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A myoelectric-controlled orthosis
A Myoelectric-controlled Orthosis--C. Hamonet, D. Boulongne, S. Simon and P. Bedhet
A M Y O E L E C T R I C - C O N T R O L L E D ORTHOSIS Recent Development
C. H A M O N E T , D. BOULONGNE, S. SIMON and P. BEDHET, Paris Progress achieved by medical therapy has shown that today an extremely large number of physically-handicapped patients with four-limb deficiency can escape the deadly complications threatening them and still have high hopes for the future. We have sought to return to these patients many possibilities of function by means of powered artificial limbs that are controlled through myoelectric activity gathered from muscles which have been either fully or partially spared. Our developments are of two kinds: First an orthosis with a certain degree of freedom allowing for pinching by two or three fingers (MYO-ELEC limb); secondly, an experimental limb with 4 degrees of freedom to position the hand in space and to pinch. PRINCIPLES OF THE MYOELECTRIC PREHENSION ORTHOSIS
A single muscle can control the orthosis, simplifying its application and the training of the patients. When the muscle contracts the hand closes, the speed of the movement being proportional to the intensity of the myoelectric signal. This functional characteristic seems essential to us since we wish to approach the physiological conditions of pinching as closely as possible. The pinch may be maintained by sustaining myoelectric activity. The pinching power is also proportional to the muscular contraction. When the muscular contraction stops the hand opens. This "passive" or low-energy expenditure opening is similar to the normal action of the hand when it releases an object after it has been pinched. Active or more explosive "opening" can also be provided and is of particular use, for example, when an object is being thrown away. It is possible to stop the opening of the hand at any point and to maintain the fingers in a selected position if the patient desires to grasp an object previously released. Description of the Prehension Ortho,sis
The orthosis is made in Dural A.U.4.G. (Aluminium plus small amounts of iron, copper, magnesium, silicon and manganese), and in brass. It incorporates a wristband on which the elements that set the fingers in motion and the mechanical system of transmission are fixed. The finger pieces involve one part which maintains the thumb in opposition and another which includes the fixation rings for the second and third fingers. The fingers are articulated at the metacarpophalangeal joints. A second articulation is provided at the proximal interphalangeal joint. The mechnical transmission system and the motor are placed along the external side of the forearm in such a way that they can be hidden by the sleeve. The m,echanical system of transmission includes a cog wheel and a small driving-rod which transfer the motion of the motor to the fingers. The orthosis weighs 180 grammes. The maximum opening of fingers is eight centimetres. The pinch force is 400 grammes. The Hand--Vol. 7
No. 1
1975
63
A Myoelectric-controlled Orthosis--C. Hamonet. D. Boulongne, S. Simon and P. Bedhet
A small electric motor giving a large output torque and powered by a directcurrent, 12 volt, nickel-cadmium battery is used. This battery can provide eight hours of use. Clinical Applications
This orthosis has been fitted to eleven patients. Ten of them were quadriplegic patients due to medullary cervical-traumatic lesions. One of them had a partial lesion of the radial nerve and complete lesions of the median and ulnar nerves in the left arm. They could flex the elbow against resistance and abduct the shoulder. The extensor carpi radialis longus was insufficient for wrist extension against resistance, but the myoelectric signal from this muscle was adequate for orthosis control. All the patients controlled the orthosis after twenty minutes' training. Delicate manipulations were possible such as serving, unscrewing the cap from a tube of toothpaste, squeezing the tube or reapplying the cap. Five patients use this orthosis at home every day. The first results have been encouraging and fittings to a larger number of patients are in progress. D E V E L O P M E N T OF A M Y O E L E C T R I C A L L Y C O N T R O L L E D U N I T F O R E X T E N S I V E U P P E R LIMB PALSIES
