Recurring Meeting of Cleveland Clinic Core Team

Date: July 1, 2014

Time: 10:30 AM EST

Means: In person meeting

Attendees:

1. Ahmet Erdemir
2. Jason Halloran
3. Snehal Chokhandre
4. Katie Stemmer
5. Ed Morra

Agenda:

1. Discuss immediate action items from the last meeting.
2. Discuss tissue testing progress.
3. Discuss pilot testing preparation (to be scheduled between July 21st-25th) .
4. Decide immediate action items for the next meeting.
5. Other.

Immediate Action Items:

• Craig
  • Review specimen preparation specifications.
• Tara
  • Finalize gravity compensation for robotics testing of joints.
• Katie
  • Review specimen preparation and tissue testing specifications.
• Snehal
  • Complete and test Python script for down sampling of video data.
• Robb and Snehal
  • Evaluate processing tools to move between "right knee abstraction" and "physical representation" on previously collected data (save the day).
• Jason and Robb
  • Finalize processing tools to move between "right knee abstraction" and "physical representation" as a long term solution.

Notes:

1. Discuss immediate action items from the last meeting.
   • Ahmet updated the experimentation workflow image. The illustration was broken up into explicit sections for preparation, testing procedures, and data. The procedure numbers in the illustration correspond to list of specifications in the relevant wiki page. Ahmet also included “supporting specifications” into the list as well. The data from the experimentation was developed to correspond to the inputs in the modeling and simulation workflow chart, which is pictured further down the specifications wiki page.
   • Tissue testing specifications were not yet reviewed by the team but Snehal and Tara commit some changes to that page and provided comments. These are discussed as part of the following agenda item.
   • Craig will review the specimen preparation page.
   • Jason and Robb have iterated on the issue of moving between the “right knee abstraction” and the “physical representation” of the knee kinematics/kinetics data for another project. Snehal will talk with Robb because she needs this tool for a previous project. Jason and Robb will discuss finalizing the tools as a long-term solution for Open Knee(s).
   • The pressure calibration procedure was discussed. The current solution is to adopt a foam substitute for the calibration procedure, as opposed to using a real cartilage sample. Ahmet could not find a source for “crepe”, which appears to have a similar stiffness as cartilage (based on data from Marc Petre's MS thesis). An alternative foam with a stiff backing can be used and its thickness can be tailored to mimic indentation stiffness of cartilage. The “relaxed” stiffness of the cartilage or its stiffness at a loading rate expected during joint level testing should be used to match the material properties of the calibration foam.
2. Discuss tissue testing progress.
   • Tissue sample preparation was discussed in detail. Snehal provided images of her current procedures. The tissue harvesting sequence Snehal uses was summarized along with sample preparation. The focus is on obtaining the primary structures. Snehal may have difficulty obtaining some secondary structures and based on the feedback from the Advisory Board, this can be facilitated by bringing in a surgeon to help harvest secondary structures, e.g., joint capsule, MPFL, etc. After harvesting, all the gross tissues will be separated and will be ready for sample preparation for tissue testing. Details of this procedure are being populated on the specifications page for specimen preparation. The activity will be time consuming. Ahmet asked about keeping the tissues hydrated. Snehal noted that this should be noted in the documentation of the procedures. If it is not, she will add it. Labeling and storage was also included in the discussion. Ahmet noted that the secondary regions, if possible, should be harvested, labeled and stored for future use. Ahmet asked about tissue and/or sample preservation for future use, whether it is a primary or secondary issue. Snehal will add a “tissue preservation” section, which is the precursor to preservation of specific tissue samples for testing. The hope is to minimize the freeze-thaw cycles. The literature on freeze-thaw cycles should be obtained and documented on the wiki. Regarding specific sample preparation, Snehal covered preparation of cylindrical and dumbbell shaped samples (for compression and tension testing, respectively). Obtaining uniform thickness samples was noted as a potential issue. Thicker tissues are prepared using a cryostat, which is available in the Histology Core at the Lerner Research Institute of the Cleveland Clinic. The group discussed the potential to obtain multiple samples from the cruciate ligaments. The bundles may be separated during harvesting with a surgeon's help. A total of 18 cartilage samples will be acquired. A total of 30 tests with 28 samples currently encompasses the tissue testing protocol. It appears that the specifications page for tissue testing needs to be fine tuned. Craig will review, as well as the whole group. Katie may read in detail and potentially try to follow one tissue testing protocol, which Snehal could use as a test for completeness of the specifications. Current comments will be addressed by Snehal.
