At what point does the law have to step in and make it illegal to create things that are not protected by the layers of research, testing, and regulation.
This is more an anecdote, than an answer, but when I worked at the Rapid Prototyping Center [0] we built 3D prototypes for Johnson & Johnson including a slightly bowed rod with several holes drilled at various angles. After my roommate had an unfortunate skiing accident over winter break, we learned that the production part was milled/cast from titanium and used to repair fractured bones - as visible in his x-ray. The angled holes were used for the screws to mount the rod to the bone [1].
The parts we produced weren't used directly in bodies, but to aid the design and manufacture of parts that were.
[0] - http://rpc.msoe.edu
http://www.wired.co.uk/news/archive/2013-04/24/3d-printed-li...