biomechanics central nervous system

7/27/2019 Biomechanics Central Nervous System

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LETTERS TO THE EDITOR

J o u r n a l o f M a n i p u l a t i v e a n d Ph y s i o l o g i c a l T h e r a p e u t i c sV o l u m e 2 3 N u m b e r 3 M a r c l d A p d l 2 0 0 0

7 6 / 8 1 1 0 5 1 1 0 - Letters to t h e E d i t o r2 1 1

A R E V IE W O F B I O M E C H A N I C S F T H E C E N T R A L N E R V O U IS Y S T E M .P A R T : S P I N A L C A N A LD E F O R M A T IO N S A U S E DB Y C H A N G E S N P O S T U R ET o t h e E d i t o r :

Ti le a r t i c le by . Ha r r i son e t a l ~ i s inc om -p le te and in need o f rep ly . I t s t a tes tha t f l ex -i o n c a u s e s a n i n c r e a s e i n c a n a l d i a m e t e r a n dv o l u m e a s t h e v e r t e b r a l l a m i n a a r e s e p a r a t e da n d e x t e n s i o n c a u s e s a s m a l l d e c r e a s e i n c a n ad i a m e t e r a n d v o l u m e a s t h e v e r t e b r a l l a m i n aa p p r o x i m a t e d . T h e s e c h a n g e s a r e c i te d b y H a t ~ u , ,e t al a s a r e d u c t i o n o f l e s s t h a n 1 .5 m m i n e x t e n s io n a n d as m a l l i n c r e a s e i n fl e x i o n o f a p p r o x i m a t e l y 1 m m . T h e s ec h a n g e s a r e a c t u a l l y m u c h g r e a t e r t h a n t h o s e q u o t e d b y H a r -r i son e t a l .

Har r i son e t a l I s t a te they d id a l i t e ra tu re se a rch o f hzdexMedicus t o f i n d r e f e r e n c e s f o r t h e i r s t a t e m e n t s o f c a n a l d i -a m e t e r c h a n g e s d u r i n g f l e x i o n a n d e x t e n s i o n . M a n y r e f e r -e n c e s o n t h i s s u b j e c t t h a t d o n o t a g r e e w i t h t h e i r s t a t e m e n t sb y s u c h a u t h o r s a s S c h o n s t r o m , B o l a n d e r , F i n n e s o n , C l a r k ,Y o o , F a r m e r , Z a m a n i , W e t z e l , O n e l , E p s t e i n , L i y a n g , P e n -n i n g , W i l m i n k , S c h m i d , R e v e l , a n d G o u p i l l e a r e n o t c i t e d . Iwi l l c i t e these au thors in th i s l e t t e r .

H a r r i s o n e t a l ~ s t a te t h a t l i g a m e n t u m f l a v u m h y p e r t r o p h ya n d b u c k l i n g , a l o n g w i t h p o s t e r i o r d i s k b u l g i n g i n e x te n s i o n ,a r e n o t e n o u g h t o c a u s e c o m p r e s s i o n o f th e s p i n al c o r d o rn e r v e r o o t s i n h e a l t h y s p i n e s . T h i s i s t r u e . H o w e v e r , t h es p i n e s s e e n f o r c a r e a r e r a r e l y n o r m a l s p i n e s , a n d f a c t o r s l i k ed i s k h e r n i a t i o n , l i g a m e n t u m f l a v u m h y p e r t r o p h y , e n d p l a t eh y p e r t r o p h y , fa c e t i m b r i c a t i o n s u b l u x a t i o n , d e g e n e r a t i v ed i s k d i s e a s e , a n d s p i n a l s t e n o s i s c a n b e a c c e n t u a t e d i n e x te n -s i o n . H a r r i s o n e t a l I s t a t ed t h a t t h e c h a n g e f r o m n e u t r al t oe x t e n s i o n c a n o n l y n a r r o w t h e s p i n a l c a n a l s a g i t t a l d i a m e t e rb y 1 .1 t o 1 .5 m m b u t d o s t a t e t h a t t h e s m a l l d i f f e r e n c e o f 1 .5m m o f s te n o t i c r e d u c t i o n i n e x t e n s i o n w o u l d c o m p r e s s t h es p i n a l c o r d a n d n e r v e r o o t s i n t h e p r e s e n c e o f c a n a l s t e n o s i s .

B r e i g i s c i t e d a s th e a u t h o r v a l i d a t i n g e x t e n s i o n a s a m e t h o do f s h o r t e n i n g s p i n a l c o r d l e n g t h , w i t h t h e r e s u l ta n t r e l i e f o fn e u r a l l o n g i t u d i n a l s t r e s s . T h i s i s v a l i d r e a s o n i n g , b u t s t e n o t i cf a c t o r s m u s t a l t e r t h e a p p l i c a t i o n o f e x t e n s i o n m o t i o n . A l s o , Ic o n c u r t h a t m a r k e d f l e x i o n i s n o t g o o d t o u s e i n s t e n o t i cc a n a l s w i t h p o s t e r i o r e n d p l a te h y p e r t r o p h y b e c a u s e t h e a n t e -r i o r c o r d w i ll b e c o m p r e s s e d a n d i n d e n t e d b y s u c h p a t h o l o g y .H o w e v e r , m o s t s t e n o t i c p a t i e n t s w i l l s e e k t h e d e g r e e o f fl e x -i o n t h a t a f f o r d s t h e g r e a t e s t s a g i t ta l d i a m e t e r o f t h e s p i n a l

d o i : I 0 , 1 0 6 7 / m m t . 2 0 0 0 . 1 0 5 1 I 0

a l a n d t h u s t h e g r e a t e s t r e l i e f o f n e u r a l c o m -r e s s i o n . T h e d o r s a l a n d v e n t r a l s u b a r a c h n o i ds p a c e s v a r y i n d i a m e t e r d e p e n d i n g o n t h e d e -g r e e o f f l e x i o n a n d e x t e n s io n . P a t i e n t s s e e kthe pos tu re tha t r e l i eves the i r pa in . The duramate r a l so shows i t s g rea tes t t i s sue res i s -t ance in long i tud ina l o r ien ta t ion . 2 In te rve r te -

b r a l f o r a m i n a l d i m e n s i o n s a r e a d m i t t e d b y~ar r i son e t a l I to dec re ase dur in g ex tens ion1 inc rease dur ing f l ex ion . Th is i s t rue . Ex te n-

~ u . u c c r e a s es f o r a m i n al s i z e f r o m 2 0 % t o 3 3 % .I wi ll p resen t l i t e ra tu re c i t a t ion s on the e f fec t s o f fl ex iona n d e x t e n s i o n t h a t I f e e l w e r e v e r y n o t i c e a b l y m i s s i n g f r o mthe a r t i c le by Har r i son e t a l .F l e x i o n a n d E x t e n s i o n E f f e c t s n D i s t r a c t i o n A d j u s t i n g

F l e x i o n - d i s t r a c t i o n e f f e c t s a r e a s f o l l o w s ( F i g 1 ):1 . Th e po s te r io r d i s k sp ace inc reases in he igh t . 3"62 . F l e x i o n d e c r e a s e s d i s k p r o t r u s i o n a n d r e d u c e s s t e n o -

si s . 3-5"7-9 N o t e t h a t d i s k s p r o t r u d e a n d d e g e n e r a t e i n t o t h ec o n c a v i t y o f a c u r v e i n t o t h e s i d e o f e x t e n s i o n , io

3 . F l e x i o n s t r e t ch e s ( t a u t en s ) t h e l i g a m e n t u m f l a v u m t oredu ce s tenos i s . 3,5

4 . F l e x i o n o p e n s t h e v e r t e b ra l c a n a l b y 2 m m ( 1 6 % ) o r 3 .5 t o6 m m. 8"95 . F lex ion inc reases meta bo l i t e t r anspo r t in to the d i sk . I i6 . F l e x i o n o p e n s t h e a p o p h y s e a l j o i n t s a n d r e d u c e s p o s t e r i o r

disk stress , i t .t27 . I n t r a d i s c a l p r e s s u r e d r o p s u n d e r d i s t r a c t io n 4 t o b e l o w - 1 0 0

m m H g ) 3 O n e x t e n s i o n , t h e n u c l e u s o r a n u l u s i s s e e n t opro t ru de pos te r io r ly in to the ve r tebra l cana l . 3,7 ,14,15 Th en u c l e u s p u l p o s u s d o e s n o t m o v e o n f le xi on .~ 6

8 . I n t e r v e r t e b r a l f o r a m i n a l o p e n i n g s e n l a r g e , g i v i n g p a t e n c yt o t h e n e r v e o r d o r s a l r o o t g a n g l io n .1 2E x t e n s i o n - d i s t r a c t i o n e f f e c t s a r e a s f o l l o w s ( F i g 2 ) :

1 . T h e p o s t e r i o r d i s k s p a c e d e c r e a s e s i n h e i g h t . 32 . E x t e n s i o n c a u s e s d i s k s t o p r o t r u d e , p r o d u c i n g s t e n o -

s i s . 3 . 7 . 9 , 1 o3 . E x t e n s i o n c a u s e s t h e l i g a m e n t u m f l a v u m t o b u c k l e i n t o

t h e v e r t e b ra l c a n a l , c a u s i n g s t e n o s i s o r c a u d a e q u i n a c o m -p r e s s i o n . 3

