Effect of mesh anchoring technique in uterine prolapse repair surgery: A finite element analysis.

The female pelvic cavity involves muscles, ligaments, endopelvic fasciae and multiple organs where different pathologies may occur, namely the pelvic organ prolapse (POP). The synthetic implants are used for the reconstructive surgery of POP, but severe complications associated with their use have been reported, mainly related to their mechanical properties (e.g., implant stiffness) and microstructure. In this study, we mimicked a transvaginal reconstructive surgery to repair the apical ligaments (uterosacral ligaments (USLs) and cardinal ligaments (CLs)), by modeling, their impairment (90% and 50%) and/or total rupture. The implants to reinforce/replace these ligaments were built based on literature specifications and their mechanical properties were obtained through uniaxial tensile tests. The main aim of this study was to simulate the effect of mesh anchoring technique (simple stich and continuous stitch), and compare the displacement magnitude of the pelvic tissues, during Valsalva maneuver. The absence/presence of the synthetic implant was simulated when total rupture of the CLs and USLs occurs, causing a variation of the vaginal displacement (9% for the CLs and 27% for the USLs). Additionally, the simulations showed that there was a variation of the supero-inferior displacement of the vaginal wall between different anchoring techniques (simple stich and continuous stitch) being approximately of 10% for the simulation USLs and CLs implant. The computational simulation was able to mimic the biomechanical behavior of the USLs and CLs, in response to different anchoring techniques, which can be help improving the outcomes of the prolapse surgery.

The Effects of Tooth Brushing on Whole Salivary Flow Rate in Older Adults.

OBJECTIVES: (1) To determine whether manual (MTB), or electric, tooth brushing (ETB) modulates whole salivary flow rate in older adults who are free of systemic disease. (2) To determine the duration of the brushing-related modulation of salivary flow rate. (3) To compare salivary flow rate modulation associated with MTB and ETB. METHOD: Twenty-one adults aged 60 years and older participated in two experimental sessions during which they used a manual, or electric, toothbrush to brush their teeth, tongue, and palate. Whole salivary flow rates were determined using the draining method before, during, and after brushing. Differences in salivary flow rates across time periods, and between conditions, were examined using paired samples t-tests applying a Holm-Bonferroni sequential procedure (pcorr < 0.0045). The relationship between tooth brushing and age with respect to maximum salivary flow rate increase was examined using Pearson's correlation coefficient (p < 0.05). RESULTS/CONCLUSION: Whole salivary flow rates increased during, and for up to 5 minutes following, tooth brushing in adults aged 60 years and older who were free of systemic disease. The salivary effects of MTB and ETB were not significantly different. A moderate, positive correlation was observed between tooth-brushing-related maximum salivary flow rate increase and age.

Characterization of the passive and active material parameters of the pubovisceralis muscle using an inverse numerical method.

The mechanical characteristics of the female pelvic floor are relevant to understand pelvic floor dysfunctions (PFD), and how they are related with changes in their biomechanical behavior. Urinary incontinence (UI) and pelvic organ prolapse (POP) are the most common pathologies, which can be associated with changes in the mechanical properties of the supportive structures in the female pelvic cavity. PFD have been studied through different methods, from experimental tensile tests using tissues from fresh female cadavers or tissues collected at the time of a transvaginal hysterectomy procedure, or by applying imaging techniques. In this work, an inverse finite element analysis (FEA) was applied to understand the passive and active behavior of the pubovisceralis muscle (PVM) during Valsalva maneuver and muscle active contraction, respectively. Individual numerical models of women without pathology, with stress UI (SUI) and POP were built based on magnetic resonance images, including the PVM and surrounding structures. The passive and active material parameters obtained for a transversely isotropic hyperelastic constitutive model were estimated for the three groups. The values for the material constants were significantly higher for the women with POP when compared with the other two groups. The PVM of women with POP showed the highest stiffness. Additionally, the influence of these parameters was analyzed by evaluating their stress-strain, and force-displacements responses. The force produced by the PVM in women with POP was 47% and 82% higher when compared to women without pathology and with SUI, respectively. The inverse FEA allowed estimating the material parameters of the PVM using input information acquired non-invasively.

