Boden 1990 Abnormal Magnetic-resonance Scans of the Lumbar Spine in Asymptomatic Subjects

8/3/2019 Boden 1990 Abnormal Magnetic-resonance Scans of the Lumbar Spine in Asymptomatic Subjects

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C op yrigh t 990 by Th e Journal of B one an d J oi nt S ur ge ry . I nc or po ra te d

VOL . 72 -A , NO . 3 . MARCH 1990 40 3

Abnorm a l M agnetic-R esonan ce S can s o f th eL um bar Sp in e in A sym p tom a tic Sub jec ts

A PRO SPECTIVE IN VEST IGA TION *BY SCO TT D . BOD EN , M .D .t, D AV ID 0 . DAV IS , M .D .t , TH OM AS S . D INA , M .D .t ,

N ICHOLA S J. PA TRONA S, M .D 4 , AND SAM W . W IESEL , M .D . W ASH ING TON , D .C .F ro m the D epa rtm en ts o f O r tho pae d ic S urg ery and R a d io log y , G e org e W ash ing ton U n ive rsity M e d ic a l C e n te r, W a sh in g to n

ABSTRACT : W e per form ed m agn etic reson an ce im -ag ing on six ty -seven in d iv idua ls w ho h ad never h ad low -ba ck pa in , scia tica , or neurog en ic claud ica tion . T hescan s w ere in terp re ted independen tly b y three n eu ro -rad io lo g ists w ho had no know ledg e ab ou t th e presenceor ab sence of c lin ica l sym ptom s in th e sub jec ts . A bou ton e-th ird of th e sub jec ts w ere found to have a sub stan tia lab norm ality . O f tho se w ho w ere less than six ty y ea rso ld , 2 0 per cen t had a h ern ia ted nuc leu s pu lpo su s andon e h ad sp ina l steno sis . In the g roup tha t w as s ix ty y ea rso ld or o ld er, th e fin d ing s w ere abnorm al on ab ou t 57per cen t o f th e scan s: 3 6 p er cen t of th e sub jects h ad ahe rn iated nuc leus pu lposus and 21 pe r cen t h ad sp ina lsten osis . T h ere w as d eg en eration or bu lg in g of a d isc a ta t lea st one lum bar leve l in 3 5 p er cen t of th e sub jec tsbe tw een tw en ty and th irty -n ine y ea rs o ld and in all bu tone of th e s ix ty to e igh ty -y ea r -o ld sub jec ts. In v iew o fth ese fin d ing s in asym ptom a tic su b jects , w e conc lud edthat ab norm a litie s on m agn etic resonan ce im ages m ustbe str ic tly correla ted w ith ag e and any c lin ica l s ign s andsym p tom s be fore opera tive treatm en t is con tem p la ted .

M agne tic re son ance im ag ing is be ing used in creas ing lyfo r the d iag no sis o f co nd ition s causin g acu te h ow -b ack p ainand scia tica . S om e inv es tiga to rs h av e p ro posed tha t m ag -ne tic re son an ce im ag ing shou ld rep lace , ra the r than sup-p lem en t, m ye log raph y2 . S ev era l h ave rep orted tha t th esensitiv ity o f m agne tic re son an ce im ag in g fo r th e d iagn osiso f h e rn ia ted nu c leu s p u lpo sus an d sp in al steno sis is equ iv -a len t to o r be tter than th at o f com pu te rized tom og raph y ,even w hen com pu ter ized tom ograp hy is com bined w ith m y -e log raph y or d iscography258 . M agne tic reso nance im ag ingis sensitiv e en ough to de tec t a pa rtia l o r com ple te tea r o fth e anu lu s fib ro sus tha t is und etec tab le w ith o th e r non -in -vasiv e im ag ing m od alitie s4 .

