scholarly journals Biomechanical trade-offs in the pelvic floor constrain the evolution of the human birth canal

2021 ◽  
Vol 118 (16) ◽  
pp. e2022159118 ◽  
Author(s):  
Ekaterina Stansfield ◽  
Krishna Kumar ◽  
Philipp Mitteroecker ◽  
Nicole D. S. Grunstra
Keyword(s):  
Pelvic Floor ◽  
Element Model ◽  
Original Position ◽  
Abdominal Pressure ◽  
Fetal Head ◽  
Birth Canal ◽  
Trade Offs ◽  
Resistance To Deformation ◽  
Inner Organs ◽  
Tissue Stresses

Compared with most other primates, humans are characterized by a tight fit between the maternal birth canal and the fetal head, leading to a relatively high risk of neonatal and maternal mortality and morbidities. Obstetric selection is thought to favor a spacious birth canal, whereas the source for opposing selection is frequently assumed to relate to bipedal locomotion. Another, yet underinvestigated, hypothesis is that a more expansive birth canal suspends the soft tissue of the pelvic floor across a larger area, which is disadvantageous for continence and support of the weight of the inner organs and fetus. To test this “pelvic floor hypothesis,” we generated a finite element model of the human female pelvic floor and varied its radial size and thickness while keeping all else constant. This allowed us to study the effect of pelvic geometry on pelvic floor deflection (i.e., the amount of bending from the original position) and tissue stresses and stretches. Deflection grew disproportionately fast with increasing radial size, and stresses and stretches also increased. By contrast, an increase in thickness increased pelvic floor stiffness (i.e., the resistance to deformation), which reduced deflection but was unable to fully compensate for the effect of increasing radial size. Moreover, larger thicknesses increase the intra-abdominal pressure necessary for childbirth. Our results support the pelvic floor hypothesis and evince functional trade-offs affecting not only the size of the birth canal but also the thickness and stiffness of the pelvic floor.

scholarly journals Relationship Between High Intra-Abdominal Pressure and Compliance of the Pelvic Floor Support System in Women Without Pelvic Organ Prolapse: A Finite Element Analysis

2021 ◽  
Author(s):  
Xiaode Liu ◽  
Qiguo Rong ◽  
Jianliu Wang ◽  
Bing Xie ◽  
Shuang Ren
Keyword(s):  
Finite Element ◽  
Pelvic Organ Prolapse ◽  
Finite Element Model ◽  
Pelvic Floor ◽  
Support System ◽  
Element Model ◽  
Pelvic Organ ◽  
Abdominal Pressure ◽  
Pelvic Support ◽  
Pelvic Floor Support

Abstract Background: The objective of this study was to study the relationship between high intra-abdominal pressure and the compliance of the pelvic floor support system in a normal woman without pelvic organ prolapse (POP), using a finite element model of the whole pelvic support system.Methods: A healthy female volunteer (55 years old) was scanned using magnetic resonance imaging (MRI) during the Valsalva maneuver. According to the pelvic structure contours traced by a gynecologist and anatomic details measured from dynamic MRI, a finite element model of the whole pelvic support system was established, including the uterus, vagina with cavity, cardinal and uterosacral ligaments, levator ani muscle, rectum, bladder, perineal body, pelvis, and obturator internus and coccygeal muscles. This model was imported into ANSYS software, and an implicit iterative method was employed to simulate the biomechanical response with increasing intra-abdominal pressure.Results: Stress and strain distributions of the vaginal wall showed that the posterior wall was more stable than the anterior wall under high intra-abdominal pressure. Displacement at the top of the vagina was larger than that at the bottom, especially in the anterior–posterior direction.Conclusion: These results imply potential injury areas with high intra-abdominal pressure in non-prolapsed women, and provide insight into clinical managements for the prevention and surgical repair plans of POP.

