how can I assemble screw and vertebral body in matlab?

Hello everyone. I wrote a code in matlab that takes CT images, and read their details and convert to material properties. and give me 3file : 1. nodes 2.elements 3.materials. I can import these files to ansys and have finite element analysis in it. But now I want to insert a screw in vertebral body in MATLAB, these are my steps:

1. import screw model too matlab

2. visualizing vertebral body

3. insert screw in vertebral.

for step one I used this code: http://www.mathworks.com/matlabcentral/fileexchange/22409-stl-file-reader

but for other steps I don't have any idea.

Any feedback would be much appreciated.