Recurring Meeting of Cleveland Clinic - University of Utah

Date: October 22, 2014

Time: 2:00 PM EST

Means: Conference call

Attendees:

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

Agenda:

1. CMBBE 2014 update.
2. Update on feature implementations.

   1. In situ strain - http://wiki.simtk.org/openknee/Febio/InSituStrain

   2. Set definitions - http://wiki.simtk.org/openknee/Febio/SetDefinitions

   3. Connector elements - http://wiki.simtk.org/openknee/Febio/RigidBodyMotions

3. FEBio issues during simulations.
4. Decide action items for next meeting.
5. Other.

Immediate Action Items:

• Cleveland Clinic (Ahmet)
  • Conceptualize inverse analysis problem for in situ strain estimation.
  • Explore mechanisms to accommodate visits to Cleveland Clinic by University of Utah team members.
• University of Utah (Steve)
  • Explore Gerard Ateshian's implementation of pin joint to formulate kinematic constraints in FEBio.

  • Implement node/element/surface set support in PostView.

• University of Utah (Ben)
  • Track medical collateral ligament data for exploration of inverse analysis for in situ strain estimation.

Notes:

1. CMBBE 2014 update.
   • Ahmet and Steve iterated over CMBBE 2014 discussions. In terms of defining mechanical joints/connectors, kinematic constraints (relying on penalization of deviation from the constraint) will be implemented. Steve will first go through Gerard Ateshian's code to familiarize himself with the formulation. In the long term this feature will resolve current issue with FEBio version 2.1, which does not allow prescribing flexion while setting other rotations free. Steve may need to find an intermediate solution for this.
   • Steve provided a presentation of the in situ strain feature at CMBBE 2014. This work is essentially complete. Ahmet iterated the need for a synergistic project where in situ strains may be calculated through an inverse analysis. In situ strain can be obtained experimentally for medical and lateral collateral ligaments (as Ben noted) but this may not fit the logistics of Open Knee(s) whole experimentation workflow. Additionally, an experimental approach will still be problematic for cruciate ligaments. Inverse analysis may be useful to provide a reasonable estimate of in situ strains from known ligament (or joint) forces and moments. This will likely be an ill-conditioned optimization problem but may be worth exploring further. Ben will try to check their medial collateral ligament data in that regard.

   • As discussed by Ahmet and Steve at CMBBE 2014, set definitions were implemented for both input and output files. Nonetheless, there is not an easy way to test the utility of those tests at the output file end. Steve will add support in PostView to accommodate browsing/visualization of sets. In additions, he may be able to implement support in the input file format to request output in human readable form for any desirable set.

   • Following up the discussions at CMBBE 2014, Ahmet repeated his invitation for University of Utah members to visit the Cleveland Clinic site. This may be an opportunity to focus on certain feature development and/or analysis aspects, e.g. Python scripting, inverse analysis of in situ strain, etc.
2. Update on feature implementations.
   • All features were discussed as part of CMBBE 2014 update above.
3. FEBio issues during simulations.
   • University of Utah team (Dave Rawlins) provided a Linux binary of FEBio compiled with an older version of glib. This executable seemed to resolve segmentation fault issues faced by the Cleveland Clinic's team when using FEBio on their high performance computing cluster.
4. Decide action items for next meeting.
   • See Immediate Action Items above.
5. Other.
   • None noted.