From what I understand, the can replace the disc, which takes the pressure off of the nerve, but they can't guarantee that the pain will leave or that the nerve is not damaged. It can stop further damage.
My doc and I were kidding around today about pain and how we would be the richest people on earth if we could figure out how to cure pain.
They can physically change how your body is set up with surgery, replace parts, take parts out, etc, but when it comes to nerve pain, no one really understands it yet.
When I first saw my doctor, he said, "Oh, good, at least it is not leg pain, or sciatica because there is no cure for that".