Methods of Pre-Prosthetic Training For Upper-Extremity Amputees: Electromyographic Study

Thérèse Gouin-Décarie, Ph.D.


Laval Medical 40:366-370, April 1969.

Methodes d'Entratnement Pre-Prosthetique Chez les Amputes du Membre Superieur: Etude electromyographique.

This study of five upper-extremity amputees attempts to demonstrate the possibilities for muscular reeducation offered by electromyography. The technique, which permits study of the action potentials of muscles, is already the basis of one method of training in the control of motor unit activity. This method requires initially that voluntary effort be reinforced by audiovisual signals associated with the action potential of each motor unit activated. By this means a cycle is created, beginning with the audiovisual and proprioceptive awareness of voluntary motor activity and ending in a better controlled graded response of the same motor unit.

The choice of sites of muscular control is critical. In performing his daily activities, the patient must be able to relax or contract the muscle at the desired moment. The prosthetic system currently used is threefold: pneumatic, conventional, and myoelectric, and requires, first of all, selection of at least two sites of muscular control.

Material and Methods

Four subjects had complete shoulder disarticulations and the fifth was an above-elbow amputee. Superficial back, chest, and abdominal muscles were studied with the aid of skin electrodes for total control. For more limited muscular control, intramuscular electrodes were employed. Total control was provided by the clavicular fibers of the pectoralis major, rectus abdominis, serratus anterior, latissimus dorsi, and rhomboids. Limited control was effected by electrodes placed as near as possible to the motor points of the trapezius: (a) level with the inferior angle of the scapula; (b) under the medial third of the scapular spine; and (c) four centimeters above the preceding site in a frontal plane passing through the shoulder. Electrical potentials produced by these muscles were directed through a preamplifier to a four-track oscilloscope and loudspeaker, thus giving visual and auditory signals from each muscular response.

Training included functional muscle evaluation and graded instruction. The effects of relaxation of some sites of implantation and the electrical potential evoked by muscular activity at another part were analyzed quantitatively while the patient protracted, retracted, and elevated his acromion maximally. Study was continued with vertical extension of the head, lateral flexion toward the amputated side, and homolateral and contralateral rotation.

The first search was for individual muscular control in which the patient learned (a) to contract and to relax each site of muscular implantation; (b) to grade muscular activity from complete rest to maximum contraction; (c) to produce voluntarily controlled and gentle activity. After achieving these controls, the patient knew how much effort was needed for each level of desired contraction. He was then asked to diminish the effort of contraction slowly while maintaining the desired activity among two or three perceived residual-action potentials; an action potential from a single motor unit was recognized by a repeated pattern on the oscilloscope and by a distinctive sound. The subject also became familiar with the visual and auditory signals of a motor unit after practicing brief relaxation and contraction, increasing and decreasing the frequency of motor responses. This training was repeated for each muscular site selected.

A more complex phase of training involved simultaneous control of two sites. The subject had to contract one site at various levels while maintaining electromyographic tracing silence from a second segment. A third and then a fourth site were added with the subject having to learn the same control. Mastery of different individual contractions from each site must next be reproduced sequentially with a brief pause between each contraction. The final stage required relaxing the muscular site while moving the contralateral side, or even while walking. This control, once obtained, will permit the patient to move without affecting the prosthetic function envisioned. Finally, maximum control must be obtained without audiovisual aid. Recordings were made with an oscillographic system in order to demonstrate different stages of training and muscular behaviour.

Results

The most impressive kinesiologic observations were of the trapezius. The other muscles only demonstrated their usual functions. Movement of the acromion and of the head activated portions of the trapezius in different proportions. Muscular silence at each site of implantation during certain movements was important to permit use of these movements to activate an external commutator in a pneumatic system.

Each amputee demonstrated different training possibilities. To obtain simultaneous control of two or more sites, it was necessary to combine movements of the acromion with those of the inferior angle of the scapula. Four subjects could control three muscular sites simultaneously, and one learned to control four muscles simultaneously and consecutively. One controlled simultaneously and consecutively three segments of the trapezius, contracting each trained motor unit in sequence. Time necessary to obtain success was reduced from one hour to two seconds.

Summary and Conclusions

A method of pre-prosthetic training has been suggested for patients presenting complete absence of one or both upper extremities. Control of several sites in a single muscle or of different muscles offers interesting possibilities for prosthetic and orthotic application.

Translated and Abstracted by:

Joan E. Edelstein, R.P.T.

Thérèse Gouin-Décarie, Ph.D. is associated with the Department of Anatomy at the University of Montreal