* N o bene fits in any fo rm hav e b een rec eiv ed o r w ill b e re ceived f roma comm ercial p arty rela te d d irec tly o r in d ire ctly to the sub jec t o fth is ar tic le .N o fund s w ere re ceived in sup por t o f th is s tud y .

t G eorg e W ash ing ton U niv ersi ty M edic al C ente r, 215 0 P enn sy lvan iaA venue, NW . , W ashing ton , D .C . 20037 . P lease add res s reque sts fo rre prin ts to D r. B oden , D ep artm ent of O rtho paed ic S urg ery .1 : Depa r tment of R ad io logy , C lin ic al C enter, N ation al In sti tu te s ofH ealth , B eth esda, M a ry land . D ep artm en t o f O r tho paed ic S urg ery , G eorg etow n University M cd-ica l C enter , W ash ing ton , D .C . 20 007 .

D esp ite the h ig h sen sitiv ity o f m agne tic re son an ce im -ag ing , the re is still a q uestion abou t w he the r th e m od alityis accep tab ly sp ec if ic , e sp ec ia lly w h en it revea ls abn orm a lfind ings in the absence o f c lin ical s ign s and sym ptom s9 .Sp ecif ic ity is o rd in arily d e fined by p ercen tag es o f fa lse -pos itive and false -nega tive re su lts , and it is d ete rm ined m o sto ften in sym p tom a tic p a tien ts . H ow ev e r, a consid erab lenum ber o f ab norm a litie s are fo und on the m agne tic re so -nance im ag es o f a sym ptom a tic sub jec ts . A n abnorm a l find -in g on m agne tic re so nance im ag ing in an asym ptom aticsub jec t is no t necessa r ily a fa lse -positiv e re su lt, s in ce su cha lesio n cann o t be co rre la ted w ith an ana tom ica l le sio n insub jec ts w ho a re n o t op era ted on . T hu s, in th is rep o rt o nasym ptom a tic sub jec ts , w e u se the term m agne tic -re son an cepos itive to a llow in fe rence ab ou t th e sp ecif ic ity o f the fin d -in gs and to a llow ca lcu la tion of the p rev alence o f abn orm a lf ind ings.

Th ree stu d ie s have d em on stra ted h igh inc idences (24to 37 pe r cen t) o f abn orm a l f ind ings o n d iscogram s, m ye-lo g rams , and com pute rized tom og raph y scans o f a sym p-tom a tic su b jects3 4 3 . T o our kn ow led ge , ana lo gou s da tahave no t been g en era ted fo r m agne tic re son ance im ag ing .The pu rp ose o f th is inv estig a tio n w as to d ete rm ine th e p rey -alence o f positiv e f ind in gs on m agne tic re sonance im ageso f th e lum bar sp in e in asym ptom atic sub jec ts .

M ater ia ls and M eth odsM agne tic re so nance im ag in g o f the lum bar sp in e w as

pe r fo rmed on six ty -s ev en vo lun tee rs , w ho ranged in ag efrom tw en ty to eig h ty y ears (av e rage , fo rty -tw o y ea rs).T he re w ere th irty m en and th ir ty -seven w om en . The sub jec tsw ere rec ru ited th rou gh ad ve rtis ing in seve ra l gene ra l n ew s-pape rs , and th e re sp ond en ts , a s w e ll a s th eir sp ouses (w henelig ib le ) w ere ch osen to ob tain the co rrec t b alance o f sexand age fo r th ree g roup s (F ig . 1 ) . T h e vo lun tee rs w eresc reened w ith a stan da rd ized q uestionn aire , an d on ly thosew ho had no h is to ry o f pa in in the b ack , sc ia tica , o r n eu -rogen ic c lau d icatio n w ere inc lud ed in the stu dy . A ny ep i-sod e of no n-rad ia ting low -b ack d iscom fort th at h ad las tedm o re than tw en ty -fo u r h ours o r had necessita ted tim e offfrom w o rk w as grounds fo r ex clu d ing th e can d ida te fromthe stu dy . V o lun tee rs w ere also ex clu ded if th ey had hadsc ia tica (pa in o r sen so ry abno rm alitie s in the bu ttocks o r


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A GE (Y EA RS )FIG. I

D em ographic da ta fo r six ty -seven asym ptom a tic vo lun teers.

