Spine. Mario Crispino and Emanuela Crispino. 2.1 Normal Macroscopic Anatomy Vertebrae

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1 Spine Mrio Crispino nd Emnuel Crispino 2 The functions of the spine re pprently divergent: xil stilistion of the upright position nd moility, indispensle for the movement of the segments. The spine plys crucil role, together with the skull, in the protection of the neurxis nd enles the connection with other orgns through the formin crossed y the nervous roots. We cn therefore logiclly distinguish etween the contining prt nd the content of the spine, the first one consisting of the ones, muscles, nd ligments of the verterl column nd the second one consisting of the spinl cord nd cud equin, nervous roots, meninges, epidurl vessels, nd dipose tissue. 2.1 Norml Mcroscopic Antomy Vertere M. Crispino Dignostic nd Theurpeutic Neurordiology Unit, Deprtment of Rdiology, AO Istituti Ospitlieri di Cremon, Vile Concordi 1, Cremon 26100, Itly e-mil: m.crispino@ospedle.cremon.it E. Crispino Rdiology Unit, Ospedle S. Frncesco di Pol Pol (CS), Itly e-mil: emcrispino@hotmil.com There re 33 vertere, normlly 7 cervicl, 12 thorcic, 5 lumr, 5 scrl, nd 4 coccygel vertere; this sudivision pplies to the 20 % of the popultion only. Normlly the scrl nd the coccygel vertere re merged together. The verter numer my vry etween 32 nd 35, the cervicl portion is generlly more regulr, while the coccygel prt is more vrile. We should consider the verterl column s unique, xil element, with oth sttic nd dynmic chrcteristics. In dults, the column curves towrds the opposite directions: two concve ckwrd curvtures (cervicl nd lumr lordosis) nd two towrds the front (dorsl nd scrl kyphosis) (Fig. 2.1 ). The lumr region is suject to high degree of individul vriility; eyond these vritions, the curves my e considered pthologicl for the excessive strightening or ccentution. In the foetus, we cn oserve single concve curvture of the rchis, towrds the front. After 4 months only, cervicl lordosis ppers, nd the child lerns to hold his or her hed up; lumr lordosis nd scrum tilt tke plce when the child strts trying to chieve the upright nd wlking position, tht is, etween 10 months nd 2 yers of ge. The mechnic djustment of the curvture derives from the need of incresing the resistnce to higher lods, determined y the humn ipedl position nd movement. Bioengineering reserches show tht the physiologicl curves increse y ten times the column resistnce to the verticl compression. The first two cervicl vertere, the tls (C1) nd the epistropheus (C2) re morphologiclly different for their hed-support function nd for their cpcity of llowing the movements of rottion nd ending. The tls hs ring shpe nd its verterl ody is not completely formed. L. Olivetti (ed.), Atls of Imging Antomy, DOI / _2, Springer Interntionl Pulishing Switzerlnd

2 30 Fig. 2.1 The verterl column, AP ( ) nd LL projections ( ). () Cervicl nd lumr lordosis nd dorsl nd scrl kyphosis It consists of n nterior nd posterior rch, connected through lterl mss. The superior rticulr fcets re connected to the corresponding condyles of the occipitl one, t the crnil se, while the inferior fcets rticulte with the superior fcets of the epistropheus. From the superior prt of the epistropheus, the odontoid process develops, lso referred to s the dens epistropheus. It forms synovil joint with the posterior profile of the nterior rch of C1, it is M. Crispino nd E. Crispino supported y resistnt ligment structure, nd it is the fulcrum of rottion for the tls nd the crnium. The occipito-cervicl junction is crdn system, with two perpendiculr nd fixed xes of rottion nd n instntneous xis otined y the vrile comintion of the first two ones. In prticulr, in order to stisfy the needs of coordintion of the oculr-cervicl movements, we cn distinguish superior crdn system, in correspondence of the occipito-cervicl junction, tht enles limited ut precise movements of the hed nd n rticulr cervicl system tht enles more mple, ut less precise, movements for the flexion-extension nd the rottion towrds the sides. Such dynmics re connected to the visul function nd justify the presence of the system of muscles involved in the movement of the crnioverterl junction, overlpping the system of muscles tht enle the stilistion of the cervicl prt of the rchis. The regulr mechnicl stress of the cervicl spine justifies the frequent rthrosis involvement of this re. Except for the first two cervicl vertere, ll the other vertere consist of ody, positioned in the nterior prt, nd of posterior rch, chrcterised y the right nd left pedicle connected to the prs interrticulris. Bone protuernces re locted ove nd elow ech prs interrticulris, forming the superior nd inferior rticulr processes, connected through synovil joint to the relevnt rticulr processes of the djcent verterl odies. The interverterl joints re suject to regulr mechnicl stress tht cuses the frequent morphologicl nd structurl ltertion of the posterior rch, which my e deformed or even interrupted (isthmus), with the consequent possile ventrl slip of the verterl ody (spondylolisthesis). The posterior rch consists of two posterior lmine merging in the spinous process tht completes the ring, forming the spinl cnl. Lterlly, the posterior rches originte from the trnsverse processes tht, long with the spinous processes, llow the insertion of severl scheletric muscles (Fig. 2.2 ). In the cervicl region, we do not find the synovil joints only ut lso nother joint: the uncus or uncinte process, lterl one protuernce developing from the superior surfce of the ody of ech cervicl verter nd