4 . E x t e n s i o n c a u s e s t h e v e r t e b r a l c a n a l t o c l o s e 2 m m ( 1 6 % )o r 3 .5 t o 6 m m f r o m f l e x io n , c a u s i n g s t e n o s is , s.9

5 . E x t e n s i o n c l o s e s t h e a p o p h y s e a l j o i n t s a n d i n c r e a s e s p o s -t e r i o r d i s k s t r e s s . 3 ' 1 2

6 . T h e i n t ra d i s c a l p r e s s u r e i s h i g h e r o n e x t e n s io n . N u c l e u sp u l p o s u s a n d a n u l u s f i b r o su s m o v e p o s t e r i o r l y o n e x t e n -sion.3,5,7.12,14,17


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21 2 J o u n t a l o f M a n i p u l a t i v e a n d P h y s i o l o g i c a l T h e n ~ p e u t i c sV o l u m e 2 3 N u m b e r 3 M a r c h / A p r i l 2 0 0 0Let ters to the Editor

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.~ o ..... i - 6 .~", N..\~ ~ t~ 5i : " "

F i g I. F l e x i o n - d i s t r a c t i o n e f f e c t s .7 . E x ten s io n cau ses t h e i n t e rv e r t eb ra l fo ram in a l o p en in g s t o

close , ca using s tenosis to the nerve. 12.17R e s e a r c h a r t i c l e s v i v i d l y i l l u s t r a t e t h e c r o s s - s e c t i o n a l

s p i n a l c a n a l a n d i n t e r v e r t e b r a l f o r a m i n a l m e a s u r e m e n tch a n g e s i n b o d y p o s i t i o n s o f ex t e n s io n an d f l ex io n . 18.19T w e l v e a s y m p t o m a t i c v o l u n t e e r s h ad m a g n e t i c r e s o n a n c ei m a g i n g e x a m i n a t i o n s o f t h e ir l u m b a r s p i n e s p e r f o r m e d i nn e u t r a l , f l e x i o n , a n d e x t e n s i o n u p r i g h t s t u d i e s a n d s u p i n ee x t e n d e d p o s i t i o n s . T h e c h a n g e s i n t h e s p i n a l a n d n e u r a lcan a l s w ere a s fo l l o w s : 181 . T h e sp in a l can a l c ro s s - se c t i o n a l d i am e te r w as 2 6 8 m m 2 in

u p r ig h t f l ex io n an d r ed u ced to 2 2 4 m m 2 in u p r ig h t ex t en -s i o n , w h i c h w a s a s i g n i fi c a n t c h a n g e . T h i s w a s a 1 6 . 4 %d ecrease i n a r ea .

2 . T h e n eu ra l can a l c ro s s - sec t i o n a l a r ea s ig n i f i can t ly d e -c reased b y 2 3 . 2 % f ro m u p r ig h t n eu t r a l t o u p r ig h t ex t en -s io n an d in c reased b y 1 9 . 2 % f ro m u p r ig h t n eu t r a l t o f lex -i o n p o s it i o n s. N o n e o f t h e s e a s y m p t o m a t i c v o l u n t e e rs h a dn e rv e ro o t co m p ress io n i n an y p o s i t i o n . S ev en o f t h e 1 2v o l u n t e e r s d e s c r i b e d l o w - t o - m o d e r a t e d i s c o m f o r t i n t h eu p r ig h t p o s i t i o n s , e sp ec i a l l y t h e u p r ig h t ex t en d ed p o s i t i o n .

3 . T h e l i g am en tu m f l av u m th i ck n ess i n u p r ig h t ex t en s io nw as 4 . 3 m m , an d th a t i n u p r ig h t f lex io n w as 1 .8 m m , w h ichw a s a n i n c r e a s e o f o v e r 2. 5 m m . T h e l i g a m e n t u m f l a v u mb u c k l e s d u r i n g e x t e n s i o n b e c a u s e o f d e c r e a s e d i n t e r l a m i -nar space . 18

4 . S i g n i f i c a n t c r o s s - s e c t i o n a l d e c r e a s e o f t h e s p in a l c a n a lo ccu r r ed i n ex t en s io n .

5 . T h e i n t e rv e r t eb ra l d i sk b u lg in g n a r ro w s th e sp in a l can a ld u r in g ex t en s io n . T h e d a t a su g g es t s t h a t ev en m in o r d i skb u lg in g ex t en s io n co u ld cau se s ig n i f i can t sp in a l can a l n a r -r o w i n g b e c a u s e o f t h e l a r g e p r o p o r t i o n o f t h e s p i n a l c a na lb o r d e r f o r m e d b y t h e d i s k .

6 . T h e f a c t o r s c a u s i n g s i g n i f i c a n t d e c r e a s e o f t h e n e u r a lf o r a m e n i n e x t e n s i o n a n d i n c r e a s e i n f l e x i o n a r e t h a t i ne x t e n s i o n t h e i n t e r v e r t e b r a l d i s k b u l g e s p o s t e r i o r l y , t h eh e i g ht o f t h e f o r a m e n d e c r e a s e s b e c a u s e o f c o m p r e s s i o no f t h e p o s t e r i o r p a r t o f th e d i s k a n d d e c r e a s i n g d i s t a n c eb e t w e e n t h e p e d i c l e s , a n d t h e l i g a m e n t u m f l a v u m m a yn ar ro w th e o p en in g o f t h e n eu ra l can a l .

7 . T h e c o m b i n a t i o n o f l i g a m e n t u m f l a va , f a c e t j o i n ts , a n d t h ein t e rv e r t eb ra l d i sk can cau se sp in a l can a l s t en o s i s , an d a l lo f t h ese f a c to r s a r e acce n tu a t ed i n ex t en s io n p o s tu re . 18

F ig 2 . E x t e n s i o n - d i s t r a c t i o n e f f e c t s .R ev e l e t a1 19 co n f i rm e d th ese f i n d in g s an d n o t ed d ec rease dfo ram in a l s i ze in ex t en s io n cau sed b y p o s t e r io r b u lg in g o fth e d isk s , an t e r io r m o v em en t s o f t h e l i g am en tu m f l av a ,an d d ec rease o f th e n eu ral fo ram in a l h e igh t s . C o m p ress io np ro d u ced b y o rd in a ry w e ig h t b ea r in g i n an u p r ig h t n eu t ra lp o s i t i o n d im in i sh es t h e d i am e te r an d c ro s s - sec t i o n a l a r eao f t h e sp in a l an d n eu ra l can a l s . 2 F o ram in a l s t en o s i s i sfound to be mo st p rono unc ed in ex tensio n . 2 ]-23Z a m a n i e t a124 p e r f o r m e d m a g n e t i c r e s o n a n c e i m a g i n g o f

th e l u m b a r sp in e i n 3 0 su b j ec t s w h o w ere im a g ed in a s it t i n gp o s i t i o n w h i l e p e r fo rm in g f l ex io n an d ex t en s io n . T h e a l t e r -a t i o n s i n t h e p o s t e r i o r d i s k m a r g i n , t h e s i z e o f t h e n e u r a lf o r a m i n a , a n d t h e s i z e o f t h e c e n t r a l c a n a l w e r e m e a s u r e d .S u p i n e i m a g i n g w a s a l s o d o n e i n 1 5 o f t h e s u b j e c t s . W i t he x t e n s i o n , t h e r e w a s a n i n c r e a s e d d i s k b u l g e i n 2 7 % o f t h ed i sk s (4 0 % o f t h o se w i th d es i cca t i o n ) an d d ec rea sed cen t r a lcan a l s i ze (5 0 % ) an d fo ram in a l s i ze (2 7 % ) .

H ar r i so n e t a l ] m i sc i t ed r e f e r en ce 6 7 a s b e in g f ro m D v o -rak i n t h e j o u rn a l S p i n e as s t a ti n g , "V o lu m e d ec reases d u r in gex ten s io n w h i l e i n c reas in g d u r in g f l ex io n , r e su l t s w h ich a r en o t su rp r i s in g , d o n o t ex p l a in t h e c l i n i ca l o b se rv a t io n o f h av -in g m o re sy m p to m s an d s ig n s d u r in g f l ex io n (L h erm i t t e s ig n )as t h e au th o r s co r r ec t l y p o in t o u t . " T h a t r e f e r en ce f r o m S p i n ei s an a r t i c l e ab o u t n eck m u sc l e p a ram ete r s an d i s n o t au -th o red b y D v o rak . I can c i t e D v o rak , 25 h o w ev er , f ro m an o th e ra r t i c l e t h a t is o f i n t e r e s t. H e s t a t e s t h a t i n acu t e l u m b ar d i skh em ia t io n , ax i a l m an u a l t r ac t i o n a lo n g th e b o d y ax i s m ay b eb en e f i c i a l b y t em p o ra r i l y o r p e rm an en t ly r e l i ev in g t h e p a inan d o th e r sy m p to m s . H e i s ag a in s t u s in g t h e h ig h -v e lo c i t yth ru s t t ech n iq u e fo r t h ese cases .V e r t e b r a l C a n a l D i a m e t e r I n c r e a se s b y 2 t o 6 m m W i th F l e x io n

S c h o n s t r o m e t a l s r e p o r t t h e h y p o t h e s i s t h a t f l e x i o nin c reases t h e sag i t t a l d i am e te r o f t h e v e r t eb ra l can a l 1 6 % (2m m ) o v e r e x t e n s i o n ; t h e c r o s s - s e c t i o n a l a r e a o f t h e v e r t e br a lc a n a l i n c r e a s e d 4 0 m m 2 w h e n m o v i n g f r o m e x t e n s io n t of l ex io n . L iy a n g e t a l 9 r ep o r t t h a t t h e l u m b ar sp in a l c ap ac i tyin f lex io n -ex t en s io n l a t e r a l m y e lo g ra m m o t io n s tu d i e s o f 1 0cad av e r s sh o w ed a l a rg e r cap ac i ty o f t h e d u ra l s ac i n f lex io no v er ex t en s io n b y 3 .5 t o 6 m m . T h i s i n c reased sp in a l cap ac i -t y i s h ig h ly s ig n i f i can t an d su g g es t s m a in t a in in g t h e f l ex edl u m b a r s p i n e t o e n l a r g e t h e s p i na l c a n a l c a p a c i t y a n d m i t i -g a t e s y m p t o m s .


