Abstract
A nine year old girl with a congenital above-elbow amputation was supplied with a myoelectrically controlled arm prosthesis at the Regional Hospital, Orebro, Sweden, in May 1978. The prosthesis was equipped with an artificial hand as well as an elbow joint. The latter was designed at New York University, for switch control but adapted to myoelectric control in the Department of Clinical Neurophysiology at the Regional Hospital, Orebro. The electric signals from the biceps and triceps muscles were used for the control of hand closing and opening as well as elbow flexion and extension. Two different control methods have been applied and clinically tested.
The first is a three-level method in which slight contraction of biceps/triceps gives closing/ opening motions of the hand and a higher contraction level in these muscles gives flexion/extension of the elbow.
The second is a contraction-rate detection method in which slow contraction of biceps/triceps gives closing/opening of the hand and faster contraction of these muscles gives flexion/extension of the elbow.
Both methods have been tested on the patient in a laboratory set-up and in a clinical trial which is still going on. Small electronic control circuits have been designed and placed inside the socket of the prosthesis, which is completely self-contained.
From the different tests performed, the second control method seems to be the most suitable for the actual patient. She is using her prosthesis every day, continuously improving her controlling ability.