Three-dimensional finite element analysis of the pelvic organ prolapse: A parametric biomechanical modeling

An estimation of the biomechanical properties of the continent and incontinent woman bladder via inverse finite element analysis

Stress urinary incontinence often results from pelvic support structures' weakening or damage. This dysfunction is related to direct injury of the pelvic organ's muscular, ligamentous or connective tissue structures due to aging, vaginal delivery or increase of the intra-abdominal pressure, for example, defecation or due to obesity. Mechanical changes alter the soft tissues' microstructural composition and therefore may affect their biomechanical properties. This study focuses on adapting an inverse finite element analysis to estimate the in vivo bladder's biomechanical properties of two groups of women (continent group (G1) and incontinent group (G2)). These properties were estimated based on MRI, by comparing measurement of the bladder neck's displacements during dynamic MRI acquired in Valsalva maneuver with the results from inverse analysis. For G2, the intra-abdominal pressure was adjusted after applying a 95% impairment to the supporting structures. The material parameters were estimated for the two groups using the Ogden hyperelastic constitutive model. Finite element analysis results showed that the bladder tissue of women with stress urinary incontinence have the highest stiffness (α1 = 0.202 MPa and µ1 = 7.720 MPa) approximately 47% higher when compared to continent women. According to the bladder neck's supero-inferior displacement measured in the MRI, the intra-abdominal pressure values were adjusted for the G2, presenting a difference of 20% (4.0 kPa for G1 and 5.0 kPa for G2). The knowledge of the pelvic structures' biomechanical properties, through this non-invasive methodology, can be crucial in the choice of the synthetic mesh to treat dysfunction when considering personalized options.

Toward Patient-specific Pessary to Manage Pelvic Organ Prolapse: Design and Simulation

This study proposed a novel design and personalized approach to developing an intra-vaginal device, also known as a pessary, for the treatment of Pelvic Organ Prolapse (POP). Although POP is likely to have a more diverse dynamic than other health conditions in women, it is currently treated as a "one-shape-fits-all" problem in all cases. Pessaries are conservative devices inserted into the vagina to support its internal structure and predominantly come in a ring shape design. Failure rates as high as 50% within the first year of use have been attributed to the poor design of these pessaries; with symptoms such as irritation, bleeding, and lacerations felt by most users. To address this problem, a new base shape design was proposed and its deformation was examined using Finite Element Analysis (FEA). Based on the anatomical measurements of each patient, the base design can be adjusted accordingly. To demonstrate the effectiveness of the proposed design, a comparative study was conducted with the most commonly used support pessary, also known as the ring pessary. In order to model the large deformation of the pessaries, the hyperelastic constitutive law (Yeoh model) was fitted to the available stress-strain data of SIL 30 (a silicone urethane resin supplied by Carbon Inc.). The results showed that re-directing the reaction forces of the pessary towards the lateral walls, supported by the pelvic bones, could decrease the overall displacement of the pessaries, and provide effective symptomatic relief thereby, delaying or preventing surgical procedures.Clinical relevance- There is a clear clinical need to develop a more effective conservative therapy for managing POP. The personalized pessaries proposed in this paper can be an effective method for providing symptomatic relief and avoiding displacement, compared to the currently available devices on the market. Made-to-measure for each patient, the devices are anatomically suited and can be adjusted throughout a patient's treatment plan to allow for higher compliance and overall success rate.

Pelvic Organ Prolapse and Its Associated Factors Among Women Attending the Gynecology Outpatient Clinic at a Tertiary Hospital in Southwestern Uganda

Purpose

To determine the prevalence, clinical stage at presentation and factors associated with pelvic organ prolapse (POP) among women attending the gynecology outpatient clinic at Mbarara Regional Referral Hospital (MRRH), Uganda.

Methods

We conducted a cross-sectional study at the gynecology outpatient clinic of MRRH from September 2019 to January 2020. Women aged 18–90 years were systematically sampled and recruited into this study. An interviewer administered questionnaire was used to collect participants’ socio-demographic, obstetric, gynecological and medical factors. POP stage was obtained by using the pelvic organ prolapse-quantification system. Multivariable logistic regression analysis was done to determine factors associated with pelvic organ prolapse.

Results

Of 338 participants enrolled, the prevalence of POP was 27.5% [n = 93, 95% Cl: 23.0–32.5]. POP stages were stage I 11.8% (n = 11), stage II 63.4% (n = 59), stage III 16.1% (n = 15) and stage IV 8.9% (n = 8). Grand-multiparity (aOR 17.1, 95% CI: 1.1–66.6), birth weight more than 3.5kg (aOR 3.7, 95% CI: 1.1–12.6), perineal tears (aOR 6.5, 95% CI: 2.1–20.2), peasant farmer (aOR 6.9, 95% CI: 1.6–29.9) and duration of labour in the first delivery >24 hours (aOR 5.7, 95% CI: 1.2–29) were significantly associated with POP.

Conclusion

POP is common among women attending the gynecology clinic at MRRH with most of them presenting with stage II. There should be routine screening for POP to enable early identification and management especially in those who are grand multiparous, peasant farmers and have a history of perineal tears.

Uterus Modeling from Cell to Organ Level: towards Better Understanding of Physiological Basis of Uterine Activity

The relatively limited understanding of the physiology of uterine activation prevents us from achieving optimal clinical outcomes for managing serious pregnancy disorders such as preterm birth or uterine dystocia. There is increasing awareness that multi-scale computational modeling of the uterus is a promising approach for providing a qualitative and quantitative description of uterine physiology. The overarching objective of such approach is to coalesce previously fragmentary information into a predictive and testable model of uterine activity that, in turn, informs the development of new diagnostic and therapeutic approaches to these pressing clinical problems. This article assesses current progress towards this goal. We summarize the electrophysiological basis of uterine activation as presently understood and review recent research approaches to uterine modeling at different scales from single cell to tissue, whole organ and organism with particular focus on transformative data in the last decade. We describe the positives and limitations of these approaches, thereby identifying key gaps in our knowledge on which to focus, in parallel, future computational and biological research efforts.

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

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 cmH2O) 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.