Sacrum and Coccyx Shape Changes During Pregnancy and After Delivery.

Remodeling of the sacrum and coccyx to accommodate pregnancy and delivery has been hypothesized but not directly quantified. This study aimed to quantify the remodeling of the sacrum and coccyx by comparing midsagittal lengths, angles, curvature, and shape between nulliparous, pregnant, and parous women using both 2 and 3 dimensional measures. Ninety pelvic magnetic resonance images of the pelvis were retrospectively collected and segmented. Twelve length, angle, and curvature measurements were made using definitions from previous literature on the midsagittal plane to define the sacrum, coccyx, and combined sacrum-coccyx shape. These measures were followed by a statistical shape analysis, which returned modes of variation and principal component scores. A separate MANCOVA analysis was conducted for both the 2D and 3D measures. The 2D and 3D analyses agreed that pregnant women had a significantly straighter coccyx and combined sacrum/coccyx than nulliparous (9.1% and 5.6%, respectively) and parous (7.5% and 2.7%, respectively) subjects. All comparisons showed that, on average, a pregnant woman's sacrum and coccyx were significantly straighter than their nulliparous counterparts. Then after delivery, the sacrum/coccyx returned, but not completely back to a more curved configuration.

Effect of Squeeze, Cough, and Strain on Dynamic Urethral Function in Nulligravid Asymptomatic Women: A Cross-Sectional Cohort Study.

IMPORTANCE: In the past, urethral shape, mobility, and urodynamics have been used to retrospectively demonstrate correlations with stress urinary incontinence. Our previous work has shown a relationship between urethral function and shape in symptomatic women. OBJECTIVE: This study aimed to characterize the effect of pelvic floor squeeze and strain maneuvers on urethral shapes and pressure in a cohort of patients without pelvic floor disorders. STUDY DESIGN: In this cross-sectional study, volunteers underwent dynamic pelvic floor ultrasound examination, and a modified urodynamic study. Urethral length, thickness, and proximal and distal swing angles were measured at rest, squeeze, and strain. The midsagittal urethral walls were traced so that a statistical shape model could be performed. Means and standard deviations of imaging and urodynamic measures were calculated. RESULTS: Data from 19 participants were analyzed. On average during squeeze compared with rest, urethral length increased by 6%, thickness decreased by 42% (distal, P < 0.001), 10% (middle), and urethral pressure increased by 14%. Opposite shape changes-length decreased by 10% ( P = 0.001), thickness increased by 57% (distal, P < 0.001), 20% (middle, P < 0.001)-and increased urethral mobility were observed during strain, with larger pressure increases occurring (29%, P < 0.001). Fifty-one percent of the total shape variance described the differences between maneuvers. These differences were statistically different between groups ( P < 0.001 for comparisons, all others P > 0.05). CONCLUSIONS: Dynamic ultrasound and urodynamics allow for the establishment of baseline ranges in urethral metrics (2-dimensional measures, shape, and pressure) and how they are altered during maneuvers. These data can allow for a more objective identification of incontinence via ultrasound and urodynamic testing.

Impact of sex and aging on radiographic and functional parameters of the anal sphincter complex in patients with accidental bowel leakage.

AIMS: Treatment outcomes for accidental bowel leakage (ABL) may be influenced by age-related sarcopenia. We sought to determine if thickness of the anal sphincter complex on endoanal ultrasound correlated with function in women and men with ABL and if women demonstrated age-related anal sphincter thinning. METHODS: Consecutive patients with ABL presenting to our pelvic floor clinic from 2012 to 2017 were included. Clinical data were obtained from medical records. External anal sphincter (EAS), imaged by endoanal ultrasound at proximal, mid and distal locations, and IAS thickness were measured at 12, 3, 6, and 9 o'clock; puborectalis muscle (PRM) was measured at 4, 6, and 8 o'clock; and averaged. Anorectal manometry was conducted when clinically indicated. Data were compared using Mann-Whitney tests and linear regression. Results are reported as mean ± SD or median (IQR). RESULTS: Women (n = 136) were younger than men (n = 26) (61 ± 13 vs. 67 ± 13 years, p = 0.02). More women than men had pelvic surgery and less had colorectal surgery, spinal disorders, or a history of smoking (p < 0.05). Eighty-two percentage of women had an anal sphincter defect versus 31% of men (p < 0.01). All anal sphincter complex components were thinner in women than men with lower squeeze and resting pressures (p < 0.03), even in nulliparous women. Mean resting pressure was lower in older 6.1 (4.6-7.8) versus younger women 8.3 (5.0-12.9) mmHg, p = 0.04. CONCLUSIONS: Women, even nulliparous, with ABL demonstrate thinner and weaker anal sphincters than men, Aging correlated with an increase in anal sphincter thickness, suggesting that age-related changes in the intrinsic components of the anal sphincter complex associated with ABL are complex and are not always well demonstrated on endoanal ultrasound.