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low er lim bs) o r if w alk ing caused pa in o r a senso ry ab nor-m ality in a low er lim b .

O nce the su b jec t w as en te red in the s tudy , m u ltip lana rm agne tic-reso nance im ag in g w as done from the firs t lum barto th e firs t sac ra l v erteb ra w ith a 1 .5 - te sla im ag ing sy stem(S igna , G ene ra l E lec tric , M ilw auk ee , W isconsin ). A sag itta llo ca liz ing se ries w as pe rfo rm ed w ith a repe tition tim e of400 m illisecond s, an echo tim e of tw en ty m illis econ ds, aslice th ickn ess o f f ive m illim ete rs w ith o ne -m illim ete r in -te rva ls , and a th irty -tw o to th ir ty -six -cen tim e ter f ie ld o fv iew . For the sag itta l im ages (tw en ty -fou r-cen tim ete r f ieldo f v iew ), a m ultip le sp in -ech o techn ique w as used , w ith arepe tition tim e of 10 00 m illisecond s, to p ro duce fiv e-m il-h im ete r-th ick slice s a t on e-m illim e te r in terva ls a fte r fou rexc ita tions . Tw o echoes w ere gene ra ted ; th e f irs t had anecho tim e of tw en ty m illisecond s (T l w eig h ted ) and th eseco nd , an echo tim e ofseven ty m illisecond s (T2 w eig h ted ) .F o r ax ia l sequences, w h ich w ere ang led th rou gh th e d iscspace , fou r-m illim e te r- th ick slice s a t one -m illim e te r in te r-va ls w ere acq u ired w ith a repe tition tim e of600 m illisecond sand an echo tim e of tw en ty m illisecond s.

Th e six ty -sev en s tud ie s o f the asym ptom a tic sub jec tsw ere m ix ed ran dom ly w ith th ir ty - th ree scan s th a t had b eenm ade w ith th e sam e scan ne r on p atien ts w ho h ad w ell de -fin ed c lin ical sym ptom s o f e ithe r a he rn ia ted d isc o r sp ina lstenosis . T ho se sym ptom s corre la ted w ith an unequ ivo ca labno rm ality on th e m agne tic re son an ce im age , as p rev io uslyin te rp re ted by neuro rad io log ists w ho w ere no t a sso cia tedw ith the stu dy . Thus, 100 scan s w ere p re sen ted , in randomsequence , to th ree o f us w ho are n euro rad io log is ts (D . 0 .D . , T . S . D . , and N . J. P .) an d w ho had no in fo rm a tionab ou t the p atien ts o r the sub jects . A t th e leve l o f each d isc ,an y im portan t d iagn oses (he rn ia ted n uc leu s p u lpo sus an dsp ina l s ten osis) w ere id en tified , a s w ere f in d in gs o f le ss-

ce rta in im portance (bu lg ing and degene ra tion of a d isc ) . Inadd ition to ra tin g the seve rity o f the abno rm ality , the neu-ro rad io lo g ist ra ted h is cer ta in ty abou t the d iag nos is (d efin ite ,p ro bab le , o r p ossib le) .

S ince p rec ise rad iog raph ic de fin itions o f le sions in th elum bar d iscs rem ain su b ject to va ria tion s be tw een reade rs ,th is s tudy w as design ed to y ield a spec trum o f ind ependen tin te rp re ta tions from th ree expe rt n eu ro rad io log ists . H e r-n ia ted nu cleus p u lpo sus w as co nside red to be an ex tru sion ,m a in ly fo ca l, o f d is c m a ter ia l beyo nd the os seo us co nfineso f th e v e rteb ral bo dy , re su ltin g in d isp lacem en t o f ep id u ra lfa t, ne rv e roo t, o r thecal sac. A bu lg e w as de fin ed as ad iffuse , u su ally no n-foca l p ro trusio n of n on-os seo us m a-ter ia l beyond the no rm al d isc space . Th e basic c rite r ion fo ra d iagno sis o f stenosis o f th e sp in al cana l w as n on-d isco -gen ic lo ss o f s igna l in th e ep idu ra l fat w ith com p ressio n ofneural tissu es w ith in th e cana l. D egene ratio n o f the d isc

