Finite element modeling of maximum stress in pelvic floor structures during the head expulsion (FINESSE) study.

INTRODUCTION AND HYPOTHESIS: Several studies have assessed birth-related deformations of the levator ani muscle (LAM) and perineum on models that depicted these elements in isolation. The main aim of this study was to develop a complex female pelvic floor computational model using the finite element method to evaluate points and timing of maximum stress at the LAM and perineum in relation to the birth process. METHODS: A three-dimensional computational model of the female pelvic floor was created and used to simulate vaginal birth based on data from previously described real-life MRI scans. We developed three models: model A (LAM without perineum); model B (perineum without LAM); model C (a combined model with both structures). RESULTS: The maximum stress in the LAM was achieved when the vertex was 9 cm below the ischial spines and measured 37.3 MPa in model A and 88.7 MPa in model C. The maximum stress in the perineum occurred at the time of distension by the suboocipito-frontal diameter and reached 86.7 MPa and 119.6 MPa in models B and C, respectively, while the stress in the posterior fourchette caused by the suboccipito-bregmatic diameter measured 36.9 MPa for model B and 39.8 MPa for model C. CONCLUSIONS: Including perineal structures in a computational birth model simulation affects the level of stress at the LAM. The maximum stress at the LAM and perineum seems to occur when the head is lower than previously anticipated.

Persistent occiput posterior position and stress distribution in levator ani muscle during vaginal delivery computed by a finite element model.

INTRODUCTION AND HYPOTHESIS: Objective of this study was to develop an MRI-based finite element model and simulate a childbirth considering the fetal head position in a persistent occiput posterior position. METHODS: The model involves the pelvis, fetal head and soft tissues including the levator ani and obturator muscles simulated by the hyperelastic nonlinear Ogden material model. The uniaxial test was measured using pig samples of the levator to determine the material constants. Vaginal deliveries considering two positions of the fetal head were simulated: persistent occiput posterior position and uncomplicated occiput anterior position. The von Mises stress distribution was analyzed. RESULTS: The material constants of the hyperelastic Ogden model were measured for the samples of pig levator ani. The mean values of Ogden parameters were calculated as: µ1 = 8.2 ± 8.9 GPa; µ2 = 21.6 ± 17.3 GPa; α1 = 0.1803 ± 0.1299; α2 = 15.112 ± 3.1704. The results show the significant increase of the von Mises stress in the levator muscle for the case of a persistent occiput posterior position. For the optimal head position, the maximum stress was found in the anteromedial levator portion at station +8 (mean: 44.53 MPa). For the persistent occiput posterior position, the maximum was detected in the distal posteromedial levator portion at station +6 (mean: 120.28 MPa). CONCLUSIONS: The fetal head position during vaginal delivery significantly affects the stress distribution in the levator muscle. Considering the persistent occiput posterior position, the stress increases evenly 3.6 times compared with the optimal head position.

Obesity and its long-term impact on sacrocolpopexy key outcomes (OBELISK).

INTRODUCTION AND HYPOTHESIS: Sacrocolpopexy is the preferred contemporary approach to managing significant apical pelvic organ prolapse. Obesity is an established risk factor for several surgical procedures and can have a negative impact on outcomes. Our goal was to evaluate the impact of BMI on the safety and efficacy of laparoscopic sacrocolpopexy in women with pelvic organ prolapse. METHODS: A single-center retrospective observational study of women undergoing laparoscopic sacrocolpopexy between January 1, 2015, and December 31, 2017. RESULTS: We found 299 procedures: 82 (27.4%), 147 (49.2%) and 70 (23.4%) in women with BMI <25 (normal weight), BMI ≥ 25 - < 30 (overweight) and BMI ≥ 30 (obese), respectively. Perioperative and early postoperative complications were generally low and not statistically significantly different between the groups. At 12 months postoperatively, 81 (98.8%), 136 (92.5%) and 62 (88.6%) normal-weight, overweight and obese women attended their follow-up, respectively. All obese women attending the follow-up scored an overall Patient Global Impression of Improvement (PGI-I) of ≤ 3. The Pelvic Floor Distress Inventory (PFDI) scores showed a significant improvement in all domains and were similar between the study groups. In total, there was one (0.4%) anatomical apical compartment failure, three (1.1%) anterior compartment failures and two (0.7%) posterior compartment failures with no significant differences between the groups. Similarly, there were no differences in functional outcomes or mesh position as assessed by ultrasound. CONCLUSIONS: There were no differences in surgical, short- and long-term outcomes of laparoscopic sacrocolpopexy for pelvic organ prolapse in obese compared with non-obese women.

Metrics of perineal support (MOPS) study.