Morphological Variation in the Pelvic Floor Muscle Complex of Nulliparous, Pregnant, and Parous Women.

Specific levator ani muscle imaging measures change with pregnancy and vaginal parity, though entire pelvic floor muscle complex (PFMC) shape variation related to pregnancy-induced and postpartum remodeling has never been quantified. We used statistical shape modeling to compute the 3D variation in PFMC morphology of reproductive-aged nulliparous, late pregnant, and parous women. Pelvic magnetic resonance images were collected retrospectively and PFMCs were segmented. Modes of variation and principal component scores, generated via statistical shape modeling, defined significant morphological variation. Nulliparous (have never given birth), late pregnant (3rd trimester), and parous (have given birth and not currently pregnant) PFMCs were compared via MANCOVA. The overall PFMC shape, mode 2, and mode 3 significantly differed across patient groups (p < 0.001, = 0.002, = 0.001, respectively). This statistical shape analysis described greater perineal and external anal sphincter descent, increased iliococcygeus concavity, and a proportionally wider mid-posterior levator hiatus in late pregnant compared to nulliparous and parous women. The late pregnant group was the most divergent, highlighting differences that likely reduce the mechanical burden of vaginal childbirth. This robust quantification of PFMC shape provides insight to pregnancy and postpartum remodeling and allows for generation of representative non-patient-specific PFMCs that can be used in biomechanical simulations.

Quantifying the physiologic motions of the pelvic viscera during evacuation in nulligravid asymptomatic women.

INTRODUCTION AND HYPOTHESIS: Pelvic organ prolapse (POP) is often diagnosed during an in-office examination, which looks for motion of the vaginal wall while performing a strain maneuver. It is believed that the pelvic organs in adequately supported women are relatively stationary. This study was aimed at investigating the physiological displacements of pelvic organs using MR defecography. METHODS: This prospective cohort study included 19 volunteers. Midsagittal slices representing rest and the maximum movement of the posterior vaginal fornix during three maneuvers were identified. Normalized axes for analysis were defined as the x' (line connecting the inferior-posterior-most point on the pubic symphysis to the anterior edge of the sacrococcygeal joint) and the y' (line orthogonal to the x axis that passed through the sacral promontory). The positions of the posterior vaginal fornix, mid-vagina, bladder neck, anorectal junction, and hymen were recorded. These subjects were then analyzed using the current radiological grading system of POP to determine any overlap between asymptomatic subjects and diagnostic ranges of POP. RESULTS: Evacuation caused the most motion in the landmarks. The majority of the motion of the landmarks was along the y axis. The posterior vaginal fornix experienced significant descent (125% of the initial distance) without much anterior-posterior translation (7% of the initial distance) during defecation. All landmarks experienced similar trends. CONCLUSIONS: We have shown that there is significant rotational motion of the pelvic organs around the pubic bone in adequately supported women. This motion when described using radiological grading is likely to be considered mild or moderate prolapse, which may contribute to overdiagnosis of POP.

A Computational Procedure to Derive the Curve of Carus for Childbirth Computational Modeling.

Computational modeling serves an important role in childbirth-related research. Prescribed fetal descent trajectory is a key characteristic in childbirth simulations. Two major types of fully prescribed fetal descent trajectories can be identified in the literature: straight descent trajectories and curve of Carus. The straight descent trajectory has the advantage of being simpler and can serve as a reasonable approximation for relatively small fetal movements during labor, but it cannot be used to simulate the entire childbirth process. The curve of Carus is the well-recognized fetal descent trajectory with physiological significance. However, no detailed procedure to geometrically define the curve of Carus can be found in existing computational studies. This status of curve of Carus simulation in the literature hinders the direct comparison of results across different studies and the advancement of computational techniques built upon previous research. The goals of this study are: (1) propose a universal approach to derive the curve of Carus for the second stage of labor, from the point when the fetal head engages the pelvis to the point when the fetal head is fully delivered; and (2) demonstrate its utility when considering various fetal head sizes. The current study provides a detailed formulation of the curve of Carus, considering geometries of both the mother and the fetus. The maternal geometries were obtained from MRI data, and the fetal head geometries were based on laser scanning of a replica of a real fetal head.

