Biomechanical properties of prolapsed vaginal tissue in pre- and postmenopausal women

Platelet rich plasma as a minimally invasive approach to uterine prolapse

Pelvic organ prolapse (POP) is a major health problem that affects many women with potentially severe physical and psychological impact as well as impact on their daily activities, and quality of life. Several surgical techniques have been proposed for the treatment of POP. The FDA has published documents that refer to concerns about the use of synthetic meshes for the treatment of prolapse, in view of the severe complications that may occur. These led to hesitancy in use of these meshes and partial increase in use of other biological grafts such as allografts and xenografts. Although there seems to be an increasing tendency to use grafts in pelvic floor reconstructive procedures due to lower risks of erosion than synthetic meshes, there are inconclusive data to support the routine use of biological grafts in pelvic organ prolapse treatment. In light of these observations new strategies are needed for the treatment of prolapse. Platelet rich plasma (PRP) is extremely rich in growth factors and cytokines, which regulate tissue reconstruction and has been previously used in orthopaedics and plastic surgery. To date, however, it has never been used in urogynaecology and there is no evidence to support or oppose its use in women who suffer from POP, due to uterine ligament defects. PRP is a relatively inexpensive biological material and easily produced directly from patients' blood and is, thus, superior to synthetic materials in terms of potential adverse effects such as foreign body reaction. In the present article we summarize the existing evidence, which supports the conduct of animal experimental and clinical studies to elucidate the potential role of PRP in treating POP by restoring the anatomy and function of ligament support.

Application of Tissue Engineering to Pelvic Organ Prolapse and Stress Urinary Incontinence

Synthetic or biological materials can be used for the surgical repair of pelvic organ prolapse (POP) or stress urinary incontinence (SUI). While non-degradable synthetic mesh has a low failure rate, it is prone to complications such as infection and erosion, particularly in the urological/gynecological setting when subject to chronic influences of gravity and intermittent, repetitive strain. Biological materials have lower complication rates, although allografts and xenografts have a high risk of failure and the theoretical risk of infection. Autografts are used successfully for the treatment of SUI and are not associated with erosion; however, can lead to morbidity at the donor site. Tissue engineering has thus become the focus of interest in recent years as researchers seek an ideal tissue remodeling material for urogynecological repair. Herein, we review the directions of current and future research in this exciting field. Electrospun poly-L-lactic acid (PLA) and porcine small intestine submucosa (SIS) are two promising scaffold material candidates. Adipose-derived stem cells (ADSCs) appear to be a suitable cell type for scaffold seeding, and cells grown on scaffolds when subjected to repetitive biaxial strain show more appropriate biomechanical properties for clinical implantation. After implantation, an appropriate level of acute inflammation is important to precipitate moderate fibrosis and encourage tissue strength. New research directions include the use of bioactive materials containing compounds that may help facilitate integration of the new tissue. More research with longer follow-up is needed to ascertain the most successful and safe methods and materials for pelvic organ repair and SUI treatment.

Developing Repair Materials for Stress Urinary Incontinence to Withstand Dynamic Distension

BACKGROUND

Polypropylene mesh used as a mid-urethral sling is associated with severe clinical complications in a significant minority of patients. Current in vitro mechanical testing shows that polypropylene responds inadequately to mechanical distension and is also poor at supporting cell proliferation.

AIMS AND OBJECTIVES

Our objective therefore is to produce materials with more appropriate mechanical properties for use as a sling material but which can also support cell integration.

METHODS

Scaffolds of two polyurethanes (PU), poly-L-lactic acid (PLA) and co-polymers of the two were produced by electrospinning. Mechanical properties of materials were assessed and compared to polypropylene. The interaction of adipose derived stem cells (ADSC) with the scaffolds was also assessed. Uniaxial tensiometry of scaffolds was performed before and after seven days of cyclical distension. Cell penetration (using DAPI and a fluorescent red cell tracker dye), viability (AlamarBlue assay) and total collagen production (Sirius red assay) were measured for ADSC cultured on scaffolds.

RESULTS

Polypropylene was stronger than polyurethanes and PLA. However, polypropylene mesh deformed plastically after 7 days of sustained cyclical distention, while polyurethanes maintained their elasticity. Scaffolds of PU containing PLA were weaker and stiffer than PU or polypropylene but were significantly better than PU scaffolds alone at supporting ADSC.