   • Tara provided feedback/comments and Snehal covered the overall focus and high level details of tissue testing procedures. The list of primary and secondary tissues is included. Details about the loading procedures and measurement techniques were discussed. Snehal prepared an excel file that summarizes the tissue samples. This list should be moved into the wiki page. Snehal has conducted unconfined cartilage compression, cartilage tension and MCL tension test. Confined cartilage compression will be conducted next. Tests are currently performed in room temperature without video data. This can be added and will certainly be for the final testing. For this purpose, Snehal will complete and test a python script for down-sampling video data.
   • Snehal covered specifics for the applied conditions for each test. Current conditions for tissue testing will require 30 working days to complete. Reduction of strain levels to save time was discussed. A minimum of three strain levels may be sufficient for the stress relaxation tests. This essentially cuts the testing in half. Another option is to shorten the relaxation duration, which is currently set at 45 minutes. This will be discussed by Ahmet and Snehal, including the possibility to extrapolate to the “fully” relaxed state.
   • Snehal found that there is a debate in literature on the loading rate for preconditioning. The equilibration state of the tissue is an issue. Snehal will summarize what she learns and the team can make a decision.
   • Another focus of Snehal's upcoming tests will be prototyping the meniscus compression samples. As discussed last week, preparation of the sample is a primary concern. The group discussed the related issue of acquisition of low forces that are seen in meniscus compression testing; developing an inverse approach may still be a possibility to adequately describe the constitutive response of this tissue. Extraction of viscoelastic properties and Poison's ratio will likely be a challenge when an inverse approach is adapted.
   • Snehal also covered a study that found an inverse relationship between sample thickness and modulus measurements acquired from tensile testing of the meniscus. This will also need to be addressed; a decision will be made and the approach will be reported accordingly.
3. Discuss pilot testing preparation (to be scheduled between July 21st-25th) .
   • Snehal spoke with Shannon Donnola (from University Hospitals) about scheduling the MRI for full pilot testing of a knee joint. The facility is available on July 22, 2014. Joint testing will need to occur on that day. Ahmet proposed that in the next Open Knee(s) meeting after the World Congress of Biomechanics conference the team decide on the details of the full pilot testing, which will occur during the following week. In these tests, joint mechanics characterization relevant to Katie's project may be included. This will require prescribing joint movements pre- and post- cruciate ligament dissection to quantify cruciate ligament forces by superposition of joint kinetics data. The potential issue is recreating the exact kinematic profiles from a force control test, in order to accurately represent the joint state to apply superposition after a tissue is cut. This should be discussed, though at present it appears that logistically this may be challenging for the upcoming test.
   • Before pilot testing, Tara also needs to work on the gravity compensation to appropriately characterize joint mechanics.
4. Decide immediate action items for the next meeting.
   • Action items were assigned and agreed upon by the group. See Immediate Action Items above.
5. Other.
   • Ed Morra from Orthopaedic Research Laboratories (ORL) attended the meeting. Ed summarized the focus of ORL for the group. Snehal gave a brief overview of the Open Knee(s) project.
   • For pressure measurements within the joint, Ed said his group uses Fuji film frequently. His insight is that finite element analysis predictions of contact area match well yet comparisons of pressure distribution are not necessarily as good.
   • Ed noted that Blender, a open source geometric modeling and video editing software, recently implemented a tracking feature. This may be useful for strain measurements from video data to be collected in tissue testing, e.g. for quantifying the Poisson’s ratio.