SeekingSuggestions regarding modeling cartilage with depth dependent fiber properties

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  • Shamimur Akanda
    Member
    • Feb 2020
    • 51

    SeekingSuggestions regarding modeling cartilage with depth dependent fiber properties

    Hello,

    I want to model a cartilage using the three layer (Superficial, middle, deep zone). What is the best approach to provide depth dependent fiber properties in a cartilage model? Thank you in advance.

    Regards,
    Shamimur
  • maas
    Lead Code Developer
    • Nov 2007
    • 3400

    #2
    Hi Shamimur,

    The easiest approach is to partition the mesh into three layers and then assign a different material to each of the three parts. If you want more variability through the depth, you can assign equations to some of the material parameters (preliminary support for this is available in the beta release of FEBio Studio), or you can assign a mesh data section to the different parts (not supported yet in FEBioStudio, but available in FEBio3). If you let me know which approach you want to take, I'm happy to elaborate.

    Cheers,

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

    Comment

    • Shamimur Akanda
      Member
      • Feb 2020
      • 51

      #3
      Hi Steve,

      Thanks a lot for the reply. I am more eager to know about the second approach (mesh data section).

      Shamimur

      Comment

      • maas
        Lead Code Developer
        • Nov 2007
        • 3400

        #4
        Hi Shamimur,

        I've attached an example of a model that uses a mesh data section to spatially vary a material parameter. The line to note is line 2370

        Code:
        <ElementData var="fem.material[0].E" elem_set="Part1">
        Here is where the map is assigned to the material parameter. Also, note line 3377, which defines an output field for this parameter so you should be able to look at the map in PostView or FEBioStudio.

        Code:
        <var type="parameter['fem.material[0].E']=E"/>
        Unfortunately, we don't have much support for this yet in FEBioStudio (although we will soon!) so for now you'll have to make the changes manually in the feb file. Let us know if you have any questions about this.

        Cheers,

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

        Comment

        • kingina
          Junior Member
          • Feb 2015
          • 11

          #5
          Hi all,

          I'm also trying to model cartilage with different fiber orientations at different depths/layers. I divided my model into 3 layers and aim to specify a differently oriented fiber in each layer, (As per literature fibers oriented parallel to the surface in the Superficial layer, Random distribution in Middle layer, and fibers vertical to the surface in the Deep layer). Would you be able to advise me on what is the best fiber type to use in febio for this? I've been playing around with different fibers and was able to run the models using the 'fiber-exp-pow', '"spherical fiber distribution" and "spherical fiber distribution sbm" type. The 'fiber-exp-pow' seemed to me the easiest way to do it, but I could not figure out if there is a way to specify the density of these fibers within the tissue?

          Would you be able to point me to some literature examples of using different type of fibers and what are their advantages?

          Any help would be greatly appreciated,
          Regards,
          Kinga

          Comment

          • Shamimur Akanda
            Member
            • Feb 2020
            • 51

            #6
            Hello Steve,

            Thank you very much for the example. However, I was trying to partition my mesh into three different layers using "select elements" tool in Mesh option. But when I tried to choose one specific layer, this tool was selecting elements from other layers too. So, I could not partition the mesh correctly. Do you know if there is any other direct way to partition the mesh? Thank you.

            Regards,
            Shamimur

            Comment

            • maas
              Lead Code Developer
              • Nov 2007
              • 3400

              #7
              Hi Shamimur,

              There is an option in FEBioStudio that allows you to either ignore or respect partition boundaries in selections. It is on (i.e. respect) by default, but perhaps for some reason it got turned off. Go to Tools\Options... and then in the Options dialog box, select Selection in the left pane, and then set the Respect Partitions option to Yes. Let me know if that worked.

              Cheers,

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

              Comment

              • Shamimur Akanda
                Member
                • Feb 2020
                • 51

                #8
                Hi Steve,

                Thanks a lot for your reply. I can divide the mesh properly in three different layers in simpler geometry. But when I am using a curved geometry, somehow, I can't divide the geometry properly. If it is possible can I send you my mesh file? Thank you.

                Shamimur

                Comment

                • maas
                  Lead Code Developer
                  • Nov 2007
                  • 3400

                  #9
                  Hi Shamimur,

                  Curved geometry can indeed be more challenging to partition, but I'm happy to take a look. You may send me the file at steve dot maas at Utah dot edu.

                  Best,

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

                  Comment

                  • Shamimur Akanda
                    Member
                    • Feb 2020
                    • 51

                    #10
                    Hello Steve,

                    Can you tell me a bit how the paper "Hip chondrolabral mechanics during activities of daily living: Role of the labrum and interstitial fluid pressurization" established continuous fibril variation throughout the thickness using DataMap Plugin? Thank you in advance.

                    Regards,
                    Shamimur

                    Comment

                    • maas
                      Lead Code Developer
                      • Nov 2007
                      • 3400

                      #11
                      Hi Shamimur,

                      The datamap plugin allows you to interpolate material parameters between two surfaces. In FEBio2, this actually also required a special implementation of the material, however in FEBio3 the datamap plugin is integrated into the code and can be used with most materials. That said, I did find a bug in the code related to this in FEBio3, but if you reach out to me via email I can send you the fixed version. I've also attached an example that shows the use of the datamap feature.

                      Cheers,

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

                      Comment

                      • Shamimur Akanda
                        Member
                        • Feb 2020
                        • 51

                        #12
                        Hi Steve,

                        Thanks a lot for the file. I will reach out to you next week via email for the fixed version to use datamap.

                        Regards,
                        Shamimur

                        Comment

                        • Shamimur Akanda
                          Member
                          • Feb 2020
                          • 51

                          #13
                          Hello Steve,

                          I have been trying to implement Datamap plugin in my model for varying material properties. The file is not at all opening in febio. I guess there might be some kind of syntax/text error related to the plugin. It would be really appreciated if you can look into it. I am attaching the file here for your consideration.



                          Shamimur

                          Comment

                          • maas
                            Lead Code Developer
                            • Nov 2007
                            • 3400

                            #14
                            Hi Shamimur,

                            Which version of FEBio are you using? I am trying to get this to work in FEBio3, but I'm running into issue. The first issue is unrelated to the datamap plugin, but you are missing a "scheme" property in the "continuous fiber distribution". The other issue is related to the fact the parameters you are trying to map have not been updated in FEBio3 and this would definitely not have worked in FEBio2. I'll try to find some time to get this problem to work in FEBio3 and I'll let you know if I get it working.

                            Cheers,

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

                            Comment

                            • Shamimur Akanda
                              Member
                              • Feb 2020
                              • 51

                              #15
                              Hello Steve,

                              I have tried both FEBio 2.9 and FEBio3. I could not get this file to work. Regarding the other issue, are you referring to the semi principal axis (spa) that have not been updated in FEBio3? If that so, is there any other platform, I can map these parameters? Thank you for your time.

                              Shamimur

                              Comment

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