We have developed a unit allowing full upper limb motion simulation (shoulder, elbow and hand). The development of such a unit appeared to us as a noteworthy step in our research. Our final goal is to develop the use of such units powered by external forces and controlled by biological signals (myoelectric, in this case) for quadriplegics who were once limited in number but now increasing due to more accidents, with more cases surviving because of progress in resuscitation and nursing care. It is our belief that such an experimental tool was necessary for simulations as the unit is controlled from face, neck, shoulder and upper trunk muscles in healthy subjects and quadriplegics. The findings gave us an opportunity to define more accurately which unit was best adapted for each patient. This experimental unit also possesses the advantage of training patients and then to afford better selection of those who have a chance to succeed with a given unit. We have attempted to use a minimum of controls as the number of available muscles is limited. Our clinical experiments and limb actuation basic studies have suggested that the upper limb physiology can be restricted to two functions: - - H a n d positioning in space. --Pinching. The position of function requires both shoulder and elbow joints. The latter is not independently controlled but enslaved to the shoulder. For the pinching function, we have selected the three-finger pollici-digital pinch grip. F r o m such findings as well as the possibility of using several myoelectric signals, we were able to design our experimental instrument. 64
The Hand--Vol. 7
No. 1
1975
A Myoelectric-controlled Orthosis--C. Hamonet, D. Boulongne, S. Simon and P. Bedhet
It includes two identical upper limbs fastened on a h u m a n torso metallic base. The first development had it rest simply on a base and its height was adjustable. An improvement made it possible to bring the two centres of motion of each of the two shoulders of the wearer c~osely together. The dimensions given to the various unit segments are those of an adult of average height. This assembly is linked to an electronic cabinet in which signal processing takes place. We did not seek to miniaturise the system because this is a laboratory model. It seems that an analytical control of hand position within a spherical co-ordinates system whose start is at the shoulder, could be understood by the patient. The unit fulfills the following motions at the elbow and shoulder: Up and Down, Left to Right and N e a r and Far. The U p / D o w n , and R i g h t / L e f t hand motions are obtained through rotations about two shoulder axes. The N e a r / F a r motion is attained by the interfacing of a rotation at the shoulder and a rotation at the elbow by a slaving system.
Control System: Through Electronics Therefore, 2¢e need three parameters to position the hand in space and a fourth to actuate the hand. Such parameters can be provided simultaneously or sequentially. Our experimental model enables us to use all four in various ways: the first three with four different myoelectric signals and the last with three only. First possibility
The four myoelectric controls can be used independently or linked by two, three or four. Second possibility
Four myoelectric controls are used but hand positioning cannot be actuated at the same time as closing or opening the hand. A n y positioning actuation (shoulder and elbow) stop any hand actuation, and vice-versa. Third possibility
The four myoelectric controls can only be worked two at a time, and the use of a third, and even a fourth would tend to stop the whole unit. F o u r t h possibility
Three controls only are used. Either singly or linked in pairs, they act on the shoulder and the elbow. When the three controls are used simultaneously, the shoulder and elbow are stopped and the hand is then actuated.
