C. Rubod

Biomechanical properties of vaginal tissue: preliminary results

The aim of this study is to characterise the biomechanical properties of vaginal tissue to develop an accurate cure of pelvic organ prolapse (POP). Prolapsed vaginal tissues were extracted during the prolapse cure of five patients (POP) and on five cadavers without noticed pelvic floor dysfunction (non-pelvic organ prolapse) with agreement of the ethics committee. Uni-axial tension was performed, and the results were analysed. Individual reproducibility of experimental results was good, and the results highlight the non-linear relationship between stress (force per unit of surface) and strain (l − l0 / l0) and very large deformation before rupture appearance. This experimental study has proven for the first time that the mechanical behaviour of vaginal tissue has to be defined as hyperelastic with a large deformation. This response has to be taken into account to develop accurate synthetic prostheses for POP cure and in the numerical simulation of the pelvic floor.

Comparative analysis of pelvic ligaments: a biomechanics study

Introduction and hypothesisPelvic 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 methodsSamples 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.ResultsWe 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.ConclusionPelvic 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.

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

Introduction and hypothesisDespite 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.MethodsSamples from 11 fresh women cadavers without prolapse were collected. Uniaxial tension tests were performed and stress–strain curves were obtained.ResultsBiomechanical 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).ConclusionsSkin 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.

Bacteriological analysis of meshes removed for complications after surgical management of urinary incontinence or pelvic organ prolapse

The aim of this study is to examine the role of bacterial infection in complications following surgical management of urinary incontinence and genital prolapse using meshes. There were sixteen prostheses removed. Eight were monofilament polypropylene-knitted meshes, one was a silicone-coated polypropylene mesh, another was a collagen-coated polypropylene mesh, four were silicone-coated polyester meshes and two were polyester meshes. The most frequent cause for removal was symptomatic vaginal erosion (62%). Cultures were performed under aerobic, anaerobic and enrichment conditions. Infection was multimicrobial for 31% of meshes. When only one bacteria was found, it was Proteus mirabilis in 25% of cases. Forty-three per cent of bacterial quantifications were under 103 colony-forming units per millilitre. Bacterial contamination was found in all meshes, quantification was often low, and therefore, its exact role is not yet clear.

Histology of the vaginal wall in women with pelvic organ prolapse: a literature review

Introduction and hypothesisThe pathophysiology of pelvic organ prolapse (POP) is incompletely understood. The purpose of this study is to describe the current knowledge about histology of the vaginal wall and its possible involvement in the pathogenesis of pelvic organ prolapse.MethodsEligible studies were selected through a MEDLINE search covering January 1986 to December 2012. The research was limited to English-language publications.ResultsInvestigations of changes in the vaginal tissue that occur in women with genital prolapse are currently still limited and produced contrary results. The heterogeneity of the patients and the control groups in terms of age, parity and hormonal status, of the localization of biopsies and the histological methods as well as the lack of validation of the quantification procedures do not allow clear and definitive conclusions to be drawn.ConclusionsThis review shows that current knowledge of the histological changes observed in women with POP are inconclusive and relatively limited. More studies are needed in this specific field to better understand the mechanisms that lead to POP.

Experiments and finite element modelling for the study of prolapse in the pelvic floor system

Pelvic prolapse affects one woman in three of all ages combined and is quite common for more than 60% of patients over 60 years of age. The treatment of this pathological problem is one of the biggest challenges to the gynaecologist today. The rate of surgical intervention failure is quite significant. The recurrence of prolapse could be related to inadequate surgical technique or the pathology or/and biomechanical deficiency of the soft tissues. The modelling and simulation of the behaviour of the pelvic cavity could be a major tool for specific evaluation of pelvic status. A first stage of this model is being developed and reported. The computer-aided design model of the organs of the pelvic floor is created using magnetic resonance image data and the ligament boundary conditions are defined. A multi-organ geometric model is thus created and studied.

Fetal microchimerism: benevolence or malevolence for the mother?

For a long time, the conventional view was that the fetus and maternal vascular system are kept separate. In fact there is a two way traffic of cells through the placenta and the transplacental passage of cells is in fact the norm. The fetal cells can persist in a wide range of womans tissues following a pregnancy or an abortion and she becomes a chimera. Fetal cells have been found in the maternal circulation and they were shown to persist for the entire life in humans, thus demonstrating long-term engraftment and survival capabilities. Microchimerism is a subject of much interest for a number of reasons. Studies of fetal microchimerism during pregnancy may offer explanations for complications of pregnancy, such as preeclampsia, as well as insights into the pathogenesis of autoimmune diseases which usually ameliorate during pregnancy. The impact of the persistence of allogenic cells of fetal origin and of the maternal immunological response to them on the mothers health is still not clear. On the beneficial side, it has been proposed that genetically disparate fetal microchimerism provides protection against some cancers, that fetal microchimerism can afford the mother new mechanisms of protection to some diseases, that fetal microchimerism can enlarge the immunological repertoire of the mother improving her defense against aggressor. Fetal cells are often present at sites of maternal injury and may have an active role in the repair of maternal tissues.

