Levator ani muscle anatomy evaluated by origin-insertion pairs

Abstract

Objective: To examine the published literature and suggest a resolution to the confusion that exists in levator ani muscle descriptions and terminology.

Data sources: A MEDLINE search was performed using the keyword "levator ani," limited to human studies in women. References found in these articles were reviewed to identify research reported before 1966 and articles not included in the search.

Study selection: Studies were accepted if they contained direct observations of female specimens. Only those that contained specific descriptions or illustrations of the muscle origins and insertions in more than 5 female specimens were included. Review of 265 human studies yielded 9 qualifying articles, and reference tracing disclosed 3 additional reports.

Tabulation, integration, and results: The literature review identified 5 origin-insertion pairs consistently described in studies directly examining the levator ani muscle in women, but 16 terms were used by authors for these 5 components of the muscle. Labeled illustrations often provided more precise information than was provided in the text. Terms were reviewed for inconsistencies of usage and appropriateness of term choice. The terms puboperineal, pubovaginal, and puboanal (for components of the pubovisceral ["pubococcygeal"] muscle), along with puborectal and iliococcygeal, are sufficient to describe the divisions of the levator ani muscle.

Conclusion: Although there was great diversity and conflict in terms chosen among the original articles, the number of origin and insertion pairs was relatively consistent among authors and confusion can be avoided by standardizing terminology.

Fig. 1

Schematic view of the levator ani muscles from below after the vulvar structures and perineal membrane have been removed showing the arcus tendineus levator ani (ATLA); external anal sphincter (EAS); puboanal muscle (PAM); perineal body (PB) uniting the 2 ends of the puboperineal muscle (PPM); iliococcygeal muscle (ICM); puborectal muscle (PRM). Note that the urethra and vagina have been transected just above the hymenal ring. Copyright © DeLancey 2003. Kearney. Levator Ani Anatomy. Obstet Gynecol 2004.

Fig. 2

The levator ani muscle seen from above looking over the sacral promontory (SAC) showing the pubovaginal muscle (PVM). The urethra, vagina, and rectum have been transected just above the pelvic floor. PAM = puboanal muscle; ATLA = arcus tendineus levator ani; and ICM = iliococcygeal muscle. (The internal obturator muscles have been removed to clarify levator muscle origins.) Copyright © DeLancey 2003. Kearney. Levator Ani Anatomy. Obstet Gynecol 2004.