effect posture lumbar spine

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62 6 M . A . ADAMS , W . C . HU TTON

TH E JOURNA L O F BONE AND JO INT SURGER Y

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T he e ffec t o f p os tu re o n th e loa d in g o f the ap op hy s ea l jo in ts . In th ee rec t po s tu re th e a r tic u la r s u r fac es re s is t the in te rv e rte b ra l s he a r fo rc e(S ) a nd a p rop o r tion o fth e in te rv e rteb ra l c om pre s s iv e fo rc e (C ). E x tra -a rtic u la r im p in gem en t c an a ls o o c c u r (a s s hown b y th e s ta r). In th efle x e d p os tu re the a rtic u la r s u rfa c e s re s is t the sh ea r fo rc e bu t p lay no

pa rt in res is tin g the com p re s s iv e fo rc e .

In th e erec t postu re , the apo phy seal jo in ts res is tm o st o f the sh ea r fo rce ac ting on the sp ine (H u tto n , S to ttand C y ro n 1977) as w e ll a s abou t 1 6% o f the com pres-sive fo rce (A dam s and H utton 1 980 ). Th e resu lting stre ssbe tw een th e a rticu lar su rfaces is co ncen tra ted in thelow er m arg in s o fthe jo in t (D un lop , A d am s and H utton1984) a s sh ow n in F ig u re 2 . If th e d is c is unu sua lly na r-row and degene rate , then th e face ts m ay com e in to c loseappo sition and m ay then re sis t up to 7 0% of the com -pre ssive fo rce on the sp ine (A d am s and H utto n 1980).M uch of th is abno rm ally h ig h res is tan ce is du e to ex tra-a rticu la r im p ingem en t o f the facet tip s on the ad jacen tlam ina or p ed icle (D un lo p , A dam s and H u tton 1984). Insuch cases, th e ap ophysea l jo in ts show gross os teo arthn i-tic changes (A d am s and H u tton 1980).

In the flexed pos tu re , the apo phy sealjo in ts re sis t theshea r fo rce bu t now play n o p art in re sis tin g the in te rv er-teb ra l com pressive fo rce (A d am s and H u tton 1980 ). Th estre ss b e tw een th e an ticu la r su rfaces is low er than in th ee rec t po stu re and is concen tra ted in th e m idd ie anduppe r p a rts o f the jo in t (D un lop , A dam s and H u tton1984) a s show n in F igu re 2 . In the flexed p ostu re the re isno ex tra -ar ticu la r im p in gem en t.P ostu re and th e load ing of th e in terv ertebra l d isc . T hein te rv erteb ral d isc s and v erteb ra l bo d ie s com pris e th em a in w e igh t-bea rin g co lum n of the lum bar sp in e. P o s-tu re a ffec ts the w ay th is co lum n res is ts th e load s ap p liedto it, b u t has little e ffec t on the m agn itu de of th ese lo ad s(see be low : postu re an d m uscle ac tiv ity ) .

U nde r load , an unw edged d isc ten ds to behave as ahyd ro static bo dy exe rtin g a un ifo rm com press ive stre sson the v erteb ra l en d -p la tes (H orst an d B rin ckm ann1 98 1 ). By w edg ing a d isc w e com plicate th is sligh tly :y oung non -d eg en era te d iscs rem ain h ydrosta tic , bu tm atu re and degene ra te d isc s susta in p res su re g rad ien ts .T h is m ean s tha t w hen a m a tu re d isc is w edged in th e

e rec t po stu re. the h ighest com p ressiv e s tre sse s are trans -m itted th roug h the po ste rio r ann u lus and th e low estth ro ugh the an te rio r annu lus (H o rst an d B n inckm ann1981 ). S im ilar ly . in f lex ed p ostu re s the h ighest com p res-sive stresses a re transm itted th roug h the an te r io r annu lusan d the low est th roug h th e pos te r io r an nu lu s.

In a ll bu t the m os t d egene ra te d isc s , the n uc leu s pu l-p osu s ex h ib its hy dro sta tic p re ssu re , the m agn itu de ofw h ich is depen den t on d isc w edg in g (N ach em son 1963).A t low load leve ls (approp ria te in re laxed s ittin g an ds tan d ing p ostu re s) , p re ssu re in the n uc leu s pu lp osu s fo rth e sam e app lied com press ive lo ad is abo u t 50 % h igherin th e flexed p ositio n th an in th e e rec t po sition (cal-cu lated from N ach em son , S ch u ltz an d B erkso n 1979).A n exp lana tion of th is is g iven in the app en d ix .