Biomechanical properties of the pelvic floor muscles of continent and incontinent women using an inverse finite element analysis.

Pelvic disorders can be associated with changes in the biomechanical properties in the muscle, ligaments and/or connective tissue form fascia and ligaments. In this sense, the study of their mechanical behavior is important to understand the structure and function of these biological soft tissues. The aim of this study was to establish the biomechanical properties of the pelvic floor muscles of continent and incontinent women, using an inverse finite element analysis (FEA). The numerical models, including the pubovisceral muscle and pelvic bones were built from magnetic resonance (MR) images acquired at rest. The numerical simulation of Valsalva maneuver was based on the finite element method and the material constants were determined for different constitutive models (Neo-Hookean, Mooney-Rivlin and Yeoh) using an iterative process. The material constants (MPa) for Neo-Hookean (c1) were 0.039 ± 0.022 and 0.024 ± 0.004 for continent vs. incontinent women. For Mooney-Rivlin (c1) the values obtained were 0.026 ± 0.010 vs. 0.016 ± 0.003, and for Yeoh (c1) the values obtained were 0.031 ± 0.023 vs. 0.016 ± 0.002, (p < 0.05). Muscle displacements obtained in the numerical simulations of Valsalva maneuver were compared with the muscle displacements obtained through additional dynamic MRI. Incontinent women presented a higher antero-posterior displacement than the continent women. The results were also similar between MRI and numerical simulations (40.27% vs. 42.17% for Neo-Hookean, 39.87% for Mooney-Rivlin and 41.61% for Yeoh). Using an inverse FEA coupled with MR images allowed to obtain the in vivo biomechanical properties of the pelvic floor muscles, leading to a relationship between them for the continent and incontinent women in a non-invasive manner.

Establishing the biomechanical properties of the pelvic soft tissues through an inverse finite element analysis using magnetic resonance imaging.

The mechanical characteristics of the female pelvic floor are relevant when explaining pelvic dysfunction. The decreased elasticity of the tissue often causes inability to maintain urethral position, also leading to vaginal and rectal descend when coughing or defecating as a response to an increase in the internal abdominal pressure. These conditions can be associated with changes in the mechanical properties of the supportive structures-namely, the pelvic floor muscles-including impairment. In this work, we used an inverse finite element analysis to calculate the material constants for the passive mechanical behavior of the pelvic floor muscles. The numerical model of the pelvic floor muscles and bones was built from magnetic resonance axial images acquired at rest. Muscle deformation, simulating the Valsalva maneuver with a pressure of 4 KPa, was compared with the muscle displacement obtained through additional dynamic magnetic resonance imaging. The difference in displacement was of 0.15 mm in the antero-posterior direction and 3.69 mm in the supero-inferior direction, equating to a percentage error of 7.0% and 16.9%, respectively. We obtained the shortest difference in the displacements using an iterative process that reached the material constants for the Mooney-Rivlin constitutive model (c10=11.8 KPa and c20=5.53 E-02 KPa). For each iteration, the orthogonal distance between each node from the group of nodes which defined the puborectal muscle in the numerical model versus dynamic magnetic resonance imaging was computed. With the methodology used in this work, it was possible to obtain in vivo biomechanical properties of the pelvic floor muscles for a specific subject using input information acquired non-invasively.

Urinary Incontinence and Levels of Regular Physical Exercise in Young Women.