CONCLUSIONS Current tests with this new type of experimental model have shown that the complex units for upper limb actuations as adapted by us are enriching our knowledge by enabling us to obtain very satisfactory simulation of the use of myoelectric orthoses or prostheses. The Hand--Vol. 7
No. 1
1975
65
A Myoelectric-controlled Orthosis--C. Hamonet, D. Boulongne, S. Simon and P. Bedhet
ACKNOWLEDGEMENTS
This r e s e a r c h was s u p p o r t e d by t h e D i r e c t i o n G e n e r a l e de la R e c h e r c h e Scientifique et T e c h n i q u e , t h e Caisses R 6 g i o n a l e s d ' A s s u r a n c e M a l a d i e a n d the M i n i s t 6 r e des A n c i e n s C o m b a t t a n t s . F o r t h e i r t e c h n i c a l c o l l a b o r a t i o n we t h a n k R. M u s s o n - G c n o n , S. P a n n i e r , R. F o u r n i e r , G. C a r t e , M. B e d o i s e a u , Pr. G r o s s i o r d (Service de R 6 6 d u c a t i o n N e u r o l o g i q u e de l ' H 6 p i t a l R. P o i n c a r 6 - - G a r c h e s - - 9 2 - - F r a n c e ) a n d P. L a c e r t . BIBLIOGRAPHY
HAMONET CI., de MONTGOLFIER, A., BEDOISEAU, M., LACERT, Ph., PANNIER, S., RAOULT, J. C., FOURNIER, R., CARRE, G., MEZIER, D., and GROSSIORD, A. (1971) Appareillage de la main par une orth6se ~t commande myo-61ectrique chez le t6trapl6gique. Film 16 ram. Association Frangaise pour l'Appareillage, Paris--Avril 1970. Annales de M6decine Physique, 14:1:161-169. HAMONET, C1. and SIMARD, T. (i. (1971) M6thode d'Etude de la Commande Myo61ectrique par Orth6ses du Membrc Sup6rieur. Union m~dicale du Canada: 100: 2371-2375. HAMONET, CI., de MONTGOLFIER, A., BEDOISEAU, M., PANNIER, S. and GROSSIORD, A. (1972) Orth6ses de pr6hension ~t commande myo-61ectrique. Premi6res r6alisations International Congress of Physical Medicine, Barcelona, July 1972. HAMONET, CI., BEDOISEAU, M., de MONTGOLFIER, A., PANNIER, S., LACERT, Ph., CARRE, G., FOURNIER, R., DOTHE, G., BOULONGNE, D., and GROSSIORD, A. (1973) Orth6ses myo-61ectriques du membre sup6rieur. First International Congress on Prosthetic Techniques and Functional Rehabilitation--Vienna, March 1973. HAMONET, C1. and de MONTGOLFIER, A. (1974) A new myoelectric prehension orthosis. Inter Clinic Information Bulletin, XIII--n°J; 15-17.
66
The Hand--Vol. 7
No. 1
1975
A M Y O E L E C T R I C - C O N T R O L L E D ORTHOSIS Recent Development
C. H A M O N E T , D. BOULONGNE, S. SIMON and P. BEDHET, Paris Progress achieved by medical therapy has shown that today an extremely large number of physically-handicapped patients with four-limb deficiency can escape the deadly complications threatening them and still have high hopes for the future. We have sought to return to these patients many possibilities of function by means of powered artificial limbs that are controlled through myoelectric activity gathered from muscles which have been either fully or partially spared. Our developments are of two kinds: First an orthosis with a certain degree of freedom allowing for pinching by two or three fingers (MYO-ELEC limb); secondly, an experimental limb with 4 degrees of freedom to position the hand in space and to pinch. PRINCIPLES OF THE MYOELECTRIC PREHENSION ORTHOSIS
A single muscle can control the orthosis, simplifying its application and the training of the patients. When the muscle contracts the hand closes, the speed of the movement being proportional to the intensity of the myoelectric signal. This functional characteristic seems essential to us since we wish to approach the physiological conditions of pinching as closely as possible. The pinch may be maintained by sustaining myoelectric activity. The pinching power is also proportional to the muscular contraction. When the muscular contraction stops the hand opens. This "passive" or low-energy expenditure opening is similar to the normal action of the hand when it releases an object after it has been pinched. Active or more explosive "opening" can also be provided and is of particular use, for example, when an object is being thrown away. It is possible to stop the opening of the hand at any point and to maintain the fingers in a selected position if the patient desires to grasp an object previously released. Description of the Prehension Ortho,sis
