Maybe a reader with medical knowledge, such as a former pre-med student, can help me.

How much cushion does the spine have at the back of the neck?

I ask this because, Friday while shopping I saw this guy with a hole in the back of his neck.

Not a sore, mind you. A hole. At least three and a half inches in diameter, and a half-sphere deep.

As if someone had taken a large ice cream scooper and dug out a perfectly round hole in the back of this guy's neck.

It had been done awhile ago, because it was healed up, although there was no skin. It was red inside, where you could see the muscle, and had some sort of shiny, clear, wet-looking coating.

The question is, isn't that where the guy's spine should be? All I saw was muscle.

[Xposted to PSOD.]