3 2 Spine 31 Fig. 2.2 ( ) CT xil section of dorsl verter. ( ) Tridimensionl CT, olique projection of the lumr rchis. Verterl ody ( B ), pedicles ( P ), lmine ( L ), trnsverse pophysis ( T ), spinous process ( rrowhed ), nd costotrnsverse joint ( rrow ). The str shows the spinl cnl rticulting with depression on the inferior profile of the superior verterl ody, forming the Luschk joint, considered the lterl extension of the interverterl disc. The verterl odies, going from the crnium to the pelvis, need to support hevier nd hevier lods, nd their dimeters increse ccordingly. Not only the dimeters ut lso the shpe of the vertere chnges: the ody of the cervicl vertere is qudrngulr, the thorcic vertere hve n lmost tringulr ody, while the lumr vertere re en-shped. The xil CT nd MRI scnning perfectly demonstrtes the progressive crnio-cudl increse of the trnsversl section of ech verterl ody, due to the need to support the incresing lod nd therefore the need to increse the resistnce of the lumr spine. The spce etween the two verterl odies is occupied y the interverterl disc, whose shpe corresponds to the djoining verterl odies. Also the spinl cnl chnges its shpe: it is tringulr in the cervicl nd lumr regions nd round in the thorcic vertere. In the thorcic trct, the spinl cnl hs smller dimeter, ecuse the spinl cord is thinner in this region, while the dimeter is igger in the inferior cervicl region nd in the lumr one, in correspondence of the so-clled cervicl nd lumr protuernces. Therefore, the trnsverse sections of the spinl cord nd the spinl cnl mtch. The

4 32 M. Crispino nd E. Crispino spinl nerves exit through the neurl formin in ech verterl ody. In the cervicl spine, such formin my e morphologiclly stretched nd form chnnel surrounded y the pedicles of the djcent superior nd inferior vertere: the nterior mrgin consists of the posterior prt of the verterl ody nd the uncinte process; the pophysel msses nd the interpophysel joints form the posterior mrgin. The ventrl nd dorsl roots re locted in the inferior prt of the formen, on the level of the disc, or underneth. Also in the lumr region, the superior nd inferior mrgins of the neurl formen re formed y the pedicles; t this level, the posterior profile of the ove verterl ody nd the posterior mrgin of the elow disc form the nterior mrgin; the interpophysel joint nd smll prt of the yellow ligment form the posterior mrgin. The lumr nerve roots re loclised in the superior prt of the formen, ove the disc Interverterl Discs For the length nd the peculir shpe of the spinl column, the interverterl discs re essentil elements, representing pproximtely 1/4 of the totl length of this prt of the skeleton. The height of the lumr nd thorcic discs diminishes from the ottom to the top. The discs re lso involved in the formtion of the norml curves of the spinl column: in the cervicl nd lumr column, they re higher in the front thn in the ck; in the thorcic trct, they re insted shorter in the front thn in the ck, ut not s much s the verterl odies. The interverterl disc is composed of two prts, structurlly well distinguished ut strictly connected: the nucleus pulposus, centrl geltinous core composed of wter, proteoglycns, nd scttered collgen fires, nd n outer nnulus firosus with collgen content (Fig. 2.3 ). The nucleus pulposus rects to the lod s wter cushion nd distriutes the pressure in uniform wy, in the trnsverse surfce of the verterl ody, putting the firous ring under tension. In rest position, the nucleus is in the centre of the nnulus or slightly oriented towrds the dorsl region, such s in the thorcic nd lumr Fig. 2.3 Antomy of the verterl column, lterl view. Spinous pophysis ( ring ), interverterl disc ( circle ), interverterl formen ( curved rrow ), interspinous ligment ( doule str ), longitudinl nterior ( rrow ) nd posterior ( roken rrow ) ligments, suprspinous ligment ( rched rrow ), ligmentum flvum ( F ), nervous roots ( rrowhed ), nd verterl ody ( str ) regions. When moving, it goes towrds the side of the extension. The discs, up to the second yer of ge, ecome vsculr nd their metolism is exclusively governed y the phenomen of diffusion; in dult sujects, lood vessels pper in pthologicl conditions only. The superior nd inferior disc fcets perforte, without interruptions, the hyline crtilge of the verterl ody end pltes, where the collgen fires of the nnulus firosus re nchored. The relevnt jointure formed etween the verterl odies is termed synchondrosis. The collgen fires of the firous rings run in multiple directions, forming spirls due to the multiple forces. In prticulr, the verticl ones cn minimise the compression nd trction stresses; on the contrry, the olique ones, towrds the sides (from 30 to 45 ) form helicoidl system tht minimises the stresses of rottion nd pullout stresses. The mechnicl

