Anything medical Science says is incurable, or impossible, is just something they haven't discovered a drug or procedure for yet. I don't know if the worn bones can be repaired bling but they represent a state of disrepair in your body and I have no doubt that your body will use the fast to put that condition right in some way or another.
The only way we will ever find out the true extent of the bodies ability to repair itself while fasting would be if it did become mainstream and even a small portion of the time and money put into research with drugs and disease investigations was spent on really exploring what a fast can do. Until then we've got only the personal experiences of those who actually go on record to go by.