functional electrical stimulation 2

8/2/2019 Functional Electrical Stimulation 2

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Artif Life Robotics (2000) 4:212-219 @ ISA RO B 2000

Y o i c h i S h i m a d a 9 S h i g e r u A n d o 9 S a t o a k i C h i d a

Funct ional e lectr ical st imulat ion

Received and accepted: April 5, 2001A b s t r a c t P e r c u t a n e o u s i n t r a m u s c u l a r e l e c t r o d e s a n d a p o r -t a b l e m u l t i c h a n n e l s y s t e m w e r e u s e d t o r e s t o r e t h e f u n c t i o no f p a r a l y z e d u p p e r a n d l o w e r e x t r e m i t ie s i n s p i n a l c o r di n j u ri e s a n d h e m i p l e g i c p a t ie n t s . T h e h y b r i d f u n c t i o n a l e l e c -t r ic a l s t i m u l a t i o n ( F E S ) u s i n g p e r c u t a n e o u s i n t r a m u s c u l a re l e c t r o d e s p r o v i d e s p r a c t i c a l a m b u l a t i o n f o r p a r a p l e g ic s .F E S w a s m o r e e f f e c t i v e t h a n t h e f l e x o r h i n g e s p l i n t i ni n c r e a s i n g t h e g r a s p i n g p o w e r ( G P ) o f t e t r a p l e g i c p a t ie n t s ,a n d a s t r o n g e r a n d s t a b l e G P w h i c h w a s n o t a f f e c t e d b yw r i s t p o s i t i o n m a k e F E S p r a c t i c a l f o r i m p r o v i n g t h e a c ti v i-t i es o f d a i l y l iv i n g . A t i lt s e n s o r , w h i c h w a s p u t o n t h e t h i g h ,c o u l d b e u s e d t o m e a s u r e a g a i t cy c l e . T h i s s t u d y s u g g e s t st h a t p u t t i n g a t i l t s e n s o r o n a h e m i p l e g i c p a t i e n t ' s t h i g hi m p r o v e s t h e F E S p r o c e d u r e a n d m a y h e l p t o re s t o r e g a i t i nt h e s e p a ti e n t s . W e c o n c l u d e t h a t p e r c u t a n e o u s i n t r a m u s c u -l a r F E S i s u s e f u l f o r s p i n a l c o r d i n j u r i e s a n d h e m i p l e g i cp a t i e n t s .K e y w o r d s F E S - P e r c u t a n e o u s i n t r a m u s c u la r e l e c t r o d e

Introduct ion

R e s t o r i n g i n d e p e n d e n c e i n p e r f o r m i n g d a i l y f u n c t i o n s ist h e m a i n g o a l in t re a t i n g p a r a l y t i c p a t ie n t s . R e c e n t a d -v a n c e s i n c o m p u t e r t e c h n o l o g y h a v e m a d e i t p o s si b let o c o n t r o l p a r a l y z e d m u s c l e s b y e l e c t r i c a l s t i m u l a t i o n . W eh a v e u s e d f u n c t i o n a l e l e c t ri c a l st i m u l a t i o n ( F E S ) t o r e s t o r et h e p a r a l y z e d m u s c l e s in t h e u p p e r a n d l o w e r e x t r e m i t i e ss ince 1990 . 14

T h e r e a r e a l o t o f p o t e n t i a l b e n e f i ts t o p a r a p l e g i cp a t i e n t s i f t h e y c a n a c h i e v e F E S s t a n d in g . S t a n d i n g m a yh e l p t o p r e v e n t j o i n t c o n t r a c t u r e b y e l i m i n a t in g t h e c h r o n i c