The purpose of this study was to determine the influence of different levels of regular physical exercise on the frequency of urinary incontinence in young nulliparous women from the northern region of Portugal. Participants (n=386) self-reported demographic variables, frequency, and time spent practicing organized exercise per week, as well as completed the International Consultation on Incontinence Questionnaire-Short Form. The level of exercise was calculated based on the time (in minutes) usually spent per week in organized exercise. 19.9% of Portuguese nulliparous women reported incontinence symptoms. Considering the distribution of urinary incontinence among the different quartiles of organized exercise, women from the 4(th)quartile (those who train for competitive purposes) demonstrated highest relative frequency (p=0.000) and a 2.53 greater relative risk to develop (95% CIs,1.3-2.7) incontinence compared to women from the 1(st) quartile (inactive). Women who practice exercise for recreational purposes (2(nd) and 3(rd) quartiles) did not show significant differences in the urinary incontinence prevalence and relative risk of developing it compared to women from the 1(st) quartile. The results showed that women participating in organized exercise involving high volume training for competition are potentially at risk of developing urinary incontinence, although organized exercise undertaken without the intent to compete seems to be safe for maintaining urinary continence.

Study on the influence of the fetus head molding on the biomechanical behavior of the pelvic floor muscles, during vaginal delivery.

Pelvic floor injuries during vaginal delivery are considered a significant risk factor to develop pelvic floor dysfunction. The molding of the fetus head during vaginal delivery facilitates the labor progress, since it adjusts to the birth canal geometry. In this work, a finite element model was used to represent the effects induced by the passage of the fetus head on the pelvic floor. The numerical model used for this simulation included the pelvic floor muscles attached to the bones, and a fetus body. The model of the fetus head included the skin and soft tissues, the skull with sutures and fontanelles, and the brain. The fetus head movements during birth in vertex position were simulated: descent, internal rotation and extension. Two models of the fetus head were compared: a rigid and a deformable one, with the inclusion of the cranial sutures. The influence of the fetus head molding on the pelvic floor muscles was analyzed by evaluating their reaction forces, stretch, and stress and strain fields. Additionally, anatomical indices for the molding of the fetal skull were obtained and compared with clinical data. The passage of the deformable fetus head through the birth canal leads to a reduction of 17.3% on the reaction forces on the pelvic floor muscles when compared to the ones of a rigid head. Furthermore, the fetus head molding implies inferior resistance to rotation resulting in a reduction of 1.86% in muscle stretching. Quantitative evaluation of the fetus head molding showed good agreement with clinical experiments.

Do asymptomatic former high-impact sports practitioners maintain the ability to contract the pelvic floor muscles?

AIM: Sports are associated with pelvic floor dysfunction. This work aimed to assess, in nulliparous asymptomatic women, whether previous intense practice of high-impact sports is associated with differences in morphology and contraction of the pelvic floor muscles, when compared to women who practiced low-level physical activity. METHODS: In this prospective pilot study, 7 former high-impact sports practitioners and a control group (N.=7) were compared. Clinical evaluation and self-administered questionnaires were used to gather information about pelvic floor dysfunction and physical activity. Static and cine dynamic MR images were acquired. Morphological measures of the pubovisceral muscle area and thickness, and levator hiatus (LH) anterior-to-posterior diameter, width and area were taken in the static images. LH anterior-to-posterior diameter was again assessed in the dynamic acquisition (consecutive blocks of rest vs. maximal voluntary contraction). The relative variation between these two conditions was used as an indirect measure of contraction. RESULTS: No abnormal clinical or imaging findings were reported. Former high-impact sports practitioners evidenced decreased pubovisceral muscle thickness (right side P=0.005; left side P=0.004) and area (P=0.004), and larger levator hiatus width and area (P=0.045; P=0.005). Only its anterior-to-posterior diameter was similar (4.89cm±0.35 and 4.81cm±0.17, respectively). Their ability to perform maximum voluntary contractions seems to have decreased (8.03%±0.81 vs. 13.74%±0.95 for controls). CONCLUSION: The current results suggest that women who previously practiced high-impact sports, even being asymptomatic, may have suffered damage to the pelvic floor muscles due to the biomechanical impact of the sports. They may require pelvic floor muscle training to increase muscle thickness and hiatal closing capacity.