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J o u r n a l o f M a n i p u l a t i v e a n d P h y s i o l o g i c a l T h e r a p e u t i c sV o l u m e 2 3 N u m b e r 3 M a r c h / A p r i l 2 0 0 0

Letters to the Editor21 3

P en n in g an d W i lm in k t2 sh o w w id en in g o f t h e sp in a l can a lw i th r e l i e f o f p a in seen i n f l ex io n, w h ereas n a r ro w in g o f t h esp in a l can a l i s s een i n ex t en s io n , c r ea t i n g a "p in ce r e f f ec t "o f t h e can a l .

R am G u d av a l l i , P h D , i n p re l im in a ry u n em b ah n ed cad av e rs tu d i e s , sh o w ed th a t i n t e rv e r t eb ra l fo ram en d im en s io n s i n -c r eased u n d e r d i s t r ac t io n ad ju s t i n g a s m u ch a s 2 1 % in a rea ,12% in heigh t , and 5% in wid th dur ing f lex ion-d is t ract ion ad -ju s tm e n t a t L 4 -L 5 . 26

Ex tensi on na r r ows fo r am i n a l s i ze . F arm er an d W isn esk i 27 r e -p o r t ed t h a t ce rv i ca l sp in e ex t en s io n s ig n i f i can t ly i n c reasesn e rv e ro o t p r e s su re t o i n c rease r ad i cu l a r sy m p to m s , w h ereasre su l t s w i th n eck f l ex io n w ere v a r i ab l e . T h e re i s a d ec rease i nfo ram inal s ize in ex tens ion . Yoo et a128 repor te d on the neu ro -tb ram en s i ze o fa r th r i t i c an d h e rn i a t ed n u c l eu s p u lp o su s ce r -v i ca l sp in es w h en p l aced th ro u g h f l ex io n , ex t en s io n , an d ro t a -t i o n p o s i t io n s ; i n f l ex io n th e fo ram in a l s i ze i n c reased 8 % an d10% at 20 to 30 , respect fu l ly . Ex te nsion reduce d the fo ra-m en d i am e te r b y 1 0 % an d 1 3 % a t 2 0 an d 3 0 o f ex t en s io n .

T w o . m i l l i m e t e r c h a n g e o f c a n a l d i a m e t e r r e l ie v e s p a i n . The size oft h e v e r t e b r a l c a n a l i s a ls o v e r y i m p o r t a n t b e c a u s e C l a r k e ta129 p o in t o u t t h a t a 2 -m m d i f f e r en ce i n can a l s i ze sep a ra t e sp e r so n s w i th an d w i th o u t b ac k p a in . S u ch n a r ro w in g o f th ev e r t e b r a l c a n a l c a n b e d u e t o s t e n o s i s i n t r o d u c e d b y d i s c a lp ro t ru s io n , f ace t h y p e r t ro p h y , l i g am en tu m f l av u m h y p er t ro -p h y , o r a c o m b i n a t i o n o f s u c h f o r c e s . W h e n a n e r v e r o o t i sc o m p r e s s e d b y t h e s e s t e n o ti c c h a n g e s w i t h in t h e n e u ra l o rv e r t e b r a l c a n a l , i t i s i m p o r t a n t t o r e l e a s e t h e p r e s s u r e .E x ten s io n ca n i n c rease s t en o s i s an d n e rv e ro o t o r d or sa l ro o tg an g l io n co m p ress io n , an d th e re fo re I u se ax i a l d i s t r ac t i o nw i th ad ju s t i n g an d m o b i l i z in g sp in a l s eg m en t s . T o m e , i f th en e r v e i s c o m p r e s s e d b y d i s k b u l g e , l i g a m e n t u m f l a v u mh y p er t ro p h y , f ace t h y p e r t ro p h y , en d p la t e h y p e r t ro p h y , su b -lux a tiot~, i n s t ab i l i t y , o r a co m b in a t i o n o f th ese f ac to r s ,e x t e n s i o n w i l l n o t r e l e a s e t h e n e r v e c o m p r e s s i o n . T o r e la xth e sp in a l co rd o r n e rv e ro o t s w i l l o n ly r e l ax t h em ad j acen tt o t h e c o m p r e s s i o n s , w h i l e t h e s t e n o s e d c o m p r e s s e d n e r v erem a in s co m p ro m ised . Im a g in e a t u b e i n a v i ce . T o r e l ax t hep a r t o f t h e t u b e a d j a c e n t t o t h e c o m p r e s s e d a r e a w i l l n o tr e l e a se p r e s s u r e o n t h e c o m p r e s s e d a r e a .

T h e g re a t e r t h e p a th o lo g i c ch an g es (d i sk n a r ro w in g , b u lg -in g , s eq u es t r a t io n , o s t eo p h y tes , d i s ru p t io n o f an u l a r en th es i s ,f ib rosis o f the nucleus , long i tud inal sp l i t s in the nucleus , ex -t en s io n o f sp l it s i n to t h e an u lu s , en d p la t e d am ag e , an d v a s -cu l a r i za t i o n ), t h e m o re l i k e ly t h a t p a in d ev e lo p s . 3 Flex ion D is traction Redu ces Di sk Protrus ion

M a n y r e sea rch a r t i c l e s sh o w th e r ed u c t io n o f d i sk p ro t ru -sion on flexi on a nd distraction.3.5,7.1. l2 , 2 9 , 3 1 - 4 8O n el e t a l 5 r ep o r t ed t h a t 7 8 . 5 % o f m e d ia l , 6 6 . 6 % o f p o s -

t e ro l a t e r a l, an d 5 7 % o f l a t e r a l h e rn i a t ed d i sk s r e t r ac t ed u n d e r4 5 k g o f d i s tr ac t i o n i n 2 8 o f 3 0 p a t i en t s s t u d i ed. O n e l e t a ls t a t e t h e fo l l o w in g ab o u t d i s t r ac t i o n o f t h e l u m b a r d i sks :I . S t a t i c l u m b a r t r a c t i o n o p e n s t h e d i s c a l s p a c e s a n d

a p o p h y s e a l j o i n t s p a c e s , r e d u c e s t h e h e r n i a t e d n u c l e u sp u lp o su s , an d o p en s t h e an a to m ic s t ru c tu res o f t h e l u m b arsp ine.

2 . T h e w i d e n e d d i s k s p a c e d r o p s i n t r a d i s c a l p r e s s u r e a n dp ro b ab ly c r ea t e s a n eg a t iv e i nt r ad i sca l p r e s su re t h a t su ck sthe hern iated d isk back in to p lace.

3 . T h e an t e r io r an d p o s t e r io r l i g am en t s a r e s t r e t ch ed u n d e rd i s t r a c t i o n . T h e p o s t e r i o r l o n g i t u d i n a l l i g a m e n t i ss t r e t ch ed an d m ay "p u sh b ack " t h e h e rn i a t ed d i sk t o w ardth e d i sk sp ace . T h e re fo re t h e h e rn i a t ed n u c l eu s p u lp o su si s r ed u ced b y t h e co m b in a t io n o f t h e l o w ered i n t r ad i sca lp res su re , su ck in g th e n u c l eu s p u lp o su s b ack in to t h e d i sksp ace , a s w e l l a s p u sh in g b ack o f t h e d i sk b y r e t r ac t io n o fthe poster io r long i tud inal l igament .

