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Powered
Prosthetics
Abstract
Introduction
In 1976, Waters, Perry, Antonelli and Hislop measured the rate
of oxygen consumption of both below-knee amputees and a control
group (non-amputees) while they walked at their self-selected
walking speed. The control group (N=50) consumed only 0.16 ml
O2/kg/m while walking at a reasonably fast pace of 82 m/minute.
However, patients (N=14) who suffered a trauma induced below-knee
amputation needed 0.20 ml O2/kg/m to walk at slower pace of 71
m/minute. Even worse performance was exhibited by patients whose
amputation arose from vascular problems. These patients (N=13)
used 0.26 ml O2/kg/m to walk at only 45 m/minute.
While the control group had both lower limbs available to put
energy into their gait, the below-knee amputee group did not.
In fact, when broken down by joints, the hip contributes 22 joules/step,
the knee 27 joules/step, and the ankle 36 joules/step (Gitter,
Czerniecki, and DeGroot; 1991). Clearly, those with a lower limb
amputation suffer a severe handicap.
Our research team is interested in testing the idea that if we
could restore this lost energy, lower limb amputees would be able
to walk better.
Approach
The idea of using powered prosthetic limbs has been around for
a long time, however, most of the research and commercial activity
has been on upper limb prosthetics. Among the differences between
upper and lower limb devices are that upper limbs are used for
fine manipulation tasks with small loads, while lower limbs are
used for periodic motion (i.e. walking) with much greater loads.
These differences result in some significant design challenges.
If a multi-disciplinary team were to develop
the "perfect" lower limb prosthesis, the list of requirements
might include:
- 8 hours
of continuous operations,
- Light
weight with a high power output,
- Minimal
maintenance,
- Quiet
operation, and a
- High
level of user satisfaction.
Such a team
might spend years developing a device which meets all of these
requirements, yet it might not actually help an amputee walk any
better. What if you had the perfect, portable, artificial limb
to input energy into the amputee's gait, but they didn't walk
any faster, use less oxygen, or have a lower perceived sense of
effort? A lot of time and money would have been spent, but the
goal of helping amputee's walk better wouldn't be achieved.
Our approach is to develop a limb for laboratory use to test the
following hypotheses.
A powered prosthetic device for a below-knee amputee will:
- Reduce
the metabolic cost of locomotion.
- Reduce
the level of perceived effort.
- Improve
gait symmetry as measured by kinematic and kinetic techniques.
To test these
hypotheses, we don't need the "perfect" prosthesis, only one which
can restore the lost energy to the amputee's gait while walking
on a treadmill in the lab. If we're successful in this effort,
we'll move on to some of the more difficult design challenges
of the "perfect" prosthesis.
Specific Aims
- Design
and fabricate a powered, lower limb prosthetic device using
McKibben
artificial muscles.
- Supply
the missing energy during locomotion.
- Measure
and compare performance.
Devices
McKibben
Artificial Muscles
Publications
(*)
(*) Note: Most of the BRL
publications are available on-line in a PDF format. You
may used the publication's reference number as a link to the individual
manuscript.
[123]
G.K. Klute, J. Czerniecki, B. Hannaford,
'Development of Powered Prosthetic Lower Limb,' Proc. 1st National
Mtg, Veterans Affairs Rehab. R&D Service, Washington, DC, October
1998.
[129]
G.K. Klute, J.M. Czerniecki, B. Hannaford,
'McKibben Artificial Muscles: Pneumatic Actuators with Biomechanical
Intelligence,' IEEE/ASME 1999 Intl. Conf. on Advanced Intelligent
Mechatronics, Atlanta GA, September 19-22, 1999.
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