The e ffec ts o f postu re o n the m echan ic s o f them atu re in te rve rteb ra l d isc a re illu stra ted in F igu re s 3and 4 .P ostu re and th e nu tr ien t supp ly to th e in terver teb ra l d iscs.The lum bar d isc s are the la rgest avascu la r s truc tu re s inthe body . N u tr ien ts reach the ir ce lls by tw o rou te s: fromth e b loo d v essels in the ve rteb ra l b od ie s and from tissueflu id su rro und ing th e annu lus fib ro sus. T he re a re tw otranspo rt p ro cesse s fo r each rou te -flu id flow and d iffu -s ion -an d bo th o f these a re a ffected by postu re .

Anterior Poster ior

E rect p osture F lexed p os tureF ig .3 F ig .4

Th e e ffec t o fp os tu re on th e m atu re in te rv e rte b ra l d is c . In the e re c tpos tu res (F ig . 3 ) the c om pre s s iv e fo rc e (C ) p rod uc es the h ig he s ts tres s o n the p os te r io r a nnu lu s , w h ile in the fle x e d p os tu re (F ig . 4 )the s tres s is h igh es t o n the a n te rio r an nu lus an d the h yd ros ta tic

p res su re (p ) in th e n uc leu s is in c re ase d .

F lu id flow is cau sed b y p re ssu re chang es o n the d isc .H igh p re ssu re causes f lu id to be expe lled from th e d isc ,w h ile low pressu re ( ly ing dow n , fo r exam p le) allow s thep ro teog lycan s in the d isc to su ck in flu id from surro und -ing tissue . F lexed po stu res in c rea se th is f lu id exchangebecause they cau se m ore flu id to be exp elled from thed is c th an d o e rec t po stu re s (A d am s and H u tton 1983).T he effec t is p a rticu la rly m arked in the nu cleus pu lp osus(F ig . 5) .

D iffus ion occu rs a s a re su lt o f a chem ical con cen tra -tion grad ien t: nu tr ien ts d iffu se in to the d isc , an d w astep rodu cts d iffuse o u t o f it. In erect po stu re s d iffu sionoccurs m o re read ily in to the an te rio r an nu lu s than in tothe poste r io r annu lus (F ig . 5 ), p ro bab ly b ecause the d ische igh t dec rease s from fron t to b ack (A d am s and H utton


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E rec t po stu re

iorf te r ior

a) % Fluid lo ss in 4 h ou rs

1O I I IE 7

b ) D iffu sio n o f so lu te in to d iscF ig . 5

A exed pos tu re

The perc en tag e o f flu id los s (a ) f rom the d is c de pe nd s on th e po s tu re .Th e th ree va lues fo r e ac h d is c re fe r to th e a n te rio r an nu lus , th e nu c le uspu lposus an d the p os te rio r an nu lus . In the e re c t p os tu re s o lu tes c an d if-fus e m o re e as ily in to the an te r io r ha lfo f the d is c tha n in to th e p os te r io rha lf: th is im ba la nc e is rev e rs ed in th e f lex ed po s tu re . The num bers a rep ro po rtio na l to the am oun t o f s o lu te (b ) tha t c an d iffu s e du rin g fou r

hou r s .

1984). F lexed po stu re s reve rse th is and the ove rall ra te o fd iffu sion in to the d isc is inc rea sed . T hese re su lts can beexp la ined by the w ay flexed po stu re de fo rm s the annu lus(A dam s and H u tton 1984).Po stu re and m usc le ac tiv ity . T runk m usc le a ctiv ity isrequired to stab ilis e the sp ine and preven t it from bu ck -ling (M orris , L ucas and B resle r 19 61); o bv io usly , th eneed fo r s tab ility is g rea test w hen th e sp in e is v ertical andlea st w hen it is ho rizon ta l. T h is exp lain s w hy the activ ityo f the b ack m uscle s is reduced w hen the backre st o f acha ir is m ad e to in clin e m ore (A nd ersso n e t a l. 1975 ).How ever , fo r a g iven back re st ang le , po stu re (a s d efinedby lum bar cu rv atu re ) has o n ly a m inor e ffect o n m usc leactiv ity (A nde rs son e t a l. 1975 ). F igu re 6 illu stra te s h owtru nk m usc le ac tiv ity is d ete rm ined by th e n eed to stab il-ise the sp ine rath er than b y the lum bar cu rv atu re .Po stu re and sp ina l in ju ry . In the p rev iou s sec tion s w ehave con side red ty p ical s tand in g and sittin g p ostu re sw ith fa irly low sta tic loads on th e sp ine . In th is sec tion w e

