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Femur, cortical and trabecular bone merging/combining into one STL file for future finite element analysis

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Message 1 of 3
heyermartin97
375 Views, 2 Replies

Femur, cortical and trabecular bone merging/combining into one STL file for future finite element analysis

Dear all,

 

I am trying to produce a femur model which contains both, cortical and trabecular bone. The cortical bone is the 'outer shell' whereas the trabecular bone is contained within the cortical bone. I have segmented both of these and was able to edit them in MeshMixer. However, I would like to combine them so that the trabecular bone is within the cortical bone. I have tried to transform the trabecular bone into the cortical bone, then selecting both objects and just combining them. It's all fine and well until I upload that STL file into my finite element analysis program (FEBio). It does not recognize that the trabecular bone is its own object, thus I cannot apply its own material properties onto it.

 

I was wondering if anyone has tried something similar and if they could help me out. I added the STL file I currently have below. 

 

Kind regards,

Martin 

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Message 2 of 3
MagWeb
in reply to: heyermartin97

Sorry, don't know how FEBio expects objects. Maybe you need to add objects one by one separately???

 

Your file comes with an exterior shell defining the femur volume and a "positive"  shell inside defining the trabecular volume.

Means: The cortical volume isn't defined. Well one could calculate it via femur - trabecular using little math but it isn't set in your mesh.

To define the cortical volume you need to flip the surface normals of the trabecular shell:

  1. Generate a duplicate of the trabecular
  2. SELECT all of the trabecular duplicate (Ctrl+A) and do Edit/FlipNormals. Now EDIT/Combine it with the exterior femur shell > this way you get a hollow object.

Did it for you in the attached .mix

 



Gunter Weber
Triangle Artisan

Message 3 of 3
heyermartin97
in reply to: MagWeb

I tried adding both objects one by one, but for some reason as soon as I overlay them one objects won't allow for materials to be added onto it.

 

I understood your workflow and I see what you mean. The only issue is, that I would need to place the trabecular bone into the cortical bone. I tried to hollow the cortical bone out, however, that for some reason still doesn't work...additionally, if I don't make the objects solid then I can't mesh them in FEBio. So I am kind of lost now.

 

I would have to create a hollow solid cortical shell which contains a trabecular solid inside of it.

 

I am not sure if I am making any sense anymore. But thank you so much for your quick reply!

 

 

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