Prevalence and conditions associated with chronic pelvic pain in women from São Luís, Brazil

The objective of the present study was to estimate the prevalence of chronic pelvic pain in the community of São Luís, capital of the State of Maranhão, Northeastern Brazil, and to identify independent conditions associated with it. A cross-sectional study was conducted, including a sample of 1470 women older than 14 years predominantly served by the public health system. The interviews were held in the subject's home by trained interviewers not affiliated with the public health services of the municipality. The homes were visited at random according to the city map and the prevalence of the condition was estimated. To identify the associated conditions, the significant variables (P=0.10) were selected and entered in a multivariate analysis model. Data are reported as odds ratio and 95% confidence interval, with the level of significance set at 0.05. The prevalence of chronic pelvic pain was 19.0%. The independent conditions associated with this diagnosis were: dyspareunia (OR=3.94), premenopausal status (OR=2.95), depressive symptoms (OR=2.33), dysmenorrhea (OR=1.77), smoking (OR=1.72), irregular menstrual flow (OR=1.62), and irritative bladder symptoms (OR=1.90). The prevalence of chronic pelvic pain in Sao Luís is high and is associated with the conditions cited above. Guidelines based on prevention and/or early identification of risk factors may reduce the prevalence of chronic pelvic pain in São Luís, Brazil.

Prevalence and conditions associated with chronic pelvic pain in women from São Luís, Brazil.

The objective of the present study was to estimate the prevalence of chronic pelvic pain in the community of São Luís, capital of the State of Maranhão, Northeastern Brazil, and to identify independent conditions associated with it. A cross-sectional study was conducted, including a sample of 1470 women older than 14 years predominantly served by the public health system. The interviews were held in the subject's home by trained interviewers not affiliated with the public health services of the municipality. The homes were visited at random according to the city map and the prevalence of the condition was estimated. To identify the associated conditions, the significant variables (P=0.10) were selected and entered in a multivariate analysis model. Data are reported as odds ratio and 95% confidence interval, with the level of significance set at 0.05. The prevalence of chronic pelvic pain was 19.0%. The independent conditions associated with this diagnosis were: dyspareunia (OR=3.94), premenopausal status (OR=2.95), depressive symptoms (OR=2.33), dysmenorrhea (OR=1.77), smoking (OR=1.72), irregular menstrual flow (OR=1.62), and irritative bladder symptoms (OR=1.90). The prevalence of chronic pelvic pain in Sao Luís is high and is associated with the conditions cited above. Guidelines based on prevention and/or early identification of risk factors may reduce the prevalence of chronic pelvic pain in São Luís, Brazil.

A level set based algorithm to reconstruct the urinary bladder from multiple views.

The urinary bladder can be visualized from different views by imaging facilities such as computerized tomography and magnetic resonance imaging. Multi-view imaging can present more details of this pelvic organ and contribute to a more reliable reconstruction. Based on the information from multi-view planes, a level set based algorithm is proposed to reconstruct the 3D shape of the bladder using the cross-sectional boundaries. The algorithm provides a flexible solution to handle the discrepancies from different view planes and can obtain an accurate bladder surface with more geometric details.

Oxford Grading Scale vs manometer for assessment of pelvic floor strength in nulliparous sports students.

