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Modeling the Pelvic Floor using Shell Elements

Modeling the Pelvic Floor using Shell Elements. D. d'Aulignac (1) , J.A.C. Martins (1) , T. Mascarenhas ( 2 ) , R.M. Natal Jorge ( 3 ) and E.B. Pires (1). 3 IDMEC Faculty of Engineering University of Porto Portugal.

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Modeling the Pelvic Floor using Shell Elements

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  1. Modeling the Pelvic Floor using Shell Elements D. d'Aulignac(1), J.A.C. Martins(1), T. Mascarenhas(2), R.M. Natal Jorge(3) and E.B. Pires(1) 3IDMECFaculty of EngineeringUniversity of Porto Portugal 1Departamento de Engenharia Civil Instituto Superior Técnico Av. Rovisco Pais 1049-001 Lisboa Portugal 2S. João HospitalPortoPortugal

  2. Finite Element Simulation Anatomy Plan Data Geometry

  3. Why? • Understand working of the pelvic floor • Support of organs • Predict damages during childbirth • Stress incontinence • Prolapse • Uterine • Vaginal • Rectal

  4. Pelvic Floor Illust. From Netter

  5. MRI Images Sao Joao Hospital, Porto axial sagittal

  6. Visualisation Segmented manually from MRI data. Julia R.Fielding et al. (Harvard medical school) Rasmussen et al (University of Illinois at Chicago)

  7. Cadaver Measurements Janda et al 2003

  8. Geometry Point Set NURB Surfaces (Rhino 3d) Polygon Mesh

  9. Mesh Geometry top Frontal view of the mesh: 3068 triangles 1620 nodes side

  10. 3D Muscle Model Martins et al. 98 isotropic fibers volume

  11. Muscle Model Deformation gradient Left Cauchy-Green tensor Right Cauchy-Green tensor

  12. Muscle Model First Invariant Fibre strain Direction of fibres (deformed)

  13. Plane Stress Since incompressibility is assumed Since normal stresses are zero the plane stress is given as

  14. Passive Behaviour isotropic fibres Humphrey’s model for cardiac tissue

  15. Passive Tests u lambda

  16. Muscle Fibres

  17. Active Behaviour

  18. Muscle Activation Sum of passive and active contributions

  19. Total Stress isotropic total active fibers

  20. Discussion • Large quantitative differences between different models • Oomens • Martins • Bosboom • Gielen • Kojic • Humphrey • Comparison with other models and experimental results is essential

  21. Simulation 3068 triangular shell elements Non-linear simulation performed with ABAQUS UMAT routine decribing the material

  22. Muscle Activation

  23. The Future • Deformation of pelvic floor during childbirth • Damage, fracture of soft tissues • Prolapse of internal organs • Geometric models from MRI data • 8-node solid FE (de Sousa et al. 03)

  24. Muscle Model Deformation gradient Left Cauchy-Green tensor Right Cauchy-Green tensor

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