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The Future
Of Amputation And Limb Loss: The
Science
Tis' the season to be making grandiose
statements about the future and so
following that trend AOLM has decided to
fortell the future of amputation and limb
loss through the eyes and ears of those
who live with it every day.
To the outside universe, the world of
amputation and limb loss is a marvelous
world were surgeons are perfect and
technology can accomplish great things.
From the users perspective things are a
little less romantic and more of a
practical nature.
COMPUTER
LIMBS
We know from experience that the rate
of change in the prosthetic industry is
slow. Typically we see technologies
invented 50 years ago resurface again and
again in different materials or other
forms.
We know that many of the technologies
that currently exist have been around for
at least 30-40 years. The materials may
have changed but the application of them
has changed very little. The use of carbon
fibre as a base material has given use
lighter, more responsive and generally
more durable products. However, whilst
many of us use some carbon fibre products
some of the other products we use are much
older in origin. And so the rate of change
may not be as rapid as many believe. There
are a few things on the horizon that may
change that.
There have been numerous attempts at
integrating "computer" technology into
prosthetic limbs, the Seattle Limb
Systems; the Endolite Intelligent
prosthesis and the overly expensive Otto
Bock C leg have all made rudimentary
entries in this area.
Whilst these product are using some of
the capabilities of micro processors,
consider what the computer is designed to
do - that is process large amounts of
information at higher and higher speeds.
Human movement also consists of the human
brain processing large amounts of
information preferably at high speeds.
The ability for a computer to mimic
human physical movement has been used for
at least 25 years. The automotive industry
was one of the first large scale
industries to replace many workers with
robotic versions. The prosthetic industry
has at least recognised the importance of
the capabilities of computers in the
application of human movement, but it is a
long way from replicating the movement of
human limbs in the real world.
One the possible solutions for human
movement to be mimicked via computer
memory. For example the human body is only
capable of a finite number of body
movements on an average daily basis, even
less for one particular limb. Why then
could computer memory be used to store
movement information and then be used to
predict movement or even anticipate it in
the same way we do ? In fact ROM chips
could be used to permanently store
individual limb movements, the application
of which would be similar across the world
since we are all basically function the
same. Or we could tailor make ROM chips to
mimic a 5ft 1 female or a 6ft 5 male. The
ROM chip would have enough memory in it to
match up current movement patterns and
select which pattern suites any given
particular behaviour. Input could be
created from sensors that already exist.
Whilst ROM chips might be used to store
movement information, that movement still
has to be physically created. We are a lot
further behind in this technology in
comparison. The intricacies of the human
limb movement are very hard to replicate
with existing technologies. Add the factor
of generating the power to create the
movement and we have a lot of factors
added in. One source of power is the human
body itself. Over an average day the human
body generates hundreds of watts in power,
maybe this can be harnessed. Micro
hydraulics or the use of
Orlon
based muscles maybe the
answer.
In upper limb prosthetics the overly
stagnant myoelectric arm has had some
upgrades, but durability, weight and
battery life still remain as stumbling
blocks. Durability can be addressed by the
use of materials that regenerate just like
human tissue, weight can be relieved by
use of lighter materials but also the
attachment of the prosthesis directly to
the large bone structures of the shoulder
or arm via osseointegration. To date the
issue of osseointegration remains largely
misunderstood and unaccepted by the
prosthetic industry.
INTEGRATION OF PROSTHETIC
LIMBS AND HUMAN ANATOMY
Osseointegration lies at the heart of
integrating human anatomy to prosthetic
devices. It is already being done everyday
in dentistry and is widely accepted in
that area. However, osseointegration and
prosthetic limbs are only recently being
tried out on any significant scale outside
Sweden. Maxiofacial prosthetists utilise
osseointegration on a daily basis, since
there are very few alternatives to
securing a prosthetic part to the face.
Of course for osseintegration to live
up to its full potential there has to be a
corresponding increase in the quality and
effectiveness of the prosthetic
technology. There has to be real life
benefits other than the weight bearing
issue with osseointegration, with out the
support from the prosthetics industry, it
is doubtful the procedure will be nothing
more than a fad.
TISSUE
REGENERATION AND DEVELOPMENT
We are all familiar with the term
"cloning" however this term is often
misused under the guise of tissue
generation. Right now it is possible to
regenerate tissue in the shape of an ear
or nose by growing tissue on a framework
that dissolves over time, leaving the
tissue intact. We are a long, long way
from regenerating whole limbs, but next on
the list will be internal organs.
It is forseeable that tissue
regeneration maybe integrated with limb
reattachment to speed up the recovery
process, to fill in the gaps so to speak.
REATTACHMENT
TECHNIQUES
1999 marked the first successful limb
transplants from anonymous donors. Of all
the technologies discussed this is the
brightest and most promising. Already the
surgeons are planning the reattachment of
two arms from anonymous donors and it is
expected within 12 months a leg will also
be transplanted. However, there are
serious drawbacks related to rejection
drugs needed which cost up to $2000 per
month. Reattachment surgeries will only be
as successful in the long term as the need
for rejection drug therapies diminish.
It is already evident that the business
of replacing lost limbs will veer more and
more from its traditional path of
replacing the limb(s) with a wholly
mechanical equivalent. Whether prosthetics
can integrate more with computer,
osseointegration and body power remains to
be seen. Given the slow moving nature of
prosthetics other areas such as tissue
generation and reattachment technique may
cause the prosthetic limb to fall by the
wayside as a solution for limb loss within
50 years.
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