Targeted Muscle Reinnervation for Control of Myoelectric Arm Prostheses

1. Targeted Muscle Reinnervation for Control of Myoelectric Arm Prostheses By. Rory Makuch

2. 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....

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. Sources • http://www.amputee-coalition.org/fact_sheets/amp_stats_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/PMC3036162/ • http://archive.laptopmag.com/NR/rdonlyres/evgcu4re7rrpq7mrxmmixvapkvwm27mt2daqiwp3eqs57th6slh5zspeyoe4t74d6rrmo62rhrcw3d/ProstheticArmcrop.jpg • http://www.ric.org/conditions/po/services/bionic/ • http://www.youtube.com/watch?v=MLvwTlbj1Y8