Comparison of muscle fiber directions between different levator ani muscle subdivisions: in vivo MRI measurements in women

Betschart, Cornelia; Kim, Jin–Yong; Miller, Janis M.; Ashton‐Miller, James A.; DeLancey, John O.L.

doi:10.1007/s00192-014-2395-9

Cited by 52 publications

(39 citation statements)

References 26 publications

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“…There is also growing evidence on the function of the LAM in the activity of the pelvic floor, indicating that the PVm and PRm participate in hiatal closure. The muscle fibers of the ICm have a similar direction to those of the PVm; thus, they should have additional lifting effects [24]. According to these findings, the effects of birth-related injury to the LAM on its function depend on the region that experienced trauma.…”

Section: Discussionmentioning

confidence: 99%

Finite element model focused on stress distribution in the levator ani muscle during vaginal delivery

et al. 2016

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Introduction and hypothesisDuring vaginal delivery, the levator ani muscle (LAM) undergoes severe deformation. This stress can lead to stretch-related LAM injuries. The objective of this study was to develop a sophisticated MRI-based model to simulate changes in the LAM during vaginal delivery.MethodsA 3D finite element model of the female pelvic floor and fetal head was developed. The model geometry was based on MRI data from a nulliparous woman and 1-day-old neonate. Material parameters were estimated using uniaxial test data from the literature and by least-square minimization method. The boundary conditions reflected all anatomical constraints and supports. A simulation of vaginal delivery with regard to the cardinal movements of labor was then performed.ResultsThe mean stress values in the iliococcygeus portion of the LAM during fetal head extension were 4.91–7.93 MPa. The highest stress values were induced in the pubovisceral and puborectal LAM portions (mean 27.46 MPa) at the outset of fetal head extension. The last LAM subdivision engaged in the changes in stress was the posteromedial section of the puborectal muscle. The mean stress values were 16.89 MPa at the end of fetal head extension. The LAM was elongated by nearly 2.5 times from its initial resting position.ConclusionsThe cardinal movements of labor significantly affect the subsequent heterogeneous stress distribution in the LAM. The absolute stress values were highest in portions of the muscle that arise from the pubic bone. These areas are at the highest risk for muscle injuries with long-term complications.

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Section: Discussionmentioning

confidence: 99%

Finite element model focused on stress distribution in the levator ani muscle during vaginal delivery

et al. 2016

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“…The urogenital hiatus was defined as the shortest distance from the pubic bone to the ventral aspect of the perineal body and corresponds to the pubococcygeal line of action (Figure 1). 18 …”

Section: Methodsmentioning

confidence: 99%

Interactions among pelvic organ protrusion, levator ani descent, and hiatal enlargement in women with and without prolapse

Sammarco

Nandikanti

Kobernik

et al. 2017

American Journal of Obstetrics and Gynecology

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Background Pelvic organ prolapse has two components; 1) protrusion of the pelvic organs beyond the hymen and 2) descent of the levator ani. The Pelvic Organ Prolapse Quantification system measures the first component, however, there remains no standard measurement protocol for the second mechanism. Objectives Test the hypotheses that 1) difference in the protrusion area is greater than the area created by levator descent in prolapse patients compared with controls and, 2) Prolapse is more strongly associated with levator hiatus compared to urogenital hiatus. Study Design Mid-sagittal MRI scans from 30 controls, 30 anterior predominant and 30 posterior predominant prolapse patients were assessed. Levator area was defined as the area above the levator ani and below the sacrococcygeal inferior pubic point line. Protrusion area was defined as the protruding vaginal walls below the levator area. The levator hiatus and urogenital hiatus were measured. Bivariate analysis and multiple comparisons were performed. Bivariate logistic regression was performed to assess prolapse as a function of levator hiatus, urogenital hiatus, levator area, and protrusion. Pearson correlation coefficients were calculated. Results The levator area for the anterior (34.0±6.5cm2) and posterior (35.7±8.0cm2) prolapse groups were larger during Valsalva compared to controls (20.9±7.8cm2, p<.0001 for both); similarly, protrusion areas for the anterior (14.3±6.2cm2) and posterior (14.4±5.7cm2) were both larger than controls (5.0±1.8cm2, p<.0001 for both). The levator hiatus length for the anterior (7.2±1cm) and posterior (6.9±1cm) were longer during Valsalva compared to controls (5.2±1.5cm, p<.0001 for both); similarly, urogenital hiatus lengths for the anterior (5.7±1cm) and posterior (6.3±1.1cm) were both longer than controls (3.8±0.8cm, p<.0001 for both). The difference in levator area in prolapse patients compared with controls was greater than the difference in protrusion area (14.0 ± 7.2cm2 v. 9.4 ± 5.9cm2, p<.0002). The urogenital was more strongly associated with prolapse than the levator hiatus (OR: 12.9, 95% CI: (4.1–39.2), OR: 4.3, 95% CI: (2.3–7.5)). Levator hiatus and urogenital hiatus are both correlated with levator and protrusion areas, and all were associated with maximum prolapse size (p≤0.001, for all comparisons). Conclusions In prolapse, the levator area increases more than the protrusion area and both the urogenital hiatus and levator hiatus are larger. The odds of prolapse for an increase in the urogenital hiatus are three times larger than for the levator hiatus, which leads us to reject both the original hypotheses.

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“…Diffusion tensor MRI imaging allows the orientation of the muscle fibers to be determined and specially the orientation of each fiber of the LAM relative to a horizontal direction going through the lower edge of the pubis on a sagittal section to be measured [8]. The average angle made by the fibers of the PVM, the PRM, and the ICM and the horizontal axis were determined to be: 41+/-8°, -19+/-10°, and 33+/-8,8°, respectively with a difference of 60° between the PVM and the PRM.…”

Section: Normal and Pathological Presentation Of The Lam By Mrimentioning

confidence: 99%

The Ilio-Coccygeus Muscle (ICM) Does it have an Enabling Role in Urination?

Guerquin¹

2017

Anat Physiol

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An analysis of the literature has allowed for a redefinition of the anatomy of the ilio-coccygeus muscle (ICM) its insertions and its trajectory, the direction of its fibers and its relation to the base of the bladder. Static MRI studies have revealed its V-shaped appearance, while dynamic MRI has been used to visualize its concave contraction into a dome-shape that provides support to the levator plate, raising the base of the bladder. Histological studies have shown that the percentage of type I muscle fibers is 66% to 69%, which is comparable to the type I fiber content of the pubovisceral muscle (PVM), thus reflecting both its postural role as well as functions based on frequent voluntary contractions. Together, these data suggest an active role for the ICM which, upon urination, allows for voluntary hardening of the levator plate. The abdominal pressure from bearing down hence enables urinary draining by compressing the bladder on a hard surface. The physiological function of the ICM is therefore not only postural, but also to enable urination. From a therapeutic perspective, a multicentric study has shown that, by reinforcing the action of the ICM, use of a Diveen intrauterine device improved dysuria.

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Comparison of muscle fiber directions between different levator ani muscle subdivisions: in vivo MRI measurements in women

Cited by 52 publications

References 26 publications

Finite element model focused on stress distribution in the levator ani muscle during vaginal delivery

Finite element model focused on stress distribution in the levator ani muscle during vaginal delivery

Interactions among pelvic organ protrusion, levator ani descent, and hiatal enlargement in women with and without prolapse

The Ilio-Coccygeus Muscle (ICM) Does it have an Enabling Role in Urination?

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