TABLE ICORRELAT ION O F AG E W ITH A BNORM AL MAGN ET IC -RE SO NANC E IM AG ES

OF THE LUM BAR SP INE IN S IXTY -SEV EN A SYM PTOM AT IC SUB JECT S

P erc en tage of S ubjects W ho H ad an Abnorm a l F ind ing2 0-3 9 Y rs. O ld 40 -59 Y rs. O ld 60 -80 Y rs. O ld

(N = 35 ) (N = 18 ) (N = 14)A ll a bn orm al

f ind ingsR ead er 1 26 28 57Read e r 2 20 22 64R ead er 3 20 17 50A ve rag e* 22 (7) 22 (3) 57 (7)

H ern ia ted d iscs 2 1 22 36S pinal s ten osis 1 0 21

* F ig ure s in pa ren the ses rep resen t the num ber of sub jects in each ag egro up for w hich th e in terp reta tio ns o f al l th ree read ers w ere in com p leteagreement.


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M agnetic re son an ce im age in te rpreted by th ree n eurorad io log ists as show in g h ern iation o f the d isc be tw een th e fifth lum bar and firs t s acral ve rte bra ein a th irty - th ree-yea r-o ld su b je ct w ho had never h ad low -b ack pa in or sc ia t ica .

w as con side red to be pre sen t w h en th ere w as lo ss o f he igh to f th e d isc space and a dec reased sign a l on T 2-w eig h tedsequences.

A t the leve l o f each d isc , each neuro rad io lo g ist sco redthe find ings o f th e m agne tic re sonance im age q uan tita tive lyan d ob jec tiv e ly an d as ses sed th e im po rtance o f any abnorm a lfin d ing sub jec tiv ely . T he re su lts from each reade r w ere av -e raged , an d the d iagno sis and the seve rity o f the le sion w eretabu la ted acco rd ing to the sub jec ts age . O n ly th e find in gstha t th e in te rp re ters h ad labe led as p ro bab ly o r d efin ite lyab norm a l w ere reco rd ed as ab norm a l f ind in gs. Th e o ve r-a llnum ber o f abn orm a l m agn etic -re son an ce im ag es inc lud edon ly tho se tha t w ere consid ered to d em onstra te v e ry sub -s tan tial abn orm a litie s . F ind ings tha t w ere g rad ed as b ein gle ss im portan t to the d iagn osis w ere tabu lated sepa ra te ly .Th e con sistency of in terp reta tion am ong the n eu ro rad io lo -g ists w as a lso assessed . F in ally , th e pe rcen tage of a sym p-tom a tic sub jec ts w ho h ad abno rm al fin d ing s w as ca lcu lated ,th us estab lish in g the p rev a len ce o f abn orm a l m agne tic -res -o nance im ag es o f the lum bar d isc s o f a sym ptom a tic sub -jects .

Resul tsThe th ree neuro rad io log ists ind ep en den tly in te rp reted

th e m agn etic re son ance im ages as be ing subs tan tially ab -n o rm a l fo r abou t 2 8 pe r cen t (n in eteen ) o f the six ty -sev enasym ptom a tic sub jec ts . H ern ia ted nu cleus pu lposus w as

no ted in abou t 24 pe r cen t (s ix teen sub jec ts) an d stenosiso f the sp in a l can al, in ab ou t 4 pe r cen t (th ree sub jec ts) .T hree m o re sub jec ts h ad ev iden ce of h e rn ia ted nu cleus puh -po sus on th e m agne tic reso nance im ag e, bu t the ave rage o fthe read ing s o f the th ree neuro rad io lo g ists re su lted in a ra tingof le ss th an pro bab le . T here fo re, th e se sub jec ts w ere no tinc lud ed in the g ro up tha t h ad an abno rm al scan .