Low tru nk m usc le ac tiv ity

consider h igh dyn am ic lo ad ing ofth e sp ine and how suchloads can produ ce d ifferen t in ju r ie s in d iffe ren t p ostu re s .

L iftin g h eavy w e igh ts requ ire s h ig h back m u sc leactiv ity and re su lts in a h igh com pres sive fo rce on thesp in e. F o r y oung m en lif ting w ith m ax im um effo rt, th isfo rce can reach 8 000 -9 000 N (H utto n an d A dam s 1982).T he effec t o f such fo rces on th e lum bar sp ine h as beentes ted on cadave ric lum bar m otio n segm en ts (tw oad jacen t ve rteb rae an d the in terven in g d isc an d liga -m en ts) ; th e ou tcom e d ep en ds ve ry m uch on postu re . Ifthe m o tion segm en t is com pressed w ith ou t be ing flexed ,the re m ay be d am ag e to the v erteb ra l bod y o r en d-p la te(Pe rey 1957). If it is w edged in a flex ed pos tu re (F ig . 7 ), itsho u ld no t be dam ag ed a t a ll (H u tto n an d A dam s 1982).H ow eve r , if f lex ion is ex cess ive (h yp erfiex io n ) so tha t theposte r io r in terve rteb ra l ligam en ts are ove rstre tched , thenth e m otio n segm en t is ag ain v u lne rab le; the an te rio rve rteb ra l bo dy m ay b e c ru shed or th ere m ay be su ddenpos ter io r p ro lapse o f th e in te rv e rteb ral d is c (A dam s andH u tton 1 982 ).

F ig . 7The e ffe c t o fpo stu re o n sp ina l in ju ry . In th e ere c t po stu re , th e com p res -s iv e fo rc e o n th e sp ine (C ) c a n ca us e e nd -p la te frac tu re . In th e fle x e dpo s tu re th e s p in e h as a h igh c om pre s s iv e s tre ng th . In h ype rfiex ion Ccan c au se po s te rio r d is c p ro lap se o r d am age to the a n te rio r v e rte b ra l

body .

Activ itie s such as d igg in g or rep ea ted heavy lif tingsub jec t th e lum bar sp in e to fa tigue com pressive load in g .T he e ffect o f su ch load ing h as been investig ated by te st-ing cadave ric m o tion segm en ts to destruc tion an d , ag ain ,the re su lts d ep end on pos tu re . If the m otion segm en t isno t f lex ed , the site o f fa ilu re is in the ve rteb ral b ody andend-p la te (H ard y e t a l. 1958). If it is f lex ed , the lam e llaeo f the ann u lus can becom e d isto r ted and th is som e tim eslead s to rad ia l fissu res in the d isc (A d am s and H u tton1983).

DISCUSS IONE rec t po s tu re

H igh trun k m usc le ac tiv ityF ig . 6

Flexed pos tu re

T ru nk m u sc le ac t iv ity is d e te rm ine d b y th e n ee d to s ta b il is e the s p in era the r th an b y the lum bar c u rv a tu re . In the up pe r f igu res the sp ine iss up po rted a nd the re is low tru nk m u sc le ac tiv ity . w h e re as in th e low erfig u res the sp ine is u ns up po rted a nd the re is h ig h tru nk m us c le a c tiv ity .

T he ad van tages and d isadvan tages o f f lex ing the lum barsp in e a re summ arised in Tab le I. L e t us f irs t con side r th eadvantages.