BACKGROUND: Manual perineal protection (MPP) is an intrapartum intervention suggested to protect perineal integrity during childbirth. Proper execution of MPP is complex and evaluation of its true contribution is difficult in the clinical setting because of the large number of obstetric variables, some of which are hardly quantifiable. In this study we aimed to gather initial data on the forces executed by the accoucheur's thumb, index and middle fingers during MPP at the time of fetal head expulsion, quantify the duration of the intervention and investigate the timely interaction of the different components of MPP. METHODS: Two bespoke right-handed measurement gloves (MG), with built in sensors, were designed and produced. The MG allowed the electronic real-time measurement of applied forces during MPP and transferred this data wirelessly to an integrated computer system. Sterile gloves were worn over the MG when used at the time of birth. The study was undertaken between January and December 2019. Singleton, term pregnant women having their first vaginal birth who provided a valid written consent were enrolled into this prospective pilot study. All deliveries were undertaken by one of two obstetricians experienced in MPP. RESULTS: Twenty women were enrolled. The mean duration of execution of MPP during the last contraction was 13.6 s. In 20% it lasted < 5 s. The overall mean values of the average and maximum forces of the thumb, index and middle fingers were 26.7 N; 25.5 N; 20.2 N and 34.3 N; 32.6 N; and 27.6 N respectively. The onset of fingers and thumb activity was simultaneous in 13 cases (65%), while in seven (35%) deliveries the middle finger's force activity was initiated later. CONCLUSIONS: MPP during fetal head expulsion happens over a short period of time. In the majority of cases the thumb and fingers actions started simultaneously. There were differences in the duration of application and the forces executed by the fingers and thumb between the two practitioners, however this was only significant for thumb measurements. The results obtained will aid in improving further MPP modeling studies to optimize the technique.

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

INTRODUCTION AND HYPOTHESIS: During 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. METHODS: A 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. RESULTS: The 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. CONCLUSIONS: The 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.

Laparoscopic sacrocolpopexy as the mainstay management for significant apical pelvic organ prolapse (LAP) study.

STUDY OBJECTIVES: The primary aim of this study was to assess the clinical feasibility of a policy where laparoscopic sacrocolpopexy (LSC) is the default procedure for the management of a significant apical pelvic organ prolapse (a-POP). As a secondary aim, we wanted to evaluate LSC outcomes in relation to women's preoperative assessment of their surgical fitness using the American Society of Anesthesiologists physical status (ASA-PS) categorization. DESIGN: Retrospective cohort study. SETTING: A university affiliated urogynecology center. METHODS: All women with symptomatic a-POP (C ≥ -1) who attended the urogynecology clinic between the 1st of January and the 31st of December 2016 and had their surgery by the 31st of May 2017 were included in the study. In our unit, routine follow-up appointments are arranged at 3 and 12 months post LSC. INTERVENTIONS: Perioperative and mesh-related complications were assessed based on the Dindo-Clavien and IUGA/ICS classifications respectively. The preoperative outcome measures included Pelvic Organ Prolapse Quantification (POP-Q) stage, Pelvic Floor Distress Inventory (PFDI) and ASA-PS score. At follow-up women were asked to complete a PFDI, Patient Global Impression of Improvement (PGI-I), had their POP-Q staging and ultrasonographic assessment of mesh position and placement. The above measures are routinely collected as part of our standard practice. A preoperative ASA-PS score of <3 was used as a cut-off to dichotomies participants into low and high risk. MAIN RESULTS: A total of 220 women attended our center during the study period because of POP. Of these, 146 women were diagnosed with a significant a-POP and 142 (97.2 %) women opted for a surgical repair. Of the 142 women, 128 (90.1 %) were deemed suitable for a type of LSC and 121 had their surgery before the 31st of May 2017. There were no statistically significant differences in any of our collected perioperative, clinical, patient reported or ultrasonographic outcome measures when comparing women with ASA-PS scores of <3 or ≥3. CONCLUSION: In a specialized urogynecology healthcare setting, it is feasible and safe to rely on LSC as the mainstay surgical procedure for the repair of a significant a-POP. However, it is imperative to ensure that technical skills and equipment requirements are fulfilled and maintained.

A new musculoskeletal AnyBody™ detailed hand model.

Musculoskeletal research questions regarding the prevention or rehabilitation of the hand can be addressed using inverse dynamics simulations when experiments are not possible. To date, no complete human hand model implemented in a holistic human body model has been fully developed. The aim of this work was to develop, implement, and validate a fully detailed hand model using the AnyBody Modelling System (AMS) (AnyBody, Aalborg, Denmark). To achieve this, a consistent multiple cadaver dataset, including all extrinsic and intrinsic muscles, served as a basis. Various obstacle methods were implemented to obtain with the correct alignment of the muscle paths together with the full range of motion of the fingers. These included tori, cylinders, and spherical ellipsoids. The origin points of the lumbrical muscles within the tendon of the flexor digitorum profundus added a unique feature to the model. Furthermore, the possibility of an entire patient-specific scaling based on the hand length and width were implemented in the model. For model validation, experimental datasets from the literature were used, which included the comparison of numerically calculated moment arms of the wrist, thumb, and index finger muscles. In general, the results displayed good comparability of the model and experimental data. However, the extrinsic muscles showed higher accordance than the intrinsic ones. Nevertheless, the results showed, that the proposed developed inverse dynamics hand model offers opportunities in a broad field of applications, where the muscles and joint forces of the forearm play a crucial role.