Help with a vertebra in Rhino6: boolean difference of 2 surfaces

Hi, everyone,

I have modelled a vertebra and imported it to Rhinoceros 6. For those who don’t know about the skeleton, I have to say that bones are made of two different materials: the cortical bone, which is the strong and compact bone found on the outer layer of the bones, and the trabecular bone, which is the spongy material found in the inner part of the bone.

In my case, I have the cortical layer in Rhinoceros, which means that I have two closed solid polysurfaces: the first one (A) is the outer surface of the vertebra while the second (B) is the one between the trabecular and cortical bone. It is easy to understand that the space inside the surface B would be the trabecular bone, while the space between the surfaces A and B would be the cortical bone. Obviously, surfaces are not touching each other.

The question is: how can I export the space between the two surfaces as an unique solid?

For those that could have problems understanding this topic, just think that you have two concentric spheres of different diameters and you want to export the space between them, how can you do it?

Thank you so much

Hope you can help me

Hello- NonManifoldMerge may get you the right thing, the problem may be that the normals of the inner part will be incorrect.

Will a mesh do?