Y. Shimada ( [ ] ) - S . A nd o. S . ChidaRehabilitation Division, Akita University Hospital, 1-1-1 Hon do,Ak ita 010-8543, JapanTel. +81-18-884-6147;Fax +81-18-884-6373e-mail: [email protected]

s i tt in g p o s t u r e , a n d i t m a y r e d u c e o s t e o p o r o s i s b e c a u s e i ti n c r e a s e s w e i g h t - b e a r in g . T h e u p r i g h t p o s t u r e m a y i m p r o v et h e p o s i t i o n o f th e i n t e r n a l o r g a n s , a n d a i d b o w e l a n db l a d d e r f u n c t i o n . I t m a y a l s o r e d u c e t h e c h a n c e o f p r e s s u r es o r e s , a n d i t c o u l d a i d c i r c u l a t i o n . I n c r e a s e d f u n c t i o n a la b i li ti e s w h i l e s t a n d i n g m a y a l s o e n h a n c e p e r s o n a ls e l f - e s t e e m .

F E S e n a b l e s p a t i e n t s w i t h a s e v e r e s p in a l c o r d i n j u r y t or e c o n s t r u c t g r a s p m o v e m e n t s s u c h a s t h e p a l m a r a n d l a te r a lg r a s p s o f t h e u p p e r e x t r e m i ti e s , a n d t h e r e f o r e i t is u s e f u l f o ri m p r o v i n g t h e a c t i v it ie s o f d a il y l i vi n g ( A D L ) . H o w e v e r ,t h e r e a r e f e w re p o r t s o n h o w g r a s p in g p o w e r ( G P ) c a n b em e a s u r e d b y F E S , a s w el l as o n t h e r e la t i o n b e t w e e n G Pa n d t h e p r a c t i c a l u se s o f F E S .

F E S h a s b e e n u s e d t o i m p r o v e t h e g a i t o f s tr o k e p a t i e n t s .T h e m o s t c o m m o n m e t h o d o f c o n t r o l u s e s f o o t s w it ch e s ,a s o r ig i n al ly p r o p o s e d b y L i b e r s o n e t a l . , 4 b u t t h i s r e q u i r e sw i r e s o r t e l e m e t r y t o c o n n e c t t h e s w i t c h t o t h e s t i m u l a t o r .W i t h F E S , w e h a v e b e e n p r e v e n t i n g a fo o t - d r o p g a it , w h i c hi s c a u s e d b y s t r o k e , b y u s i n g f o o t s w i t c h e s u n d e r t h e h e e l , a si n th e A k i t a h e e l s e n s o r s y s t e m ( A H S S ) i n v e n t e d i n 1 9 9 6 . sA H S S is u s e f u l fo r f o o t - d r o p - g a i t p a t i en t s . S o m e p o t e n t i a li m p r o v e m e n t s i n c l u d e t h e e a s e o f i n s ta l li n g t h e s y s t e m o nt h e p a t i e n t ' s h e e l s , d u r a b il i t y , a n d a p p e a r a n c e . I n 1 9 9 6 , D a ie t a l. 6 r e p o r t e d t h a t w i t h F E S t h e t i l t s e n s o r s n e e d t o b e p u to n t h e c a l f i n o r d e r t o p r e v e n t a f o o t - d r o p g a i t. A m i n i a t u r ef o o t - d r o p s t i m u l a t o r w a s d e s i g n e d w i t h a m a g n e t o r e s i s t i v et i lt s e n s o r b u i l t in ; n o e x t e r n a l s e n s o r c a b l e s w e r e r e q u i r e d .T h e o r y h a s i t t h a t i f t h e t i l t s e n s o r i s p u t o n t h e t h i g h , i t w i l ls t i l l b e p o s s i b l e t o d e t e c t s t e p s i n t h e g a i t . P a t i e n t s c a n a l s op u t t h e s e n s o r s o n m o r e e a s il y .

H e r e w e d e s c i b e t h e c l i n ic a l a p p l ic a t i o n s o f F E S i np a r a p l e g i a , a n d e v a l u a t e t h e r e l a t i o n b e t w e e n G P a n d t h ep r a c t i c a l u s e s o f F E S f o r a t e tr a p l e g i c p a t i e n t . W e a l s oe v a l u a t e t h e d e t e c t i o n o f a n o r m a l a n d a f o o t - d r o p - g a i tc y c l e u s i n g a t il t s e n s o r p l a c e d o n t h e a n t e r i o r p o r t i o n o f t h et h i g h .


