Modelling of Soft Connective Tissues to Investigate Female Pelvic Floor Dysfunctions

Abstract

After menopause, decreased levels of estrogen and progesterone remodel the collagen of the soft tissues thereby reducing their stiffness. Stress urinary incontinence is associated with involuntary urine leakage due to pathological movement of the pelvic organs resulting from lax suspension system, fasciae, and ligaments. This study compares the changes in the orientation and position of the female pelvic organs due to weakened fasciae, ligaments, and their combined laxity. A mixture theory weighted by respective volume fraction of elastin-collagen fibre compound (5%), adipose tissue (85%), and smooth muscle (5%) is adopted to characterize the mechanical behaviour of the fascia. The load carrying response (other than the functional response to the pelvic organs) of each fascia component, pelvic organs, muscles, and ligaments are assumed to be isotropic, hyperelastic, and incompressible. Finite element simulations are conducted during Valsalva manoeuvre with weakened tissues modelled by reduced tissue stiffness. A significant dislocation of the urethrovesical junction is observed due to weakness of the fascia (13.89 mm) compared to the ligaments (5.47 mm). The dynamics of the pelvic floor observed in this study during Valsalva manoeuvre is associated with urethral-bladder hypermobility, greater levator plate angulation, and positive Q-tip test which are observed in incontinent females.

Simulation of vaginal uterosacral ligament suspension damage, mimicking a mesh-augmented apical prolapse repair

“…Previous studies showed that the laxity in the cardinal/uterosacral ligaments might cause abnormal bladder emptying and uterine prolapse. 28,36 Nevertheless, the implantation of the meshes in the simulation reduced the displacement magnitude in the asymptomatic uterus, to 25.6% using A mesh and 9.8% using B mesh. The implant B allowed an approximation of the uterus behavior to the asymptomatic model.…”

“…Previous studies showed that the laxity in the cardinal/uterosacral ligaments might cause abnormal bladder emptying and uterine prolapse. 28,36…”

“…Additionally, for mesh A, with rectangular pore and differences in the diameter of the fiber filament, the behavior is expected to be orthotropic, as found in. 28 For this mesh only the longitudinal direction, which corresponds to the higher resistance direction, was considered for the averaged curves of Figure 1. For mesh B its behavior is closer to isotopic, due to the round pores and constant filament diameters.…”

“…In order to simulate the mechanical behavior of the pelvic cavity tissues, Yeoh and Ogden constitutive models were used (the viscosity, temperature and time-dependent effects were not taken into account). 31 These are simple models that employ a nonlinear relationship between stress and strain to describe incompressible hyperelastic materials. They have proved to correctly approximate the tensile curves of different pelvic floor tissues, used in the simulation of the biomechanical behavior of the PFM during the simulation of Valsalva maneuver 17,18 and the impairment of the pelvic ligaments.…”

Pathogenese, funktionelle und anatomische Aspekte der weiblichen Belastungsinkontinenz

“…Das Parakolpium, die urethrovesikalen Ligamente und die Ligamente der Faszia pelvis geben der In der Simulation konnten wesentliche Aspekte der Integraltheorie bestätigt werden, insbesondere die Erschlaffung der vaginalen Bänder bzw. die Aufhängung der Scheidenwand als Ursache für Prolaps und Harninkontinenz[11].UrethradruckDer Rolle des verminderten urethralen Druckes als Ursache für eine Belastungsinkontinenz wird wieder zunehmend mehr Beachtung geschenkt[12]. Der maximale Urethraverschlussdruck in cm H 2 O unter Ruhe-bzw.…”