Embedding digitized fibre fields in finite element models of muscles

Abstract

Finite element (FE) models of muscle are able to represent both complex muscle geometry and internal fibre architecture. However, due to an inability to capture fibres in detail by conventional imaging, most current models assume simple fibre distributions. These are often registered from a minimal set of contrived templates. To improve realism, we propose to use detailed fibre fields, digitized from a cadaver, for defining the internal muscle structure in models. We present a workflow for registering these detailed digitized descriptions to subject-specific muscle geometries, which can then be incorporated into the FE model for use with a transversely isotropic constitutive law. The importance of capturing this detail is emphasized with two examples of muscle groups found in the forearm: the extensor carpi radialis longus and the flexor digitorum superficialis. We show that simplified fibre fields can lead to a 10–20% difference in predicted muscle force and equally significant differences in contracted geometries.

Keywords::

• finite element analysis
• muscle modelling
• muscle fibre architecture
• biomechanical simulation
• subject-specific models

Acknowledgements

We graciously thank Benjamin Gilles (INRIA) for the surface-to-surface registrations; James Li, Dongwoon Lee and Anne Agur (U of T) for the digitized muscle fibre data and wrapping surfaces; and Poul Nielson (University of Auckland) for providing template volumetric meshes. We also gratefully acknowledge the Parametric Human group for their input and support.

Additional information

Funding

This work is partially funded by the NSERC Canada, GRAND, UBC and Autodesk Research.