4 . T h e i n t e r sp in o u s sp aces a r e s een t o i n c rease d u r in g d i s -t r ac ti o n , w i th t h e l i g am en tu m f l av u m b eco m in g th in n e r. I ti s b e l i ev ed th a t t h e re i s s ep a ra t i o n o f t h e f ace t j o in t s an ds t r e t ch in g o f t h e p o s t e r io r l o n g i tu d in a l l i g am en t .I n t e r v e r t e b r a l d i s k h e i g h t in c r e a s e w i t h d i s t r a c t i o n a d j u s t i n g . Our

d i s t ra c t i o n s t u d y o f a 5 7 - y e a r -o l d w h i t e m a l e u n e m b a l m e dc a d a v e r s h o w e d L 5 - S 1 d i s k s p a c e t o i n c r e a s e b y 3 m m a n dL 4 -L 5 to i n c rease b y 1 . 8 7 m m . T h e f l ex io n an g le a t t a in eddur ing d is t ract ion was 6 a t L5-S 1 and 3 .5 a t 1 4 -L5 . 4 9t ig a m e n t u m f l a v u m p r o t r u d e s 2 . 9 6 m m t o 3 . 5 m m o n e x t e n s i o n .F l e x i o n a l l o w s t h e l i g a m e n t u m f l a v u m t o s t r e t c h a n dd ec rease i t s b u lg in g i n to t h e v e r t eb ra l can a l, w h ereas ex t en -s io n cau ses b u lg in g o f t h e l i g am e n tu m f l av u m in to t h e can a lto c r ea t e s t en o s is an d fu r th e r n e rv e ro o t co m p ress io n (F ig s 1a n d 2). 3 .5 T e n f r e s h c a d a v e r s s t u d i e d i n h y p e r f l e x i o n a n dh y p erex t en s io n sh o w ed th a t t h e l i g am en t w as e lo n g a t ed an db e c a m e t h i n n e r i n h y p e r f l e x i o n a n d s h o r t e n e d , t h ic k e n e d ,an d p ro t ru d ed in to t h e ce rv i ca l can a l i n h y p e rex t en s io n (3 . 5m m a t C 5 -C 6 , 3 . 2 5 m m a t C 4 - C 5 , a n d 2 .9 6 m m a t C 6 - C 7 ) .S e g m e n t a l s t e n o s i s w a s n o t e d a t t h e l e v e l o f t h e d i s k i nh y p erex t en s io n . 5

F l e x i o n i m p r o v e s d i s k m e t a b o l i s m . B e i n g a v a s c u l a r , t h e d i s krece iv es n u t r i en t s f ro m tw o so u rces : f ro m th e b lo o d v esse l sin t h e v e r t eb ra l b o d ies an d t i s su e f l uid su r ro u n d in g th e an u -lu s f i b ro su s . F lu id f l o w in to t h e d i sk d ep en d s o n ch an g in gp res su res w i th in t h e d isk s t ru c tu re . H ig h p res su re o c cu r s i nc o m p r e s s i o n a n d w e i g h t b e a r i n g a n d f o r c e s f l u id o u t o f t h ed i sk , w h ereas l o w p res su re , a s i n l y in g d o w n , a l l o w s f l u id t ob e s u c k e d u p b y t h e d i s k, p r i m a r i l y t h e n u c l e u s p u l p o s u s .F l e x i o n i m p r o v e s t h e t r a n s p o r t o f m e t a b o l i t e s i n t h e - i n te r -v e r t eb ra l d i sk , r ed u ces t h e s t r e s ses o n t h e ap o p h y sea l j o in t san d o n t h e p o s t e r io r h a l f o f t h e an u lu s f i b ro su s , an d g iv es t h esp in e a h ig h co m p re ss iv e s t r en g th . ~ !

T h e e r ec t u p r ig h t p o s tu re a l l o w s d i f fu s io n m o re r ead i ly i n toth e an t e r io r an u lu s t h an t h e p o s t e r io r an u lus . T h e i n n e r p o s t e -r i o r an u lu s i s t h e m o s t c r i t i ca l a r ea o f t h e d i sk t o b e d ep r iv ed o fn u t ri en t s; f l ex io n im p ro v es t r an sp o r t o f m e tab o l i t e s i n to t h ein n e r p o s t e r io r an u lus . 5~ Im p ro v in g th e m e tab o l i c t r an sp o r t o fth e d i sk is o f r ea l v a lu e b ecau se t h e su p p ly o f g lu co se t o t h ed i sk i s b a re ly ad eq u a t e . 52 D ef i c i en t m e tab o l i t e t r an sp o r t h a sbeen l inked w i th deg enerat iv e chan ges in the d isk . 53,54

T i l a ro 55 s t a t e s t h a t r ed u c in g in t r ad i sca l p r e s su re c r ea t e s ad i f fu s io n g rad i en t i n to t h e d i sk , a l l o w in g im p ro v ed n o u r i sh -m e n t o f t h e n u c l e u s p u l p o s u s a n d r e d u c e d l a c t a t e l e v e l s ,l _n tr ad iscal p r e s s u re h ig h e r t h an ca p i l l a ry p res su re im p ed e sd i f fu s io n an d h ea l in g .


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21 4 Journal of Manipulative and Physiological TherapeuticsVolume 23 Number 3 - March/April 2000Let ters to the Editor

I n t ra d i s c a l P r e s s u r e a n d T a b l e M o t i o nV e r s u s D u r a t io n o f T r e a t m e n t. 0 6 0 0mm

o J \ . _ / / , )q l

c~ -12 " ;D u r a t i o n o f T r e a tm e n t ( S e c s . )F ig 3 . Intradiscal pressure and table motion versus duration oftreatment.

W hat A re the Intradisca l PressureChanges on Distraction?A s p a r t o f a C h i r o p r a c t i c D e m o n s t r a t i o n s P r o j e c t s G r a n t

P r o g r a m ( H e a l t h R e s o u r c e s a n d S e r v i c e s A d m i n i s t r a ti o nG r a n t # 1 R 1 8 A H 1 0 0 0 1 - 0 1 A 1) e n t it l e d " B i o m e c h a n i c s o fL o w B a c k F l e x i o n - D i s tr a c t i o n T h e r a p y , '2 6 w h i c h w a s f u n d -e d f r o m 1 9 9 4 t o 1 9 9 7, 5 w h o l e u n e m b a l m e d c a d a v e r s w e r es t u d i e d f o r i n tr a d i s c a l p r e s s u r e c h a n g e s d u r i n g d i s t r a c t io na d j u s ti n g . T h e s t u d y w a s a c o l l a b o r a t i v e s t u d y b e t w e e n t h eN a t i o n a l C o l l e g e o f C h i r o p r a c ti c a n d t h e D e p a r t m e n t o fO r t h o p e d i c S u r g e r y a t t h e L o y o l a U n i v e r s i t y S t ri t ch S c h o o lo f M e d i c i n e . T h e r e s u l t s h a v e b e e n p r e s e n t e d a t t h e 1 9 9 7m e e t i n g o f t h e I n t e r n a t i o n a l S o c i e t y f o r t h e S t u d y o f th eL u m b a r S p i n e 56 a n d T h e A m e r i c a n S o c i e t y o f M e c h a n i c a lE n g i n e e r s i n N o v e m b e r 1 9 97 57 b y M . R . G u d a v a l l i , P h D ,p r i n c i p l e i n v e s t i g a t o r . T h e s e a r t i c l e s a r e p r e s e n t l y u n d e rr e v i s i o n o r b e i n g w r i t t e n f o r p u b l i c a t i o n . T h e i n t r a d i s c a lp res su re s tu d i e s w e re n o t a p a r t o f t h e fu n d ed s tu d y , b u t th eyw e r e p e r f o r m e d w i t h i t.

M e a s u r e m e n t s o f i n tr a d i s c a l p r e s s u r e s d u r i n g d i s tr a c t i ona d j u s t i n g c o u p l e d w i t h f l e x i o n , e x t e n s i o n , l a t e r a l f l e x i o n ,a n d c i r c u m d u c t i o n m o t i o n s o f th e l u m b a r s p i n e w e r e p e r -f o r m e d o n 5 u n e m b a l m e d c a d a v e r s b y p l a c i n g t w o m i n i a t u rep res su re t r an sd u c e r s i n to t h e n u c l eu s p u lp o su s o f t h e L 2 -L 3 ,L 3 - L 4 , a n d L 4 - L 5 d i s k s . W e c o n n e c t e d t h e p r e s s u r e t r a n s -d u c e r s t o a c o m p u t e r t h r o u g h a s i g n a l a m p l i f i e r a n d a n a l o g -to -d ig i t a l co n v e r t e r . W e p l ac ed th e cad av e r s i n a p ro n e p o s i -t i o n o n t h e f l ex io n -d i s t r ac t i o n t ab l e , w h ich w as s im i l a r t o t h ep o s i t i o n in g fo r a l i v in g p a t i en t . T h e d ro p in i n t r ad i sca l p r e s -s u r e w i t h t a b l e f l e x i o n d i s t r a c t i o n m o t i o n ( p e r f o r m e d w i t hf i v e 4 - s e c o n d d i s t r a c t i o n m o t i o n s o f t h e i n t e r v e r t e b r a l s e g -m e n t ) i s s h o w n i n F i g 3 , w h i c h a l s o s h o w s t h e t a b le m o t i o n .T h e d r o p i n i n tr a d i s c a l p r e s s u r e w a s 3 9 m m H g t o 1 9 2 m mH g o f n e g a t i v e p r e s s u r e ( T a b l e 1 ) , w h i c h w a s a s i g n i f i c a n td e c r e a s e i n i n t r a d i s c a l p r e s s u r e d u r i n g t h e f l e x i o n - d i s t r a c -t i o n p r o c e d u r e f o r l o w b a c k p a i n . T h e p r e s s u r e i n c r e a s e dd u r in g ex t en s io n m o t io n o f t h e t ab l e . 58

