Doctors re-attach boy's head after car accident thanks to 'amazing' surgery
foxnews.com
foxnews.com
My guess is, the nerves and blood vessels were still connected but nothing was holding them in place.
Also, it looks like about 1/3 of people survive these [1, 2, 3]. So this isn’t a “first known success”, but still pretty impressive [1] https://www.sciencedirect.com/science/article/abs/pii/S15299.... [2] https://en.m.wikipedia.org/wiki/Atlanto-occipital_dislocatio... Talk,cases result in immediate death. [3] https://www.cbsnews.com/amp/news/what-is-internal-decapitati...
It's an internal decapitation so more work spent on stabilizing the two halves so that things can fuse back into place.
They got the bones back together while protecting his spinal cord - a great achievement - and he's walking around today.