scholarly journals Strength of pelvic floor in men: reliability intra examiners

2018 ◽  
Vol 31 (0) ◽  
Author(s):  
Patricia Zaidan ◽  
Fabio Dutra Pereira ◽  
Elirez Bezerra da Silva
Keyword(s):  
Pelvic Floor ◽  
Physical Therapist ◽  
High Reliability ◽  
Intraclass Correlation ◽  
Internal Consistency Reliability ◽  
Urinary Continence ◽  
Abdominal Pressure ◽  
Strength Assessment ◽  
Male Patients ◽  
The Moment

Abstract Introduction: The obtaining of urinary continence is due to the strength of the pelvic floor muscles (MAPs) at the moment of muscle contraction, when there are sudden increases in intra-abdominal pressure, which increases urethral closure pressure and decreases the possibility of urinary loss. Objective: To verify the reliability, type: stability, intra-examiner, of the measure of the strength of MAPs held with Peritron. Methods: Test and retest study to assess the intra-rater reliability of Peritron to measure the strength of MAPs. The sample consisted of 36 male patients, mean age 65.3 ± 7.2 years, all with urinary incontinence (UI) after radical prostatectomy. The physical therapist conducted a training for familiarization with the procedures of MAPs strength assessment with Peritron for two weeks. The strength of MAPs was measured by a perineometer of the Peritron brand (PFX 9300®, Cardio-Design Pty. Ltd, Baulkham Hills, Australia, 2153). Results: The intraclass correlation coefficient (ICC) was equal to 0.99; P = 0.0001. The typical measurement error (ETM) was equal to 3.1 cmH2O and ETM% of 4. Conclusion: Peritron showed high reliability for measuring the strength of MAPs in men, both for clinical practice and for the production of scientific knowledge. It should be noted that such measures were carried out in stability, so it is suggested that in internal consistency reliability is equivalent.

Large Vessel Nozzle Penetration Geometric Optimisation Study in 3D Incorporating Design of Experiments Techniques

2012 ◽  
Author(s):  
Adam Towse ◽  
Michael Martin ◽  
Adrian Allen ◽  
Chris Andrews
Keyword(s):  
Pressure Vessel ◽  
Shell Thickness ◽  
Element Model ◽  
Structural Effects ◽  
Independent Variables ◽  
Trade Offs ◽  
Large Pressure ◽  
Full Factorial ◽  
Structural Influence ◽  
Geometric Optimisation

This paper describes the results of an optimisation study into the effects of changing geometrical variables local to the nozzle entry on a large pressure vessel. The purpose of the study was to quantify the effects of altering the geometry, and thereby provide trade-offs between key responses such as primary strength and shakedown performance. A 3D Finite Element model was built of a 90 degree sector of the pressure vessel which was sufficiently detailed to allow the thermal and structural effects of the vessel remote from the nozzle to be included. Specifically, this included the thermal and structural influence of the closure head and bolting assembly. The model was then parameterised for 5 independent variables, including the extent of the nozzle reinforcement, crotch corner fillet radius and nozzle thickness. The parameterised model was then subjected to a number of thermal and structural transient analyses during Level A operation, as well as a representative strength loadcase. A full factorial design study was undertaken, comprising of separate 243 analysis runs covering the 5 independent variables at 3 levels. A number of output metrics were monitored, and the effects on the output metrics resulting from changes to the inputs were quantified. Due to the full factorial nature of the experimental design, interactions between variables could also be investigated. The response for each output metric was then fitted to a response surface, which allows a polynomial (meta-model) of each metric to be calculated. These responses were input to a simple Excel chart which allows the designers to perform rapid what-if design scenarios, and see the resulting effects of their changes on the responses. This allows the trade-offs between responses, for example shakedown and strength trade-off for shell thickness, to be easily seen and quantified.