5 2 Spine resistnce of the firous peripherl re of the disc is, in generl, cple of resisting trumtic lesions, nd therefore, in the event of trum, the verterl ody my frcture without dislocting or reking the disc. The interverterl discs control the mplitude of the movements etween verterl odies, while the rticulr processes ffect the movement directions, limiting them, like rils. Protrusions of the crtilge of the interverterl disc through the verterl plte, nd into the djcent verter, my occur, forming discl hernis, ecuse the pltes my get weker with dvncing ge, the so-clled Schmorl s nodes in Scheuermnn s disese (Fig. 2.4 ). During the dy, in upright position, the interverterl discs reduce their volume, nd miniml mount of fluid is in fct squeezed out y the pressure of the ody; lso the rticulr crtilges 33 my fltten fter prolonged pressure. In the evening, therefore, the overll stture of the ody my e round 3 cm shorter thn in the morning. As we get older, the stture vrition during the dy ecome less visile; in older people, the verterl discs re less flexile due to their physiologicl progressive dehydrtion, nd the stture reduction gets permnent. The ltertions of the nnulus firosus pper reltively erlier, etween the 20th nd the 40th yer of ge. When the nucleus pulposus is under pressure, it tends to move nd put pressure on the firous ring, which is lredy wek; protrusion, or herni, my occur nd push the content, generlly the nerve roots, inside the spinl cnl or the junction formin. The interverterl disc is innerved, especilly on the nterior side, nd this justifies the discl origin of specific ck pin. Fig. 2.4 X-ry, ltero-lterl projection ( ) nd detiled view of the middle-inferior dorsl trct ( ): nterior wedge-shped deformtion of the verterl odies nd irregulrity of the verterl pltes, more visile on the trgeted projection, typicl of Scheuermnn s diseses. ( c ) Sgittl T2-weighted imge of the sme ptient, supporting the rdiogrphic evidence nd showing some Schmorl s little nodules in the verterl pltes

6 34 c Fig. 2.4 (continued) Ligments The verterte odies nd the interverterl discs re connected to severl ligment structures. The nterior longitudinl ligment goes from the se of the crnium to the scrum nd dheres to the nterior mrgin of the verterl odies nd discs; the posterior longitudinl ligment goes from C2 to the scrum, well dhering to the verterl pltes nd to the posterior mrgin of the disc ut seprted from the middle posterior portion of the verterl ody y the interior-nterior epidurl venous plexus nd the sl verterl veins. The superior extension of the posterior longitudinl ligment is the tectoril memrne tht goes from C2 to the inferior prt of the clivus. In the elstic system of the verterl disc odies, tension is mintined through the ligments, nd such system is contrsted y the tension on the verterl rches, mintined y the yellow ligments. M. Crispino nd E. Crispino The yellow ligments (ligment flv) re flt; they connect the lmin of the verterl hemirch in crnio-cudl direction; the nme is due to the yellowish colour of the previling elstic fires tht my extend considerly, without lcertion, nd tht relese the energy ccumulted during the trction; such cpcity is reduced with dvncing ge. The ligment flv, which re longer nd more roust in the lumr region nd thinner in the cervicl region, work under strong tension nd tend to stretch the spinl column; they oppose, long with the long dorsl muscles, to the nterior msses of the trunk tht would otherwise end the ody forwrds. The yellow ligments hve sttic function lso for their support to the posterior order of the neurl formin: in fct, their nterolterl order reches the interverterl joint nd dheres to the nterior side of the cpsule; in such wy, the vessels nd nerves crossing the formen len on the smooth surfce of the yellow ligment, rther thn on the rough surfce of the rticulr cpsule. The spinous processes re connected through the suprspinous nd interspinous ligments (Fig. 2.3 ). In the crnio-verterl junction, we find other ligments whose function is to stilise the tlntoxil rticultion nd the crnio-cervicl joint. The nterior tlntooccipitl memrne connects the nterior mrgin of formen mgnum to the nterior rch of C1; the corresponding posterior tlntooccipitl memrne runs from the posterior mrgin of the formen mgnum to the posterior rch of C1. Another importnt ligment is the crucite ligment of tls, consisting of the trnsverse ligment, strong horizontl component etween lterl msses of C1, pssing ehind the dens nd keeping it together with the nterior rch of C1, nd the crnio-cudl component, firous nd running from the trnsverse ligment nd inserted superiorly (long with the tectoril memrne) in the cudl portion of the clivus. The picl ligment connects the pex of the dens to the nterior mrgin of the formen mgnum while the lr ligments run lterlly, from the dens to ech occipitl condyle (Fig. 2.5 ).