R educ ing the h igh stre sse s tha t can b e foun d on th etip s of th e face t jo in ts m ay w ell b e s ign ificant. In a br-do tic pos tu re , the stre ss be tw een the face t su rfaces canexceed the peak leve ls foun d in the a rticu la r ca rtilage o fthe h ip an d kn ee (D un lop , A dam s and H utton 1984) andm ay b e re spo nsib le fo r the ve ry h igh in cid ence ofosteo arth r itis in th ese jo in ts (L ew in 1 964 ; A dam s and


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Table I. F le xe d p os tu re

.4dvaniugtsR educe d s tres se s a t th e ap oph y s ea l jo in tsR ed uce d com pres s iv e s tres s Of l the po s te rio r an nu lusIm p rov ed tran sp o rt o f d is c m e tab o li tesHigh com p re s s iv e s tren g th o fthe sp ineDl . 1 (IV ( l?11U, g t SIn c re as ed com p res s iv e s tre s s on th e an te rio r a nn u lu sIn c re as ed hyd ro s ta tic p re s s u re in th e nuc leu s a t low loa d lev e ls

M f

T fl a ) c)

mM f

b ) Erec t postu re cO fle xed pos tu reF ig . 8

N on -lin ea r e la s tic b eh av iou r o f the d is c , il lus tra ting th e e ffec ts o fbe nd ing (M ) a nd o fc om p res s iv e fo rc e (C ).

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TH E JOURN A L O F BON E AND JO IN T SURGERY

H utton 1 980 ). A lso , th e poss ib le ex tra -a rticu la rim p ing em en t b etw een th e face t tip and the ad jacen tlam in a or ped ic le in a lo rd o tic po stu re cou ld be a sou rceo fb ow back pa in , especia lly if the jo in t capsu le is trap pedb etw een the bony su rfaces.

S im ila r ly . reduc in g the com p ressiv e s tre ss o n thep oste rio r ann u lus m ay be of clin ica l s ign if ican ce, s inceth is stress causes o u tw ard b u lg in g of the po ster io r annu -bu s in to the sp ina l can al and in terve rteb ra l fo ram in a(B row n . H an sen and Y o rra 1957). In m any peop le , th ism ay lead to com p ression of the dural sac and cause p ain(P enn ing and W ilm ink 1981 ). T he re is also ev id en ce froman im a l ex pe rim en ts tha t h igh com pressive load in g of thepos te r io r ann u lus can even tua lly lead to degene ra tivechang es in th is pa rt o f the d isc (L in dbbom 1957).

Im prov in g th e m e tab o lite transp ort in the d isc m u stbe o f rea l v alu e sin ce its o ve ra ll sup p ly o f g lucose hasbeen d esc ribed as ba re ly adequa te (M aroud as c i a l.1975 ) . M oreove r , the pa rt o fth e d isc w ith the m o st c riti-cal su pp ly . the in ne r pos ter io r annubus (N ach em son1976 ), is p rec ise ly the pa rt m ost h elp ed b y a flex ed p os-tu re (A d am s and H u tto n 1984 ). D efic ien t m e tabo litet ranspor t has b een link ed w ith degene ra tive ch an ges inth e d isc (N achem son ci a !. 1 970 ; H o lm and N achem son1982).

A ltho ugh the h igh com p ressive streng th o f a f lexedlum bar sp in e is p ro bab ly im portan t, th e com pressivefo rce in th is area can none the le ss b e redu ced in life byin tra -ab dom ina l p ressu re (B a rte link 1957) . Howev er ,f la tten ing (f lex ing ) the lum bar sp ine g iv es it an ex tra m ar-g in o f sa fe ty , w h ich m ay b e im portan t in ac tiv itie sin vo lv ing repeated bend ing and lif ting . T he inc rea sedcom pressive stren g th o f a f lexed lum bar sp ine m ay beex p la ined by the no n-lin ear e las tic behav iou r o f th e d isc ,as ou tlined in th e ap pend ix .

N eith er o f the d is ad van tages lis ted in T ab le I seem sto be o f m uch sig n if icance . The an te rio r annu lus is theth ick es t and stif fe st pa rt o f th e ann u lus (G alan te 1 967 )an d is ev iden tly w e ll cap ab le o f re sis ting the s tre sse sap p lied to it s ince it is usua lly the la st pa rt o f th e d isc toex h ib it d eg en era tive ch an ges (R itch ie an d F ah rn i 1 970 ).

