Recurring Meeting of Cleveland Clinic - University of Utah

Date: February 26, 2014

Time: 3:00 PM EST

Means: Conference call

Attendees:

1. Ahmet Erdemir (Cleveland Clinic)
2. Jason Halloran (Cleveland Clinic)
3. Jeff Weiss (University of Utah)
4. Steve Maas (University of Utah)
5. Ben Ellis (University of Utah)

Agenda:

1. Progress on in situ strain test problem.

   • http://wiki.simtk.org/openknee/Febio/InSituStrain

2. Update on set definitions in FEBio input and output.

   • http://wiki.simtk.org/openknee/Febio/SetDefinitions

3. Update on local coordinate systems and connector elements.

   • http://wiki.simtk.org/openknee/Febio/RigidBodyMotions

4. Decide action items for next meeting.
5. Other.

Immediate Action Items:

• Cleveland Clinic (Ahmet) and University of Utah (Jeff)
  • Evaluate the progress of in situ strain feature for submission to CMBBE 2014.
• Cleveland Clinic (Jason)
  • Help Steve to acquire background on kinematic and kinetics of joints between rigid bodies.
• University of Utah (Steve)
  • Complete three-dimensional ligament example to evaluate in situ strain feature.
  • Continue learning about kinematic and kinetics of joints between rigid bodies and identify strategies for their implementation in FEBio.

Notes:

1. Progress on in situ strain test problem.
   • Steve updated material properties for the simple test problem. The model now exhibits tension-compression nonlinearity. As expected for compression, the construct is more compliant solely based on the ground substance properties.
   • Some of the input syntax is hard coded. Steve will iron out usability related implementation details for this feature, which will be provided in FEBio version 2.0. Following this release, Steve will provide the input file for this test model for Cleveland Clinic team to use it as an example.

   • It is possible to write a conference abstract on this topic for CMBBE 2014; deadline for submission is April 15, 2014. The team will explore this opportunity. Other candidate scientific meetings include those of the Orthopaedic Research Society and Biomedical Engineering Society.

   • Steve is also working on the implementation of the three-dimensional ligament problem. A few issues were noted based on typographical errors in the manuscript targeted to be reproduced. These are resolved. Steve will summarize the goals of this analysis, including a brief description of the previously published work, in the wiki.
   • Ahmet provided a summary of and links for a cardiovascular test problem.
   • A publication may emerge from this work within 2014. This will likely require completion of the simple test problem along with the three-dimensional ligament problem and the cardiovascular example. Implementation of this feature, its general purpose usability, and wide-spread availability of this capability (within FEBio) will be strengths.
2. Update on set definitions in FEBio input and output.
   • Set definitions have already been implemented for FEBio input file. Steve is confident that the implementation of set definitions will be accomplished for the FEBio output file without any surprises. Steve requested to focus more on the connector problem (see below) as it seems more challenging. The Cleveland Clinic team agreed to this change of priorities.
3. Update on local coordinate systems and connector elements.
   • Steve is trying to understand the joint coordinate system for the knee. He is also learning more about connectors. Abaqus utilizes Lagrange multipliers or Augmented Lagrangian to enforce constraints associated with kinematic joint descriptions. FEBio utilizes reduced degrees of freedom to enforce constraints, which may raise implementation difficulties for kinematic joint descriptions.
   • Steve needs further clarification for the application of forces and torques in connectors, e.g. how to apply a moment around an axis? Ahmet and Jason will help Steve to identify different implementation paths to decompose the connector forces and torques to proximal and distal bodies. Robotics literature, e.g. Denavit-Hartenberg convention, may be of help.
4. Decide action items for next meeting.
   • See Immediate Action Items above.
5. Other.
   • No other issues were discussed.