Table I. Me a n i n t ra d isc a l p re s su re s d u r i n g t h e f l e x i o n -d is t ra c t i o n~rocedure (d isks no t pressurized )

Pressure in initial Pressure in Decrease inCadaver prone position distracted pressureNo. Joint (ram Hg) position (mnl Hg) (mm Hg)3 L3-L4 27 (22) -165 (37) 192 (37)4 L2-L3 24 (7) -15 (2) 39 (3)5 L3-L4 13(13) -4 8( 2) 61 (12)L4-L5 -87( 37) -150( 11) 63(1 0)

Table 2. Me a n i n t ra d i sc a l p l e s su re s d u t q n g t h e l o w b a c k t r e a t m e n t~ t v c e d u re s ( j o i n t L3 -L4 )

Pressure in Pressure ininitial prone distracted Decrease inposition position pressureTable motion (mm Hg) (ram Hg) (mm Hg)

Flexion 228 - 19.5 247.5Extens ion 228 1250 1022Right lateral flexion 226 747 521Left lateral flexion 226 - 151 377Right lateral circum duction 240 530 290Left lateral circumduction 240 -12 0 360

T a b l e 2 a n d F i g 4 a r e t he i n t r a d i s c a l p r e s s u r e s m e a s u r e dd u r in g t h e m o v em en t s o f f l ex io n , ex t en s io n , l a t e r a l f l ex io n ,a n d c i r c u m d u c t i o n o f t h e f a c e t j o i n t s . T h e p r e s s u r e s h a v ein c reased d u r in g r i g h t l a t e r a l m o t io n , w h ereas t h e p res su resh a v e d e c r e a s e d d u r i n g t h e l e f t l a t e r a l m o t i o n . D u r i n g c i r -cu m d u c t io n , t h e p res su re h as d ec reased d u r in g t h e l e f t l a te r -a l an d f l ex io n m o t io n s , w h ereas i t h as i n c reased d u r in g t h er i g h t l a t e r a l a n d f l e x i o n c o m b i n e d m o t i o n s . I n a ll o f th em o t io n s , t h e p res su res r e tu rn ed to t h e i r o r ig in a l v a lu es w h enth e sp in e w as b ro u g h t b ack t t h e i n i ti a l p ro n e p o s i t i o n . O n eo f t h e r e a s o n s f o r t h e i n c r e a s e a n d d e c r e a s e d u r i n g l a t e r a lm o t i o n s i s d u e to t h e f a c t t h a t t h e t r a n s d u c e r w a s i n s e r t e din to t h e r i g h t s i d e o f t h e d i sk , an d a s p o in t e d o u t ea r l i e r i nt h i s a r t i c le , d i s k s b u l g e i n t o t h e c o n c a v i t y o f a c u r v e . T h er e s u l t s c l e a r l y s h o w t h a t t h e p r e s s u r e s a r e a f f e c t e d d u r i n gd i f f e r en t m o t io n s o f t h e sp in e a s so c i a t ed w i th t h e m o t io n s o fth e t ab l e .

F ro m T ab le 2 an d F ig 4 , n o t e t h a t t h e i n tr ad i sca l p r e s su rein ex t en s io n r each ed 1 2 5 0 m m H g , t h e h ig h es t p r e s su re t h a tc o u l d b e m e a s u r e d o n t h e t r a n sd u c e r , m e a n i n g a n i n c r e a s e o f1 0 22 m m H g f r o m t h e n e u t ra l p o s i t i o n i n t o e x t e n s io n . T h i si s m y r e a s o n t o a v o i d e x t e n s i o n m o v e m e n t i n c o n ta i n e d d i s kh e rn i a t i o n s an d th e r easo n th a t p e r so n s w i th sc i a t i ca s t an d ina f l ex e d , s c i a t i c - ty p e s c o l i os i s p o s i t i o n - - t h e y s e e k t o l o w e rt h e i n t ra d i s c al p r e s s u r e b y m e a n s o f p o s t u r e a d a p a t io n .

R a m o s a n d M a r t i n 59 r e p o r t e d o n t h e i n t r a di s c a l p r e s s u r ed u r i n g a v e r t e b r a l a x i a l d e c o m p r e s s i o n p r o c e d u r e p e r f o r m e do n 3 p a t i en t s m easu red i n t r ao p e ra t i v e ly . T h e r e su l t s sh o w edt h a t t h e d i s k p r e s s u r e s r e d u c e d d u r i n g t h e v e r t e b r a l a x i a ld e c o m p r e s s i o n t h e r a p y . T h e y d e m o n s t r a t e d t h a t t h e d i s kp r e s s u r e s c a n g o a s l o w a s - 1 6 0 m m H g . T h e r e s u l t s o f t h ep resen t s t u d y a r e i n g en e ra l ag ree m e n t w i th th e s tu d y r ep o r t -e d b y R a m o s a n d M a r t i n . A n d e r s s o n e t a l 6 r e p o r t e d t h ein t r ad i sca l p r e s su res a t t h e L 3 -L 4 d i sk o n 4 v o lu n t ee r s d u r -


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J o u r n a l o f M a n i p u l a t i v e a n d P h y s i o l o g i c a l T h e r a p e u t i c sV o l u m e 2 3 N u m b e r 3 M a r c h / A p r il 2 0 0 0

Letters to the Editor

I n t e rv e rt e bra l D i s c Pre s s ure C ha nge s D ur ing Low B a c k Tre a l me nt P ro c e dure sExtension/Flexion

D u r at io n a T r W n w t ( , ' ~ . )F ig 4. Intela,ertebral disk pressure ch anges during low bac k treatme nt procedures.

21 5

i n g s t a n d i n g , l y i n g , a c t i v e t r a c t i o n , a n d p a s s i v e t r a c ti o n . T h ef i n d i n g s s h o w e d a n i n c r e a s e i n t h e d i s k p r e s s u r e d u r i n g b o t ha c t i v e a n d p a s s i v e t r a c t i o n . T h e r e s u l t s f r o m t h e p r e s e n ts t u d y d o n o t a g r e e w i t h t h e r e s u l t s re p o r t e d b y A n d e r s s o n e ta l . A p o s s i b l e r e a s o n c o u l d b e t h a t t h e m u s c l e s o f th e i n v i v os u b j e c t s c o u l d h a v e b e e n c o n t r a c t i n g w h i l e u n d e r a c t i v e a n dp a s s i v e t r a c t i o n . W o r k i s i n p r o g r e s s t o m o n i t o r t h e m u s c l ea c t i v i t y d u r i n g i n v i v o s i t u a t i o n s o f t r e a t i n g t h e p a t i e n t s b yu s i n g f l e x i o n - d i s t r a c t i o n p r o c e d u r e s .L i g a m e n t l o a d s w i t h d i s t r a c t io n a d j u s t i n g . G u d a v a l l i 61 r e p o r t e dt h a t t h e l i g a m e n t l o a d s a p p l i e d t o t h e l u m b a r s p i n e d u r i n gd i s t r a c t i o n a d j u s t i n g s h o w l e s s t h a n 5 0 % o f t h e i r u l ti m a t es t r e n g t h f o r f a i l u re .Summat ion

F i n a l l y , e x t e n s i o n i s q u e s t i o n e d i n t r e a t in g l o w b a c k p a i n .A s t u d y s h o w e d t h a t s p i n a l m a n i p u l a t i o n a n d a n o n g o i n gf l e x i o n a n d e x t e n s i o n e x e r c i s e p r o g r a m r e s u l t e d i n m o r er a p id r e s o l u t io n o f s y m p t o m s a n d i m p r o v e m e n t i n f u n c ti o n a ll i m i t a t i o n s t h a n a n e s t a b l i s h e d e x t e n s i o n p r o g r a m a l o n e . 62O t h e r w e l l - d o n e a r t i cl e s 6 36 6 q u e s t i o n t h e e x t e n s i o n p r i n c i -p l e s c i t e d b y H a r r i s o n e t a l . I T h i s d o e s n o t m e a n e x t e n s i o np o s t u r i n g i s n o t h e l p f u l b u t r a t h e r t h a t i t i s p a r t o f t h e r a p y .T h e s a m e i s tr u e o f f le x i o n p o s t u r i n g - - i t i s n o t t h e t o ta l a n -s w e r f o r b a c k p a i n b u t o f f e r s a s i g n i f ic a n t b e n e f i t t o b e u s e db y t h e p r a c t i c i n g c h i r o p r a c t o r i n t h e d a i l y c a r e o f p at i e n t s.

R a t h e r t h a n o n l y b e i n g a 1 - t o 1 . 5 - m m c h a n g e i n t h e s ag i t -t a l d i a m e t e r o f t h e s p i n a l c a n a l a n d i n t e r v e r t e b r a l f o r a m e n i ne x t e n s i o n m o t i o n , a s s t a t e d b y H a r r i s o n e t a l , ! th e a r t i c l e sc i t ed i n t h i s r e p ly s h o w t h a t th e c o m b i n e d n a r r o w i n g i n e x -t e n s i o n b y t h e d i s k h e r n i a t i o n , l i g a m e n t u m f l a v a l h y p e r t r o -p h y , a n d b u c k l i n g c a n a p p r o a c h 1 0 m m . T h e s e t r u e c h a n g e si n c a n a l d i a m e t e r o n m o t i o n d e m a n d t h e ra p e u t ic c o n s i d e r a -t i o n a n d d e m a n d p a t i e n t t o l e r a n c e t e s t i n g b e f o r e f l e x i o n o re x t e n s i o n a d j u s t i n g i s u n d e r t a k e n .