7 2 Spine 35 c Fig. 2.5 CT sgittl ( ), coronl ( ), nd xil ( c ) reconstruction, with lgorithm for soft prts, showing the min ligments of occipito-cervicl junction. ( ) The tectoril memrne ( rrowhed ), crnil prt of the posterior longitudinl ligment ( curved rrow ), picl ligment ( rrow ), nd tlntooccipitl memrne ( empty rrow ) Verterl Cnl The cylindricl spce, going from the occipitl formen to the scrum, is the verterl cnl, nd it is, therefore, the first content structure of the verterl column; it hs the form of tue, structurlly irregulr for the lterntion of rigid (vertere) nd elstic (interverterl discs) elements nd for the presence of the lterl formin Cervicl cord ( M ) contined in the hypointense cererospinl fluid of the surchnoid spce ( str ). ( ) The lr ligment ( rrows ), trnsverse ligment ( rched rrow ), tectoril memrne ( rrowhed ), nd odontoid process ( O ). (c ) The trnsverse ligment ( rrowhed ), horizontl prt of the crucite ligment, inserting into the internl tuercles ( neurl formin) (Fig. 2.3 ). The verterl cnl, during the spine movements, is under mechnicl stress; this is the reson why its ntomy is so complex; it is structured for the protection of the nerve structures contined therein. The structure of the verterl cnl chnges ccording to the kinemtics of the rchis; in prticulr, the vritions in flexion-extension determine sensile vritions in the ehviour of

8 36 M. Crispino nd E. Crispino the osteoligmentous wlls: for exmple, during extension, the verterl cnl reduces from 5 to 9 cm, ccording to the different moility, which is not equl in ll the rchis trcts nd tht increses in the cervicl nd lumr regions. The trnsversl section dimensions of ech verterl cnl trct vry on n individul sis nd hve een suject to severl reserches ecuse of their clinicl relevnce. If the chnnel is too nrrow, the dptility of the spinl cord to the cnl one wlls is limited. In verterl cnls smller thn the norml, ny pthologicl issue, especilly of degenertive-rthrosic nture, my determine direct compression of the nerves (in prticulr, in the cervicl-lumr region) or involve the vsculr systems nd therefore indirectly ffect the nerves. The mesurement of the dimeters of the verterl cnl, previously sed on the direct rdiogrphy or tomogrphy, is currently crried out with computed tomogrphy (CT) or mgnetic resonnce imging (MRI). For such purpose, it is importnt to remind tht the pthologicl vritions of the cnl dimeters cn e lmost exclusively performed with sgittl section nd, in dults, dimeters inferior to 11.5 mm should e considered norml. The trnsverse dimeter is lwys wider thn the sgittl one, in ll regions of the spine; the mximum dimeters re locted in the cervicl nd lumr regions Meninges The spinl cord nd its roots re enveloped y the meninges rriving from the crnil cvity. The djcent dur nd rchnoid mter (only virtully seprted) surround the surchnoid spce, whose internl order is determined y the pi mter, strictly dherent to the spinl cord nd the nerve roots (Fig. 2.6 ). In the firous durl sc, very resistnt nd closely dherent the nterior wll of the verterl cnl, the dur mter seprtes the cererospinl fluid which freely circultes into the surchnoid spce (the spce etween the rchnoid nd pi mter) nd the ventriculr system round nd inside the rin nd spinl cord from the epidurl spce, where two components ply n essentil role: the dipose tissue, plugging the spces etween the Fig. 2.6 Antomy of the spinl cord. Dur mter ( str ), dherent to the rchnoid ( circle ). The rrow shows spinl gnglion nd the rrowhed shows the dur mter in section durl sc nd the verterl ones orders, nd the venous plexuses, drining the lood coming from the tissues of the verterl spongios, functioning s n hydrulic cushion for the externl stresses received y the nerve structures Spinl Cord The spinl cord, prolongtion of the rin nd the rinstem, contined in the verterl cnl is component of the centrl nervous system (CNS), more similr, in comprison with other components, to the primitive neurxis; lso when completely developed, it mostly preserves, in fct, the shpe of the emryonic neurl tue.