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Fig. 3. In sertion o f percutaneous intramuscular electrode

Table 2. MMT before reconstructionR L

ShoulderFlexion G + G +Abduction G + G +ElbowFlexion N NExtension T TForearmPronation F FSupination N- N -WristFlexion Z ZExtension G GFingerFlexion Z ZExtension Z ZMMT, muscle manual testing

Fig. 4. Ent ry points of electrodes at anterior thighs

p r o b l e m a s s o c i a t e d w i t h e l e c t r o d e m o v e m e n t . S t i m u l a t i o nof the musc les was con duc t ed f or 5 min , th r ee t imes da i ly a tthe beg inning . Af te r 5 weeks , the s t imula t ion was appl iedfor 30min, f ive t imes dai ly. Af ter exercis ing l ike this formor e than 3 months , s tanding and wa lk ing t r a in ing s ta r ted .

FES f or t e t r ap leg iaA 20- year - o ld f emale pa t ien t wi th C6 comple te t e t r ap leg ia( F r enke l A, Zancol l i 2B- 2) was eva lua ted . I n or d e r to a s sess

her GP , 31 nor mal f emale s tudents , aged 19- 24 yea r s ( X =21) , wer e used as cont r o l s .The p a t ien t was in jur ed in a t r a ff ic acc ident in June 1995.S h e w a s a d m i t t e d t o o u r h o s p i t al f o r t h e p u r p o s e o f r e c o n -s t r u c t i n g u p p e r - e x t r e m i t y f u n c t i o n b y F E S i n N o v e m b e r1996. Bef o r e r econs t r uc t ion , M M T o f he r upper ex t r emi t ie ss h o w e d o n l y T i n e l b o w e x t en s i o n , a n d F i n f o r e a r m p r o n a -t ion . W r is t ex tens ion was r e la t ive ly be t te r a t G. W r is t f l ex-ion and f inger f l ex ion and ex ten s ion wer e b o th Z ( Table 2) .Ther e was l i t t l e jo in t cont r ac tur e and spas t ic i ty .

B e c a u s e h e r p a l m a r g r a s p w a s o f n o p r a ct i c a l u s ebecaus e o f the e f f ec t o f dynam ic tenodes i s , dev ices wer eneces sa r y f or ea t ing , t ee th- br ush ing , g r oomin g , and wr i t ing .

P e r c u t a n e o u s i n t r a m u s c u l a r e l e c t r o d e s w e r e i m p l a n t e don D ece mb er 6 , 1997 , 18 mon ths a f te r the injur y . I n or de r tor econs t r uc t f inger ex tens ion mot ion , the implan ta t ion r e -g i o n s w e r e t h e d e e p b r a n c h o f t h e r a d ia l n e r v e , t h e e x t e n s o rd ig i to r um, th e ex te nsor ind ic i s, the ex tensor po l l i c is longus ,the abduc tor po l l i c i s b r ev is , and the opponens po l l i c i s . I nor der to r econs t r uc t f inger f l ex ion mot ion , the implan ta t ionr eg ions wer e the f lexor d ig i to r um super f ic ia l i s , the f lexord ig i to r um pr of undus , the f lexor po l l i c i s longus , the adduc-tor poll ic is , and the f ir s t dorsal interosseous .