J a m e s M . C o x , D C , D A C B R3 1 2 5 H o b s o n R o a d

F o r t W a y n e , I N 4 6 8 0 5

REFERENCES1. Harrison DE , Cailliet R , Harrison DD , Troy anov ich SJ, Hard-son SO. A review o f biomechanics of the central nervous sys-tem. Part 1: Spinal canal deformations resulting f rom changesin posture. J Manipulative Physiol Ther 1999;22:227-34.2. Runza M, Pietrabissa R, Mantero S, Albani A, Qualgl ini V,Contro R. Lum bar dura mater biomechanics: experienced char-ac te r iza t ion and scann ing e lec t ron m ic roscopy obse rva t ions .In: Anesthesia and analgesia . Balt imore: Lippin cott Will iams& Wilkins; 1 999. p. 1317-21.3 . F inneson B E Low back pa in . Ph i lade lph ia : JB L ipp inco t t ;1973. p. 258-9.4. Burton CV. Gravity lumbar reduction. In: Kirkaldy-Willis WH,editor. Managing low back pain. New York: Churchill Living-stone; 1983. p. 191-8.5. Oriel D, Tuzlaci M , Sari H, Dem ir K. Computed tom ographicinves t iga t ion o f the e f fec t o f t r ac t ion on lumb ar d i sc he rn ia -tions. Spine 1989; 14:82-90.6 . Cox JM. L ow back pa in : mechan ism, d iagnos i s, t rea tment.Fifth ed. Baltimore: Williams & Wilkins; 1990. p. 437-66.7. Epstein NE, H yma n RA, Epstein JA, Rosenthal A D. Technicalno te : "dyna mic" MR I scann ing o f the ce rv ica l sp ine . Sp ine1988;13:937-8.8 . Schons t rom N, L inc iah l S , Wi len J , H ansson T . Dyn amicchang es in dimensions o f the lumba r spinal canal: an experi-mental study in vitro. J Orthop Res 1989;7:115-21.9 . L iyang Da i , Y inkan X, W enming Z , Zh ihua Z . The e f fec t o ff lexion-extension motion o f the lumbar spine on the capa city ofthe spinal cord. S pine 1 989; 14:523-5.10. Lindb olm K. Intervertebral disc degenerat ion considered as a

pressure atrophy. J Bo ne Joint Surg Am 1957;39A:933-4.11. Adams MA , Hut to nW C. T he e f fec t o f pos tu re on the lumbarspine. J Bone Joint Surg B r 1985;67B:625-9.12. Penning L , Wilmink JT. Posture depend ent bi lateral com pres-s ion o f L4 on L5 ne rve roo t s in face t hyper t rophy : a dynamic CT-myelographic study [abstract]. Spine 1987;12:488.13. Ram os G, M artin W . Effects of vertebral axial deco mpressionon intradiscal pressure. J Neur osurg 1994;81:350-3.14. Gil l K, V ideman T, Shimizu T, M ooney V. The effect of repeatedextensions on the discographic dye patterns in cadaverie lum barmotion segments. Clin Biom ech 1987;2:205,10.15. Se rouss i RE, Krag MH , M ul le r DL, Pope MH . In te rna l de fo r-mations o f intact and denulceated hum an lumb ar discs Subject-ed to compression, f lexion, a n d e x t e n s i o n loads. J O~rthopR e s1989;7:122-31.


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16. Vanharan ta H, Ohnm eiss D. S t i th W, Rashbaum R , Hochschu le rS , Guy er R . e t a l . E f fec t o f repea ted t runk ex tens ion and f lex ionmovements a s seen by CT/Discography [abs t rac t ] . Or tho T ran1989;13:28.1 7. A d a m s M , D o l a n P , H u t t o n W . T h e l u m b a r s p i n e i n b a c k w a r dbend ing [abs t rac t ] . Sp ine 1988 ; 13 :1019.1 8. S c h m i d M R , S t u c k i G , D u e w e l l S . W i l d e r m u t h S , R o m a n o w s k iB , H o d l e r J . C h a n g e s i n c r o s s - s e c t i o n a l m e a s u r e m e n t s o f t h esp ina l cana l and in te rve r teb ra l fo ramin a as a func t ion o f a bodypos i t ion : in v ivo s tud ies on an open-conf igura t ion MR sys tem.AJ RA m J Roen tgeno l 1999;172 :1095-102 .1 9. R e v e l M , M a y o u x - B e n h a m o u M A . A a r a n o n C , A m o r B .M o r p h o l o g i c a l v a r i a ti o n s o f t h e l u m b a r f o r a m i n a d u r i n g f l e x -i o n - e x t e n s i o n a n d d i s c c o l l a p s e . R e v R h u m M a l O s t e o a r t i c1988;55:361-6.2 0 . N o w i c k i B H , Y u S , R e i n a r t z J , P i n t a r F , Y o g a n a n d a n N ,H a u g h t o n V M . E f f e c t o f a x i a l l o a d i n g o n n e u r a l f o r a m i n a a n dnerve roo ts in the lumb ar sp ine . Rad io logy 1990;176 :433-7.2 1 . N o w i c k i B H , H a u g b t o n V M , S c h m i d t T A , L i m T H , A n H S ,R i l e y L H 3 r d , e t a l. O c c u l t l u m b a r l a t e r a l s p i n a l s t e n o s i s inn e u r a l f o r a m i n a s u b j e c t ed t o p h y s i o l o g i c l o ad i n g . A J N R A m JNeuroradiol 1996;17:1605-14.

2 2 . S o r t l a n d O , M a n g n a e s B , H a u g e T . F u n c t i o n a l m y e l o g r a p h yw i t h m e t r i z a m i d e i n t h e d i a g n o s i s o f l u m b a r s p i n a l s t e n o s i s .Ac ta Rad io l 1977 ;355(Supp l ) :42 -54 .2 3 . A m u n d s e n T , W e b e r H , L i l l e a s F , N o r d a l H J , A a b d e l n o o r M ,M a g n a e s B . L u m b a r s p i n a l s t e n o s i s : c l i n i c a l a n d r a d i o l o g i cfeatures. Spine 1995;20:1178-6.2 4 . Z a m a n i A A , M o r i a r t y T , H s u L , W i n a l s k i C S , S c h a f f e r J L ,I s b i s t e r H , e t a l . F u n c t i o n a l M R I o f t h e l u m b a r s p i n e i n e r e c tp o s i t i o n i n a s u p e r c o n d u c t i n g o p e n - c o n f i g u r a t io n M R s y s t e m :pre l im inary resu l ts . J Magn Reson Im ag ing 1998;8 :1329-33.2 5 . D v o r a k J . I n a p p r o p r i a t e i n d i c a t i o n s a n d c o n t r a i n d i c a t i o n s f o rmanu a l the rapy . J Ma nua l M ed 1991 ;6 :85-8 .2 6 . G u d a v a l l i M R . B i o m e c h a n i c s o f l o w b a c k f l e x i o n - d i s t r a c t i o nt h e ra p y , C h i r o p r a c t i c D e m o n s t r a t i o n s P r o j e c t s G r a n t P r o g r a m -F i s c a l y e a r 1 9 97 G r a n t s . H e a l t h R e s o u r c e s a n d S e r v i c e sA d m i n i s t r a t i o n ; 1 9 97 . G r a n t N o . 1 R 1 8 A H 1 0 0 0 1 - 0 1 A 1 . I npress .2 7 . F a r m e r J C , W i s n e s k i R J . C e r v i c a l s p i n e n e r v e r o o t c o m p r e s -sion. Spin e 1994;19:1850-5.2 8 . Y o o J R , Z o u D , E d w a r d s W T , B a y l e y J , Y u an H A . E f f e c t o fc e r v i c a l s p i n e m o t i o n o n t h e n e u r o f o r a m i n a l d i m e n s i o n s o fhuman ce rv ica l sp ines . S p ine 1992; 17:1131-6 .2 9 . C l a r k G A , P a n j a b i M M , W e t z e l F T . C a n i n f a n t m a l n u t r i t i o ncause adu l t ve r teb ra l s tenos is? Sp ine 1985; I 0 :165-70 .3 0 . G o u p i l l e P , J a y s o n M I V , H o y l a n d J A , V a l a t M P, F r e e m o n t A J .A s s o c i a t i o n b e t w e e n i n c r e a s e d e x t e n d a n d m u l t i l e v e l l e s i o n sw i t h l o w b a c k p a i n : a c a d a v a r i c s t u d y [ a b s t r a c t ] . A r t h r i t i sRheum 1998;41:343.3 1 . W h i t e A A , P a n j a b i M M . C l i n i c a l b io m e c h a n i c s o f t h e s p i n e .Ph i lade lph ia : JB L ipp inco t t ; 1978 . p . 7 .