CONCLUSIONS

Therefore, prolonged mechanical distension in vitro causes polypropylene to fail. Materials with more appropriate mechanical properties for use as sling materials can be produced using PU. Combining PLA with PU greatly improves interaction of cells with this material.

Biodegradable scaffolds designed to mimic fascia-like properties for the treatment of pelvic organ prolapse and stress urinary incontinence

There is an urgent clinical need for better synthetic materials to be used in surgical support of the pelvic floor. The aim of the current study was to construct biodegradable synthetic scaffolds that mimic the three-dimensional architecture of human fascia, which can integrate better into host tissues both mechanically and biologically. Therefore, four different polylactic acid (PLA) scaffolds with various degrees of fibre alignment were electrospun by modifying the electrospinning parameters. Physical and mechanical properties were assessed using a BOSE electroforce tensiometer. The attachment, viability and extracellular matrix production of adipose-derived stem cells cultured on the polylactic acid scaffolds were evaluated. The bulk density of the scaffolds decreased as the proportion of aligned fibres increased. Scaffolds became stronger and stiffer with increasing amounts of aligned fibres as measured along the axis parallel to the fibre alignment. In addition, more total collagen was produced on scaffolds with aligned fibres and was organised in the direction of the aligned fibres. In conclusion, the electrospinning technique can be easily modified to develop biodegradable scaffolds with a spectrum of mechanical properties allowing extracellular matrix organisation towards human-like fascia.

Biomechanical properties of synthetic surgical meshes for pelvic prolapse repair

Synthetic meshes are widely used for surgical repair of different kind of prolapses. In the light of the experience of abdominal wall repair, similar prostheses are currently used in the pelvic region, to restore physiological anatomy after organ prolapse into the vaginal wall, that represent a recurrent dysfunction. For this purpose, synthetic meshes are surgically positioned in contact with the anterior and/or posterior vaginal wall, to inferiorly support prolapsed organs. Nonetheless, while mesh implantation restores physiological anatomy, it is often associated with different complications in the vaginal region. These potentially dangerous effects induce the surgical community to reconsider the safety and efficacy of mesh transvaginal placement. For this purpose, the evaluation of state-of-the-art research may provide the basis for a comprehensive analysis of mesh compatibility and functionality. The aim of this work is to review synthetic surgical meshes for pelvic organs prolapse repair, taking into account the mechanics of mesh material and structure, and to relate them with pelvic and vaginal tissue biomechanics. Synthetic meshes are currently available in different chemical composition, fiber and textile conformations. Material and structural properties are key factors in determining mesh biochemical and mechanical compatibility in vivo. The most significant results on vaginal tissue and surgical meshes mechanical characterization are here reported and discussed. Moreover, computational models of the pelvic region, which could support the surgeon in the evaluation of mesh performances in physiological conditions, are recalled.

Tactile Imaging Markers to Characterize Female Pelvic Floor Conditions

The Vaginal Tactile Imager (VTI) records pressure patterns from vaginal walls under an applied tissue deformation and during pelvic floor muscle contractions. The objective of this study is to validate tactile imaging and muscle contraction parameters (markers) sensitive to the female pelvic floor conditions. Twenty-two women with normal and prolapse conditions were examined by a vaginal tactile imaging probe. We identified 9 parameters which were sensitive to prolapse conditions (p < 0.05 for one-way ANOVA and/or p < 0.05 for t-test with correlation factor r from -0.73 to -0.56). The list of parameters includes pressure, pressure gradient and dynamic pressure response during muscle contraction at identified locations. These parameters may be used for biomechanical characterization of female pelvic floor conditions to support an effective management of pelvic floor prolapse.

Recent studies of genetic dysfunction in pelvic organ prolapse: the role of collagen defects

Gynaecologists are becoming increasingly aware that women with a family history of prolapse are at an increased risk of prolapse refractory to treatment. In the past five years, several genetic mutations have been shown to correlate with increased prolapse susceptibility. These mutations can result in disordered collagen metabolism, which weaken the fascial support of the pelvic organs. This review examines the contemporary evidence regarding the role of collagen in prolapse.

