Modeling the Biomechanics of Modeling the Biomechanics of Stress Urinary IncontinenceStress Urinary Incontinence
Thomas Spirka Margot DamaserThomas Spirka Margot Damaser
Cleveland Clinic Cleveland Clinic Cleveland State UniversityCleveland State University
Cleveland OHCleveland OH
Stress Urinary IncontinenceStress Urinary IncontinenceWhat is it?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. 21:167-178, 2002.
Stress Urinary IncontinenceStress Urinary IncontinenceWhy should we care?Why should we care?
Urinary IncontinenceUrinary Incontinence 20-50% of women20-50% of women
Risk FactorsRisk Factors– Age Age – Vaginal ChildbirthVaginal Childbirth
Mechanics of Stress Urinary Mechanics of Stress Urinary IncontinenceIncontinence
Little known regarding mechanics of Little known regarding mechanics of continence maintenancecontinence maintenance
Limited to two conflicting theoriesLimited to two conflicting theories– Mechanics of have never been validated in Mechanics of have never been validated in
either caseeither case
Project GoalsProject Goals
Gain insight into the mechanics by which Gain insight into the mechanics by which continence is maintained when abdominal continence is maintained when abdominal pressure is increased through finite element pressure is increased through finite element modeling.modeling.
Use finite element modeling to test the Use finite element modeling to test the mechanics behind the two theories of mechanics behind the two theories of continence.continence.
Project GoalsProject Goals
Key to understanding this continence Key to understanding this continence mechanism is understanding how structures mechanism is understanding how structures of the pelvic floor and lower urinary tract of the pelvic floor and lower urinary tract deform in relation to one another when deform in relation to one another when abdominal pressure is increasedabdominal pressure is increased
Finite Element Modeling of Finite Element Modeling of BiomechanicsBiomechanics
Goal is to gain insight and understanding that cannot be Goal is to gain insight and understanding that cannot be obtained experimentallyobtained experimentally
Modeled situations are complex and not well characterizedModeled situations are complex and not well characterized– Require several assumptions to be made and testedRequire several assumptions to be made and tested
Sensitivity Analysis and Parametric Testing frequently Sensitivity Analysis and Parametric Testing frequently required to determine effects of assumptions and required to determine effects of assumptions and understand how model is performingunderstand how model is performing
Mechanics of Stress Urinary Mechanics of Stress Urinary IncontinenceIncontinence
Structures that must be incorporated into modelStructures that must be incorporated into model– Pelvic BonesPelvic Bones– BladderBladder– UrethraUrethra– VaginaVagina– Levator Ani (Pubococcygeus, Illiococcygeus, Levator Ani (Pubococcygeus, Illiococcygeus,
Puborectalis)Puborectalis)– Arcus Tendinius Fascia PelvisArcus Tendinius Fascia Pelvis– Endopelvic FasciaEndopelvic Fascia– Pubourethral LigamentsPubourethral Ligaments
Modeled by Xiao Long Li
ModelingModeling
Need to account forNeed to account for– Mechanics of each structureMechanics of each structure
How does each structure deformHow does each structure deform Material Properties (Non-Linear)Material Properties (Non-Linear)
– Contact between structuresContact between structures How do the structures deform in relation to one How do the structures deform in relation to one
anotheranother How much support do the various structures provide How much support do the various structures provide
to one anotherto one another
ModelingModeling
Need to account forNeed to account for– Fluid Structure InteractionsFluid Structure Interactions
Is urine entering the urethra as a result of the Is urine entering the urethra as a result of the abdominal pressure loadsabdominal pressure loads
Is urine traveling the length of the urethra and leaking Is urine traveling the length of the urethra and leaking outout
– Transient LoadsTransient Loads Sharp transient events do not lend themselves to Sharp transient events do not lend themselves to
quasi-steady state modelingquasi-steady state modeling
– Forces arising from muscle contractionsForces arising from muscle contractions
Computational NeedsComputational Needs
HardwareHardware– Computational PowerComputational Power
Simple simulations are taking days to complete on desktop Simple simulations are taking days to complete on desktop equipmentequipment
Ability to run multiple parametric simulations if not concurrently Ability to run multiple parametric simulations if not concurrently then in at least a timely fashionthen in at least a timely fashion
SoftwareSoftware– LS DynaLS Dyna
Dynamic Finite Element SolverDynamic Finite Element Solver
– Pre/Post Processing Pre/Post Processing Mesh Generation Mesh Generation Display ResultsDisplay Results