Thanks for this extremely valuable information. If only I'd known this forty years ago! I was always taught to stand and sit up straight, and often received compliments on my "good" posture. Eventually when I sought medical attention for severe neck pain and numbness in my left arm and hand, an x-ray revealed a literally straight neck. Talk about scary! Three and a half years ago I had C-3 and C-4 fused, complete with screwed in titanium plate (my x-ray now looks like Frankenstein, with a straight neck). I believe this could have all been avoided had this information been available to me those forty years ago.Too bad patients with a neurosurgeon breathing down their neck, pun intended, don't have access to this information. One more little tidbit...the surgeon released me with these instructions for follow-up care..."You can't hurt the procedure!"Does anyone out there know of a good chiropractor? I would appreciate references.