Developing a tissue engineered repair material for treatment of stress urinary incontinence and pelvic organ prolapse-which cell source?

AIMS

Synthetic non-absorbable meshes are widely used to augment surgical repair of stress urinary incontinence (SUI) and pelvic organ prolapse (POP); however, there is growing concern such meshes are associated with serious complications. This study compares the potential of two autologous cell sources for attachment and extra-cellular matrix (ECM) production on a biodegradable scaffold to develop tissue engineered repair material (TERM).

METHODS

Human oral fibroblasts (OF) and human adipose-derived stem cells (ADSC) were isolated and cultured on thermo-annealed poly-L-lactic acid (PLA) scaffolds for two weeks under either unrestrained conditions or restrained (either with or without intermittent stress) conditions. Samples were tested for cell metabolic activity (AlamarBlue® assay), contraction (serial photographs analyzed with image J software), total collagen production (Sirius red assay), and production of ECM components (immunostaining for collagen I, III, and elastin; and scanning electron microscopy) and biomechanical properties (BOSE tensiometer). Differences were statistically tested using two sample t-test.

RESULTS

Both cells showed good attachment and proliferation on scaffolds. Unrestrained scaffolds with ADSC produced more total collagen and a denser homogenous ECM than OF under same conditions. Restrained conditions (both with and without intermittent stress) gave similar total collagen production, but improved elastin production for both cells, particularly OF. The addition of any cell onto scaffolds led to an increase in biomechanical properties of scaffolds compared to unseeded scaffolds.

CONCLUSIONS

OF and ADSC both appear to be suitable cell types to combine with biodegradable scaffolds, in the development of a TERM for the treatment of SUI and POP. Neurourol. Urodynam. 33:531-537, 2014. © 2013 Wiley Periodicals, Inc.

Changes in the rheological behavior of the vagina in women with pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

Pelvic organ prolapse is a common condition impacting the quality of life of millions of women worldwide. Although vaginal estrogen is widely used in women with prolapse, little is known regarding estrogen's benefits on the biomechanical properties of vaginal tissue. Here, we aimed to examine the effect of prolapse on the biomechanical properties of the vagina and determine alterations in vaginal mechanics in the presence and absence of hormone therapy (HT).

METHODS

We characterized the viscoelastic properties of vaginal biopsies from age-matched premenopausal women without (n = 12) and with prolapse (n = 8) and postmenopausal women with prolapse on (n = 18) and off HT (n = 9). Utilizing a single-lap shear testing protocol, full-thickness anterior vaginal biopsies were subjected to ±10% shear strain over a range of frequencies (1-90 Hz). This applied energy is either dissipated (viscous) or stored (elastic) as a function of frequency due to compositional or structural differences in the tissue.

RESULTS

Prolapsed tissue was more stiff (higher complex modulus) under shear deformation resulting from increases in both elastic (elastic modulus) and viscous (loss modulus) contributions, with non-prolapsed premenopausal women being the least stiff. Postmenopausal women with prolapse currently on HT were the most stiff of all the groups.

CONCLUSIONS

These data suggest that prolapsed tissue has an increased elastic contribution likely resulting from changes in biochemical constituents, and hormones increase the viscous contribution of prolapsed tissue. Overall, this study design characterized the viscoelastic properties of vaginal biopsies and may be utilized to conduct longitudinal studies to better understand the mechanisms of prolapse development and progression.

Comparison of candidate scaffolds for tissue engineering for stress urinary incontinence and pelvic organ prolapse repair

OBJECTIVES

To identify candidate materials which have sufficient potential to be taken forward for an in vivo tissue-engineering approach to restoring the tissue structure of the pelvic floor in women with stress urinary incontinence (SUI) or pelvic organ prolapse (POP).

MATERIALS AND METHODS

Oral mucosal fibroblasts were seeded onto seven different scaffold materials, AlloDerm ( LifeCell Corp., Branchburg, NJ, USA), cadaveric dermis, porcine dermis, polypropylene, sheep forestomach, porcine small intestinal submucosa (SIS) and thermoannealed poly(L) lactic acid (PLA) under both free and restrained conditions. The scaffolds were assessed for: cell attachment using AlamarBlue and 4,6-diamidino-2-phenylindole (DAPI); contraction using serial photographs; and extracellular matrix production using Sirius red staining, immunostaining and scanning electron microscopy. Finally the biomechanical properties of all the scaffolds were assessed.