A s fo r the secon d d isad van tage (inc rea sed hyd ro -sta tic p ressu re in th e nuc leus pu lp osus ), th is m ay seemm o re ser iou s un til it is rea lised tha t th e p re ssu re inc rea sehas been dem onstra ted o n ly at low lo ad leve ls , w h erethe re is n o lik elih ood of m echan ical dam ag e: in sitting o rstand in g p ostu re s, the com press ive fo rce o n the lum bar

sp ine is abo u t 10 00 N , o r le ss th an o ne -ten th o fthe fo rcerequ ired to cau se fa ilu re (H u tton and A dam s 1982).

Th ere is o ne o the r p ossib le ob jec tion to th e flex edpos tu re: becau se flex ion can lead to d isc d am age unde rfa tigue loads (see po stu re and sp ina l in ju ry sec tion ) , itm igh t lead to sim ilar dam ag e w hen the lo ad lev els a relow bu t p e rsis t fo r long pe rio ds o f tim e. G en e ra lly , astru c tu re can su ffe r fa tigu e dam age a t low lo ad leve lsp ro v ided enough load ing cyc le s a re app lied . H ow eve r ,the re is a lw ay s a cu t-o ff v alu e o fb oad , be low w hich nodam age accum u late s no m a tte r how long th at load isapp lied . In the case o f the lum bar d isc s , the cu t-o ffload is p robab ly abov e th at n o rm a lly encoun te red inflexed sittin g po stu res, s ince p eo p le w ho hab itu ally s itw ith th e ir lum bar sp in es flexed h av e les s d isc d isea se(F ahrn i and T ruem an 1965); it thu s seem s un lik e ly thatth e flexed sitting p ostu re cou ld b e d am ag ing to the ird iscs .

In th is p ape r w e h av e investig ated the e ffec ts o f p os-tu re o n a no rm a l. sym p tom -free sp ine : o u r co nc lusio nsdo no t necessa rily ap p ly to the sp in e o f a pe rson w ithb ack pa in . O n b alan ce , h ow ev er , it is m ech an ica lly andnu trit iona lly advan tageou s to fla tten th e lum bar sp in ew hen s itting and w hen lif ting h eavy w e igh ts .

A P PEND IXNon -lin ear ela stic behaviou r of th e d isc . In order toexp lain w hy w edg ing a d isc in flex io n in crease s the p re s-su re in the n uc leu s pu lp osus , and w hy a flexed sp ine has ah ig h com press ive streng th . a s im p le m ode l o f th e d isc isp resen ted .

F ig u re 8 sh ow s a d is c a s th ree pa ra lle l sp ring s rep re-sen ting resp ec tive ly th e an ter ior annu lu s, th e nucleu spu lp osu s an d the po ster io r ann u lus. T hese sp rin gs a renon -lin ea r, tha t is , th ey b ecom e stiffer th e m ore th eyare com pressed or stretched . In the fig u re , th e w id th o feach sp rin g is d raw n in p ro portion to the fo rce actin gon it.


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F igure 8 a sh ow s th e d isc un de r n o ex terna l fo rcesn or w ith an y bend ing m om en t actin g on it. In F igu re 8bth e d is c is sub jec ted to a com pressive fo rce (C ) b u t w ithn o bend in g m om en t (a s in the e rec t postu re ) . In F ig u re8c the d isc is su b jected to a bend ing m om en t (M ) bu t n ocom p ressiv e fo rce : h ere the cen tre o f ro ta tion lie s in theposte r io r ha lf o f the d isc (R o lande r 196 6) so tha t theb en d ing m om en t is res is ted by th e an te rio r ann u lus andth e nuc leus in com pres sion and by th e p oste rio r annu lusin ten sion . In F igu re 8d , the bend ing m om en t andcom p ressiv e fo rce a re com b ined , a s in a flexed postu re .C om paring 8d w ith 8b w e see tha t p re ssu re in the nu cleusp u lpo sus is h igh er in flexed p ostu re s.

The abov e on ly app lie s to low va lues o f C , app li-

cab le to stand in g and sitting pos tu re s. A t h igh va lues o fC , app licab le to lift in g , th e non-linear ity o f th e sp rin gsbecom es im portan t and w e can now exp lain th e h ighcom press ive stren g th o f a f lexed sp in e (see F ig . 8d ). T hean te r io r ann u lus sp rin g is co nsid erab ly sh orten ed an d ,because o f non -linea rity , w ill be stif fe r th an the n uc learsp ring . If com pressive fo rce (C ) is in creased to h ighleve ls , the ad d ition al load w ill be bo rn e prim arily by thean te r io r ann u lus , to th e advan tage o fthe nuc leus. B y th ism echan ism the pressu re in th e nu c leu s is p reven ted fromris ing to lev e ls tha t w ou ld fractu re the w eak cen tra l po r-tion o f th e en d-p la te. W hen h ig h lo ad s a re app lied in thee rec t p ostu re (b ) , th is m echan ism does n o t occu r and thesp ine is m an ife stly w eake r .

