Modelling of Soft Connective Tissues to Investigate Female Pelvic Floor Dysfunctions

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

Virgin Passive Colon Biomechanics and a Literature Review of Active Contraction Constitutive Models

The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel–Gasser–Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill’s three-element model, Murphy’s four-state cross-bridge chemical kinetic model and Huxley’s sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine

Shifting and Shaping Perceptions: Towards the Characterization and Literacy of Female Pelvic Organ Support

Pelvic Organ Prolapse (POP) is a pelvic floor condition characterized by the unnatural descent of pelvic organs into the vagina. It occurs as the result of compromised connective tissues and musculature following vaginal delivery and/or changes in tissue composition due to aging. Approximately 50% of women in the United States experience some degree of POP during their lifetime, with symptoms that include altered urination and defecation, physical discomfort, depression, and anxiety. Over the last decade, POP treatments have gained public notoriety due to surgical complications and recurrence of prolapse after surgical repair. Both outcomes stem, in part, from gaps in knowledge regarding the complex interactions of pelvic viscera, tissues, and musculature, and is exacerbated by the significant time span between events surrounding vaginal birth injuries and symptomatic prolapse. Over the last century, fields such as cardiovascular medicine and orthopedics have made significant strides to improve the human condition through the application of biomechanics, diagnostic imaging techniques, and modeling. Such methods have been used to reliably differentiate normal and diseased anatomy with respect to orientation, location, and other geometric attributes. In contrast, urogynecology remains decades behind as a result of a failure to adopt new interdisciplinary methods, limiting our ability to effectively treat POP. Thus, approximately 80% of women with symptomatic POP choose to suffer in silence. This is troubling, given that POP and related disorders will become increasingly prevalent due to the advancing age of the global population. This dissertation explores the assessment and development of diagnostic tools that improve our ability to quantify the position of the vagina with respect to physiologic changes that may occur over the lifespan within the normal range. These tools provide valuable information regarding the physical changes that occur over time and the differences between populations while serving as a potential standard by which pelvic anatomy can be quantified. Furthermore, this work explores our knowledge, perceptions, and attitudes regarding female pelvic health to challenge misconceptions surrounding normal and abnormal physiological functions, foster attitudes of empathy and acceptance for disorders, and improve health literacy by illustrating the impact that it has on lives worldwide