RESULTS

Of the seven, there were two biodegradable scaffolds, synthetic PLA and natural SIS, which supported good cell attachment and proliferation. Immunostaining confirmed the presence of collagen I, III and elastin which was highest in SIS and PLA. The mechanical properties of PLA were closest to native tissue with an ultimate tensile strength of 0.72 ± 0.18 MPa, ultimate tensile strain 0.53 ± 0.16 and Young's modulus 4.5 ± 2.9 MPa. Scaffold restraint did not have a significant impact on the above properties in the best scaffolds.

CONCLUSION

These data support both PLA and SIS as good candidate materials for use in making a tissue-engineered repair material for SUI or POP.

Deterioration in biomechanical properties of the vagina following implantation of a high-stiffness prolapse mesh

OBJECTIVE

To define the impact of prolapse mesh on the biomechanical properties of the vagina by comparing the prototype Gynemesh PS (Ethicon) to two new-generation lower stiffness meshes, SmartMesh (Coloplast) and UltraPro (Ethicon).

DESIGN

A study employing a nonhuman primate model.

SETTING

University of Pittsburgh, PA, USA.

POPULATION

Forty-five parous rhesus macaques.

METHODS

Meshes were implanted via sacrocolpopexy after hysterectomy and compared with sham. Because its stiffness is highly directional, UltraPro was implanted in two directions: UltraPro Perpendicular (less stiff) and UltraPro Parallel (more stiff), with the indicated direction referring to the position of the blue orientation lines relative to the longitudinal axis of the vagina. The mesh-vaginal complex (MVC) was excised in toto after 3 months.

MAIN OUTCOME MEASURES

Active mechanical properties were quantified as the contractile force generated in the presence of 120 mmol/l KCl. Passive mechanical properties (a tissue's ability to resist an applied force) were measured using a multiaxial protocol.

RESULTS

Vaginal contractility decreased by 80% following implantation with the Gynemesh PS (P = 0.001), 48% after SmartMesh (P = 0.001), 68% after UltraPro Parallel (P = 0.001) and was highly variable after UltraPro Perpendicular (P = 0.16). The tissue contribution to the passive mechanical behaviour of the MVC was drastically reduced for Gynemesh PS (P = 0.003), but not for SmartMesh (P = 0.9) or UltraPro independent of the direction of implantation (P = 0.68 and P = 0.66, respectively).

CONCLUSIONS

Deterioration of the mechanical properties of the vagina was highest following implantation with the stiffest mesh, Gynemesh PS. Such a decrease associated with implantation of a device of increased stiffness is consistent with findings from other systems employing prostheses for support.

Biomechanical properties of vaginal tissue in women with pelvic organ prolapse

BACKGROUND/AIMS

To compare biomechanical properties of vaginal tissues between women with and without pelvic organ prolapse (POP) and investigate factors that may influence these properties.

METHODS

Forty patients submitted to POP surgery and 15 non-POP cadavers were evaluated. The tissue was excised from anterior and posterior middle third vagina. The biomechanical properties considered were stiffness (E) and maximum stress (S), and they were evaluated by means of uniaxial tension tests.

RESULTS

POP patients were associated with higher values of E (13.1 ± 0.8 vs. 9.5 ± 0.7 MPa; p < 0.001) and S (5.3 ± 0.5 vs. 3.2 ± 0.9 MPa; p < 0.001) in the anterior vaginal wall compared to the posterior wall. In contrast, non-POP women presented lower values of E (6.9 ± 1.1 vs. 10.5 ± 1.0 MPa; p = 0.01) and S (2.6 ± 0.4 vs. 3.5 ± 0.4 MPa; p = 0.043) in the anterior wall. The occurrence of POP was the only independent predictor of higher values of E and S in anterior vaginal samples (p = 0.003 and p = 0.008, respectively). Women with severe anterior vaginal prolapse presented higher levels of E and S in the anterior sample compared to those with lower POP stages (p = 0.001 and p = 0.01; respectively).

CONCLUSION

Women with POP present significant changes of biomechanical properties in the vagina.

