Modeling the Biomechanics of Stress Urinary Incontinence Thomas Spirka Margot Damaser Cleveland Clinic Cleveland State University Cleveland OH

Stress Urinary Incontinence What is it? Increased Abdominal Pressure Increases Bladder Pressure Urine Leakage Cough The complaint of involuntary leakage of urine on effort or exertion, or on sneezing or coughing. Abrams, et al. Neurourol. & Urodyn. 21: , 2002.

Stress Urinary Incontinence Why should we care?  Urinary Incontinence 20-50% of women 20-50% of women  Risk Factors –Age –Vaginal Childbirth

Mechanics of Stress Urinary Incontinence  Little known regarding mechanics of continence maintenance  Limited to two conflicting theories –Mechanics of have never been validated in either case

Project Goals  Gain insight into the mechanics by which continence is maintained when abdominal pressure is increased through finite element modeling.  Use finite element modeling to test the mechanics behind the two theories of continence.

Project Goals  Key to understanding this continence mechanism is understanding how structures of the pelvic floor and lower urinary tract deform in relation to one another when abdominal pressure is increased

Finite Element Modeling of Biomechanics  Goal is to gain insight and understanding that cannot be obtained experimentally  Modeled situations are complex and not well characterized –Require several assumptions to be made and tested  Sensitivity Analysis and Parametric Testing frequently required to determine effects of assumptions and understand how model is performing

Mechanics of Stress Urinary Incontinence  Structures that must be incorporated into model –Pelvic Bones –Bladder –Urethra –Vagina –Levator Ani (Pubococcygeus, Illiococcygeus, Puborectalis) –Arcus Tendinius Fascia Pelvis –Endopelvic Fascia –Pubourethral Ligaments

Modeled by Xiao Long Li

Modeling  Need to account for –Mechanics of each structure  How does each structure deform  Material Properties (Non-Linear) –Contact between structures  How do the structures deform in relation to one another  How much support do the various structures provide to one another

Modeling  Need to account for –Fluid Structure Interactions  Is urine entering the urethra as a result of the abdominal pressure loads  Is urine traveling the length of the urethra and leaking out –Transient Loads  Sharp transient events do not lend themselves to quasi-steady state modeling –Forces arising from muscle contractions

Computational Needs  Hardware –Computational Power  Simple simulations are taking days to complete on desktop equipment  Ability to run multiple parametric simulations if not concurrently then in at least a timely fashion  Software –LS Dyna  Dynamic Finite Element Solver –Pre/Post Processing  Mesh Generation  Display Results