T he preva len ce o f abn orm a l f ind in gs w as the sam e inthe asym ptom a tic m en and w om en , bu t it v ar ied acco rd ingto the ag es o f th e sub jec ts (T ab le I) . In the tw en ty to th irty -n in e-yea r-o ld and fo rty to fif ty -n ine -year-o ld g rou ps, thep reva lence o f abno rm al scans av eraged abou t 20 p e r cen t(s ev en of th ir ty -fiv e an d fou r o f e ig h teen , re spec tive ly ) . Inthe six ty to eig h ty -yea r-o ld g rou p , how ev er , it ave ragedabou t 57 pe r cen t (e igh t o f fou rteen ). Th e m ost comm onim po rtan t ab norm a litie s in the o ldest g roup w ere he rn ia tednu cleus pu lp osu s (abo u t 36 p er cen t, o r fiv e o f fou rteen )and stenosis (abou t 2 1 pe r cen t, o r th ree o f fou rteen ) ,w he reas a ll bu t on e of the sub jec ts w ho w ere less than s ix tyyea rs o ld and had an abno rm a lity had a h ern ia ted d is c.

F igu re 2 show s a m agn e tic re son an ce im age of a th ir ty -th ree -yea r-o ld sub jec t w ho n ev e r h ad b ack p ain . A ll th reein te rp re ters thou gh t tha t the scan show ed a subs tan tiallyhe rn ia ted d isc b etw een th e fif th lum bar an d firs t sac ra l v er-teb rae . M os t o f the h ern ia ted d isc s w ere be tw een the fou rthan d fif th lum bar o r th e f ifth lum bar and firs t sac ra l leve ls(F ig . 3 ).


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a-zz-J.(I-0U-0wC,4I-zwC-)LUa-

HNP D ISC LEVELFtr ; . 3

D istr ibu tion o f he rn iated nu cleus pu lpo sus (H NP ) as seen on m agneticresonance im ag es of the lum bar sp in e in asym p tom atic ind iv id ua ls.Tw en ty-n ine leve ls in tw enty-o ne volun teers w e re in vo lved .

A t least o ne bu lg ing d isc w as seen in abo u t 54 pe r cen t(n in e teen ) o f th ir ty -fiv e sub jec ts w ho w ere le ss than six tyyea rs o ld an d in 79 pe r cen t (e leven ) o f the fo u rteen sub jec tsw ho w ere six ty yea rs o ld o r o lde r . S im ila rly , at leas t on edegene rated d isc w as no ted in 34 pe r cen t ( tw elv e) o f theth ir ty -five su b jects in th e y oungest g ro up and in a ll bu t on eof the su b jec ts in the o ld es t g rou p (F ig . 4 ). In the su b jectsw ho w ere less th an six ty y ears o ld , th e d egene ra tion in -vo lv ed an ave rage o f tw o leve ls , w he reas in each of thesub jec ts w ho w ere six ty years o ld o r o ld e r, it invo lved anav erage of th ree leve ls . A pp ro x im a te ly h alf o f th e deg en -e ra ted d isc s also b u lged , an d th is p reva len ce d id no t va rywith ag e . In con tra st, the p ropo rtion o f bu lg ing d isc s tha tw ere also d egene ra ted in creased from abou t o ne -th ird in thesub jec ts w ho w ere le ss th an six ty yea rs o ld to abo u t tw o-th ird s in the o ld er g roup .

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In a ll bu t on e o f the th ir ty - th ree sym ptom atic p atien ts ,the find ings on the m agne tic re so nance im age corre latedw ith the o pe ra tive d iagno sis . In the ex cep tio na l p a tien t, w hohad sp ina l sten osis , o ne o f the inv o lved leve ls w as n o tiden tif ied by tw o of the th ree reade rs .