Real-time in vivo assessment of levator ani muscle deformation in women

OBJECTIVE

To study the deformation of the levator ani muscle in vivo with the use of real-time ultrasound imaging of the pelvic floor.

STUDY DESIGN

Thirty-two women with symptoms of pelvic floor dysfunction underwent real-time in vivo assessment of the strain of the pelvic floor during Valsalva effort. All participants underwent clinical examination, urodynamics and 3D/4D translabial ultrasound scan of the pelvic floor. The deformation curves of the levator ani muscle were plotted and the difference in compliance according to the grade of urogenital prolapse was measured. One-way ANOVA and Spearman's correlation were used to test for significance of the relationship between variables (significance level P<0.05). Test-retest analysis of the ultrasound measurements of the levator hiatal dimensions was also conducted using intra-class correlation coefficient (ICC).

RESULTS

The deformation curve of the levator hiatus showed a non-linear relationship with gradually increased Valsalva force, which was quite pronounced in the pubourethralis subdivision of the levator ani muscle complex. Women with significant pelvic organ prolapse demonstrated a less compliant levator ani muscle close to its origin from the pubic bone than women with non-significant prolapse (median maximum strain 26% vs 32%, respectively, P=0.03).

CONCLUSIONS

Real-time in vivo assessment of levator ani muscle deformation in women is feasible and yields significant information.

Biomechanical properties and associated collagen composition in vaginal tissue of women with pelvic organ prolapse

PURPOSE

The pelvic tissue of women with pelvic organ prolapse is stiffer than that of controls but there are scant data on the collagen composition that corresponds to these mechanical properties. We evaluated human vaginal wall stiffness using the novel scanning haptic microscope and correlated these measurements to collagen expression in women with and without pelvic organ prolapse. In this simultaneous biomechanical and biochemical assessment we evaluated the usefulness of this measurement technology for pelvic floor disorder research and confirmed an association between mechanical properties and composition.

MATERIALS AND METHODS

The elastic constant (a measure of stiffness) of vaginal wall tissue was measured with the scanning haptic microscope. Protein expression of collagen types I and III of the same tissues were determined by Western blot. The Student t test was used for comparisons between groups.

RESULTS

The anterior and posterior vaginal walls of premenopausal and postmenopausal women with pelvic organ prolapse were significantly stiffer than those of controls (p <0.05). Collagen III protein expression in the anterior vaginal wall in the control group was higher than in menopausal women. Collagen I expression was not significantly different between controls and cases.

CONCLUSIONS

The scanning haptic microscope produced reliable mechanical measurements in small tissue samples without tissue destruction. Vaginal wall tissues are stiffer in women with pelvic organ prolapse than in controls. This vaginal wall stiffness was associated with lower protein expression of collagen III in the vaginal wall compared to that in asymptomatic controls.

Comparative analysis of pelvic ligaments: a biomechanics study

INTRODUCTION AND HYPOTHESIS

Pelvic organ prolapse (POP) affects one third of women of all ages and is a major concern for gynecological surgeons. In pelvic reconstructive surgery, native ligaments are widely used as a corrective support, while their biomechanical properties are unknown. We hypothesized differences in the strength of various pelvic ligaments and therefore, aimed to evaluate and compare their biomechanical properties.

MATERIALS AND METHODS

Samples from the left and right broad, round, and uterosacral ligaments from 13 fresh female cadavers without pelvic organ prolapse were collected. Uniaxial tension tests at a constant rate of deformation were performed and stress-strain curves were obtained.

RESULTS

We observed a non-linear stress-strain relationship and a hyperelastic mechanical behavior of the tissues. The uterosacral ligaments were the most rigid whether at low or high deformation, while the round ligament was more rigid than the broad ligament.

CONCLUSION

Pelvic ligaments differ in their biomechanical properties and there is fairly good evidence that the uterosacral ligaments play an important role in the maintenance of pelvic support from a biomechanical point of view.

Quantifying vaginal tissue elasticity under normal and prolapse conditions by tactile imaging

INTRODUCTION AND HYPOTHESIS

Vaginal tactile imaging (VTI) is based on principles similar to those of manual palpation. The objective of this study is to assess the clinical suitability of new approach for imaging and tissue elasticity quantification under normal and prolapse conditions.

