a protective role for the components which come from or go towards the clitoris, by crossing it. This role especially involves providing an additional protection for the dorsal nerve of the clitoris, whose trajectory is particularly complex at this level, with the rise of the angle of the clitoral body and whose contribution of the vegetative contingent, via the arrival of the thin and fragile cavernous nerve, must be carefully protected. In this protection, it is necessary to recall the very important role played by the fatty tissue, whose small islands within the collagen tissue are preferential areas of transit for the nerves.
· Lastly, it should be recalled that the ligament (and especially its base) has a particularly high content in Pacini’s corpuscles. This is most certainly due to the proximity of the dorsal nerves of the clitoris, but also to a potential role played by the ligament as a specialised receptor, a starting point for proprioceptive impulses. This suspensory ligament may therefore be more than just a simple support structure. It may even contain specific sensors (neurotendinous spindles).
It will therefore be necessary to conduct more research work in this field in order to improve our understanding of this ligament, which has always intrigued researchers.
Footnotes
1
From a surgical viewpoint, the deep part of the suspensory ligament and the retro-crural fascia detach relatively easily from the pre-symphysis fibrous coating, thus providing numerous accesses (urethra, bone pubis, etc.) for surgical purposes.
2
This superficial part of the ligament was unknown for a long time. Its description by Charpy, in 1901, was largely ignored by the authors of anatomy books.
3
All the veins of the suspensory ligament communicate with the sinuses of the cavernous bodies, especially via emissary veins crossing through the peri-cavernous albuginea (Fig. 7.1).