Recurring Meeting of Cleveland Clinic - University of Utah

Date: December 9, 2015

Time: 2:00 PM EST

Means: Conference call

Attendees:

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

Agenda:

1. Discuss immediate action items from the last meeting.
2. Future directions for Open Knee(s) related FEBio features.

   • http://wiki.simtk.org/openknee/Specifications/FebioFeatures

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

Immediate Action Items:

• Cleveland Clinic (Ahmet)
  • Invite Joy Ku from Stanford University to January 2016 conference call with the University of Utah team.
• University of Utah (Jeff)
  • Explore manuscripts for membrane/shell element formulations suitable for implicit analysis.
• University of Utah (Steve)
  • Explore contact between springs and surfaces for springs with wrapping feature.
• University of Utah (Ben)
  • Check teaching schedule for participation of Open Knee(s) conference calls.

Notes:

1. Discuss immediate action items from the last meeting.
   • Ahmet talked to Joy Ku from Stanford University for a conference call between teams. He anticipated that the conference call will be during a previously scheduled time to catch up with Stanford University or University of Utah groups. It would be easier for Joy to attend the Cleveland Clinic - University of Utah conference call during January. During spring semester, Jeff and Steve are flexible. Ben may have teaching duties at the set date and time. If so, he will inform the group. Otherwise conference calls will be at the currently scheduled day and time of the month.
   • Jeff did not have a chance to look for manuscripts on membrane and shell elements. He will follow up.
   • Steve sent Ahmet the model with in situ strains. Ahmet mentioned that he will likely pass the model to a former summer student for evaluation. Steve noted that there may problems to use the plug in in Linux. Dave Rawlins at University of Utah may be of help if this turns out to be true. Ahmet noted that the student may contact Steve with questions.
2. Future directions for Open Knee(s) related FEBio features.
   • Ahmet asked the University of Utah group whether they had a chance to prioritize prospective features to implement. Based on the previous discussions there are four candidates: springs with wrapping, definition of parts, auto contact, shell/membrane element formulations. Jeff prioritized springs with wrapping and parts feature followed by auto contact and shells. Ahmet confirmed that a robust way to define springs and possible representation of model components as parts will have utmost value for Open Knee(s) simulations.
   • Steve has done some work with springs, e.g. for their serial arrangement. Yet, a contact formulation need to be implemented, e.g. node based, to allow their wrapping on surfaces. Jeff noted that a shape function based contact may be necessary. The group also acknowledged that the springs may not be stable and cause convergence difficulties. There may be approaches to circumvent this. Steve will keep moving forward on this feature.
   • Steve noted that it may be possible to have a workaround for other features (listed above).
   • Ben wondered how much of Gerard Ateshian's work on shell elements relate to shell and membrane formulations that the group is looking for. Gerard's work mostly focuses on transport through shell type boundaries, e.g. cell membrane. Open Knee(s) related shell and membrane elements will likely help representation of thin ligaments and cartilage.
3. Decide action items for next meeting.
   • See Immediate Action Items above.
4. Other.
   • Out of curiosity. Ahmet wondered if FEBio team has been thinking about implementing plasticity to the software. There already is a damage model provided by Gerard Ateshian. Steve mentioned that he implemented a plasticity formulation yet it was not working appropriately and therefore was not advertised. It may be interesting to have this feature particularly for implant analysis.