9 2 Spine Its distl extension my vry ccording to ge. From the functionl point of view, the spinl cord cn e considered s tidy series of overlpping cylindricl segments (myelomeres) responsile for the nervous regultion of n equl mount of corresponding corporl segments. The intersegmentl connections re responsile for the coordintion etween the vrious segments, while the neurl pthwys, scending (sensory pthwys) or descending (motor pthwys) the mrrow, re responsile for the overll integrtion of the orgnism. The spinl cord gurntees the connection of the CNS periphery with the superior levels nd, t the sme time, through the individul medullry centres, the execution of essentil nd complex functions. The spinl cord represents the 2.5 % of the CNS only, ut it governs the motor, sensory, nd vegettive functions of the whole orgnism. A very importnt element, from the clinicl point of view, is the reltion etween verterl segments nd myelomeres. During the intruterine development up to the third month, the verterl column nd the spinl cord hve the sme length ecuse oth of them originte from the metmeric segmenttion of the xil mesolst. At this point, spinl roots emerge horizontlly from the corresponding neurl formin. At lter stge, for the different growth (llometry) of the spinl cord nd the column, the pex of the medullry cone goes up towrds the front of the first lumr verterl ody (L1), in dults, with possile vrition from the twelfth thorcic interverterl spce to the second lumr one. The cone continues into the terminl filum, delicte pil strnd (its dimeter is less thn 2 mm), nchoring the terminl cone to the first coccygel segment. For the different length of the spinl column nd spinl cord, the disprity in the levels of the verterl nd medullry segments increses in crniocudl direction. As consequence, the nerve roots pthwys ecome progressively more verticl long the thorcic region nd elow the pex of the cone, where the lumr nerve nd scrl roots ecome more elongted, prllel, nd verticl (cud equin). On the contrry, the crnil roots nd in prticulr the cervicl ones run horizontlly, ecuse the medullry segment of origin remins t the sme level of the correspondent interverterl formin. We lso need to remind tht the spinl 37 roots hve to go through the interverterl formen of the metmer which is emryologiclly correspondent to their myelomere of origin; therefore, when they re completely developed, the gngli of the nervous roots of the lumr myelomeres, situted in their primitive interverterl formin, ctully hve their corresponding insertion point in the spinl cnl t the level of the dorsolumr pssge. The precise knowledge of the existing reltions is essentil in the neurologicl ssessment of trumtic lesions of the rchis; in fct, it is not otherwise possile to estlish the exct plce of the dmged myelomere (Fig. 2.7 ). The spinl cord is long, tuulr cordon, whose dimeter is not uniform ecuse of the forementioned cervicl nd lumr enlrgements from where the nerve roots of the lims originte. The length of the spinl cord depends from the size of the person; in dults, it is generlly round 45 cm; the mximl trnsverse dimeter, in the cervicl region, mesures 14 mm. The reltion etween the spinl cord nd the verterl cnl is not regulr throughout the crnio- cudl extension: dorslly, the dimeter of the spinl cord diminishes in comprison with the cnl; in this region, in fct, the compression tolernce is lower thn in the cervicl nd lumr regions, where the hrd verterl cse is more spcious. The spinl cnl size hs high degree of interindividul vriility. The structurl conformtion of the spinl cord is identicl from the crnil to the cudl region, with centrl xis of grey mtter (contining nerve nd myelinic fire elements) nd circulr envelope of white mtter (contining myelinic fires). The medullry grey mtter hs utterfly or H shpe: the motor roots originte from the nterior extremities (horns), while the posterior ones receive the sensory roots. In the white medullry mtter, we find the nterior, lterl, nd posterior firous undles, scending or descending, with different origin, development, nd destintion (Fig. 2.8 ). Thin nerve roots lso emerge from the nterior nd posterior lterl sulci of the spinl cord, forming the ventrl nd dorsl nerve roots. The ventrl-motor nd dorsl- sensory roots merge into the spinl nerves. There re eight pirs of cervicl nerve roots nd seven cervicl verterl odies only. The first seven cervicl nerves emerge ove the pedicles of the corresponding verterl

10 38 M. Crispino nd E. Crispino Fig. 2.8 Axil section of the spinl cord with grey nd white mtter. Spinl gnglion ( 1 ), spinl nerve ( 2 ), nd nterior ( 3 ) nd posterior roots ( 4 ). Ascending (light lue ) nd descending pthwys ( ornge ) Fig. 2.7 Lterl view of the spinl column section. It shows the difference etween the verterl column nd the spinl column length, with the medullry cone in norml position, t the level of the L1 ody; the nerve roots re more nd more olique, oriented downwrds, from the dorsl trct, nd get lmost verticl t the level of the cud equin. Cervicl nerves ( red ) nd dorsl ( green ), lumr ( ornge ), scrl, nd coccygel ( light green ) nerves ody. Given the different length of the spinl cord nd rchis, the more cudl scrococcygel roots need to verticlly cross (s previously explined) the verterl chnnel, in order to rech the corresponding pir of interverterl formin. On the wy, the roots re freely floting into the cererospinl fluid of the durl sc nd wrpped round the terminl filum (Fig. 2.9 ). Fig. 2.9 Coronl section of the spinl column, with the spinl nerves exiting from the neurl formin. It clerly shows the verticl course of the cud equin. The rteries supplying the spinl cord re lso clerly identifile

