Recurring Meeting of Cleveland Clinic Core Team

Date: June 3, 2014

Time: 10:30 AM EST

Means: In person meeting

Attendees:

1. Ahmet Erdemir
2. Jason Halloran
3. Craig Bennetts
4. Snehal Chokhandre
5. Katie Stemmer
6. Robb Colbrunn
7. Tara Bonner

Agenda:

1. Discuss immediate action items from the last meeting.
2. Revisit joint testing coordinate systems.
3. Revisit anatomical imaging.
4. Discuss tissue testing progress.
5. Decide immediate action items for the next meeting.
6. Other.

Immediate Action Items:

• Jason
  • Finish registration marker error analysis and upload singular value decomposition (SVD) script.
• Tara
  • Provide detailed information on location of accessories and supplies to prepare extensor mechanism of the patellofemoral joint.
• Robb
  • Provide processing tools to move between "right knee abstraction" and "physical representation" of knee data collected during joint testing.
• Snehal
  • Write a Python script to read and plot tissue testing files.
  • Provide Martin Garon (Biomomentum Inc.) ACL data to illustrate the problem in displacement data collection.
  • Fine tune confined/unconfined compression and uniaxial tension protocols by further tissue testing.
• Snehal and Craig
  • Design an image-based thickness measurement system.

Notes:

1. Discuss immediate action items from the last meeting.
   • Jason uploaded the code for sphere fit algorithms. These scripts can be used to find centers of registration markers attached on femur, tibia, and patella.
   • Jason and Tara updated quadriceps tendon preparation procedure. An image of the setup was uploaded and a description of how to prepare the tendon was added. Tara will provide detailed information on location of accessories to prepare the extensor mechanism. A description of the “tube” or cup used to contain the liquid nitrogen for tendon/clamp freezing during testing should also be added.
   • The setup for the new tissue testing laboratory is still ongoing. The eye wash station should be installed this week. The tissue testing machine will be moved to the new location after that. Manufacturing of the “tall” bath for tissue testing is still in discussion. There has been some back and forth about whether the flat faces would be glass or plastic. A decision should be made and documented so that this issue can move forward. Snehal will let Tony Shawan (Prototype Core) know that use of glass is fine and he should finish building the bath.
   • Elvis finished his tissue testing last week and Snehal has all his data. Most of the data files are very large files (particularly when collected at high sampling frequencies) and are serially compartmentalized based on the loading sequence. Snehal was working on a Matlab script to parse and plot the data. Instead, she will create a Python script to provide as part of Open Knee(s) utilities. Raw data for the anterior cruciate ligament were plotted and it is apparent that the erroneous displacement data points during the hold cycle were populating the results. This will hinder deciphering the real response and will require post-processing to remove this undesirable data collection artefact. For the ligament, the force response appears to have a large error bandwidth (around 6 grams), which is greater than the resolution (0.5 grams) of the transducer. Robb theorized that there may be electrical noise in the results but this is yet to be determined. Also, the range of forces does not seem comparable to previous ligament testing. This data may be difficult to use. Snehal will evaluate tissue testing protocols with additional tissue samples in the upcoming week(s). In particular, another ligament will be tested, with video included, to troubleshoot any remaining issues with the new system, including the heating system.
   • Craig and Snehal worked on the thickness measurement approach using a foam sample. Five measurements were acquired using both the optical approach and the constant pressure LVDT probe. The LVDT measurements were lower in average and both systems had similar variability (approximately 0.02 mm for 1 mm thickness, 2% error). Softer tissues may exhibit more variability, particularly with the contact approach. During the first round of Open Knee(s) tests, both measurement methods should be employed for redundancy. A specification for how to handle optical measurements during tissue testing needs to be developed. Essentially, a jig to reliably hold the tissue sample and measurement apparatus should be designed and implemented. A separate system, including a camera, stage, ruler and computer, will be configured for the optical measurement setup.
2. Revisit joint testing coordinate systems.
   • Robb provided a document covering the conventions used to describe the joint coordinate systems, and resulting differences between the right and left knee conventions. The group discussed the general approach for collection and reporting of joint kinematics/kinetics and established the sign conventions. The kinematics follow the convention of the Grood and Suntay convention whereas the kinetics is reported as forces and moments resulting in anatomical movements of tibia's motion, with axis orientations aligned with the tibia coordinate system. The distinction between "right knee abstraction" and "physical representation” was made. The robotics testing system treats all knees as right knees during joint kinematics/kinetics data collection (right knee abstraction). For left knees, post-processing of the data is necessary to return back to actual left knee coordinate systems (physical representation). For right knees, right knee abstraction and physical representation are the same. While the document reflects this, additional clarification will be helpful. Also, a second document will be developed to describe data processing to move between right knee abstraction and physical representation.
3. Revisit anatomical imaging.
   • Ahmet received a spreadsheet from Shannon from the imaging facility at the University Hospitals. Imaging parameters from previous imaging trials are provided in the spreadsheet. These parameters will be used to finalize the imaging specifications. Craig will also take a look at these settings to ensure they make sense.
4. Discuss tissue testing progress.
   • This agenda item was discussed as part of the discussions of the immediate action items from the last meeting (see above).
5. Decide immediate action items for the next meeting.
   • Action items were discussed and agreed on. See Immediate Action Items above.
6. Other.
   • Robb provided an update on the robotics joint testing system upgrades. Dylan is currently replacing the motors.
   • Tara updated the group on the gravity compensation issue of the robotics joint testing system. Apparently the issue is related to the fasteners not being tightened appropriately. The compensation algorithm will be retested for repeatability.