Urethral support in female urinary continence part 1: dynamic measurements of urethral shape and motion.

INTRODUCTION AND HYPOTHESIS: Urethral closure mechanism dysfunction in female stress urinary incontinence (SUI) is poorly understood. We aimed to quantify these mechanisms through changes in urethral shape and position during squeeze (voluntary closure) and Valsalva (passive closure) via endovaginal ultrasound in women with varying SUI severity. METHODS: In this prospective cohort study, 76 women who presented to our tertiary center for urodynamic testing as preoperative assessment were recruited. Urodynamics were performed according to International Continence Society criteria. Urethral pressures were obtained during serial Valsalva maneuvers. Urethral lengths, thicknesses, and angles were measured in the midsagittal plane via dynamic anterior compartment ultrasound. Statistical shape modeling was carried out by a principal component analysis on aligned urethra shapes. RESULTS: Age, parity, and BMI did not vary by SUI group. Ultrasound detected a larger retropubic angle, urethral knee-pubic bone angle (a novel measure developed for this study), and infrapubic urethral length measurements at Valsalva in women with severe SUI (p = 0.016, 0.015, and 0.010). Shape analysis defined increased "c" shape concavity and distal wall pinching during squeeze and increased "s" shape concavity and distal wall thickening during Valsalva (p < 0.001). It also described significant urethral shape differences across SUI severity groups (p < 0.001). CONCLUSIONS: Dynamic endovaginal ultrasound can visualize and allow for quantification of voluntary and passive urethral closure and variations with SUI severity. In women with severe SUI, excessive bladder neck and distal urethra swinging during Valsalva longitudinally compressed the urethra, resulting in a proportionally thicker wall at the mid-urethra and urethral knee.

Urethral support in female urinary continence part 2: a computational, biomechanical analysis of Valsalva.

INTRODUCTION AND HYPOTHESIS: In Part 1, we observed urethral mechanics during Valsalva that oppose current continence theories. In this study, we utilize a finite element model to elucidate the role of supportive tissues on the urethra during Valsalva. By determining the sensitivity of urethral motion and deformations to variations in tissue stiffnesses, we formulate new hypotheses regarding mechanisms of urethral passive closure. METHODS: Anatomy was segmented from a nulliparous, continent woman at rest. The model was tuned such that urethral motion during Valsalva matched that observed in that patient. Urethra and surrounding tissue material properties were varied using Latin hypercube sampling to perform a sensitivity analysis. As in Part 1, urethral length, proximal and distal swinging, and shape parameters were measured at peak Valsalva for 50 simulations, and partial rank correlation coefficients were calculated between all model inputs and outputs. Cumulative influence factors determined which tissue properties were meaningfully influential (≥ 0.5). RESULTS: The material properties of the urethra, perineal membrane, bladder, and paraurethral connective tissues meaningfully influenced urethral motion, deformation, and shape. Reduction of the urethral stiffness and/or the perineal membrane soft constraint resulted in simulated urethral motions and shapes associated with stress urinary incontinence in Part 1. CONCLUSIONS: The data from Parts 1 and 2 suggest that connective tissues guide the controlled swinging motion and deformation of the urethra needed for passive closure during Valsalva. The swinging and kinking quantified in Part 1 and simulated in Part 2 are inconsistent with current continence theories.

Obstructed Defecation Symptom Severity and Degree of Rectal Hypermobility and Folding Detected by Dynamic Ultrasound.

