Answer to
Question 5
The
severity and persistence of low back pain is difficult to explain when there
seems to be no tissue damage. Undoubtedly much pain is muscular but this is not
a full explanation and rarely provides a solution.
The mechanical
structure of the spine, pelvis and associated muscles provides a reason for
such severity. To an engineer the layout is obviously an “over-centre
mechanism” (like the clips often used on a suitcase to provide extra force for
the last bit of closing –and on a multitude of other clamping mechanisms)
This is an “over centre
mechanism” because the point of attachment of the muscles (mainly via the
erector spinae aponeurosis) is
below the hinge point in the
spine.
The seriousness of such an extrusion
of the nucleus is obvious and fully explains the evolution of a severe and
persistent pain
if there is a source for such a
pain before tissue damage occurs.
The answer to Question 4 provides just such a
source and it so happens, probably by chance, that the angle of spinal flexion
that begins to become dangerous, corresponds to the flexion through and beyond
the parallel sided shape (for the lowest two disks as shown below.)
This is, I suggest, the reason that low back pain
has evolved to be so severe and persistent. The Evolution of Low Back Pain
(1) Adams MA, Hutton WC Prolapsed Intervertebral
Disc. A Hyperflexion Injury Spine 7: 184-191, 1982