Answer to Question 4
“Intervertebral disc (IVD) problems, principally excessive migration of the nucleus pulposus (NP), -------------- are generally accepted to be one of the main causes of nonspecific back pain” This is the opening paragraph of one of the papers (1) from the research in Aberdeen, Scotland based on upright MRI scans.
I have selected flexed and extended scans to show the migration.
Note; These scans may not be of the same subject. However this paper (1) and other papers and presentations, based on the same research, do clearly show the expected migration of the nucleus on extension and flexion.
If one accepts the hypothesis proposed, then in the “normal” spine there will never be flexion beyond the parallel sided shape at L4-5 or L5-S, and the nucleus will always remain anterior in the disk. If for some mechanical reason, flexion to a wedge shape similar to “Flexed” above, does occur, then the nucleus will for the first time for that individual migrate posteriorly. It will then be much closer to the nerves in the posterior annulus. It should be expected that this will cause pain
(1) The Response of the Nucleus Pulposus of the Lumbar Intervertebral Discs to Functionally Loaded Positions Alexander et al SPINE Volume 32, Number 14,