[Lovewyrm]

Well, if magic can remove bone in whichever configuration they are arranged, then maybe a regrow spell can also restore bone in whichever configuration they need to be (after all, it probably does so on a cell level anyway).

But it's probably a better story/drama if the hand has to come off for it, though.

Makes the enemy more menacing, too, although just making bones disappear is pretty damn terrifying in itself without the need to take someone apart to fix it.