Targeted Muscle Reinnervation for Control of Myoelectric Arm Prostheses

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Targeted Muscle Reinnervation for Control of
Myoelectric Arm Prostheses
By. Rory Makuch
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Need for a functional upper limb Prosthetic

• 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....

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Myoelectric Arm Prostheses

• 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.

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Targeted Muscle Reinnervation

• 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.

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Technical Information

• 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
  prosthesis to perform different operations.

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Testing

• 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 improvement over two weeks.

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Limitations

• 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.

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Sources

• http//www.amputee-coalition.org/fact_sheets/amp_s
  tats_cause.html
• http//www.amputee-coalition.org/inmotion/nov_dec_
  07/history_prosthetics.html
• http//www.myoelectricprosthetics.com/
• http//www.ncbi.nlm.nih.gov/pmc/articles/PMC303616
  2/
• http//archive.laptopmag.com/NR/rdonlyres/evgcu4re
  7rrpq7mrxmmixvapkvwm27mt2daqiwp3eqs57th6slh5zspeyo
  e4t74d6rrmo62rhrcw3d/ProstheticArmcrop.jpg
• http//www.ric.org/conditions/po/services/bionic/
  
• http//www.youtube.com/watch?vMLvwTlbj1Y8