Ther apeut ic e lec t r ica l s t imula t ion was s ta r ted 13 daysa f te r the implan ta t ion oper a t ion . Pa lmar and la te r a l g r aspsw e r e r e c o n s t r u c t e d i n t h e r i g h t u p p e r e x t r e m i t y b y m e a n s o fa p o r t a b l e m u l t i c h a n n e l F E S s y s t e m ( F E S M A T E C E 1 2 3 0 ,N E C M e d i c a l S y s t em s , T o k y o , J a p a n ) 8 w e e k s a f t e r t h eoper a t ion ( F ig . 5 ) . Fo l lowing FES r econs t r uc t ion , the pa -t i e n t w a s a b l e t o p e r f o r m m a n y a c t i o n s u s i n g t h e p a l m a rand l~ te r a l g r asps . FES enabled he r to dr ink canned ju ice ,ea t wi th a spoon , wr i te wi th a pen , b r ush he r ha i r , and tu r na tap on a nd of f wi thout us ing devices .

T h e G P o f p a l m a r g r a s p s w e r e m e a s u r e d i n th e r i g h tu p p e r e x t re m i t ie s o f b o t h t h e c o n t r o l g r o u p a n d t h e p a t i e n tu s in g A J A M A R h y d r au l i c h a n d d y n a m o m e t e r ( P C -5030J1 , P r es ton , USA) ; l a te r a l g r asp s t r ength was measur edu s i n g a h a n d f i n g e r d y n a m o m e t e r s e t ( S P R - 6 5 0 0 , S A K A IMedica l Co . , J apan) . I n the pa t ien t , pa lmar gr asps wer eper f or med by the dynamic tenodes i s e f f ec t , the f lexor h inge


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Fig. 5. A Prehension o f drink canwith a palmar grasp, and B pre-hension of a spoon with a lateralgraspA B

215

Hg. 6. Measurement position ofA palmar grasp, and B lateralgrasp

A B

sp lin t, and wi th FES . La te r a l g r asp was pe r f o r med wi th FESonly .

B o t h t h e c o n t r o l g r o u p a n d o u r p a t i e n t w e r e m a d e t o s i tr igh t back in a whee lcha i r f o r the measur ements . I n addi -t ion , the r igh t upper ex t r emi ty was hung down bes ide thehand r im na tur a l ly , wi th the e lbow jo in t ex tended , tomeasu r e pa lmar gr asps ( Fig . 6A) . On e- th i r d of the d i s ta lf or ea r m was p laced l igh t ly on the desk to measur e the la t -e r a l g r asp ( F ig . 6B) . The gr ip size of the han d d yna mo met e rwas 2 inches . For the cont r o l g r oup , th r ee GP measur e -m e n t s w e r e t a k e n f o r e a c h p e r s o n , a n d t h e m e a n o f t h ela r ges t va lue in each se t o f th r ee was ca lcu la ted . I n thep a t i en t , G P v a l u e s w e r e m e a s u r e d i n t h e s a m e m a n n e r t h r e et imes dur ing 1 week , and a mean va lue was ca lcu la ted .

F E S f o r h e m i p l eg i aThe cont r o l sub jec t s wer e ten hea l thy males , whose aver ageage was 26 ( 23- 29) yea r s . One s t r oke p a t ien t ( 56 yea r s o ld)was a l so measur ed .

The t i l t s ensor used in th i s s tudy ( Mode l UA- 1) ( F ig . 7 )w a s f r o m M i d o r i A m e r i c a n C o r p o r a t i o n . I t w as p u t o n t h eante r ior m iddle p or t ion o f the th igh ( F ig . 8 ). W e m easu r edthe t i l t o f the th igh dur ing ga i t us ing the t il t s ensor anda n a u t o m a t i c c o o r d i n a t i o n s y s t e m s i m u l t a n e o u s l y . F o r c e -sens ing r es i s to r s wer e p laced under the hee l and toe topr ovi de r e f e r en ce po in t s f o r the s tep cyc le . Us ing a pe r cen t -age of the ga i t cyc le, we nor ma l ized the ang ula r chan ge ofthe th igh dur ing one comple te mot ion . W e a l so pa id a t ten-t ion to the p o in t o f in f lec tion in the angula r change of theth igh dur ing a ga i t cyc le . The po in t i s c lose to toe - of f , and i tac t iva tes the swi tch to come on and s t imula te in the swingphase ( F ig . 9 ). Al l po in t s o f in f lec t ion in the ang ula r cha ngeo f t h e t h i g h w e r e c o m p a r e d w h i l e t h e s u b je c ts w a l k e dnor mal ly , wi th a ga i t speed o f 0 .5m/s ; and a s tep length o f50cm. The subjec t s wer e measur ed in t en t r i a l s .