11 2 Spine 39 Fig ( ) Axil section of the dorsl prt of the verterl column. The rrowheds highlight the posterior intercostl rteries. Ao ort. ( ) Detiled ntomy of the spinl cord: the nterior horn ( 1 ), posterior horn ( 2 ), nterior commissure ( 3 ), nterior cordon ( 4 ), lterl ( 5 ) nd posterior cordon ( 6 ), centrl ependyml cnl ( 7 ), nterior root ( 8 ), posterior root ( 9 ), nd spinl gnglion ( str ) Roots nd Spinl Nerves In the spinl cord, the efferent nterior motor roots differ from the fferent posterior sensory ones; the dimeter of these lst ones is three times wider thn the nterior ones. The root insertion tkes plce on the verticl prt of the spinl cord s lterl wlls; the nterior roots re unique nd the posterior ones multiple, formed y xil thin wires, from 4 to 8, verticlly positioned. Spinl gngli re usully locted in correspondence of the interverterl formen; such topogrphicl reltion enles to identify them through CT nd MR imging. Ech spinl gnglion hs its corresponding nterior root in the front, efore the nterior root merges its fires into the sensory ones, forming the mixed spinl nerve (Fig ). This nerve, originted from the merger of the nterior nd the posterior spinl roots, when exiting the formen, splits into the nterior nd posterior rmifictions. In the scrl region, the spinl gngli re contined in the rdiculr cnls. In the neurl formen, long with the roots nd the spinl gnglion, there re dipose tissues nd epidurl veins. The reltive freedom of roots nd nerves t the level of the interverterl formin llows the myelin- rdiculr complex dpttion to the dynmics of the spine Vsculristion The lood supply to the spinl cord is crried out y wide nterior spinl rtery, vsculrising 1/3 4/5 of the nterior spinl cord, nd y two smll posterior spinl rteries, supplying the remining prt. The posterior nd nterior spinl rteries re symmetriclly nd irregulrly supplied, with few connections mong them, y the medullry rmifictions of the rdiculrmedullry rteries, originting from the verterl, intercostl, nd lumr rtery. At the crnil se, the medullry rmifictions of the verterl intrcrnil rteries merge into the nterior spinl rtery. An dditionl rtery supply is oserved in correspondence of other two or three cervicl levels. The superior thorcic spinl cord, until the fourth thorcic verter (T4), is vsculrised. The rtery supply, previling in the lomothorcic region, consists of the rteri rdiculris mgn, or the rtery of Admkiewicz, originting from the intercostl rteries nd rmifictions of the thorcic ort, usully etween T9 nd L2, on the left (in 88 % of cses), ut it is vrile (Fig ). It determines typicl curve when forming the nterior scending, or descending, spinl rtery.

12 40 M. Crispino nd E. Crispino Fig ( ) Antomy of the rteril vsculristion of the spinl cord. Rdiculr rtery ( 1 ) nd nterior spinl rtery ( 2 ). () Representtion of the possile origins of the rtery of Admkiewicz (rteri rdiculris mgn): generlly from the intercostl rteries ( I ), rmifiction of the thorcic ort ( Ao ), on the left side, etween T9 nd L2 (88 %). Typicl curve ( rrow ) of the rtery of Admkiewicz forming the nterior spinl rtery ( rrowheds )

13 2 Spine The venous system roughly reflects the rterious system, with multiple medullry veins, drining into the pil veins nd communicting with the mjor posterior spinl vein nd the smller nterior spinl ones. The rdiculr veins, long the nervous roots t different levels, drin the pil veins in the verterl internl venous plexus, locted in the epidurl spce nd surrounded y dipose tissue. The internl verterl venous plexus goes into the externl one through the siloverterl vein or the epidurl longitudinl nterior veins, drining through the formen. The venous externl verterl plexus empties into the zygos system. 2.2 Imging Norml Antomy The spinl imging is difficult to perform. Contrry to the crnium, chrcterised y firly regulr volume nd composition of the tissues, the column presents higher degree of interindividul vriility. Different dignostic techniques re ville, nd they complete ech other in the clinicl prctice Conventionl Rdiology The conventionl rdiology (CR) is still considered the first choice for the exmintion of the spine. The lterl, frontl, nd olique projections llows the precise exmintion of the one structures, the rticulr surfce morphology, nd the posterior lignment of the verterl wll in kyphosis nd lordosis. The CR ccurtely shows the ones norml ntomy nd llows to perform dynmic studies ut does not llow the exmintion of the spinl cord, the interverterl disc nd the crtilge, or the cpsulr ligmentous complex Generl Fetures Verterl Body The size increses from the ottom to the top; in the qudrilterl shpe, we cn clerly distinguish the superior nd inferior verterl pltes, flt nd slightly concve, from the nterior nd 41 posterior mrgins. The orders re composed of corticl one, delimiting the treculr or spongy prt, less evident in the nterior prt of the ody, which is more delicte nd suject to trumtic events. Between the verterl pltes, we find the interverterl disc, not visile through CR. Posterior Arch Pedicle : the posterior ody rch connection; the superior mrgin is slightly indented, while the inferior one is clerly concve; the pedicles of djcent vertere surround the neurl formin. Prs interrticulris nd superior or inferior rticulr processes : ilterl in ech verter; the superior process rticultes through fcet, with the inferior fcet of the ove verter nd vice vers; fcets hve different morphology in the vrious trcts of the rchis. Isthmus : the prt etween the superior nd inferior rticulr processes. Trnsverse process : with different vriles in the different trcts of the spine, lterlly projected from the prs interrticulris, lmost horizontlly. Lmin : the portion of the rch fter the trnsverse process tht joins the contrlterl lmin towrds the medin line. Spinous process : medin nd uneven, of different mplitude nd orienttion in the vrious trcts of the rchis, it closes the verterl rch on the ck. Between the posterior rch nd the verterl ody, there is the verterl formen; the series of verterl formin, in rticulting vertere, forms the spinl cnl, which is not directly detectle through conventionl rdiogrphy Specil Fetures The verterl rdiogrphic morphology, s generlly descried herein ove, sensily chnges in the vrious spine trcts. Cervicl Rchis The first, second, nd lst of the seven cervicl vertere hve peculir chrcteristics. The first cervicl verter, or the tls, connected to the crnil se, is wider thn the other ones; it is devoid of the verterl ody, replced

