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M Swanepoel
07-01-1998, 01:17 AM
Hi All,

I have found two (fairly old) references on the effect of cyclic
loading on limb joint cartilage. I would guess that limb bones must show
the same sort of adaptation to loading as the articular cartilage
which is present at its ends - in fact naively I would expect the
deposition of bone in response to loads of different frequencies to
mirror the production of PGs in response to the frequency of
articular joint contact loads. The papers are:

Parkkinen JJ, Lammi MJ, Ikonen J, Helminen HJ and Tammi M (1992):
The influence of cyclic hydrostatic pressure on cultured articular
cartilage and chondrocytes. Paper given at the 19th Symposium of the
European Society for Osteoarthrosis and Arthritis, Noordwijkerhout,
the Netherlands, 24-27 May, 1992. WB van den Berg, of the University
of Nijmegen was the chairperson of that session.

Urban J and Hall A (1992) Physical modifiers of cartilage metabolism.
Chapter 27 of "Articular Cartilage and Osteoarthritis", edited by K
Kuettner et al., Raven Press Ltd, New York, pp 393-406

Both these papers considered the effect of varying loading
frequencies on PG production. I would surmise that if osteoporotic sufferers
subjected their limbs to loading regimes that mimicked those known to keep
articular cartilage cultures producing their maximal output of PGs, then their
bones would also benefit greatly. Anyhow - its worth a trial!

However its probably easier to keep chondrocytes and articular cartilage
explants "happy" in vitro than bone, so I suppose that there have
been very few studies of bone precipitation and removal, and the
metabolism of osteocytes, -blasts and -clasts, in vitro (or for that
matter, in vivo)? If someone knows of work similar to that
referenced here, but for bone, I'd like to know, because I'm trying
to develop a model to explain the adaptation of all the different
Southern African antelope limb bones and joints to loading. (The
advantage of antelope is that these are Eocene mammals having put in
an appearance in the last 2,5 million years, and are still closely
related. Some of the species in the same genus differ widely in
mophology, but are still very closely genetically related - hence
much of the difference betwen their limb bone structures and joints
must be explainable on the basis of physical loading. I have a good
model of how joints adapt to loading - but collecting and examining the
physical evidence is daunting!)

Mark W Swanepoel
School of Mechanical Engineering
University of the Witwatersrand

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