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21 6ResultsFES f or pa r ap leg iaAl thou gh a ll pa t ien t s could s tand and wa lk wi th a hybr idFES using an AFO (Fig. 10) , the cl inical results for themax imu m dur a t ion of cont inuous s tanding an d the maxi -mu m dis tance of cont inuous w a lk ing wer e shown wi ththe hybr id or thos i s be ing used in da i ly l i f e . The maximumdur a t ion of standing wi th e lec t r ica l s t imula t ion on ly was60rain in case 5, with an AFO it was 25rain in cases 1 and 3,wi th a W alkabout i t was 150min in case 6 , wi th a RGOit was 60min in case 6, and with an AKJ i t was 30min incase 3 . The max imu m dis tance w a lked wi th e lec tr ica l s t imu-

Fig . 7 . T i l t s ens o r (UA-1)

l a t ion on ly was 120m in case 5 , wi th an AFO i t was 30min cases 1 and 3, with a Walkabout i t was 300m in case6 , wi th a RGO i t was 70m in case 6 , and wi th an AKJ i twas 40m in case 3 . The maximal ga i t speed was 0 .5m/swi th FES only , 0 . 1m/s with an AFO , 0 .33m/s wi th aW alka- b out , 0 . 22m/s wi th a RG O, and 0 .1 m/s wi th an AK J( Table 3) .

Only one e lec t r ode br oke ( 0 .6%) . This was in case 1 a t as i t e deep in the i l iopsoas musc le . The los s o f an adequa tecont r ac t ion f or ce due to move men t of the e lec t r odes r e -qu i r ed ten e lec t r odes to be r e implan ted ( 5 .6%) . On tenoccasions (5.6%) there was a superf ic ial infect ion around

s t a n d i n g p h a s e s w i n g p h a s e

5 04 0302 010

0-1 0

~\ t i lt sensor d,\ - - - automatic coordination system/It/ ///

% g a i t c y c l ep o i n t o f i n f le c t i o nFig. 9. Poin t of inf lect ion in the gai t cycle

F ig . 8 . T i l t s e ns or on the th igh


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Fig. 11. Grasping power of palmar and lateral grasps in the controlgroup, in the patient with a dynamic tenodesis effect, with a flexorhinge splint, and with FES. Light shading, palm ar grasp; dark shading,lateral grasp

Fig. 10. Standing with complete paraplegia by functional electricalstimulation (FES)

Table 4. Comparison of point of inflection in percent of gait cycle(mea n _+ SD)Healthy males Stroke patient

Tilt sen sor UA -1 60.1 _+ 6.5% 94.7 _+ 0.4%Au tom atic coo rdin ation system 65.0 _+ 5.8% 79.8 _+ 1.8%

Tab le 3. ResultsCase Hyb rid Continuous Continuous Gait speedortho sis standin g (rain) walking (m) (m/s)1 AF O 25 30 0.12 AF O 20 25 0.13 AF O 25 30 0.1AK J 30 40 0. lWalk abou t 80 100 0.254 Walk abou t 60 60 0.25 Pure 60 120 0.56 RG O 60 70 0.22Walk abou t 150 300 0.337 Walk abou t 60 60 0.2

t h e s i t e o f e l e c t r o d e i n s e r t i o n . T h e s e i n f e c t i o n s w e r e t r e a t e db y t o p i c a l s t e r i l i z a t i o n o f t h e s k i n a n d o r a l a n t i b i o t i c s. N oe l e c t r o d e s h a d t o b e r e m o v e d , a n d n o v i s c e r a l c o m p l i c a -t i ons occur r ed i n t h i s s e r i e s .