METHODS

The study subjects included 31 women with normal and prolapse conditions. The tissue elasticity (Young's modulus) was calculated from spatial gradients in the resulting 3-D tactile images.

RESULTS

Average values for tissue elasticity for the anterior and posterior compartments for normal conditions were 7.4 ± 4.3 kPa and 6.2 ± 3.1 kPa respectively. For Stage III prolapse the average values for tissue elasticity for anterior and posterior compartments were 1.8 ± 0.7 kPa and 1.8 ± 0.5 kPa respectively.

CONCLUSIONS

VTI may serve as a means for 3-D imaging of the vagina and a quantitative assessment of vaginal tissue elasticity, providing important information for furthering our understanding of pelvic organ prolapse and surgical treatment.

Biomechanical properties of prolapsed or non-prolapsed vaginal tissue: impact on genital prolapse surgery

INTRODUCTION AND HYPOTHESIS

Our aim is to characterize prolapsed and non-prolapsed vaginal tissue, and thus offer a better understanding of the genital prolapse physiopathology and an improvement of surgical treatments.

METHODS

Vaginal tissue was collected in 30 patients with prolapse (POP) and ten fresh cadavers without prolapse (nPOP) with a favorable advice of Ethics Committee. Uniaxial tension tests were performed. Statistical comparisons of rigidity under moderate deformation and under large deformation have been performed

RESULTS

POP is significantly stiffer than nPOP tissue, both on anterior and posterior walls. A significant difference between POP and nPOP tissues was highlighted when anterior or posterior vaginal walls were respectively compared.

CONCLUSIONS

These results might explain the higher rate of relapse when repair is autologous, using already defective and more rigid vaginal tissue. This study suggests that it might be interesting to adapt the characteristics of prosthetic implants to the vaginal face concerned by the prolapsus.

Vagina, abdominal skin, and aponeurosis: do they have similar biomechanical properties?

INTRODUCTION AND HYPOTHESIS

despite minimal fundamental works, there is an increasing use of meshes in urogynecology. The concept is mainly based on experiences with abdominal wall surgery. We aimed to compare the biomechanical properties of vaginal tissue, abdominal aponeurosis, and skin.

METHODS

samples from 11 fresh women cadavers without prolapse were collected. Uniaxial tension tests were performed and stress-strain curves were obtained.

RESULTS

biomechanical properties of the vagina, aponeurosis, and skin differed significantly. The aponeurosis was much more rigid and less extendible than the vagina and skin. Vaginal tissue was less rigid but more extendible than skin. There was no difference between the vagina and skin at low strains (p = 0.341), but a highly significant difference at large strains (p = 0.005).

CONCLUSIONS

skin and aponeurosis are not suited to predict vaginal tissue biomechanics. We should be cautious when transferring experiences from abdominal wall surgery to vaginal reconstructive surgery.

Vaginal tactile imaging

Changes in the elasticity of the vaginal walls, connective support tissues, and muscles are thought to be significant factors in the development of pelvic organ prolapse, a highly prevalent condition affecting at least 50% of women in the United States during their lifetimes. It creates two predominant concerns specific to the biomechanical properties of pelvic support tissues: how does tissue elasticity affect the development of pelvic organ prolapse and how can functional elasticity be maintained through reconstructive surgery. We designed a prototype of vaginal tactile imager (VTI) for visualization and assessment of elastic properties of pelvic floor tissues. In this paper, we analyze applicability of tactile imaging for evaluation of reconstructive surgery results and characterization of normal and pelvic organ prolapse conditions. A pilot clinical study with 13 patients demonstrated that VTI allows imaging of vaginal walls with increased rigidity due to implanted mesh grafts following reconstructive pelvic surgery and VTI has the potential for prolapse characterization and detection.

In vivo assessment of anterior compartment compliance and its relation to prolapse

INTRODUCTION AND HYPOTHESIS

The objective of the study was to compare anterior compartment compliance between women with and without pelvic organ prolapse and to explore factors determining the extent of anterior compartment prolapse.