The orthosis is made in Dural A.U.4.G. (Aluminium plus small amounts of iron, copper, magnesium, silicon and manganese), and in brass. It incorporates a wristband on which the elements that set the fingers in motion and the mechanical system of transmission are fixed. The finger pieces involve one part which maintains the thumb in opposition and another which includes the fixation rings for the second and third fingers. The fingers are articulated at the metacarpophalangeal joints. A second articulation is provided at the proximal interphalangeal joint. The mechnical transmission system and the motor are placed along the external side of the forearm in such a way that they can be hidden by the sleeve. The m,echanical system of transmission includes a cog wheel and a small driving-rod which transfer the motion of the motor to the fingers. The orthosis weighs 180 grammes. The maximum opening of fingers is eight centimetres. The pinch force is 400 grammes. The Hand--Vol. 7
No. 1
1975
63
A Myoelectric-controlled Orthosis--C. Hamonet. D. Boulongne, S. Simon and P. Bedhet
A small electric motor giving a large output torque and powered by a directcurrent, 12 volt, nickel-cadmium battery is used. This battery can provide eight hours of use. Clinical Applications
This orthosis has been fitted to eleven patients. Ten of them were quadriplegic patients due to medullary cervical-traumatic lesions. One of them had a partial lesion of the radial nerve and complete lesions of the median and ulnar nerves in the left arm. They could flex the elbow against resistance and abduct the shoulder. The extensor carpi radialis longus was insufficient for wrist extension against resistance, but the myoelectric signal from this muscle was adequate for orthosis control. All the patients controlled the orthosis after twenty minutes' training. Delicate manipulations were possible such as serving, unscrewing the cap from a tube of toothpaste, squeezing the tube or reapplying the cap. Five patients use this orthosis at home every day. The first results have been encouraging and fittings to a larger number of patients are in progress. D E V E L O P M E N T OF A M Y O E L E C T R I C A L L Y C O N T R O L L E D U N I T F O R E X T E N S I V E U P P E R LIMB PALSIES
We have developed a unit allowing full upper limb motion simulation (shoulder, elbow and hand). The development of such a unit appeared to us as a noteworthy step in our research. Our final goal is to develop the use of such units powered by external forces and controlled by biological signals (myoelectric, in this case) for quadriplegics who were once limited in number but now increasing due to more accidents, with more cases surviving because of progress in resuscitation and nursing care. It is our belief that such an experimental tool was necessary for simulations as the unit is controlled from face, neck, shoulder and upper trunk muscles in healthy subjects and quadriplegics. The findings gave us an opportunity to define more accurately which unit was best adapted for each patient. This experimental unit also possesses the advantage of training patients and then to afford better selection of those who have a chance to succeed with a given unit. We have attempted to use a minimum of controls as the number of available muscles is limited. Our clinical experiments and limb actuation basic studies have suggested that the upper limb physiology can be restricted to two functions: - - H a n d positioning in space. --Pinching. The position of function requires both shoulder and elbow joints. The latter is not independently controlled but enslaved to the shoulder. For the pinching function, we have selected the three-finger pollici-digital pinch grip. F r o m such findings as well as the possibility of using several myoelectric signals, we were able to design our experimental instrument. 64
The Hand--Vol. 7
No. 1
1975
A Myoelectric-controlled Orthosis--C. Hamonet, D. Boulongne, S. Simon and P. Bedhet
It includes two identical upper limbs fastened on a h u m a n torso metallic base. The first development had it rest simply on a base and its height was adjustable. An improvement made it possible to bring the two centres of motion of each of the two shoulders of the wearer c~osely together. The dimensions given to the various unit segments are those of an adult of average height. This assembly is linked to an electronic cabinet in which signal processing takes place. We did not seek to miniaturise the system because this is a laboratory model. It seems that an analytical control of hand position within a spherical co-ordinates system whose start is at the shoulder, could be understood by the patient. The unit fulfills the following motions at the elbow and shoulder: Up and Down, Left to Right and N e a r and Far. The U p / D o w n , and R i g h t / L e f t hand motions are obtained through rotations about two shoulder axes. The N e a r / F a r motion is attained by the interfacing of a rotation at the shoulder and a rotation at the elbow by a slaving system.
