Many of us take out dexterity for
granted. However, for amputee patients, the simplest takes such as grabbing a
cup of water or using a fork can be tremendously challenging or even
impossible. Even with the help of some of the prosthetics on the market, amputees
still experience a diminished quality of life as many prosthetics are clunky, intuitive,
and extremely hard to get accustomed to since they require the amputee to move proximal
muscles that aren’t associated with the desired muscle movement. For example,
the body powered prosthetic (shown in the picture) requires the user to use
their upper arm and shoulders to control a hand clamp.These clunky movements make
it difficult for users to learn how to use them or get used to using them.
Consequently, the amputee will use the prosthesis less and less until they stop
using it altogether which is usually after a few months.
In a
seminar at Loyola University Dr. Dumanian, a plastic and reconstructive surgeon,
presented his finding on amputations and described one of his methods to make
upper body prosthetics easier and more efficient to use. Rather than making a
prosthetic that is operated by moving unassociated part of the body, Dr.
Dumanian set out to find a method that allowed amputees to operate their prosthetic
arm and hand by simply thinking about the motion.
Allowing
amputees to control a prosthetic device means that there needs to be some sort
of integration between the brain and the prosthetic. To create this integration,
Dr. Dumanian used nerves at the amputation site that were once used to send
signals down the arm and reinnervated them to the pectoralis muscles. This
allowed the nerves to be closer to the surface of the skin and provided a
target muscle for the neurons to attach to.
To
complete the integration between the brain and the prosthetic, Dr. Dumanian
used a myoelectric prosthesis that could read the electrical signals generated
from the nerves on the amputee’s chest. This resulted in the amputee being able
to control the prosthesis through thought alone, thereby allowing the amputee
to make intuitive fluent movement that was not possible with another
prosthetics. One of the reasons this method produces more flexibility and fluid
movement is because the prosthetics and receive multiple inputs at one which
eliminates a lot of the jerky motions observed in other prosthetics.
Additionally, since the amputee only has to think about the action to make the
prosthetic operate, there is little to no learning curve and it is much easier
for the patient to become accustomed to the device.
Dr.
Dumanian’s amazing method significantly improves the experience and quality of
life of the amputees. However, for this method to work it depends on the
presence of health undamaged nerves, which means that individuals born without
limbs or the innervating nerves to control them would not benefit from this procedure.
However, a group of scientists at Newcastle University in the UK are working on
a different type of prosthetic that would require no thought. Unlike Dr.
Dumanian’s method, Dr. Nazarpour, one of the
scientists working on this project, uses a prosthetic hand that attaches to an arm
and doesn’t need preexisting nerves to operate. Dr. Nazarpour has integrated
more sensors and cameras into the prosthetic so that the amputee doesn’t even
have to think to control the hand. Instead, the camera and sensors detect the
targeted object and adjust the prosthetic accordingly. Each interaction allows
the hand to learn new objects and become smarter and more efficient in the
future. Compared to Dr. Dumanian’s method, this new prosthetic can be used by
individuals with damaged and unusable nerves or people born without hands. The
integration of both methods could result in a seamless marriage between amputee
and the prosthetic to create efficient prosthetics that can keep up with the
biological limbs.
References
Todd A Kuiken, Laura A Miller, Robert D Lipschutz, Blair A Lock, Kathy Stubblefield, Paul D Marasco, Ping Zhou, Gregory A Dumanian, Targeted reinnervation for enhanced prosthetic arm function in a woman with a proximal amputation: a case study, The Lancet, Volume 369, Issue 9559, 3–9 February 2007, Pages 371-380, ISSN 0140-6736, https://doi.org/10.1016/S0140-6736(07)60193-7. (http://www.sciencedirect.com/science/article/pii/S0140673607601937)
- https://phys.org/news/2017-05-amputees.html
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