Th e th ree neuro rad io lo g ists ag reed reg ard ing th e p re s-ence o r absence of ab norm a l fin d ing s on the m agn etic re s-on an ce im ag e a t 99 p er cen t o f the 500 d isc lev els (fiv e ineach sub jec t) from bo th the sym ptom atic pa tien ts an d theasym p tom a tic su b jec ts . T h e sub jec tive asse ssm en ts o f theseve rity o f th e f ind ings va ried som ew ha t, bu t o ve r-a ll theth ree reade rs ag reed com ple te ly on th e ex act d iag nos is a t86 p er cen t o f the leve ls , tw o agreed on the d iagn osis a t 98pe r cen t, an d the re w as no con sensu s rega rd ing th e d iagno sisat o n ly 2 pe r cen t o f the leve ls . W ith reg ard to the 335 d iscleve ls o f the asym ptom a tic su b jects a lone , a ll th ree neu-ro rad io hog ists ag reed on th e d iagno sis a t 9 0 p e r cen t o f thelev els , and tw o agreed on the d iag nosis at 99 pe r cen t. W henthe re w as d isag reem en t, it u sua lly d id no t in vo lv e the p re s-ence o r absence of an abnorm a lity bu t rath er th e p rec isesco re o f its seve rity an d im portan ce .

Discus s ionSubstan tia l pe rcen tages o f ind iv idu als w ho neve r h ad

low -back pa in o r scia tica bu t had ab norm a l m ye log ram s (24pe r cen t), com pu te rized tom ography scans (36 pe r cen t), o rd iscog ram s (3 7 p er cen t) have b een reported3 4 3 . In th ep resen t stu dy , abo u t 3 0 pe r cen t o f an asym ptom atic p op-u latio n h ad a m a jo r ab no rm a lity on a m agne tic reso nanceim ag e o f the lum bar sp in e. T he find in g th at an asym p tom a ticin d iv id ua l has m ore th an a o ne -in -fou r chance of hav in g anab norm a l m agn etic -re son an ce im age em ph as ize s the dang ero f p red ica ting a dec ision to o pe ra te o n the basis o f anyd iagno stic te sts in iso la tion , w itho u t c lin ical in fo rm a tion .A d iag nos is tha t is b ased on m agn e tic re son an ce im ag ing ,

U ST ENOS ISD BULGING DISC0 D EGEN DISC

AGE (YEARS )F IG . 4

Inc idence s of hern ia ted nuc leu s p u lp osus (H NP ), sp ina l s teno sis . a bu lg in g disc . a nd a deg ene rated d isc o n th e m agnetic resonance im ag es of six ty -sev en a sym ptom atic ind iv id uals.


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in the ab sen ce of ob jec tive clin ica l find ings , m ay no t be thecau se o f the pa tien ts pa in , an d an a ttem p t a t op era tiveco rrectio n co u ld be th e firs t s tep tow ard d isa ste r.

C om pariso n o f the re su lts o f the p re sen t stu dy w iththose o f investig atio ns o f o the r typ es o f im ag ing in asym p-tom a tic sub jec ts m ust be und ertaken w ith cau tio n . A s w ehave n o ted , m any abno rm a l f ind in gs are age -d ep en den t. T hestudy of d iscogram s by H olt an d th e s tu dy of m yelo g ram sby H its elb erge r and W itten d iffe red from ou r study w ithrega rd to the m ean ag e o f the sub jec ts . In fac t, the resu ltso f the o the r tw o s tud ie s w ere no t an aly zed acco rd ing to ag e.In con tra st, W iesel et a l. s tud ied com pute r ized tom og raph yscan s in an asym ptom atic po pu la tion in w hich the d is tri-bu tio n of age w as com parab le w ith tha t in ou rs . F o r thesub jec ts w ho w ere le ss than fo rty years o ld , th e in cid en ceso f abn orm alitie s w ere sim ila r in th e tw o stud ie s , b u t fo r thesub jec ts w ho w ere fo rty o r o ld er , o u r da ta sugg ested th atm agne tic re so nance im ag ing m ay y ie ld few er p ositiv e fin d -ings th an com pu ter ized tom ograp hy do es (ap prox im ate ly 3 5pe r cen t com pared w ith ap prox im ate ly 50 p er cen t) . M ag-ne tic re sonan ce im ag ing m ay be even m o re sup erio r th anthe stud ies sugg ested b ecause the com pute rized tom og raph yw as d one at th e fou rth and fif th lum bar and the fif th lum baran d firs t sac ra l leve ls on ly , w h ile th e m agne tic re son an ceim ages dem onstrated he rn iated d isc s a t th e th ird and fou rthlum bar leve ls a s w e ll. In fact, 13 p er cen t (fou r) o f a lltw en ty -n ine he rn iated d isc s in ou r a sym p tom a tic sub jectsw ere a t the se lev els .