Control System: Through Electronics Therefore, 2¢e need three parameters to position the hand in space and a fourth to actuate the hand. Such parameters can be provided simultaneously or sequentially. Our experimental model enables us to use all four in various ways: the first three with four different myoelectric signals and the last with three only. First possibility
The four myoelectric controls can be used independently or linked by two, three or four. Second possibility
Four myoelectric controls are used but hand positioning cannot be actuated at the same time as closing or opening the hand. A n y positioning actuation (shoulder and elbow) stop any hand actuation, and vice-versa. Third possibility
The four myoelectric controls can only be worked two at a time, and the use of a third, and even a fourth would tend to stop the whole unit. F o u r t h possibility
Three controls only are used. Either singly or linked in pairs, they act on the shoulder and the elbow. When the three controls are used simultaneously, the shoulder and elbow are stopped and the hand is then actuated.
CONCLUSIONS Current tests with this new type of experimental model have shown that the complex units for upper limb actuations as adapted by us are enriching our knowledge by enabling us to obtain very satisfactory simulation of the use of myoelectric orthoses or prostheses. The Hand--Vol. 7
No. 1
1975
65
A Myoelectric-controlled Orthosis--C. Hamonet, D. Boulongne, S. Simon and P. Bedhet
ACKNOWLEDGEMENTS
This r e s e a r c h was s u p p o r t e d by t h e D i r e c t i o n G e n e r a l e de la R e c h e r c h e Scientifique et T e c h n i q u e , t h e Caisses R 6 g i o n a l e s d ' A s s u r a n c e M a l a d i e a n d the M i n i s t 6 r e des A n c i e n s C o m b a t t a n t s . F o r t h e i r t e c h n i c a l c o l l a b o r a t i o n we t h a n k R. M u s s o n - G c n o n , S. P a n n i e r , R. F o u r n i e r , G. C a r t e , M. B e d o i s e a u , Pr. G r o s s i o r d (Service de R 6 6 d u c a t i o n N e u r o l o g i q u e de l ' H 6 p i t a l R. P o i n c a r 6 - - G a r c h e s - - 9 2 - - F r a n c e ) a n d P. L a c e r t . BIBLIOGRAPHY
HAMONET CI., de MONTGOLFIER, A., BEDOISEAU, M., LACERT, Ph., PANNIER, S., RAOULT, J. C., FOURNIER, R., CARRE, G., MEZIER, D., and GROSSIORD, A. (1971) Appareillage de la main par une orth6se ~t commande myo-61ectrique chez le t6trapl6gique. Film 16 ram. Association Frangaise pour l'Appareillage, Paris--Avril 1970. Annales de M6decine Physique, 14:1:161-169. HAMONET, C1. and SIMARD, T. (i. (1971) M6thode d'Etude de la Commande Myo61ectrique par Orth6ses du Membrc Sup6rieur. Union m~dicale du Canada: 100: 2371-2375. HAMONET, CI., de MONTGOLFIER, A., BEDOISEAU, M., PANNIER, S. and GROSSIORD, A. (1972) Orth6ses de pr6hension ~t commande myo-61ectrique. Premi6res r6alisations International Congress of Physical Medicine, Barcelona, July 1972. HAMONET, CI., BEDOISEAU, M., de MONTGOLFIER, A., PANNIER, S., LACERT, Ph., CARRE, G., FOURNIER, R., DOTHE, G., BOULONGNE, D., and GROSSIORD, A. (1973) Orth6ses myo-61ectriques du membre sup6rieur. First International Congress on Prosthetic Techniques and Functional Rehabilitation--Vienna, March 1973. HAMONET, C1. and de MONTGOLFIER, A. (1974) A new myoelectric prehension orthosis. Inter Clinic Information Bulletin, XIII--n°J; 15-17.
66
The Hand--Vol. 7
No. 1
1975