ABSTRACT: We used dynamic pelvic floor ultrasound to investigate the relationship between obstructed defecation symptom (ODS) severity and the degree of rectal hypermobility/folding. In this retrospective study, women who presented with ODS from October 2017 to January 2019 and underwent an interview, pelvic examination, and pelvic floor ultrasound were recruited. Patients were diagnosed with abdominal constipation, dyssynergia, or pelvic constipation. Pelvic constipation patients were categorized based on their reported frequency of incomplete emptying of stool (<50% or ≥50% of bowel movements) representing mild and severe ODS, respectively. Using dynamic ultrasound, rectal hypermobility was quantified via rectovaginal septum length at rest and Valsalva and its compression ratio, where shorter lengths and larger compression ratios are indicative of increased rectal hypermobility. One hundred twenty-one patients (41 with abdominal constipation, 7 with dyssynergia, and 73 with pelvic constipation) were included. Compression ratios were higher in women with severe versus mild ODS (17.36 ± 16.89 vs 36.38 ± 25.82, P = 0.0039). The risk of having severe symptoms was 4 times greater (odds ratio = 4.2, 95% confidence interval = 1.4 to 12.6, P = 0.01) among those with a high compression ratio (≥20%) after controlling for age, body mass index, and levator plate descent angle. Incomplete emptying was weakly, positively, linearly correlated with rectal hypermobility/folding (r = -0.2724, -0.3767 to 0.3922, and P = 0.0197, 0.0010, 0.0006, respectively). Women with more severe ODS experienced more rectal hypermobility/folding as measured via dynamic ultrasound-a cheaper, effective alternative to magnetic resonance defecography for evaluation of obstructed defecation.

Novel Application of Photogrammetry to Quantify Fascicle Orientations of Female Cadaveric Pelvic Floor Muscles.

Although critical for understanding and simulating pelvic floor muscle function and pathophysiology, the fascicle arrangements of the coccygeus and levator ani remain mostly undetermined. We performed close-range photogrammetry on cadaveric pelvic floor muscles to robustly quantify surface fascicle orientations. The pelvic floor muscles of 5 female cadavers were exposed through anatomic dissections, removed en bloc, and photographed from every required angle. Overlapping images were mapped onto in silico geometries and muscle fascicles were traced manually. Tangent vectors were calculated along each trace; interpolated to define continuous, 3D vector fields; and projected onto axial and sagittal planes to calculate angles with respect to the pubococcygeal line. Contralateral and ipsilateral pelvic floor muscles were compared within each donor (Kuiper's tests) and using mean values from all donors (William-Watsons tests). Contralateral muscles and all but one ipsilateral muscle pair differed significantly within each donor (p < 0.001). When mean values were considered collectively, no contralateral or ipsilateral statistical differences were found but all muscles compared differed by more than 10° on average. Close-range photogrammetry and subsequent analyses robustly quantified surface fascicle orientations of the pelvic floor muscles. The continuous, 3D vector fields provide data necessary for improving simulations of the female pelvic floor muscles.

Statistical shape modeling of the pelvic floor to evaluate women with obstructed defecation symptoms.

Obstructed defecation (OD) is common and may be related to compromised pelvic floor integrity. Magnetic resonance (MR) defecography and statistical shape modeling were used to define pelvic floor shape variations, hypothesizing that State (rest vs peak evacuation) and Group (control vs case) would significantly influence shape. 16 women underwent MR defecography (9 cases vs 7 controls). Midsagittal, 2D pelvic floors were segmented and aligned by corresponding points. Principal component scores were compared using a Two-Way Mixed MANOVA. Three modes described differences between State (p < 0.001) and Group (p = 0.023). The pelvic floor shape differed significantly between women with and without OD and during evacuation.

Pelvic floor shape variations during pregnancy and after vaginal delivery.