OBJECTIVES: To compare pelvic floor muscle strength in nulliparous sports students measured using the modified Oxford Grading Scale and a Peritron manometer; and to compare the manometric measurements between continent and incontinent subjects. DESIGN: Cross-sectional study. All subjects were evaluated twice on the same day; first by vaginal digital examination and subsequently by vaginal pressure using a Peritron manometer. PARTICIPANTS: Forty-three nulliparous female sports students [mean age 21 (standard deviation 4) years] from the Sports Faculty of the University of Porto. RESULTS: This study found a significant moderate correlation between the Oxford Grading Scale score and peak pressure on manometry (r=0.646, P=0.002). Mean maximal strength for the entire group was 70.4cmH2O (range 21 to 115cmH2O). Out of 43 subjects, 37% (n=16) demonstrated signs of incontinence. On manometry, no significant differences were found in vaginal resting pressure or peak pressure between the continent and incontinent groups. CONCLUSIONS: There was moderate correlation between peak pressure on manometry and the Oxford Grading Scale score. Peritron manometer measurements of pelvic floor muscle contractions showed no significant differences in vaginal resting pressure and peak pressure in continent and incontinent subjects.

Mechanical characterization and constitutive modelling of the damage process in rectus sheath.

The aim of this study is to characterize and model the damage process in the anterior rectus abdominal aponeurosis (anterior rectus sheath) undergoing finite deformations. The resistance of the anterolateral abdominal aponeuroses is important when planning the surgical repair of incisional hernias, among other medical procedures. Previous experiments in prolapsed vaginal tissue revealed that a softening process occurs before tissue rupture. This nonlinear damage behaviour requires a continuum damage theory commonly used to describe the softening behaviour of soft tissues under large deformations. The structural model presented here was built within the framework of non-linear continuum mechanics. Tissue damage was simulated considering different damage behaviours for the matrix and the collagen fibres. The model parameters were fit to the experimental data obtained from anterior rectus sheath samples undergoing finite deformations in uniaxial tension tests. The tests were carried out with samples cut along the direction of the collagen fibres, and transversal to the fibres. Longitudinal and transverse mechanical properties of human anterior rectus sheath are significantly different. The damage model was able to predict the stress-strain behaviour and the damage process accurately. The error estimations pointed to an excellent agreement between experimental results and model fittings. For all the fitted data, the normalized RMS error ε presented very low values and the coefficient of determination R(2) was close to 1. The present work constitutes the first attempt (as far as the authors know) to present a damage model for the human rectus sheath.

Segmentation of female pelvic cavity in axial T2-weighted MR images towards the 3D reconstruction.

The anatomies of pelvic structures are critical for the diagnosis of pelvic floor dysfunctions. However, because of the complex background, the imaging appearances of pelvic organs and muscles are frequently distorted by noise and partial volume effect. Magnetic resonance imaging with its clear imaging quality of the female pelvic cavity is preferred for many studies. As such, correct segmentations of the pelvic structures on MR images are required for accurate diagnoses. Effective algorithms for axial T2-weighted MR images have been proposed, which are based on the imaging features of different structures and various image clues. In this paper, we review these algorithms and evaluate their performance, and discuss implementation issues and aspects towards constructing the three-dimensional models.

Novel approach to segment the inner and outer boundaries of the bladder wall in T2-weighted magnetic resonance images.

Diagnosis of bladder-related conditions needs critical measurements which require the segmentation of the inner and outer boundaries of the bladder wall. In T2-weighted MR images, the low-signal intensity bladder wall can be identified due to the large contrast with the high-signal intensity urine and perivesical fat. In this article, two deformable models are proposed to segment the bladder wall. Based on the imaging features of the bladder, a modified geodesic active contour is proposed to segment the inner boundary. This method uses the statistical information of the bladder lumen and can handle the intensity variation in MR images. Having obtained the inner boundary, a shape influence field is formed and integrated with the Chan-Vese (C-V) model to segment the outer boundary. The shape-guided C-V model can prevent the overlapping between the two boundaries when the appearance of the bladder wall is blurred. Segmentation examples are presented and analyzed to demonstrate the effectiveness of this novel approach.

An approach on determining the displacements of the pelvic floor during voluntary contraction using numerical simulation and MRI.

