Effect of bladder and rectal loads on the vaginal canal and levator ani in varying pelvic floor conditions

Abstract

ABSTRACTThe female pelvic floor is a complex system, in which the pelvic organs such as the urinary bladder, rectum, vaginal canal and the pelvic floor muscles interact in different ways over the course of a women's life. To date, the pelvic floor mechanics is poorly understood by doctors and medical practitioners, which is the key to understand the various pelvic floor defects such as child-birth complications and pelvic organ prolapse (POP). Currently, millions of women suffer from child birth trauma and POP in the United States and across the globe. While experimental studies are being performed on human subjects to understand the various qualitative trends in pelvic floor defects, recently, computational modeling has allowed researchers to better understand the mechanics of the pelvis. Based on a recent review on the state of the art knowledge on numerical modeling of pelvic floor mechanics by Chanda et al., a lack of computational study on the interaction between the pelvic organs and the muscles were highlighted. In the current work, a full-scale female pelvic system model (comprising of the urinary bladder, rectum, vaginal canal, uterus and the pelvic floor muscle levator ani) was developed using a magnetic resonance imaging (MRI)-based image segmentation process, and the effect of bladder and rectal loads on the vaginal canal in varying pelvic floor conditions (healthy and prolapsed) were quantified. Nonlinear material models were adopted to simulate pelvic tissue properties and a novel deteriorating material model was developed to simulate pelvic floor muscle degradation in different degrees of prolapse. The results from this study highlight the significance of the inclusion of the pelvic floor muscles in the study of the mechanics of the pelvis. Also, the mechanics of pelvic degradation and its effect on the vaginal walls and levator ani were studied to understand discomfort associated with prolapse. To date, such a detailed study on the interaction of pelvic organs in prolapse has not been conducted, the results of which would be indispensable for better understanding of pelvic floor mechanics and allow doctors to device better surgical planning strategies.