14 42 M. Crispino nd E. Crispino Fig Crnio-verterl junction () AP rdiogrphy for the exmintion of the dens of the epistropheus. ( ) CT coronl reconstruction with one lgorithm, high resolution: tlntooccipitl joint ( rrowhed ), tls-epistropheus joint ( rrow ). Atls (ring ), occipitl condyle ( circle ), nd odontoid process of the epistropheus ( str ) y the nterior rch, nd of the spinous process, replced y tuercle (spinous tuercle). Insted, C1 fetures two lterl msses united y n nterior nd posterior verterl rch. The second cervicl verter, or epistropheus, differs from the other cervicl vertere for the presence, in the superior side of the ody, of conoid process going upwrds, the epistropheus dens or odontoid process tht reches the posterior fce of the tls nterior rch to form the medil tlntoxil joint (Fig ). The lst cervicl verter is similr to the thorcic verter; this is the reson why the following rdiogrphic description refers to the centrl cervicl vertere. The verterl ody is smll; t the level of the superior plte, there re uncinte processes rticulting with the ove verter. The spinous process is poorly developed, slightly tilted (the grde increses in the lst vertere); it ends in the two seprte tuercles. The superior rticulr processes re oriented upwrds nd ckwrds; the inferior ones, downwrds nd towrds the front (Fig ). In ddition to the ove-mentioned rdiogrphic spects, the cervicl vertere differ from the other ones for the following chrcteristics, documented in CT nd MRI: the trnsverse processes terminte in two tuercles, the nterior nd posterior ones, nd originte from wide root with the centrl trnsverse formen, in which we find the verterl rtery nd vein. The verterl formen hs tringle shpe. Thorcic Spine We the exception of the trnsitionl vertere (the first nd the lst three ones), the other eight thorcic vertere cn e discriminted for their more voluminous ody, in comprison with the cervicl vertere, devoid of uncinte process nd chrcterised y n rticulr fcet for the costl hed. The trnsverse processes re well developed nd roust, with fcet for the rticultion of the ri tuercles. The rticulr processes hve verticl fcets, the superior ones orientted towrds the ck nd the inferior ones towrds the front. The lmine re higher, connected through spinous process, well developed nd progressively more olique up to the ninth verter nd getting horizontl gin in the lst vertere (Fig ). Lumr Spine The verterl ody is more voluminous nd the trnsverse dimeter is clerly wider. The mjor distinctive chrcter is the presence of ri-like process, originting from the prs interrticulris, with olique orienttion outwrds,

15 2 Spine nd corresponding to the merger of the outline of the trnsverse process with ri rudiment. The rticulr processes re verticlly locted, with the superior rticulr concve fcet looking towrds the medil nd posterior direction, while the inferior one, convex, towrds the front nd the side. The spinous process is thick, short, nd horizontl (Fig ). Scrum-Coccyx The lterl projection clerly shows the convex posterior fcet nd the concve nterior one. The nterior-posterior projection shows the four pirs of the scrl formin, leding into the scrl cnl, homologous to the spinl cnl. Besides 43 the first two scrl formin, the prs interrticulris develops into the so-clled scrl wings. The coccyx, typiclly formed y the fusion of four or five rudimentry vertere, is more visile in ltero-lterl projection (Fig ) Computed Tomogrphy With regrd to CT imging, the need to reduce the ptient rdition exposure suggests to perform specific studies on single spine segments. However, the modern multidetector CT, thnks to specific improvements such s the cre dose, llows to regulte the rdition exposure (mas Fig Cervicl spine X-ry in AP ( ), LL ( ), OAD ( c ), nd OAS ( d ) projections. C7 spinous pophysis ( circle ), posterior tls rch ( rrowhed ), left costotrnsverse rticultion of T1 ( curved rrow ), C3 verterl ody ( rrow ), interverterl formin ( strs ), nd C4 C5 interverterl spce ( empty rrow )

