A biofidelic computational model of the female pelvic system to understand effect of bladder fill and progressive vaginal tissue stiffening due to prolapse on anterior vaginal wall

Abstract

Treatment of anterior vaginal prolapse (AVP), suffered by over 500,000 women in the USA, is a challenge in urogynecology because of the poorly understood mechanics of AVP. Recently, computational modeling combined with finite element method has been used to model AVP through the study of pelvic floor muscle and connective tissue impairments on the anterior vaginal wall (AVW). Also, the effects of pelvic organ displacements on the AVW were studied numerically. In our current work, an MRI-based full-scale biofidelic computational model of the female pelvic system composed of the urinary bladder, vaginal canal, and the uterus was developed, and a novel finite element method framework was employed to simulate vaginal tissue stiffening and also bladder filling due to expansion for the first time. A mesh convergence study was conducted to choose a computationally efficient mesh, and a non-linear hyperelastic Yeoh's material model was adopted for the study. The AVW displacements, mechanical stresses, and strains were estimated at varying degrees of bladder fills and vaginal tissue stiffening. Both bladder filling and vaginal stiffening were found to increase the stress concentration on the AVW with varying trends, which have been discussed in detail in the paper. To our knowledge, this study is the first to estimate the individual and combined effects of bladder filling and vaginal tissue stiffening due to prolapse on the AVW. Copyright © 2016 John Wiley & Sons, Ltd.

Biofidelic soft composites–experimental and computational modeling

“…For each of the tests, the load (Newtons) versus extension (mm) graphs were plotted and postprocessed to obtain stress versus stretch plots, which were used for further analyses. It should be mentioned here that silicones simulating skin tissues typically exhibit a high cut-out or breaking strengths in the range of [15][16][17][18][19][20][21][22][23][24][25]154,156], while other tissues such as pelvic tissues (Ultimate tensile strength of 1-6 MPa) [7,9,144,157] and brain tissues (Ultimate tensile strength of 300-900 kPa) [1,158,159] may have lower cut-out strengths. Sutures on the other hand have extremely high cut-out strengths in the range of 100-500 MPa [95].…”

“…Based on previous studies on mesh convergence and optimization of the female pelvic floor by the authors [170,171], a semi-fine mesh was chosen for all the pelvic organs with a total of 34,282 tetrahedral elements. Figure 5.2 shows the meshes of the pelvic organs and muscles in four different colors.…”

Biofidelic Conductive Synthetic Skin Composites

“…Soft tissues, polymers and rubbers exhibit a non-linear stress versus strain response which can be characterized using hyperelastic constitutive material models such as Fung, Mooney-Rivlin, Yeoh, Veronda-Westmann, and Humphrey [10,12,13,[16][17][18][19][20][21][22][23]. Hyperelastic curve fit models are based on the definition of the strain-energy function (denoted as Ψ), which depends on the type of material [24,25].…”

Female pelvic floor biomechanics

“…These simulations suggest that measuring pressures in a clinical setting may not provide an adequate indication of deterioration of the anterior vaginal wall. This demonstrates that there may be a role for diagnostic and computational models to be used in conjunction with clinical measurements to improve clinical care [9]. …”

“…As the pelvic floor comprises the primary load bearing structure of the pelvic organs, it has become increasingly clear that mechanics contributes to the onset of prolapse, and the failure of surgical interventions. With the ultimate goal of effectively preventing and treating POP, defining the loading conditions of the pelvis over the female lifespan is paramount [9]. …”