THE RUSSIAN MYO-ELECTRIC ARM

The possibility of using myo-electric potentials to control the operation of prostheses was shown by Battye, Nightingale and Whillis in 1955. The first indication of the work being undertaken in Russia came in a paper by Kobrinski and by co-workers read in Moscow in 1960. The first model to go into production as a result of this work is now being tested in this country. This arm is intended only for patients with forearm amputation and provides means of controlling the opening and closing of an artificial hand by the electrical potential produced by active use of the forearm muscles of the stump. Surface electrodes are mounted in the socket of the prosthesis in apposition to the flexor and extensor groups of muscles, and a neutral electrode or “ earth “ is placed over the olecranon or some other suitable site. The muscle potential is fed to an amplifier which is of relatively low impedance and has two channels, one for the flexors and one for the extensors. The output is used as an on/off signal to control the motor which drives the hand. The closure and opening ofthe hand therefore occurs at a fixed speed and the force ofgrasp can be modulated only by timing. The hand is of reasonably acceptable appearance and is covered with a cosmetic glove. The drive causes the index and middle fingers and the thumb to move awa