Could a punch to the back cause a fractured spine? or not likely?

Not likely: But possible. Fractures of the transverse processes for the lumbar vertebrae can occur from direct trauma. Usually a fist punch can't generate enough force to cause this but it can happen sometimes. Best to get checked out. Thanks for trusting HealthTap!

Unlikely: This would be unlikely unless you have an underlying bone disorder. If you have had unexplained fractures of bones in the past, you might want to have a further work-up. However, in normal circumstances, the bones in the spine should be able to withstand the force of a punch. A punch in the neck can cause injury to the important blood vessels there.