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37 . Gi l l s t rom P , E r icson K, Hindmarsh T . Cornpu ted tomographye x a m i n a t i o n o f t h e i n f l u e n c e o f a u t o t r a c ti o n o n h e r n i a t i o n o fthe lum bar d isc . Arch O r thop T rauma Surg 1985 ; 104 :289-93 .38 . C ox JM, Aspegren DD. A hypo thes is in troduc ing a new ca lcu la -tion for discal reduction: emph asis on stenotic factors aJld manip-ulative treatment. J Ma nipulative Physio l Ther 1987; 10:287-94.3 9 . K e s s l e r R M . A c u t e s y m p t o m a t i c d i s k p r o l a p s e . P h y s T h e r1979;59:978-87.4 0 . C y r i a x J . T e x t b o o k o f o r t h o p e d i c m e d i c i n e . 8 t h e d . L o n d o n :Ba i l l ie re T inda l l : 1982 . p . 315-16 .41 . Ca l l ie t te R . Low back syndrome. 3 rd ed . Ph i lade lph ia : Dav is ;1981.42 . Wyk e BD. Neuro log ica l a spec ts o f low back pa in . In : Jayson M,ed . The lum bar sp ine and back pa in . London : Sec to r Pub l i sh ing ;1976. p. 189-256.4 3 . D e S e z e S , L e v e r n i e u x J . L e s t r a c t i o n s v e r t e b r a l e s . P r e m i e r se t u d e e x p e r i m e n t a l e s e t r e s u l t a t s t h e r a p e u t i q u e s d ' a p r e s u nexper ience de qua t re annees [abs t rac t ]. Semaine o le hosp i ta lesParis 1951 ;27:2085.4 4 . M a t h e w s J A , Y a t e s D A H . T r e a t m e n t o f s c i a t i c a [ a b s t r a c t ] .Lancet 1974;1:352.4 5 . N e u g e b a u e r J . R e - e s t a b l i s h i n g o f t h e i n t e r v e r t e b r a l d i s c b ydecom press ion [abs t rac t ]. Med W el t 1976 ;27 :19 .4 6 . T i e n - Y o u F . L u m b a r i n t e r v e r t e b r a l d i s c p r o t r u s i o n , n e wm e t h o d o f m a n a g e m e n t a n d i t s t h e o r e t i c a l b a s i s . C h i n M e d J(Engl) 1976; I : 183-94.47 . Kram er J . In te rve r teb ra l d isc d iseases : causes , d iagnos is , t rea t -men t , and p ro phy lax is . Ch icag o : Year Book Pub l i sh e rs : 1981 .p. 164-6.48 . Yefu L , J ix iang E Z u l iang L , Zhenq ian L . T rac t ion and man ip -u l a t i v e r e d u c t i o n f o r t h e t r e a t m e n t o f p r o t r u s i o n o f l u m b a ri n t e r v e r te b r a l d i s c - - a n a n a l y s i s o f 1 ,4 55 c a s e s . J T r a d i t C h i nMed 1986;6:31-3.49 . P i lo t p ro jec t repor ted in b iom echan ics o f low back f lex ion-d is -t r a c t io n t h e r a p y . C h i r o p r a c t i c D e m o n s t r a t i o n s P r o j e c t s G r a n tP r o g r a m - - F i s c a l y e a r 1 99 7 G r a n t s . H e a l t h R e s o u r c e s a n dS e r v i c e s A d m i n i s t ra t i o n . G r a n t N o . 1 R 1 8 A H 1 0 0 0 1 - 0 1 A I . I np ress .5 0 . L i a n - s h u n J , Q u i a n g S , D e - y u C , W e n - m i n g Z . D y n a m i cc h a n g e s o f c e r v i c a l l i g a m e n t a l f l a v u m i n h y p e r e x t e n s i o n -h y p e r f l e x i o n m o v e m e n t a n d t h e i r m e a s u r e m e n t s . C h i n M e d J1990; 103:66-70.5 1 . N a c h e m s o n A L . T h e l u m b a r s p i n e : an o r t h o p e d i c c h a l l e n g e .Spin e 1976; 1:59-71.5 2 . M a r o u d a s A , S t o c k w e l l R A , N a c h a m s o n A , U r b a n J . F a c t o r si n v o l v e d i n th e n u t r i t i o n o f th e h u m a n l u m b a r i n t e r v e r t e b r a ld i s c ; c e l l u l a r i t y a n d d i f f u s i o n o f g l u c o s e i n v i t r o . J A n a t1975;120:113-30.5 3 . N a c h e m s o n A L , L e w i n T , M a r o u d a s A , F r e em a n M A R . I nv i t r o d i f f u s i o n o f d y e t h r o u g h t h e e n d p l a t e s a n d t h e a n u l u sf i b r o s u s o f h u m a n i n t e r v e r t e b r a l d i s c s . A c t a O r t h o p S c a n d1970;41:589-607.

54 . H o lm S , Nache mson A . Nutr i t iona l changes in the can ine in te r -ve r teb ra l d isc a f te r sp ina l fus ion . C l in Or thop 1982; 169:234-58 .55 . T i la ro F . An overv iew o f ve r teb ra l ax ia l decom press ion . Can JC l in Med 1998.5 6 . G u d a v a l l i M R , C o x J M , B a k e r J A , C r a m e r G D , P a t w a r d h a nA G . I n t e r v e r t e b r a l d i s c p r e s s u r e c h a n g e s d u r i n g t h e f l e x i o n -d i s t r a c ti o n p r o c e d u r e f o r l o w b a c k p a i n . I n t e r n at i o n a l S o c i e t yf o r t h e S t u d y o f t h e L u m b a r S p i n e ; 1 9 9 7 .5 7 . G u d a v a l l i M R , C o x J M , B a k e r G D , C r a m e r G D , P a t w a r d h a nAG . In te rve r teb ra l d isc p ressu re changes dur ing a ch i roprac t icp r o c e d u r e . D a l l a s [ T X ] : A m e r i c a n S o c i e t y o f M e c h a n i c a lEng ineers ; 1997.5 8 . G u d a v a l l i M R , C o x J M , B a k e r J M , C r a m e r G C , P a t w a r d h a nAG . In te rve r teb ra l d isc p ressu re changes dur ing a ch i roprac t icp rocedure . A dv B ioeng in eer ing 1997;36:215-6.


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J o u r n a l o f M a n i p u l a t i v e a n d P h y s i o l o g i c a l T h e r a p e u t i c sV o l u m e 2 3 N u m b e r 3 M a r c h / A p r i l 2 0 0 0

Letters to the Editor21 7

59. Ra mo s G, Martin W. Effects of vertebral axial deco mp ressio non intradiscal pressure. J Neurosurg 1994:81:350-3.60. Andersson G BJ, Schultz AB, Nachemson A L. Intervertebral discpressures during traction. Scand J Rehabil 1983;9(Suppl):88-91.61. Gudavall i MR. Biomechanics research on f lexion-distract ionprocedure. In: Gudavall i MR, editor .Low back pain: mecha-nism, diagnosis, and treatment. 6th ed. Philadelphia: Williams& Wilkins: 1999 . p. 269-71.62. E rhard RE . Delitto A, Cibulka MT. Relative effectiveness of anex tens ion p rogram and a combined p rogram of m anipu la t ionand flexion and extension exercises in patients with acute lowback syndrome. Phy s The r 1994;74:1093- 100.63. Riddle D. M cKen zie system : popular but how rel iable?Backletter 1992;7:1-2.64. Fernando CK. L etter to the editor, Spine 1991 ; 16:1008.65. Riddle DL . Rothstein JM. Intertester reliability o f Mc Ken zie'sclassif icat ion-of the syndrome types present in pat ients withlow bac k pain. Spine 1993;18:1333-44.66. Beattie PF. Brooks WM, Rothstein JM. Sibbitt WL Jr. RobergsR.A, Ma cLea n T, et al. Effec t of lordosis on the position of thenucleus pulposus in supine subjects: a study using MRI. Spine1994; 19:2096-102.I n R e s p o n s e :T h a n k y o u f o r a l l o w i n g u s t o r e s p o n d t o D r C o x ' s l e t t e r t ot h e e d i to r c o n c e r n i n g o u r r e c e n t r e v i ew a r t ic l e c o n c e r n i n gs p i n a l c a n a l d e f o r m a t i o n s p u b l i s h e d i n J M P T . J

A f t e r g o i n g i n t o a l o n g r e v i e w o f d i s k h e r n i a t i o n s , w h i c hh a d n o t h i n g t o d o w i t h o u r o r i g in a l p a p e r , D r C o x w a n t s t ov a l i d a t e f l e x i o n a s a t r e a t m e n t f o r l o w b a c k p a i n . D r C o x ' sw h o l e l e t t e r c o n c e r n s c a n a l s t e n o s i s . W e s p e c i f i c a l l y s t a t e dt h a t w e r e v i e w e d c a n a l d e f o r m a t i o n s i n t h e a b s e n c e o fs t e n o s i s, a s t h e f o l l o w i n g q u o t e i n d i c a t e s :

