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The finite element muscle modelling cookbook

The finite element muscle modelling cookbook. And the importance of fibres. C. Antonio Sánchez* Dept of Elec & Comp Eng University of British Columbia Vancouver, BC, Canada antonios@ece.ubc.ca. John E. Lloyd Dept of Elec & Comp Eng University of British Columbia

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The finite element muscle modelling cookbook

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  1. The finite element muscle modelling cookbook And the importance of fibres C. Antonio Sánchez* Dept of Elec & Comp Eng University of British Columbia Vancouver, BC, Canada antonios@ece.ubc.ca John E. Lloyd Dept of Elec & Comp Eng University of British Columbia Vancouver, BC, Canada lloyd@cs.ubc.ca *presenting author

  2. Finite Element(FE) Muscle Models Extensor Carpi RadialisLongus Masseter

  3. FE Muscle Models Fibre Field(s) Volumetric Mesh Constitutive Law (Blemker, 2005)

  4. Fibre Geometries Fibre templates (Blemker& Delp, 2005) Digitized Fibres (Ravichandiran et al., 2009)

  5. Fibre Geometries Digitized Template Point-to-Point (Axial)

  6. Fibres matter! Digitized Template 81% overlap Point-to-Point (Axial) 88% overlap 45

  7. Fibres matter! Axial has same force-length relationship Template force is scaled 1.46x

  8. Fibre-Rich FE Muscle Ingredients • Target surface geometry • Template volumetric mesh • Fibre geometry Directions • Create Volumetric Mesh • Register template to target • Recondition elements • Register Fibre Field • Wrap fibres with surface • Register to target • Assign element properties • Extract directions from fibres

  9. Fibre-Rich FE Muscle Ingredients • Target surface geometry • Template volumetric mesh • Fibre geometry Directions • Create Volumetric Mesh • Register template to target • Recondition elements • Register Fibre Field • Wrap fibres with surface • Register to target • Assign element properties • Extract directions from fibres

  10. Volumetric Meshes • Muscles are highly deformable • Structured hexahedral meshes preferred • Most are hand-crafted • International Union of Physiological Sciences (IUPS) Physiome Project • Collection of template meshes • Register template shapes to target geometry

  11. Volumetric Meshes Deformable Registration Element Conditioning Poor Good

  12. Fibre-Rich FE Muscle Ingredients • Target surface geometry • Template volumetric mesh • Fibre geometry Directions • Create Volumetric Mesh • Register template to target • Recondition elements • Register Fibre Field • Wrap fibres with surface • Register to target • Assign element properties • Extract directions from fibres

  13. Fibre Registration (Lee et al., 2012)

  14. Fibre Registration (Gilles et al., 2007) Video courtesy of Benjamin Gilles, INRIA Grenoble

  15. Fibre-Rich FE Muscle Ingredients • Target surface geometry • Template volumetric mesh • Fibre geometry Directions • Create Volumetric Mesh • Register template to target • Recondition elements • Register Fibre Field • Wrap fibres with surface • Register to target • Assign element properties • Extract directions from fibres

  16. Extracting Orientations • Evaluated at integration points • Find fibres in neighbourhood

  17. Extracting Orientations • Evaluated at integration points • Find fibres in neighbourhood

  18. Finite Element(FE) Muscle Models Extensor Carpi RadialisLongus Masseter

  19. … AND THE IMPORTANCE OF FIBRES ?

  20. Preliminary simulations • What level of detail is important? • Axially along muscle • Minimal set of templates • Fibres typically run between tendon sheets • Are there important intricacies? • Simulation: • Isometric contraction • Generic muscle properties • Ignored tendon component

  21. Fibre Geometries Digitized Template Point-to-Point (Axial)

  22. Extensor Carpi Radialis

  23. Flexor DigitorumSuperficialis

  24. Flexor DigitorumSuperficialis Axial 84% overlap Template 79% overlap Axial force scaled 1.12x Template force is scaled 1.26x

  25. Implications and Future Work • Implications: • Might not be sufficient to use simple templates • Geometric deformation is sensitive to fibre orientations • Questions to answer: • How much detail is enough? • Can fibres be registered between subjects? • Future Work: • Include tendon structures • Accurate attachment sites • Mesh-Free Implementation

  26. EXTRA SLIDES

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