ANALYSIS OF HAND MOVEMENT INDUCED BY FUNCTIONAL ELECTRICAL STIMULATION IN TETRAPLEGIC AND HEMIPLEGIC PATIENTS

Abstract

We analyzed several hand movements of two tetraplegics and one hemiplegic using functional electrical stimulation (FES). For this purpose, we made a ten-channel stimulator on an experimental basis. Stimulation was carried out using cathodal rectangular pulse trains at 20Hz with a pulse duration of 0.2 msec. Stimulus amplitude was varied from 0 to -25V and adjusted to obtain the desired muscle contraction. The electrodes we used were percutaneous stainless steel wires after Caldwell and Peckham. Six nerves supplying the muscles of the forearm and hand were stimulated separately or simultaneously.
As to individual motion of the hand, five patterns were obtained as follows:
1. Extention of the thumb and fingers by stimulation of a deep branch of the radial nerve.
2. Opposition and abduction of the thumb by stimulation of a recurrent branch of the median nerve.
3. Flexion of the thumb by stimulation of muscle branches to the flexor pollicis longus.
4. Flexion of the fingers by stimulation of muscle branches to the flexor digitorum superficialis and profundus.
5. Flexion of the MP joints of the thumb and fingers with thumb adduction by stimulation of the ulnar nerve.
It is necessary to combinate these motions to obtain practical hand movements for ADL. For this purpose, two or three nerves were stimulated in combination, and four patterns of of the movements were obtained as follows:
1. Opening of the hand with the thumb in opposition by stimulation of a deep branch of the radial nerve and a recurrent branch of the median nerve.
2. Power grasp or precision grasp by stimulation of a recurrent branch of the median nerve, muscle branches to the flexor digitorum superficialis, profundus and flexor pollicis longus.
3. Lateral pinch by stimulation of muscle branches to the flexor digitorum superficialis, profundus and flexor pollicis longus.
4. A movement that holds a newspaper or a hand of cards by stimulation of the ulnar nerve and a recurrent branch of the median nerve.