METHODS

Ten women with normal pelvic support and nine with anterior compartment prolapse were analyzed. Abdominal pressure was measured during Valsalva and simultaneous midsagittal dynamic MR imaging. The distance between the most dependent anterior vaginal wall point and a previously determined average nulliparous anterior vaginal wall point was measured. A best-fit line was determined when anterior vaginal wall displacement was plotted relative to abdominal pressure. The slope of this line is a measure of anterior compartment compliance. Multivariate analyses and t tests were performed.

RESULTS

Mean compliance (centimeters per centimeter of water) was higher for cases [0.05 +/- 0.006 standard error of the mean (SEM)] than controls (0.03 +/- .007, p = 0.039). Degree of anterior compartment prolapse correlated best with compliance (R (2) = 0.75, p < 0.01) and also with resting anterior vaginal wall point (R (2) = 0.55, p < 0.01).

CONCLUSIONS

Women with anterior compartment prolapse have a 67% more compliant support system compared with those with normal support. Both compliance and resting anterior vaginal wall location are predictors of the degree of anterior compartment prolapse.

Effects of age on levator function and morphometry of the levator hiatus in women with pelvic floor disorders

Introduction and hypothesis

Epidemiological data supports the hypothesis that ageing is a risk factor for pelvic organ prolapse. In this study, we intended to determine the effect of age on levator function and morphometry in women with pelvic floor disorders.

Methods

Three hundred seventy-five patients underwent an interview, physical examination and transperineal ultrasound. Clinical assessment included palpation using the Modified Oxford Scale. Ultrasonography was performed to diagnose levator defects and assess levator hiatal morphometry.

Results

Pelvic floor muscle strength was weakly associated with patient age (r = −0.25, p < 0.01). This remained true after accounting for the confounders parity and levator defects. Morphometry of the levator hiatus was weakly positively correlated with age.

Conclusions

Ageing seems to have a limited effect on contractility and distensibility of the pelvic floor muscle. The small effect of ageing results in reduced contraction strength and increased hiatal diameters. This effect is partly confounded by parity and levator defects.

Biomechanical Properties of the Human Soft Palate

Objective:

To measure biomechanical properties of the human soft palate and the variation across anatomic regions.

Design:

Ex vivo analysis of human tissue.

Patients/participants:

Ten palates harvested from 10 normal adult human cadavers (age range, 37 to 90 years).

Interventions:

Computer-controlled uniaxial stress-relaxation mechanical properties tested in physiological saline at 37°C.

Main Outcome Measures:

Measurement of Young modulus, Poisson ratio, and determination of viscoelastic constants c, τ1, and τ2 by curve-fitting of the reduced relaxation function to the data.

Results:

One hundred sections were tested from the 10 palates, representative of 10 anatomic zones. The mean Young modulus range was 585 Pa at the posterior free edge to 1409 Pa at regions of attachment. The mean Poisson ratio in the inferior-superior direction was 0.45 (SD 0.26) and in the lateral direction, was 0.30 (SD 0.21). The mean viscoelastic constants for 1-mm extensions were C  =  −0.1056 (±0.1303), τ1  =  11.0369 (±9.1865) seconds, and τ2  =  0.2128 (±0.0792) seconds, and for 2-mm extensions were C  =  −0.1111 (±0.1466), τ1  =  14.3725 (±5.2701) seconds, and τ2  =  0.2094 (±0.0544) seconds.

Conclusions:

The results show agreement with values of the Young modulus estimated by authors (Ettema and Kuehn, 1994; Berry et al., 1999) undertaking finite element modeling of the palate. However, other modulus measurements based on closing pressure are considerably different. The spatial distribution of viscoelastic parameters across the palate shows good consistency.

Biomechanical properties of synthetic and biologic graft materials following long-term implantation in the rabbit abdomen and vagina

OBJECTIVE

We sought to evaluate the effects of anatomic location and ovariectomy on biomechanical properties of synthetic and biologic graft materials after long-term implantation.

STUDY DESIGN

A total of 35 rabbits underwent ovariectomy or sham laparotomy and were implanted with polypropylene (PP) mesh (n = 17) or cross-linked porcine dermis (PS) (n = 18) in the vagina and abdomen. Grafts were harvested 9 months later and underwent mechanical properties testing.