F E S f o r t e t ra p l e g i aT h e G P o f p a l m a r a n d l a t e r a l g r a s p s w e re 3 3 . 2 + / - 3 . 1 k ga n d 8 . 3 + / - 1 . 0 k g , r e s p e c ti v e ly , i n th e c o n t r o l g r o u p . I n t h ep a t i en t , g r a s p in g p o w e r w a s n o t m e a s u r a b l e b e c a u s e o f t h ed y n a m i c t e n o d e s i s e f f e c t . P a l m a r g r a s p s t r e n g t h w i t ht h e fl e x o r h i n g e s p l i n t w a s 2 . 2 + / - 0 . 3 k g , a n d w i t h F E S , itw a s 5 . 3 + / - 1 . 5 k g , i .e ., a p p r o x i m a t e l y 1 6 % o f t h a t o f t h ec o n t r o l g r o u p , a n d 2 . 4 t i m e s g r e a t e r t h a n t h a t w i t h t h ef l e x o r h i n g e s p l i n t . L a t e r a l g r a s p s t r e n g t h w i t h F E S w a s

1 . 1 + / - 0 . 2 k g , i .e ., a p p r o x i m a t e l y 1 3 % o f t ha t o f t h e c o n t r o lg roup (F i g . 11) .

F E S f o r h e m i p l a g i aT h e c o r r e l a t i o n s b e t w e e n t h e s i g n a l o f t h e t i l t s e n s o r o n t h et h i g h a n d t h e f o o t - c o n t a c t e v e n t s w e r e r e c o r d e d s i m u l t a -n e o u s l y . T h e c h a n g e o f a n g l e u s i n g a t i l t s e n s o r w a s s i m i l a rt o t h a t u s i n g a n a u t o m a t i c c o o r d i n a t i o n s y s t e m . T h e p o i n to f i n f l ec t i on i n hea l t hy su b j ec t s was 60 .1 --+ 6 .5% of t he ga i tcyc l e , and t h i s po i n t i n a pa t i en t was 94 .7 + 0 .4% of t he ga i tc y c l e i n a n g u l a r m o t i o n o f t h e t h i g h u s i n g t h e t i lt s e n s o r.T h e p o i n t i n h e a l t h y s u b j e c t s u s i n g a n a u t o m a t i c c o o r d i n a -t i on sys t em was 65 .0 -+ 5 .8% of t he g a i t cyc le , and t he po i n ti n a pa t i en t was 79 .8 1 .8% of t he g a i t cyc l e (T ab l e 4 ) . I nn o r m a l g a i t , t h e s l o p e o f t h e r e l a t i o n b e t w e e n t h e t i m i n g o ft oe -o f f i n a ga i t cyc l e and t he po i n t o f i n f l ec t i on i n a ti l ts enso r was 0 .57 (P = 0 .007) . T h ere w as a cor r e l a t i on wi t ht he t i mi ng o f t oe -of f i n a ga i t cyc l e .

DiscussionF E S f o r p a r a p l e g i aT h e r e a r e t h r e e s t i m u l a ti o n m e t h o d s : s u r f a c e e l e c t ro d e s ,p e r c u t a n e o u s e l e c t r o d e s , a n d i m p l a n t e d e l e c t r o d e s . S u r -f a c e e l e c t ro d e s r e q u i r e d a i l y p l a c e m e n t a n d r e m o v a l . I na d d i t i o n , s o m e p a t i e n t s f e e l d i s c o m f o r t w h e n e x c e s s i v e


