I got whiplash once. Rammed in the back by a drunk. Had my left hand on the steering wheel, and the next day my left shoulder and thumb hurt. Bad. Thought I jammed the arm or something. The doctor did X-rays and said the nerves leading out of the cervical vertebrae had been bruised. I think the C-5 nerve goes to the shoulder, and the C-6 to the thumb. And the holes on the sides of the vertebrae they pass through (radiating out from the spinal column to the body) are called foramen. When I got whacked, the whiplash caused the edges of those calcium holes to pinch the nerves, bruising them. He said that as I get older I might have trouble. Calcification can make the foramen shrink as time goes by, and the pinching can become chronic. He said steroids (I think) is the recommended treatment. I did some physical therapy, some kind of overpriced exercise thing that actually does help. You bend your neck certain ways to relieve pressure on the cervical nerves. Anyway, I was amazed that a neck injury one day could lead to intense thumb pain the next. Something to be aware of.