A new look at the M. Levator Ani in asymptomatic women

A new look at the M. Levator Ani in
asymptomatic women
Snoeck Th.¹ ², Provyn S.¹,Caufriez M.², Bouchant B.², Balestra C.², Clarys J.P.¹
Objective
The aim of this study is to demonstrate that the descriptions in the anatomy atlases (fig 1.) and
texbooks, based on dissections, do not thoroughly correspond with the reality observed in healthy invivo women. To do so the Cadaveric evidence has been questioned with the in-vivo circumstances.
Material and methods
Eleven nulliparous women aged between 22 and 26 years (23,64 +/- 1.12 years) and nine multiparous
women aged between 28-37 years (mean 33,4 +/- 3,5 years), both with no clinical symptoms (urology,
gynaecology, proctology) participated in the study. Magnetic Resonance Images were produced in frontal
planes, (21 slices, sequenced every 5mm, using the T2 Turbospinecho, TR=4600ms TE=89ms) analysis
sequence en séquence T1) and in saggital paramedian planes using the same paradigm allowing to study
of the ilio-coccygeal parts of the M. Levator Ani.
The analysis of the arch concavity of the Levator Ani, found in the images has been performed using the
classical Reuleaux (1875) technique. (Fig. : 2) Both the “dome arch” center and the curve radius.
Frontal plane : the centre of the Dome arch was calculated and the differences between the curves and
Fig 1.: Superior concavity of the levator ani
the radii of the domes were analysed (fig 3).
form an “Hammock” morphology
Sagittal plane : the anterior - posterior ratio was compared between domes in order to precisely locate the
arches (fig 3.).
The data were treated with a Fisher’s exact test and a Student t-test for unpaired groups when
appropriate.
Results
All women, nullipareous or not,
showed ilio-coccygeal bundles in a
double dome topography with a
inferior and posterior concavity. The
left dome arches are the highest
(p=0.0166) and the most anterior
(p=0.0216) in the nullipareous
women while the opposite is shown
Fig 3. : Frontal and coronal view of Levator Ani. Both incidences show an
inferior concavity
In the multipareous group,
characterised by significantly less
concave (p=0.0360) and more
posterior oriented dome arches
(p=0.0038).
Fig 2. : Analysis of a dome arch according
to the Reuleaux technique (1875)
Conclusion
Against the atlases evidence supported by dissections; the in vivo M. Levator Ani does not have a hammock shape. Its concavity is oriented
interiorly and superiorly. In asymptomatic women; the Magnetic Resonance Images and the ad hoc calculations, lead us to propose an
opposite topography. One can assume that the principle of a vault with its pillars and with an inferior and posterior concavity allows for a better
absorption of loads (forces) generated by daily abdominal pressure and a more efficient protection of pudental plexus. The reason for such an
architecture is actually a matter of suppositions, nevertheless the cause of this particular muscular shape should be explained.
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1.Experimentele anatomie - Vrije Universiteit Brussel - Laarbeeklaan, 103 – 1090 Brussels - Belgium
2.Laboratoire de physiologie environnementale et occupationnelle - Haute école Paul Henri Spaak - Avenue Charles Schaller, 91 - 1160 Brussels – Belgium
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