"We do not deny the clinical significance of this issue, nordo we intend to minimize i t . However, we bel ieve that anequally important issue, and more prevalent , has typical lybeen un der appreciated by ma ny cl inicians and researchers.This issue being neural tissue stress and strain in the absenceof s tenotic condit ions. Since stenotic canals are present inonly a m inori ty of individuals , we feel that the lat ter condi-t ion may encom pass a l a rge r vo lume of pa t i en ts and neuro-logic conditions. T his is because altered alignment o f uprightposture, v iewe d as rotations and translations in three dimen -s ions , and poor e rgonomics a re re la t ive ly common p laceamong todays pat ient populat ions. This review is presentedwith emphasis on this position. qF i r s t, D r C o x w o u l d h a v e u s b e l i e v e t h a t th e v a s t m a j o r i t y

o f o u r p a ti e n t s h a v e n e r v e r o o t c o m p r e s s i o n a n d c a n a l s t e n o -s i s , w h e n i n f a c t t h e s e p a t i e n t s r e p r e s e n t l e s s t h a n 5 % o fp a t i e n t s c o m i n g t o h e a l t h c a r e p r o v i d e r s w . it h l o w b a c k p a i n( n o t w i t h s t a n d i n g n e c k p a i n , t h o r a c i c p a i n , h e a d a c h e , a n do t h e r d i s e a s e s ) . 2 '3 " P u r e o s t e o l i g a m e n t o u s l a t e ra l s t e n o s i s i sa f a i rl y u n c o m m o n c o n d i t io n . '4 T h u s 9 5 % o f t h e p a ti e n tst h a t w e c l i n i c ia n s t a k e c a r e o f h a v e n e i t h e r I V F e n c r o a c h -m e n t n o r c a n a l s t e n o s i s a s a c a u s e o f t h e i r c o m p l a i n t s .

S e c o n d , w e p r e s e n t e d a r e v i e w o f c a n a l d e f o r m a t i o n i n t h ew h o l e s p i n e , w h e r e a s D r C o x w o u l d l i k e t o r e s t ri c t u s to t h el u m b a r s p i n e o n l y . H e c i t e d a r t i c l e s o n l u m b a r d i s k b u l g i n g ,d i s k r u p t u r e , a n d l i g a m e n t a f l a v a o s s i f i c a t i o n ( O L F ) . B e f o r ea d d r e s s i n g s o m e o f h i s l u m b a r s t u d i e s , w e n o t e t h a t i t i s g o o dt h a t h e r e s t r i c t s h i m s e l f t o t h e l u m b a r a r e a b e c a u s e c e r v i c a l

a n d t h o r a c i c d i s k r u p t u r e , d i s k b u l g i n g , a n d O L F a r e r a r e .T h e c e r v i c a l d i s k a n a t o m y i s c o m p l e t e l y d i f f e r e n t f r o m t h el u m b a r d i s k a n a t o m y , 5 a n d c e r v i c a l d i s k h e r n i a t i o n o c c u r son ly in t r auma t ic rup tu re . ~' Oss i f i ca t ion o f the th orac ic l iga -men ta f l ava is ve ry ra re . 7 Th orac ic d i sk rup tu res a re ra re s andacco un t fo r on ly 1% of a l l in te rve r tebra l d i sks t r ea ted su rg i -ca l ly . 9 In f l ex ion-ex tens ion the thorac ic cag e m ove s as i f i t isone r ig id bod y . In

C e r v i c a l O L F i s a l s o r a re , a n d e v e n w h e n p r e s e n t o n c o m -p u t e d t o m o g r a p h y s c a n s , i t o n l y c o m p r e s s e s t h e c o r d i n as m a l l p e r c e n t a g e o f c a s e s i n h y p e r e x t e n s i o n . H o u s e r e t a l I Ie v a l u a t e d 9 3 p a t i e n t s w i t h c e r v i c a l s p o n d y l o t i c s t e n o s is a n da s s o c ia t e d m y e l o p a t h y b y u s i n g c o m p u t e d t o m o g r a p h i cm y e l o g r a p h y . H y p e r t r o p h y o f t h e l ig a m e n t u m f l a vu m w a sp r e s e n t i n 2 5 % o f th e s u b j e c ts . H o w e v e r , t h e y r e p o r t e d d i s -p l a c e m e n t o f t h e p o s t e r i o r s p i n a l c o r d i n h y p e r e x t e n s i o n i no n l y t w o c a s e s . T h i s s t u d y s u g g e s t s t h a t a p p r o x i m a t e l y 2 %o f i n d i v i d u a ls w i t h c a n a l s t e n o s i s o r 8 % o f i n d iv i d u a l s w i t hh y p e r t r o p h y o f t h e l i g a m e n t u m f l av u m m i g h t h a v e a n a b n o r -m a l c o r d c o m p r e s s i o n d u r i n g c e r v i c a l h y p e r e x t e n s io n . I n as t u d y o f 9 9 7 J a p a n e s e s u b j e c t s ( a g e r a n g e , 1 5 - 7 9 y e a r s ), c e r -v i c a l o s s i fi c a t i o n o f t h e p o s t e r i o r l o n g i t u d i n a l l i g a m e n t o n l yo c c u r r e d i n 2 . 1 % o f t h e s u b je c ts .1 2 C o n c e r n i n g s t e n o s i s i nt h e l u m b a r s p i n e , c o m p r e s s i o n o f t h e c a u d a e q i n a c a n b ec a u s e d b y t h i c k e n e d p o s t e r i o r v e r t e b r a l e l e m e n t s , f a c e tjo in t s , marg ina l os teoph y tes , o r so f t t i s sue s t ruc tu res . J3

T h e s p i n a l c o r d e n d s a t a p p r o x i m a t e l y L 1 , a n d t h e c a u d ae q u i n a o c c u p i e s t h e l u m b a r c a n a l b e l o w t h a t l e v e l . S t e n o s i so f t h e l u m b a r s p in e m o s t c o m m o n l y a f f e ct s t he m i d d l e - a g e da n d e l d e r l y p o p u l a t io n s .1 3 " I n t y p i c a l f o r m s o f d e g e n e r a t i v es t e n o s i s , t h e d i s k i s n o t i n v o l v e d i n n e u r a l c o m p r e s s i o n . '4B e c a u s e p r e f e r r e d m e d i c a l t r e a t m e n t f o r t h e s y m p t o m a t i cl u m b a r s t e n o s i s i s u s u a l l y s u r g i c a l d e c o m p r e s s i o n , D r C o x ' st e c h n i q u e m i g h t o f f e r a n i m p o r t a n t a l t e r n a t iv e i n s u c h c a s e sb u t n o t i f a n y a n t e r o s p o n d y l o l i s t h e s i s i s p r e s e n t . H o w e v e r ,a n o t h e r i m p o r t a n t c o n s e r v a t i v e a l t e r n a ti v e w h e n t h e s t e n o s isi s c a u s e d b y d i s k b u l g e o r r u p t u r e i s a l u m b a r t o r s i o n m a n i p -u l a ti o n . L u m b a r t o r s io n m a n i p u l a t io n s h a v e b e e n s h o w n t oi m m e d i a t e l y r e d u c e p a i n f u l d i s k l e s i o n s i n 5 0 % t o 8 0 % o fpa t ien t s wi th rup tu red d i sks .~4" la The requ i red equ ipment fo rl u m b a r t o r s i o n m a n i p u l a t i o n ( l o w b a c k b e n c h ) i s v e r y c o s te f f e c t i v e c o m p a r e d w i t h a f l e x i o n - d i st r a c t i o n t a b le .

F l e x i o n , s p e c i f i c a l l y p r o l o n g e d f l e x i o n , i s b a d f o r t h es p i n e , e s p e c i a l ly i n p a t h o l o g i c c o n d i t i o n s . I n d e e d , D r C o xh a s i g n o r e d 4 0 y e a r s o f t e x ts b y A l f B r e i g , 19"2~ B r e i g ' s I n d e xM e d i c u s a r t i c l e s , 2 2" 3 a n d l i t e r a t u r e t h a t s u p p o r t s B r e i g ' sf i n d i n g s . 3 j- 47 A l s o , w e n o t e t h a t e x t e n s i o n m o v e m e n t s h a v eb e e n s h o w n t o c e n t r al i z e p a in i n t h e M c K e n z i e m e t h o d s p r o -t o c o l s . 4 s'6 1 T h e f u n d a m e n t a l f l a w i n a v o i d i n g e x t e n s i o nb e c a u s e o f th e m i n u t e c h a n g e s i n s p i n a l c a n a l d i a m e t e r i ne x t e n s i o n ( u s u a l l y 1 - 2 m m ) w a s r e c e n t l y d i s c u s s e d b yD v o r a k . 62 H e n o t e d t h a t f l e x i o n i n c r e a s e s a n d e x t e n s i o nr e d u c e s p a i n i n m o s t s u b j e c t s . D r C o x c i t e s h y p e r e x t e n s i o na r ti c le s f o r b a d e f f e c t s , w h e n " s l i g h t " e x t e n s i o n m e a n s l o r -d o s i s a n d i s t h e p r e f e r r e d p o s i t i o n o f t h e l u m b a r s p i n e .

M o s t s t ud i e s o n c a n a l d i a m e t e r c h a n g e s d u r i n g f l e x io n ,e x t e n s i o n n e g l e c t t h e f a c t t h a t o n l y e x t e n s i o n r e l a x e s t h e

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