REFERENCESAdam s MA , H u tton W C . The e ffec t o f p os tu re on the ro le o f the

a po ph y s ia l jo in ts in res is tin g in te rv e rteb ra l c om p re s s iv e fo rc e s .J B o ne J o in t S u rg [B r] 1 980 :6 2 B : 3 58 6 2 .

Adam s MA , Hu tto n W C . T he re lev an ce o f to rs ion to th e m e ch an ic ald er an ge me nt o ft he lu mb ar sp in e. Spine 1981:6:241-8.

Adam s M A , H u tton W C . P ro la ps ed in te rv e rte b ra l d is c : a hyp e r flex ioninjury. Spine 1982 :7 : I84 91.

Adam s M A , Hu tto n W C . T he e ffe c t o f po stu re on the flu id con te n t o flum bar in te rv e rte b ra l d is c s . Sp ine 1 983 :8 :66 5 71 .

Adam s M A , Hu tto n W C . Th e e ffe c t o f fa tig ue o n the lum bar in te rv e rte -b ra l d is c . J B on e Jo in t S u rg [B r] 19 83:65 -B : 1 99 -20 3.

Ad am s M A , Hu tto n W C . T he e ffe c t o f po s tu re o n d iffus ion in to lum barin te rve rteb ra l d isc s. On /to p Trans 19 84 :8 :415 6 .

Adam s MA , H u tton W C , S to tt JRR . Th e re s is tan ce to fle x io n o f thelum bar in te rv e r teb ra l jo in t. Sp ine I 9 80 :5 : 245 -5 3.

Ande r s son BJ, O rten g re n R , N a ch em son A L , E lfs trom G , B rom an H .T he s ittin g po s tu re : an e lec trom y og rap h ic a nd d is c om etric s tu dy .O rtliop C li ii N o rth A m l 97 S: 6 ( I ): 1 0 5- 20 .

Ande rs s on C BJ , M urp hy RW , O rte ng ren R , N a chem son A L . T hein flu enc e o f b ac k re s t in c lina t ion an d lum bar s u pp o rt on lum barl o rdos is . Spine 1979 :4 :S2 - - 8 .

B ar te l ink D L . T he ro le o fa bd om ina l p res su re in re l iev ing the p res su reo n th e lu mb ar in te rv erte bra ld is cs . J BoneJo in t S urg [B r] 1957:39 -B:718 25.

B row n T , H ansen R J , Yo rra A J . S om e m ec ha n ic a l tes ts on the lum bo -sac ra l sp ine w ith pa rtic u la r re fe re nce to the in te rv e rte b ra l d is c s : apre lim ina ry repo rt. J B on e Jo in t S u rg [A n t] I 957 :39 -A : 1 1 3 5 64 .

Dun lop RB . Ad am s MA , Hu tto n W C . D isc sp ac e n arrow ing and th elu m ba r fa ce tjo in ts . J B on eJ oi n t S urg [B r ] l 984 :6&-B :706 - - lO .

Fahrn i W H, T ru em an G E . C om pa ra tive ra d io lo g ic a l s tud y o fthe sp ineso f a p rim itiv e po pu la tio n w ith N or th Am eric an s an d N or the rnEuropeans . J BoneJo in t Sur g [Br ] 196S:47 - -B :S52 - - 5 .

Far fan HF , H ub erd eau RM , Dubow H I. Lum bar in te rve rte b ra l d is cdegenera t ion . J B o ne Jo in t S u rg [A m ] I 972 :54 -A :492 - 5 l0 .

G alan te JO . Tens ile p ro pe r tie s o f the h um an lum bar an nu lus fib ros us ..4 ( t ( I O r tho p Seand 19 67 :Su pp l 10 0 .