BACKGROUND AND OBJECTIVE: Strong evidence suggests that pelvic soft tissues soften during pregnancy to facilitate vaginal delivery while protecting against maternal birth injury. We hypothesized that these adaptations likely result in changes to the shape of the pelvic floor. Thus, this study aimed to compare midsagittal pelvic floor shapes from MRIs of nulliparous, gravid, and vaginally parous women using statistical shape modeling. METHODS: A retrospective study of 22 nulliparous, 29 gravid (vaginally nulliparous), and 18 vaginally parous women who underwent pelvic MRI was performed. The pelvic floor was segmented from pubic symphysis to coccyx as a 2D polyline in the midsagittal plane. Once corresponding landmarks were computed and the variances between them determined by principal component analysis, the principal component scores were calculated for modes that explained variance greater than noise. These became the dependent variables in a MANOVA with univariate ANOVAs, linear regressions, and Benjamini-Hochberg corrections post hoc. Two initial statistical shape analyses were conducted to analyze differences based on gestational age (1st/2nd vs 3rd trimester) and vaginal parity (VP1 vs VP2-4). There were significant differences based on gestational age, but not vaginal parity. Thus, the final statistical shape analysis evaluated pelvic floor shapes of nulliparous, 3rd trimester gravid, and all vaginally parous subjects. RESULTS: In the final analysis, six modes described variance-a measure of shape variability-greater than noise. Groups differed significantly for modes 1, 2, and 4 (p < 0.001, p = 0.021, and p = 0.015, respectively) and only differed between the nulliparous and gravid groups (p < 0.001, p = 0.018, and p = 0.012, respectively). Anatomically, these modes described levator plate relaxation and level III support protrusion in gravid compared to nulliparous subjects while the parous group straddled the other two. CONCLUSIONS: The shape of the pelvic floor changes significantly during pregnancy and some of those changes are present after vaginal delivery. The fact that the nulliparous and gravid groups differ while the parous is similar to both suggests that some parous women regain their nulliparous shape after pregnancy and delivery while others do not. This indicates that remodeling during pregnancy and/or injury during vaginal delivery can have lasting effects on the pelvic floor.

New Zealand white rabbit: a novel model for prolapse mesh implantation via a lumbar colpopexy.

INTRODUCTION AND HYPOTHESIS: New Zealand white rabbits are an inexpensive large-animal model. This study explored the rabbit as a model for mesh-augmented colpopexy using the intra-abdominal vagina. We hypothesized that polypropylene mesh would negatively impact rabbit vaginal smooth muscle (VSM) morphology and contractile function, similar to the nonhuman primate (NHP)-the established model for prolapse mesh evaluation. METHODS: Restorelle was implanted onto the vagina of ten rabbits via lumbar colpopexy after a hysterectomy. Ten rabbits served as sham. Twelve weeks post-implantation, the vagina was excised and VSM morphology and vaginal contractility were assessed. Outcome measures were compared using independent samples t and Mann-Whitney U tests with a Bonferroni correction, where appropriate. Results from the rabbits were compared with published NHP data. RESULTS: Animals had similar age, parity and BMI. VSM was 18% thinner after Restorelle implantation, P = 0.027. Vaginal contractility was 43% decreased in response to 120 mM KCl (P = 0.003), similar to the 46% reduction observed in the NHP vagina implanted with Restorelle (P = 0.027). Three meshes wrinkled in vivo, resulting in dramatic thinning of the underlying vagina in the area of the mesh causing a mesh exposure. CONCLUSIONS: Polypropylene mesh negatively impacts VSM morphology and vaginal contractility in the rabbit, similar to the NHP, suggesting that the rabbit may serve as an alternative large-animal model. The vaginal thinning and appearance of a mesh exposure in the area of a mesh wrinkle suggest the rabbit may also serve as a model for understanding the pathophysiology of mesh exposure.

Novel simulations to determine the impact of superficial perineal structures on vaginal delivery.

This study's aim was to determine whether the inclusion of superficial perineal structures in a finite-element simulation of vaginal delivery impacts the pubovisceral muscle and perineal body, two common sites of birth-related injury. The hypothesis, inferred from prevailing literature, was that these structures would have minimal influence (differences less than ±10%). Two models were made using the Visible Human Project's female cadaver to create a rigid, fixed pelvis, musculature held by spring attachments to that pelvis, and a rigid, ellipsoidal fetal head prescribed with an inferior displacement to simulate delivery. Injury site stretch ratios and fetal head and perineal body displacements and angles of progression were compared between the Omitted Model (which excluded the superficial perineal structures as is common practice) and the Included Model (which included them). Included Model stretch ratios were +107%, -9.84% and -14.6% compared to Omitted Model perineal body and right and left pubovisceral muscles, respectively. Included Model peak perineal body inferior displacement was +72.5% greater while similar anterior-posterior displacements took longer to reach. These results refute our hypothesis, suggesting superficial perineal structures impact simulations of vaginal delivery by inhibiting perineal body anterior-posterior displacement, which stretches and inferiorly displaces the perineal body.