RESULTS

After implantation, PS was similar in strength (P = .52) but was twice as stiff as PP (P = .04) and had a maximal elongation only half that of PP (P < .001). Degradation of PS was associated with decreased ultimate tensile strength (P = .03) and elastic modulus (P = .046). Vaginal PP grafts shrunk more (P < .001) and were less stiff than abdominal PP grafts (P = .049) but were not different in strength (P = .19). Ovariectomy had no effect (P > .05).

CONCLUSION

Cross-linked PS undergoes long-term degradation resulting in compromised biomechanical properties and thus is likely inferior to lightweight PP meshes for pelvic organ prolapse and incontinence procedures.

Tissue mechanics, animal models, and pelvic organ prolapse: a review

Pelvic floor disorders such as pelvic organ prolapse, urinary incontinence, and fecal incontinence affect a large number of women each year. The pelvic floor can be thought of as a biomechanical structure due to the complex interaction between the vagina and its supportive structures that are designed to withstand the downward descent of the pelvic organs in response to increases in abdominal pressure. Although previous work has highlighted the biochemical changes that are associated with specific risk factors (i.e. parity, menopause, and genetics), little work has been done to understand the biomechanical changes that occur within the vagina and its supportive structures to prevent the onset of these pelvic floor disorders. Human studies are often limited due to the challenges of obtaining large tissue samples and ethical concerns. Therefore, it is necessary to investigate the use of animal models and their importance in understanding how different risk factors affect the biomechanical properties of the vagina and its supportive structures. In this review paper, we will discuss the different animal models that have been previously used to characterize the biomechanical properties of the vagina: including non-human primates, rodents, rabbits, and sheep. The anatomy and preliminary biomechanical findings are discussed along with the importance of considering experimental conditions, tissue anisotropy, and viscoelasticity when characterizing the biomechanical properties of vaginal tissue. Although there is not a lot of biomechanics research related to the vagina and pelvic floor, the future is exciting due to the significant potential for scientific findings that will improve our understanding of these conditions and hopefully lead to improvements in the prevention and treatment of pelvic disorders.

Biomechanical properties of the vaginal wall: effect of pregnancy, elastic fiber deficiency, and pelvic organ prolapse

OBJECTIVE

The purpose of this study was to identify pregnancy-induced changes in biomechanical properties of the vaginal wall and to compare these with fibulin-5 knockout mice (Fbln5(-/-)) with and without prolapse.

STUDY DESIGN

Mid-vaginal segments of nonpregnant and late-pregnant wild-type mice, Fbln5(-/-) with prolapse mice and Fbln5(-/-) mice without prolapse were studied. Tissue length at failure, maximal strain, maximal stress, and tissue stiffness were determined.

RESULTS

Compared with nonpregnant mice, vaginas of pregnant and Fbln5(-/-) (with prolapse) mice exhibited decreased maximal stress, increased distensibility and strain, and decreased stiffness. Tissues from Fbln5(-/-) mice without prolapse were similar to nonpregnant wild-type animals.

CONCLUSION

Pregnancy confers remarkable changes in the vaginal wall that include increased distensibility and decreased stiffness and maximal stress. Elastinopathy alone is insufficient to cause significant changes in these properties, but prolapse confers additional alterations in distensibility and stiffness that are similar to those changes that have been observed in pregnancy. These changes may contribute to the poor durability of many restorative surgical procedures for prolapse.

Depression and heart disease: therapeutic implications

The consequences of depression and coronary artery disease (CAD) were reviewed in the literature. The comorbidity of depression and CAD results in an increased cardiovascular mortality. We reviewed possible explanations for this increased morbidity, which include: toxicity of tricyclic antidepressants that can cause cardiac arrhythmias, abnormalities in platelet function leading to increased platelet aggregation due to abnormalities in serotonin in the platelet (an abnormality that possibly causes depression in the central nervous system), diffuse atherosclerosis causing central nervous system abnormalities including depression (vascular depression), as well as the possibility that depressed patients are less compliant with their medications and physician-directed health recommendations. Recent reports of selective serotonin reuptake inhibitors (SSRIs) causing a reduced cardiovascular mortality may be related to serotonin platelet abnormalities in depressed patients that are effectively treated by SSRIs (SADHART and ENRICHD trial). It is possible that these trials reveal a mechanism of depression that also effects platelet function and can be improved with SSRI therapy, suggesting a preferential therapeutic pathway for the treatment of depressed patients with CAD.