Histotopographic study of the pubovaginalis muscle

The levator ani muscle is considered the most important supportive system of the pelvic floor and has been divided into many portions, according to their attachments or physiological functions. Standring et al.1 subdivide the levator ani muscle into the ischiococcygeus, iliococcygeus and pubococcygeus portions. The pubococcygeus muscle is often subdivided into separate parts according to the pelvic viscera to which they relate, i.e. pubourethralis and puborectalis in the male, pubovaginalis (PVM) and puborectalis in the female. At the level of the vagina and the rectum, the muscle bundles of the pubococcygeus muscle are continuous with those controlateral, forming a sling (pubovaginalis and puborectalis). From the functional point of view, Hanzal et al.2 and Ashton-Miller and De Lancey 3 describe three regions of the levator ani muscle: the iliococcygeal portion (that is flat and relatively horizontal and spans the potential gap from one pelvic sidewalls to the other), the pubovisceral muscle (the portion of the levator ani that arises from the pubic bone on either side attaching to the walls of the pelvic organs and the perineal body), and the puborectal muscle. The pubovisceral muscle consists of three subdivisions: the puboperineus, the PVM and the puboanalis. Shafik 4-5 suggests that the levator ani muscle consists essentially of the pubococcygeus, the iliococcygeus being rudimentary in humans; the puborectalis muscle does not belong to the levator ani muscle, having different origin, innervation and function (the former being a constrictor, the latter a dilator of the intrahiatal organs). Kearney et al.6 found sixteen terms used for the different portions of the levator ani muscle, differences that may be in consequence of the preponderance of studies conducted on male subjects. The difference of opinions concerning the anatomy of the levator ani 7 reflects also on the description and terminology of the PVM. Lawson 8 called the muscular fibers that join the vaginal wall to the pubic bone as the ‘pubovaginalis/pubourethralis’, whereas the same structure has been called as the ‘pubococcygeus’ by Curtis et al.9 and Roberts et al.,10 ‘puborectalis’ by Courtney,11 ‘pelvic fibers of anterior layer’ by Ayoub 12 and ‘superficial perineal layer of anterior fibers’ by Bustami.13 Furthermore, Smith 14 states that these muscular fibers arising from the pubis just run adjacent but do not insert into the wall of the vagina. The “Terminologia Anatomica” 15 mentions the PVM, referring to those bundles of the pubococcygeus which surround the vagina, intermingling with the controlateral ones. The microscopic anatomy of the PVM is poorly described. DeLancey and Starr 16 studied the histology of the connection of the vagina with the medial portion of the levator ani muscles, in the region of the proximal urethra. Thus, the term ‘pubovaginalis’ has also been used for the ‘pubourethralis’ muscle, defined as the portion of the levator ani muscle that is attached to the urethral supports. A damage of this part of the levator ani muscle might affect urethral support.6 The aim of the present study was to investigate the histological structure, the characteristics and topography of the PVM in order to evaluate its role in static and dynamic of the pelvic floor.