The present study was conducted in order to establish a methodology based on the finite element method to simulate the contraction of the pelvic floor (PF) muscles. In the generated finite element model, a downward pressure of 90 cm H(2)O was applied, while actively contracting the PF muscles with different degrees of muscular activation (10, 50 and 100%). The finite element methodology of the active contraction behaviour proposed in this study is adequate to simulate PF muscle contraction with different degrees of muscular activation. In this case, in particular, for an activation of 100%, the numerical model was able to displace the pubovisceral muscle in a range of values very similar to the displacement found in the magnetic resonance imaging data. In the analysed case study, it would be possible to conclude that an intensity contraction of 50% would be necessary to produce enough stiffness to avoid possible urine loss.

Mechanical characterization of the softening behavior of human vaginal tissue.

The mechanical properties of vaginal tissue need to be characterized to perform accurate simulations of prolapse and other pelvic disorders that commonly affect women. This is also a fundamental step towards the improvement of therapeutic techniques such as surgery. In this paper, the softening behavior or Mullins effect of vaginal tissue is studied by proposing an appropriate constitutive model. This effect is an important factor after the birth, since vaginal tissue has been supporting a high load distribution and therefore does not recover its original behavior. Due to the anisotropy of the tissue, the mechanical testing of vaginal tissue, consists in loading-unloading uniaxial tension tests performed along the longitudinal and transverse axes of the vagina. A directional pseudo-elastic model was used to reproduce the inelastic behavior of the tissue. The obtained results may be helpful in the design of surgical procedures with autologous tissue or smart prostheses. A good qualitative agreement has been found between the numerical and experimental results for the vaginal tissue examples, indicating that the constitutive softening model can capture the typical stress-strain behavior observed in this kind of fibrous soft tissue.

Prediction of nonlinear elastic behaviour of vaginal tissue: experimental results and model formulation.

The mechanical properties of the vaginal tissue need to be characterised to perform accurate simulations of prolapse and other pelvic disorders that commonly affect women. This is also a fundamental step towards the improvement of therapeutic techniques such as surgery. Issues like the efficiency of using autologous tissue in pelvic reconstruction may be addressed. The goal of this study was to characterise the elastic behaviour of vaginal tissue. For this purpose, prolapsed vaginal tissue from eight different post-menopausal patients, excised during prolapse corrective surgery, was mechanically tested. The mechanical testing of vaginal tissue, consisting of uniaxial tension tests performed along the longitudinal axis of the vagina, revealed the nonlinear mechanical behaviour of the tissue. The material model parameters were fit to the experimental data using the Levenberg-Marquardt optimisation algorithm. All the curve fittings showed a good agreement between experimental and theoretical results, evidenced by R² values close to 1 and by very low ε values.

A review of algorithms for medical image segmentation and their applications to the female pelvic cavity.

This paper aims to make a review on the current segmentation algorithms used for medical images. Algorithms are classified according to their principal methodologies, namely the ones based on thresholds, the ones based on clustering techniques and the ones based on deformable models. The last type is focused on due to the intensive investigations into the deformable models that have been done in the last few decades. Typical algorithms of each type are discussed and the main ideas, application fields, advantages and disadvantages of each type are summarised. Experiments that apply these algorithms to segment the organs and tissues of the female pelvic cavity are presented to further illustrate their distinct characteristics. In the end, the main guidelines that should be considered for designing the segmentation algorithms of the pelvic cavity are proposed.

Experimental study and constitutive modeling of the viscoelastic mechanical properties of the human prolapsed vaginal tissue.

In this paper, the viscoelastic mechanical properties of vaginal tissue are investigated. Using previous results of the authors on the mechanical properties of biological soft tissues and newly experimental data from uniaxial tension tests, a new model for the viscoelastic mechanical properties of the human vaginal tissue is proposed. The structural model seems to be sufficiently accurate to guarantee its application to prediction of reliable stress distributions, and is suitable for finite element computations. The obtained results may be helpful in the design of surgical procedures with autologous tissue or prostheses.