A s w ith com pu ter ized tom og raph y , su b jects w ho w eresix ty yea rs o ld o r o lde r w ere fou nd to have a far h ighe rpe rcen tage o f abno rm al m agn e tic-re so nance scan s than d idthose w ho w ere young er th an six ty . Th us, an abn orm a lm agne tic -re sonance im ag e in a younge r pa tien t is m orelike ly to be a tru e ind ica tion of th e cause o f th e com pla in ts .Fo r ind iv idua ls w ho a re six ty yea rs o ld o r o ld er , it is lesslike ly tha t the le sio ns dem on stra ted by m agne tic resonanceim ag ing a re o f c lin ical im portance .

Th e in te rp reta tion s o f the th ree neuro rad ioho g ists in ourstudy va ried su bstan tia lly le ss than those o fthe investig ato rso f the com pu ter ized tom ograp hy scan s3 . In our study , theneuro rad io log is ts ag reed com p lete ly abou t 60 pe r cen t o fthe scans, w he reas the in vestiga to rs d id so abou t on ly 1 1pe r cen t o f the com pute rized tom ograp hy scan s. A s no tedea rlier , the d isag reem en ts in ou r study m a in ly con cernedthe seve rity o f the fin d ing s. A cco rd in g ly , o ne m igh t in fe rtha t m agne tic re son an ce im ag ing is b ette r than com pute rizedtom ograp hy fo r a sse ssing the s ize an d im portan ce o f le sio nsan d of neura l com p ressio n . H ow eve r, tha t in ference cou ldbe v alid ated on ly if the sam e team of rad io log ists in te rp retedbo th com pu ter ized tom og raph y scan s and m agne tic re so -n an ce im ages fo r the sam e grou p o f pa tien ts .

T he sen sitiv ity o f m agne tic re son an ce im ag ing a lsoen ab led u s to stud y the inc idence and d istr ibu tion o f bu lg ingan d degene ra ted d isc s. In add ition to the su rp ris ing ly h ig hprev alence o f those find ings in asym p tom a tic sub jec ts o f allages ( tw en ty yea rs o ld o r o ld er), the in te rre latio nsh ip s o fthe tw o fin d ing s d iffe red from w ha t h ad been exp ec ted .

A lth ough m any au tho rs have con side red b u lg in g o f a d iscto be cau sed by degen era tion5 6 , in o ur asym ptom a tic sub -jec ts on ly h alf o f the deg en era ted d isc s bu lged , and on lyha lf o f th e b u lg in g d isc s w ere a lso d eg en era ted . In add ition ,in th e o lde r sub jec ts , the p reva lence o f degene ra tion w asm ore inc rea sed than tha t o f bu lg ing . Th ese re la tion sh ipsm ay sugg est tha t fac to rs o the r than d eg ene ra tion resu lt inbu lg ing , o r pos sib ly tha t th e T 2-w eig h ted m agne tic -reso -nance -im ag in g seq uences do no t d e tec t all le sio ns th at a reind ica tive o f degene ra ted d isc s5 .

In ana lyz in g the re liab ility o f d ata h ike ou rs , it is im -portan t to cons ide r the se lec tion o f sub jec ts a s re lated to th edesign of the stu dy . F or the asym p tom a tic sub jects in th isstudy , the d istr ibu tio n of ag e an d sex (F ig . 1 ) w as sim ilarto the typ ical sp ec trum fo r p atien ts w ho have h ow -b ackpa in 0 . O ur th ree g ro ups con tain ed ap prox im ate ly eq ua lnum bers o f m en and w om en (by design ) and m o st sub jec tsw ere le ss than six ty y ears o ld . In add itio n , in ou r stu dy , th ed istr ibu tion o f th e lev els o f the h ern ia ted d isc s w as s im ila rto tha t in a la rg e stud y of pa tien ts w ho w ere treated fo rhe rn iatio n of a lum bar d isc .

