Despite being well trained, I've had one kickback. It put a hole in my garage door and I had to drive to the emergency room in shock to get a partially detached finger reattached. Expensive lesson.
IIUC, fixing severed nerves in the spinal cord is beyond the state of the art in medicine.
So when someone goes to the ER with a cut-off finger, how is it possible for the finger to be reattached, and for the proper nerve connections to be re-established?
The peripheral nervous system can regrow nerve tissue but only if it has an intact pathway. So when they sew on a finger, if they can repair the myelin sheath, new nerves will grow down the old conduit at a rate of about an inch a month.
So they sew your finger on and you have to wait a few weeks to see if you're going to get any feeling back. That waiting would drive me nuts.