Low
Back Pain –home page
All of my work on low
back pain is based on the following explanation of the problem:
The lordosis in the human spine is difficult to
explain in engineering terms. In fact
it's impossible and all engineering explanations have been wrong. The real reason was shown by the
anthropologist Owen Lovejoy in "The Obstetric Pelvis of Lucy". It is simply the maintenance of an adequate
birth canal in the pelvis. (Full details of this, and all other, references
are in the paper ‘The Obstetric reason
for Lordosis. . . . . . . . . ’ at http://www.naturaljointmobility.info/publications%20njm.htm
)
The birth canal defines the shape and angle of the
sacrum and this in turn results in the lowest two discs of the spine being
wedge shaped by about 20 degrees.
(Thick edge of disk anterior, thin edge posterior at L4/5 and L5/S.)
But note that this 20 degrees is far greater than
the mobility of these joints in flexion, (Max nine to fifteen degrees. Piercy, Portek and Shepherd, Jonk and van
Niekerk etc.) meaning that these discs will always remain wedge shaped in the
same direction, even in full flexion-- as a long as there is nothing that
distorts this evolved situation.
Sadly there is.
It is one of the most common items in our civilised lifestyle. It is the chair or seat with a backrest.
A backrest will always tend to flex the lowest
joints of the spine in comparison with unsupported sitting while at the same
time extending or hyperextending those higher up. This should be predicted by any engineer and was clear from the
tabulations in "The Influence --
-- -- Of Lumbar Support -- --" by Anderson, Nachemson et all.
Well, maybe it won't matter that these discs, instead
of always remaining wedge shaped as they were evolved, are made to flex and
extend like any other discs of the spine.
Sadly it does matter. It matters
very much, for the following reason.
In the chimpanzee, the strength of the spine
increases with flexion of the lowest joints.
This is because of the location of the origins of the back muscles on
the pelvis. With the changed shape of
the human pelvis, this situation is reversed and the strength of the spine is
reduced by flexion of the lowest joints and can be reduced to almost nothing.
To an engineer it is an obvious ‘over-centre mechanism’. This would mean that the human spine could
be broken like a chicken leg where it connects to the pelvis.
This problem does not have an easy mechanical
solution. It must have happened
frequently to our earliest bipedal ancestors and some of them would very
quickly have become food for the predators and scavengers of the savannah.
However, before the spine lost all its strength,
there would be a phase when the lowest discs just began to flex beyond the
parallel-sided shape to the situation where the posterior edge of the disk was
a bit thicker than the anterior edge.
The nucleus would then, for the first time for that individual, tend to
move towards the posterior edge of the disk.
The proximity of the nucleus would be a new and unusual event for the
nerves in the posterior annulus of the disk.
Nerves that experience an unusual event will produce pain. In some individuals the pain would have been
marginal or just a feeling and they would have ignored it. They would go on to break the spine and be
gobbled up.
In other individuals the pain would have been
sufficiently strong to stop them lifting or bending. Even if they suffered further pain they would survive. The more severe the pain was, the more that
these individuals would stop doing anything that might further damage the
spine.
This Is the ‘Evolution of Low Back Pain’. It has
evolved to be an amazingly severe and persistent pain. It is also a very successful warning
pain. Real damage is relatively rare
and only develops progressively.
We all know that many joints and structures of the
spine become involved and are eventually damaged when a low back problem has
started. This makes it difficult to analyse
the real cause of the problem. Many
causes and components have been proposed.
Do the known statistics of the problem support the
cause proposed here?
The only clear statistical association is with
driving cars. This was first shown by
Kelsey and Hardy in 1970 and has been confirmed by many studies since. Would we expect this mechanically? The answer is definitely yes. Car seats tip the thighs and therefore the
pelvis further back than almost any other seat. Car seats incorporate far more direct support for the lumbar
spine than any other seats. We sit still in a car seat for far longer than we
ever sit anywhere else. This mechanical situation could not be better designed
to cause the problem outlined above.
If we combine Kelsey and Hardy's work with the
surveys by Mark Porter, Professor of Ergonomics at Loughborough University, UK
it appears that a high mileage car driver is about twelve times as likely to
have a serious low back problem as anyone who never uses a car at all. (This work was published in the trade
magazine Automotive Interiors International)
This combination may not be good statistics but
it's very good common sense. It
suggests a far higher correlation between driving cars and low back pain than
between smoking and lung cancer.
Comparison of these two surveys also suggests that the situation is far
worse for the high mileage driver in the late nineties than it was in the late
sixties. Is this compatible with the
mechanical argument proposed?
Yes. It is
more than compatible. It's
predictable. In the eighties and
nineties the angle of the sitting surface of car seats was tilted further
backwards in order to counter the problem of slipping under the seat belt in an
accident. At the same time lumbar
support was introduced generally into car seats. The combination of these two is bound to increase the flexion
force in the spine at the lowest spinal joints. We should expect the statistical situation to be worse and
judging by these published statistics it is.
What can we do about this problem before it
results in serious damage to the spine?
We need to find some way of limiting the flexion of the lowest two discs
to the designed or evolved shape defined above. Our civilised lifestyle causes
the problem so obviously modifications of this are one part of the solution.
This is what Natural Joint Mobility is all about and obviously backrests must
incorporate pelvic support not lumbar support.
But even with this knowledge of what we
need to do, it can be a slow process to correct the distortions caused by a
lifetime of civilised sitting. People want, and deserve, a more instant and
complete solution.
One of the medical procedures currently
used is sclerosing injections into the ligaments at this level to reduce the
mobility. In principle this will help but the ligaments are not suitably
oriented. There is no supraspinous ligament at these joints. It stops at L4 (Rissanen). We could however build up a supra-spinous
ligament from the spinous process of L4 to some points on the sacrum. This should be nylon or carbon fibre so that
it does not simply stretch plastically under the flexion forces defined above.
This solution is a simple and
obvious result of being able to define exactly how far these discs (L4/5 and
L5/S.) should flex. It might turn out
to be a very effective corrective measure in the early stages of a low back
problem. I am interested in working
with an orthopaedic surgeon who wishes first of all to fully understand this
proposal and then to develop his or her own method of implementing it. (Preliminary
Suggestions on how this might be implemented can be found at www.naturaljointmobility.info/Prosthetic%20supraspinous%20Ligament.htm)
This explanation is covered in more detail in the book “The Evolution of
Low Back Pain” which is a free download at www.naturaljointmobility.info/publications%20njm.htm
More will be added to this section in due course but for the moment the
following links are available. John Gorman Feb 07