A no the r im portan t aspect o f ou r selec tion o f sub jec tsw as the exc lusio n o f tho se w ho had an y h is to ry o f backpa in , s cia tica, o r neu rog en ic claud icatio n . It is p ossib le,e spec ially w ith o lde r pa tien ts , th a t an ep isod e of pa in in th eback m igh t be fo rgo tten , bu t w e tr ied to m in im ize th is erro rby us ing a standa rd ized q uestion na ire th at e licited th e nec -e ssa ry in fo rm a tion w ith seve ra l d iffe ren t av enues o f ques-tion in g . S ub jec ts w hose re liab ility w as q uestion ab le o r w hohad prob lem s w ith m em ory w ere ex clu ded from th e stud y .

W e desig ned the p ro spec tive stud y to m ax im ize th ere liab ility o f the neuro rad io lo g ists es tim a tes o f th e abn or-m ah itie s on the m agne tic re sonan ce im ages. T he asym pto -m a tic vo lun tee rs w ere ex am ined w ith a com ple te andstanda rd ized im ag in g pro toco l tha t w as iden tical to th e oneused fo r th e sym ptom a tic pa tien ts . P recau tions w ere takenso th at the scan s o f th e asym p tom a tic sub jects cou ld no t bed istin gu ish ed o n a tech n ica l b as is from those o f the sym p -tom a tic p atien ts . W e rand om ized the sequ ence in w hich th escan s w ere read so tha t the n eu ro rad io log ists in terp re tatio nw ou ld be b lin d and unb ia sed b y know ledge of th e c lin ica ls itua tion . Th e fo rced -cho ice design of the sco re sh ee t ne -cess itated eva lua tion o f each d isc leve l fo r the fou r o b jectiv efin d ing s and w as in tend ed to m in im ize inadv erten t un de r-repo rting of f ind in gs. F in ally , ou r th ree neuro rad io log istsd iffe red in train ing , exp erience, and ty pe o fp rac tice (p riva teo r acad em ic ), so th a t the spectrum of in terp reta tion fo r eachscan w ou ld b e as w ide as pos sib le .

In co nc lusio n , the h ig h inc idence of bu lg ing an d de -gene ra ted lum bar in te rv erteb ral d iscs seen on the m agn eticre son an ce im ages o f asym ptom a tic su b jects con firm s ob-se rva tion s tha t have b een m ad e w ith com pu ter ized tom og-raph y an d m yelo g rap hy stud ie s tha t th ese fin d ing s a re pa r tof a norm a l, o r a t lea st comm on , ag ing proces s. T he fin d ingof an ab norm a l lum bar d isc on a m agne tic re so nance im ageis m os t re liab le in sym ptom atic pa tien ts w ho a re le ss th ansix ty years o ld . It is le ss re liab le in o lde r pa tien ts . In th is


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ThE JO URNA L OF BONE AND JO INT SURGERY

stu dy , th e p reva lence o f abn orm a l m agne tic -resonance im - pe r cen t o f asym p tom a tic sub jec ts em phasizes the dange rsages fo r a sym p tom a tic su b jects w ho w ere les s than fo rty o f p red icatin g a d ec ision to op era te o n the b asis o f d iag nosticy ea rs o ld w as com parab le w ith tha t repo rted b y W iese l e t tes ts - ev en w hen a sta te -o f- the -a r t m oda lity is used -a l. fo r com pute rized tom ograp hy scans. F in ally , the f ind ing w ith ou t p rec ise co rrela tion w ith c lin ica l s ig ns an d sym p-o f su bstan tia l abno rm alitie s o f the lum bar sp ine in abou t 28 tom s .

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Boden 1990 Abnormal Magnetic-resonance Scans of the Lumbar Spine in Asymptomatic Subjects

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Transcript of Boden 1990 Abnormal Magnetic-resonance Scans of the Lumbar Spine in Asymptomatic Subjects