pose the arm how you want it and select File , Export, Wavefront obj and follow the prompts. You should get a display to select what gets exported so select the parts you want (probably shoulder, lower arm, hand and all fingers) . Then import that obj (Figure, Import, etc) and that will be your ripped off arm.

If the camera angles are good, and the missing bit at the shoulder looks ok then you are done.

 

I did not find the props to close off the arm openings.  :(