H ard y WG , L is sn er HR , W ebster JE , G urd jia n ES . R ep ea te d l oad ingtes ts o f th e lum bar s p ine : a p re lim ina ry rep o rt. S u rg F oru m 1 9 5 8 :9:6 90 S.

Ho lm S , N achem son A . N utr itio na l c h ang es in the ca n in e in te rv e rteb ra ld is c a fte r s p in a l fus ion . C /in O rt/ io p 1 98 2 : 1 69 :24 3 58 .

Ho rs t S , B rinc km ann P . Meas urem en t o f the d is tribu t ion o f ax ia l s tre s son the en d -p la te o fthe ve r teb ra l b od y . Sp ine 1981 :6 :21 7 32 .

Hu tto n W C , A dam s MA . Can th e lum bar s p ine b e c rus he d in he av y li ft-ing? Spine 1 98 2: 7: 58 6- 9 0.

Hu tto n W C , S to tt JR R , C y ro n BM . Is spo nd y lo ly s is a fa tig ue fra ctu re ?Spiize 1977:2:2 02 9.

L ew in T . O s te oa rth r itis in lum bar s yn ov ia l jo in ts : a m orp ho log ic a ls tudy . A c ta O rtho p S can d 19 64 :S upp l 7 3 .

L in db lom K . In te rv e r teb ra l-d is c d eg en e ra tio n c on s id e re d as a p res su rea t r ophy . J B o ne J o in t S u rg [A n :] 19 57 :39 A :9 33 --4 5.

Ma ro ud as A , S to ckw e ll RA , N ach em son A , U rban J . Fa cto rs inv olv edin th e n u tritio n o f th e hum an lum ba r in te rv e rteb ra l d is c : c e llu la r -i ty an d d if fus ion o fg lu c o se in v itro . J . A na t 1975 :120 :113 - 30 .

Mo rr is JM , Lu ca s D B , B res le r B . R o le o f the trun k in s ta b il ity o f th esp ine . J B on e Jo in t S urg [Am ] I 961 :4 3 A : 32 7 -S I.

N a c h ems on AL . T he in flu en ce o f s p in a l m ov em en ts o n th e lum barin trad is c a l p re s s u re an d on the ten s ile s tre s se s in th e a nn u lu s fib ro -sus. A e ta O rtho p S tan d 19 63 :33 : 1 83 20 7 .

Nach em son A , L ew in T , M aro ud as A , F reem an M AR . In v it ro d iffus ionof dy e th rou gh th e en d -p la tes a nd the an nu lus fIb ros us o f h um anin te r-v e rteb ra l d is c s . A e ta O rtho p S ean d 1970 :41 :S89 - 607 .

N a c h ems on AL . The lum bar sp in e : an o rth op aed ic cha lle ng e . Sp ine1976 :1 :S9 - 71 .

Nach em son AL , Schu ltz A B , B e rk son M H . M ec han ic a l p rop e r ties o fh um an lum ba r s p ine m o tio n s egm en ts : in flu en ces o fag e , s ex , d is cle ve l a nd d eg en era tio n. Spine 197 9 :4 : 1 - 8 .

P ea rc y M . Po rte k 1 , Sh ep he rd J . T h re e -d im en s ion a l X -ra y an a ly s is o fn o rm a l m ov em en t in th e lum ba r s p ine . Sp ine 1984:9:294 7.

P enn ing L , W ilm ink JT . B iom ech an ic s o f lum bos ac ra l d u ra l s a c : as tu dy o f flex ion -e x te ns ion m ye log rap hy . Sp ine 1 98 1 :6 : 3 98 -4 08 .

P erey 0 . F rac tu re o f th e ve rte b ra l e ndp la te in the lum bar s p in e : a ne xp e rim en ta l b iom e ch an ic a l inv es t iga tio n . .4c ta O rt liop S c an d1 95 7 : S upp l 2 5 .

R itch ie JH , Fah rn i W H . E xp erim en ta l s u rg ery : ag e chang es in lum ba rin te rv e rte b ra l d is c s . C a n J S urg I 9 70 : 13 :6 7 1.

R o lan de r SD . M o tio n o f the lum ba r sp in e w ith spec ia l re fe re nce to th es ta b iliz ing e ffe c t o f p os te rio r fu s io n : an e xp e rim en ta l s tu dy ona uto ps y s pe cim en s. A cta O rth op S ca nd l9 66 :S upp l 90 .

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