2. VAGINISMUS, VULVODYNIA AND PELVIC FLOOR MUSCLE ACTIVITY

Sexual Health ◽  
2007 ◽  
Vol 4 (4) ◽  
pp. 285
Author(s):  
R. Sapsford
Keyword(s):  
Pelvic Floor ◽  
Muscle Activity ◽  
Pelvic Floor Muscle ◽  
Normal Function ◽  
Pelvic Floor Muscles ◽  
Abdominal Pressure ◽  
Abdominal Muscles ◽  
Physiological Factors ◽  
Muscle Groups ◽  
Postural Support

The pelvic floor muscles form the base of the abdominal cylinder and work in synergy with other muscles around the cylinder - the abdominal muscles and the diaphragm. Activity in each muscle group affects the others. Coordinated recruitment of these muscle groups is necessary for generation and maintenance of intra-abdominal pressure, postural support of the trunk, and during functional tasks such as lifting, coughing and nose blowing. Coordinated release of these groups is required for micturition, while defaecation may need activity in some muscles and release in others. Vaginismus and vulvodynia both have a component of over activity of the pelvic floor muscles which impairs normal function, though this over activity may only occur at the time of attempted penetration. Some of the physiological factors that contribute to this overactivity come from outside the pelvic floor muscle complex itself and can be ameliorated by understanding and management of these muscle synergies. An EMG study of muscle activity of the abdominal and pelvic floor muscles during a simulated body posturing for female sexual arousal will help to explain how the pelvic floor muscle over activity in vaginismus arises. Treatment programmes that have been used to successfully address these problems will be explained.

scholarly journals Development of anatomically based customizable three-dimensional finite-element model of pelvic floor support system: POP-SIM1.0

2019 ◽  
Vol 9 (4) ◽  
pp. 20190022 ◽  
Author(s):  
Mark T. Gordon ◽  
John O. L. DeLancey ◽  
Aaron Renfroe ◽  
Andrew Battles ◽  
Luyun Chen
Keyword(s):  
Finite Element ◽  
Magnetic Resonance ◽  
Pelvic Floor ◽  
Support System ◽  
Structural Parameters ◽  
Vaginal Wall ◽  
Abdominal Pressure ◽  
Fe Model ◽  
Vaginal Length ◽  
Pelvic Floor Support

To develop an anatomically based customizable finite-element (FE) model of the pelvic floor support system to simulate pelvic organ prolapse (POP): POP-SIM1.0. This new simulation platform allows for the construction of an array of models that objectively represent the key anatomical and functional variation in women with and without prolapse to test pathomechanism hypotheses of the prolapse formation. POP-SIM1.0 consists of anatomically based FE models and a suite of Python-based tools developed to rapidly construct FE models by customizing the base model with desired structural parameters. Each model consists of anatomical structures from three support subsystems which can be customized based on magnetic resonance image measurements in women with and without prolapse. The customizable structural parameters include presence of levator ani (LA) avulsion, hiatus size, anterior vaginal wall dimension, attachment fascia length and apical location in addition to the tissue material properties and intra-abdominal pressure loading. After customization, the FE model was loaded with increasing intra-abdominal pressure (0–100 cmH 2 O) and solved using ABAQUS explicit solver. We were able to rapidly construct anatomically based FE models with specific structural geometry which reflects the morphology changes often observed in women with prolapse. At maximum loading, simulated structural deformations have similar anatomical characteristics to those observed during clinical exams and stress magnetic resonance images. Simulation results showed the presence of LA muscle avulsion negatively impacts the pelvic floor support. The normal model with intact muscle had the smallest exposed vaginal length of 11 mm, while the bilateral avulsion produced the largest exposed vaginal length at 24 mm. The unilateral avulsion model had an exposed vaginal length of 18 mm and also demonstrated a tipped perineal body similar to that seen in clinical observation. Increasing the hiatus size, vaginal wall length and fascia length also resulted in worse pelvic floor support, increasing the exposed vaginal length from 18 mm in the base model to 33 mm, 54 mm and 23.5 mm, respectively. The developed POP-SIM1.0 can simulate the anatomical structure changes often observed in women with prolapse. Preliminary results showed that the presence of LA avulsion, enlarged hiatus, longer vaginal wall and fascia length can result in larger prolapse at simulated maximum Valsalva.

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