Post-View Springs

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  • lexiedm14
    Junior Member
    • Nov 2019
    • 26

    Post-View Springs

    Hello,

    I am working on simulating an anterior drawer test on an ACL. I have the bony anatomy and have the ligaments modeled as non-linear springs. In Post-view, I am able to see the displacement of the tibia, however, I am not able to gather data on the ACL springs.

    How do I go about doing this?

    Thanks,
    Lexie
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hi Lexie,

    Currently, FEBio doesn't store any of the spring data (like stretch, and force) in the plot file. This is something we can definitely add and I don't think it would take very long. Asides from stretch and force, what other data would you be interested in?

    Cheers,

    Steve
    Department of Bioengineering, University of Utah
    Scientific Computing and Imaging institute, University of Utah

    Comment

    • lexiedm14
      Junior Member
      • Nov 2019
      • 26

      #3
      Hi Steve,

      Thank you for getting back to me so quickly.

      Instead of using springs to represent the ligaments, Open Knee has the geometry of the ligaments available as separate STL files. In Preview, is it possible to connect/join the bone and ligaments together even though they have different global coordinate system points?

      Thanks,
      Lexie

      Comment

      • maas
        Lead Code Developer
        • Nov 2007
        • 3400

        #4
        Hi Lexie,

        After you import the ligaments into PreView (or FEBioStudio), you can move, rotate, and scale the meshes into the correct position so it should be possible to align them correctly with the bones. I suggest to give it a try and let us know if you run into any difficulties.

        Best,

        Steve
        Department of Bioengineering, University of Utah
        Scientific Computing and Imaging institute, University of Utah

        Comment

        • lexiedm14
          Junior Member
          • Nov 2019
          • 26

          #5
          Hi Steve. I have been working on the knee model with 2 rigid bodes for the tibia and femur and Trans Iso Mooney Rivlin material for the ACL. The ACL is a mesh geometry.

          Using a basic knee model with the spring, I was able to simulate the anterior drawer test. However, when I apply this to the new model, it doesn't work. I am not sure if the ACL needs to be connected to both the tibia and femur and if I am having the correct BC and constraints. I am still new to FEA so I am not sure how to go about this.

          So far, this is what I have in my Preview file:

          Steps:
          - Initial:
          ---Constraints:
          1. Rigid Fixed: Femur Fixed: (x, y, z, x-rot, y-rot, z-rot) are all selected
          2. Rigid Fixed: Tibia Fixed (all dof are selected expect x-disp).
          *Based on how the geometry is setup, the tibia needs to move in the negative x-direction to simulate the anterior drawer test.
          3. Rigid Force: Rigid material=tibia; var=x-force; value=-10

          - Step 1: Analysis step

          Using these constraints, I was able to get the tibia to move in the anterior direction when the ACL was modeled as nonelastic spring.

          Is there something special that has to be added so that the posterior aspect of the ACL will move with the tibia and the anterior aspect will stay with the femur?

          How do you recommend simulating the anterior drawer test using this methodology?

          Thanks,
          Lexie

          Comment

          • maas
            Lead Code Developer
            • Nov 2007
            • 3400

            #6
            Hi Lexie,

            I am not sure if the ACL needs to be connected to both the tibia and femur and if I am having the correct BC and constraints.
            Yes, you would have to connect the ACL to both the tibia and femur. You can do this by using rigid interfaces (menu Physics > Add Contact ..., and then select "rigid") and connecting the surfaces of both ends of the ACL to the corresponding rigid body.

            I'm only vaguely familiar with the drawer test, but it sounds like you're on the right track. If you still struggle with the model, you may send it to me (steve dot maas at Utah dot edu) and I'd be happy to take a closer look.

            Best,

            Steve
            Department of Bioengineering, University of Utah
            Scientific Computing and Imaging institute, University of Utah

            Comment

            • konris87
              Member
              • Nov 2019
              • 36

              #7
              Mr Maas,

              I was searching information about Postview spring data and just found this thread. Is this something that is going to be implemented? Because i also work in a similar project where the ligaments are modeled as springs and it would be useful to have information about spring force and stretching per time.

              Thanks a lot,
              Konstantinos
              Konstantinos Risvas
              Dipl.-Ing. MSc Electrical and Computer Engineer
              Ph.D. Candidate, Research Associate, VVR group
              Department of Electrical and Computer Engineering
              University of Patras
              26500, Rio-Patras, Greece

              Comment

              • maas
                Lead Code Developer
                • Nov 2007
                • 3400

                #8
                Hi Konstantinos,

                We are working on this and it will be available in the next release of FEBio (and FEBioStudio.) We are also happy to set you up with our current development version to try it out, but it might still be a couple of weeks before we have this done. I suggest to check in in about two weeks, if you have not heard back from me by then.

                Best,

                Steve
                Department of Bioengineering, University of Utah
                Scientific Computing and Imaging institute, University of Utah

                Comment

                • konris87
                  Member
                  • Nov 2019
                  • 36

                  #9
                  Greetings mr Maas,

                  any update to this post analysis spring feature?

                  Kind regards,
                  Konstantinos
                  Konstantinos Risvas
                  Dipl.-Ing. MSc Electrical and Computer Engineer
                  Ph.D. Candidate, Research Associate, VVR group
                  Department of Electrical and Computer Engineering
                  University of Patras
                  26500, Rio-Patras, Greece

                  Comment

                  • maas
                    Lead Code Developer
                    • Nov 2007
                    • 3400

                    #10
                    Hi Konstantinos,

                    In our upcoming release of FEBioStudio and FEBio3, we will have support for storing and visualizing spring data. Currently, support for stretch and force are implemented, but we can easily add other variables if needed.

                    Cheers,

                    Steve
                    Department of Bioengineering, University of Utah
                    Scientific Computing and Imaging institute, University of Utah

                    Comment

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