Changes in elastin density in different locations of the vaginal wall in women with pelvic organ prolapse

Introduction and hypothesisThe purpose of this study was to analyze the histomorphometric properties of the vaginal wall in women with pelvic organ prolapse (POP).MethodsIn 15 women undergoing surgery for POP, full-thickness biopsies were collected at two different sites of location from the anterior and/or posterior vaginal wall. Properties of the precervical area (POP-Q point C/D) were compared with the most distal portion of the vaginal wall (POP-Q point Ba/Bp) using histological staining and immunohistochemistry. The densities of total collagen fibers, elastic fibers, smooth muscle cells, and blood vessels were determined by combining high-resolution virtual imaging and computer-assisted digital image analysis.ResultsThe mean elastin density was significantly decreased in the lamina propria and muscularis layer of the vaginal wall from the most distal portion of the prolapsed vaginal wall compared with the precervical area. This difference was statistically significant in the lamina propria for both anterior (8.4 ± 1.2 and 12.1 ± 2.0, p = 0.048) and posterior (6.8 ± 0.5 and 10.1 ± 1.4, p = 0.040) locations, and in the muscularis for the anterior (5.2 ± 0.4 and 8.4 ± 1.2, p = 0.009) vaginal wall. There were no statistically significant differences in the mean densities of collagen fibers, smooth muscle cells or blood vessels between the two locations.ConclusionsIn this study, we observed changes in elastin density in two different locations of the vaginal wall from women with POP. The histomorphometric properties of the vaginal wall can be variable from one place to another in the same patient. This result supports the existence of most vulnerable locations within the vaginal wall and the potential benefit of site-specific prolapse surgery.

3D simulation of pelvic system numerical simulation for a better understanding of the contribution of the uterine ligaments

Introduction and hypothesisGenital prolapse remains a complex pathological condition. Physiopathology remains poorly understood, aetiology is multi-factorial, surgery is not always satisfying, as the rate of relapse cannot be overlooked. More over a good anatomical result will not always guarantee functional satisfaction. The aim of our study is to have a better understanding of the involvement of uterine ligaments in pelvic statics via 3D simulation.MethodsSimulation of pelvic mobility is performed with a validated numerical model in a normal situation (standing up to lying down) or induced pathological ones where parts of the constitutive elements of the model are virtually “cut” independently. Displacements are then discussed.ResultsNumerical results have been compared with dynamic MRI for two volunteers. Dynamic sequences had 90 images, and 180 simulations have been validated. Results are coherent with clinical data and the literature, thus validating our mechanical approach. Uterine ligaments are involved in pelvic statics, but their lesions are not sufficient to generate a genital prolapse. Round ligaments play a part in uterine orientation; the utero-sacral ligaments support the uterus when standing up.ConclusionsPelvic normal and pathological mobility study via modelling and 3D simulation is a new strategy in understanding the complex multifactorial physiopathology of genital prolapse. This approach must be validated in a larger series of patients. Nevertheless, pelvic ligaments seem to play an important role in statics, especially, in agreement with a literature survey, utero-sacral ligaments in a standing position.

Cystocele and functional anatomy of the pelvic floor: review and update of the various theories.

Introduction and hypothesisWe updated anatomic theories of pelvic organ support to determine pathophysiology in various forms of cystocele.MethodsPubMed/MEDLINE, ScienceDirect, Cochrane Library, and Web of Science databases were searched using the terms pelvic floor, cystocele, anatomy, connective tissue, endopelvic fascia, and pelvic mobility. We retrieved 612 articles, of which 61 matched our topic and thus were selected. Anatomic structures of bladder support and their roles in cystocele onset were determined on the international anatomic classification; the various anatomic theories of pelvic organ support were reviewed and a synthesis was made of theories of cystocele pathophysiology.ResultsAnterior vaginal support structures comprise pubocervical fascia, tendinous arcs, endopelvic fascia, and levator ani muscle. DeLancey’s theory was based on anatomic models and, later, magnetic resonance imaging (MRI), establishing a three-level anatomopathologic definition of prolapse. Petros’s integral theory demonstrated interdependence between pelvic organ support systems, linking ligament–fascia lesions, and clinical expression. Apical cystocele is induced by failure of the pubocervical fascia and insertion of its cervical ring; lower cystocele is induced by pubocervical fascia (medial cystocele) or endopelvic fascia failure at its arcus tendineus fasciae pelvis attachment (lateral cystocele).ConclusionsImproved anatomic knowledge of vaginal wall support mechanisms will improve understanding of cystocele pathophysiology, diagnosis of the various types, and surgical techniques. The two most relevant theories, DeLancey’s and Petros’s, are complementary, enriching knowledge of pelvic functional anatomy, but differ in mechanism. Three-dimensional digital models could integrate and assess the mechanical properties of each anatomic structure.