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218stimulation is given by surface electrodes. It is difficultto stimulate the deep muscles, such as the iliopsoas muscle,by surface electrodes. Implanted electrodes need anotheroperation when the electrodes break or move. In thepast, percutaneous electrodes have failed at a high rate.Marsolais and Kob etic 12 repor ted that 35% failed within 4months, and only 30% continued to function 1 year later,with 20% surviving for 2 years, giving an average failurerate of 2.5 electrodes per month that required replacementin a 48-electrode system. In our series, the rate of breakageand movement of electrodes was only 6.5% for an average2.2 years. H and a et al., 8 using the s ame electrodes, repo rtedthat the rate of breakage was 1.3% in 457 electrodes. Thehelically coiled structure of the electrode has demonstratedresistance to breakage even when the electrode was im-plant ed into bulky leg muscles. 7-9 These results suggestedthat the ultrafine intramuscular electrode was practical andavailable for long-term use in paraplegic patients. In restor-ing locomoti on in paraplegics, it is necessary to cont rol thehip, knee, and ankle joints, and to maintain muscle activityto sustain an upright posture during standing and walking.Muscle fatigue is a major problem for restoration by FES.Ichie 3 described several attempts to resolve this problem:(1) by controlling all the muscles which are related tolocomotion and antigravity posture, TM (2) by introducing awithdrawal reflex for making locomotive motion, (3) bydecreasing the loads on the antigravity muscles with anorthosis, and (4) by introducing a closed-loop control sys-tem with sensors. 14 We believe that reducing t he amount ofstimulation of the muscles can be achieved using a hybridorthosis and closed-loop control. The closed-loop controlsystem requires joint position sensors that pr ovide feedbac kinformation to the host computer to prevent falling, regu-late the amount of stimulation, and determine the timing ofstimulations. We have recently developed a new stimulatorfor a closed-loop control system with our percutaneouselectrodes. 3

We have used several types of hybrid orthosis. Thehybrid FES with an AFO was superior to the others incosmesis, donning-doffin g, standing up, and using a wheel-chair. The Walkabout and RGO were superior in stability,reducing muscle fatigue, energy consumption, and mainte-nance of standing. The AKJ was intermediate in thesehybrid FES systems.

We conclude that hybrid FES using percutaneousintramuscular electrodes provides practical ambulationfor paraplegics.FES for tetraplegiaHat ta et al. is explains that because finger muscle forces andmoto r hand skills show different aspects of upper extremityfunction, we should measure both force and skill whenevaluating upper extremity functions. Accordingly, weshould also measure the finger muscle strength of graspingand pinching when evaluating upper extremity functionreconst ructed by means of FES. Peckh am et al. 16 has sug-gested that generally I kg is the minimal acceptable strength

Fig. 12. High practical prehension: brushing the hair. Stable prehen-sion was maintained even during wrist joint flexion

for the pinch grasp. FES reco nstruct ion made it possible forour patient to perform many actions using palmar and lat-eral grasps in daily life. Brushing her hair and turni ng a tapon and off were the most practical skills that FES allowedher to do. Both o f these tasks require a strong and stable GPnot aff ected by wrist position. Alt houg h the grasping powerin our patient is less than that of the normal group, it isbetter than the standard established by Peckham. As Fig.12 shows, stable prehension was maintained even duringwrist joint flexion. It is likely that such advantages makeFES practical for ADL, and better than the flexor hingesplint.

FES for hemiplegiaThe point of inflection measured by the tilt sensor wasdetected earlier in a gait cycle than the point of inflectionmeasured by an automatic coordination system. However,it correlated with the timing of toe- off in the gait cycle, andwas assumed to be available to signal the timing of thestimulation of the peroneal nerve which was synchronizedwith the swing phase of the gait. By timing the gait cycle inthe stroke patient's gait, the point of inflection measured bythe tilt sensor was detected later than the point of inflectionmeasured by the automatic coordination system. The stan-dard deviati on in the point of inflection measured by the tiltsensor was as small as +0.4, and there was reproducibilityof this point. We think that we can stimulate the peronealnerve synchronized with the swing phase of the gait ofstroke patients by using a setting which is specific to eachstroke patient.


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