Transcript Targeted Muscle Reinnervation for Control of Myoelectric Arm

Targeted Muscle Reinnervation for
Control of Myoelectric Arm
Prostheses
By. Rory Makuch
Need for a functional upper limb
Prosthetic
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There are an estimated 1.7 million people in the United
States alone that have had an amputation of some kind.
Between 1988 and 1996, 68.6 percent of trauma related
amputations were upper limb amputations.
There are Three main types of arm prostheses
Cosmetic- provide realistic looking replacement.
Body Powered- use body and shoulder muscles to
move arm prosthesis.
Myoelectric....
Myoelectric Arm Prostheses
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Myoelectric prostheses are artificial limbs controlled
through sensors connected to remaining muscles of
the arm
Sensors pick up Electromyograph signals which are
processed and converted to movements by a
computer.
This method is sometimes not intuitive because the
patient has to flex muscles not normally associated
with a movement to complete the movement.
Some patients cannot generate strong enough signals
to be picked up. Others such as shoulder
disarticulation amputees simply do not have the
muscles necessary.
Targeted Muscle Reinnervation
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A surgical process where the residual nerves in the
arm are transported to the shoulder upper chest or
back.
After 11-70 months of recovery, nerve impulses from
the brain to the amputated limb will activate the muscle
areas that the nerves have been transplanted to.
This new muscle activation serves as an amplifier for
EMG signal detection.
It allows patients without any arm muscles to be fitted
with a myoelectric prosthesis, as well as allowing more
intuitive control of the prosthesis.
Technical Information
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For testing twelve
EMG electrodes are
placed on the patient
in the new muscular
activation areas.
When the patients
think about a certain
movement the
activation of the EMG
sensors is mapped
and processed.
This data is used to
train a myoelectric
Testing
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This type of prosthesis interface is still in the research
phase.
Five amputees that had undergone targeted muscle
reinnervation and five non amputees were chosen to
test the interface.
The first tests were done on a virtual arm, patients
chose 11 arm motions including 3 different grips to
attempt.
The control subjects completed the motions 97% of the
time and the amputees 88% of the time.
Three of the TMR participants were then chosen to
attempt to manipulate a real prosthesis. They were able
to attain proficiency in the first day. With great
Limitations
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One of the limitations of the device is movement
reaction time. While the results are much better than
without TMR, the reaction speed is nowhere near non
prosthesis speeds.
Weight of the device. The patient has to wear a small
computer on their back for processing and retraining
on the go.
The amputation must be recent (within 10 years) and
there cannot be severe nerve damage.
Sources
http://www.amputeecoalition.org/fact_sheets/amp_stats_cause.
html
http://www.amputeecoalition.org/inmotion/nov_dec_07/history_p
rosthetics.html
http://www.myoelectricprosthetics.com/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC
3036162/
http://archive.laptopmag.com/NR/rdonlyres/ev