Mark Swanepoel's recent post on the effects of spinal manipulation by
chiropractors raises some important and controversial issues. As the person
who seemed to initiate this line of discussion a good while ago, I have been
asked by the listserve chief to remind contributors of the biomechanical focus
of this group, since some of the discussion has tended to wander into other
less directly related territory.

Thus, it would be of value to analyse and offer appropriate references which
relate to the mechanical and anatomical effects of various types and patterns
of mobilisation and manipulation on the spine. This would certainly be of
benefit in placing on a firmer scientific footing some clinical methods which
are applied by physical therapists and chiropractors.

So far, feedback on this issue has commented on the differences between the
very subtle realignments or reduction of 'subluxations' and the more gross
manipulations which purport to stretch or deform connective tissues which are
vitro has been shown to be highly resistant to the magnitude of forces or
strains which may be offered by therapists. It has been suggested that some
of the beneficial effects are due to well-known nerve-stretching methods or by
reducing spasm.

Though this may explain the amelioration of some of the musculoskeletal
problems, this does not offer satisfactory explanation of successes claimed in
the management of systemic or non-localised disorders.

Comments have been made concerning the release of dissolved gases in the
cerebrospinal fluid and the possible skewing of interpretations by the
existrence of placebo effects. Anecdotal or clinical results have been cited
in reasonable abundance, but, as yet, there appears to be no consensus on the
precise nature of the mechanical effects on the various physical structures,
especially in the case of presumed pathology or simply for restoring general
health via regular spinal 'readjustment'.

It is this issue which is central to what Dr Swanepoel has commented on in his
latest post. So, before some contributors feel tempted to address the problem
from the point of view of personal experiences, anecdotal success or failure
stories, or opinions of influential leaders in the field of manipulative
therapy, let us attempt to invoke the methods of biomechanics in approaching
this task.

The topic has many wide-ranging clinical implications, especially since it
underlies much of the philosophy of some forms of therapy, so it is a worthy
task for interested biomechanists. I am sure that all of us look most forward
to reading some solid biomechanical discourses on this subject, some of which
may well stimulate postgraduate students to research any defective links which
need serious attention.

Dr Mel C Siff
Littleton, CO, USA

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