16 44 M. Crispino nd E. Crispino c d Fig (continued) nd kvp), ccording to the density of the trget tissues nd to the ptient size, enling, in short period of time ( few second will suffice), pnormic exmintions nd multiple plne reconstructions, decresing the exposure without penlising the qulity of the dignosis. CT shows tht the verterl odies contin thin one trecule in the medullry spce, surrounded y the well-visile corticl one. In the pedicles nd the trnsverse processes, the corticl prt is more evident, nd the sponge content is less voluminous. The lmine nd the spinous processes of the cervicl nd thorcic spine contin spongy one, while in the lumr region, we cn usully oserve single one plques. The rticulr surfces of the dense nd smooth fcets re generlly iconvex in the cervicl rchis, nd they re insted flt in the thorcic nd lumr regions (Fig ). The interverterl discs, such s the other soft tissues, re homogeneous ( UH), nd the nnulus firosus cnnot e distinguished from the nucleus pulposus. The yellow ligment, with density similr to the soft tissues, connects the interlminr spces (Figs nd 2.19 ). In the lumr rchis, the yellow ligment is normlly 3.5 mm lrge, nd it is considered thickened if lrger thn 5.5 mm. The posterior longitudinl ligment is contined in the nterior epidurl spce together with ft nd vessels. The dipose tissue is contined in the lterl recess which, in the lumr region, is delimited y the verterl odies; in the front nd lterlly, the pedicles; nd ehind, the rticulr superior fcets; they re normlly 3 5 mm in size; if shorter thn 3 mm, they re considered stenotic.

17 2 Spine 45 Fig Thorcic spine X-ry in AP ( ) nd LL projections ( ). Verterl T12 ody ( str ) with ri hypoplsi; T10 T11 interverterl formin ( circle ); T11 right peduncle ( rrowhed ) Mgnetic Resonnce Imging Only with MRI, we cn directly disply the spinl cord, with firly good imge resolution. For the length of the spinl column, its posterior position, nd the smll size of the content of the spinl cnl, we need to use specific superficil coils tht increse the signl-noise rtio, while for the sptil resolution, we need to use smller fields of view (from 16 to 24 cm); for the spinl cord pproximtely 1 cm dimeter nd nerve roots 1 mm or less, we need to use n excellent sptil nd contrst resolution. For the complete exmintion of the spinl column, we need to use multicoil technology tht comines the signls coming from different superficil coils locted on the xes of the column. The newer reconstruction softwre hve further enhnced the cpcity of fst exmintion of the whole verterl xes, comining seprted series of high-resolution dt into single imge (Fig ). MRI shows the verterl end pltes s thin hypointense stripe, oth in T1 nd T2 sequences, weighted ccording to their structure: corticl one, with low level of proton density, covered with crtilge (Fig ). The intensity of the signl of the spongy tissue of the verterl odies depends on the quntity nd type of one mrrow contined. Normlly, the reltion etween the red nd the yellow mrrow is good, ut with dvncing ge, the yellow mrrow increses, producing high-intensity signl on T1 spin-echo (SE) sequences nd T2 fst spin-echo (FSE) sequences. However, in the one mrrow, we cn oserve, t ny ge, spot imges showing the lck of red mrrow; such finding shll not e considered pthologicl (Fig ).

18 46 M. Crispino nd E. Crispino Fig Lumr spine X-ry in AP ( ) nd LL ( ) projections. ( ) left scrl l ( circle ), L2 spinous pophysis ( curved rrow ), L3 left trnsverse process ( rrowhed ), L3 pedicle ( empty rrow ), nd scroilic synchondrosis ( rrow ). ( ) Neurl formin of L4 L4( str ) nd interverterl spce of L5 S1 ( lck rrow ) In spin-echo (SE) imging, or grdient-echo (GE) T2-weighted sequences, the verterl odies show low signl intensity; however, the signl intensity is intermedite or high on fst spin-echo (FSE) sequences which re used more frequently for their superior imging qulity, ssocited with reduced exmintion time. After rdiotherpy, the verterl odies ecome hyperintense in T1 sequences ecuse the dipose tissue sustitutes the elements of the one mrrow. The norml one mrrow shows homogeneous enhncement fter gdolinium intrvenous dministrtion. The rticulr crtilge enveloping the interpophysel joints usully presents low signl in T1- nd T2-weighted sequences, nd it is difficult to distinguish from the corticl one; however, it shows n increse in signl in GE sequences.

19 2 Spine 47 Fig Scrl ( ) promontory nd coccyx ( ) X-ry in LL projection. Coccyx ( rrowhed ), scrl crest ( rrows ), L5 ody ( str ), nd S1 ody ( circle ). The curve rrow shows the cetulr roof nd the coxofemorl joint MRI of the interverterl discs reflects the wter contined therein; normlly, the signl intensity is lower in T1-weighted sequences nd higher in T2-weighted sequences (Fig ). The nnulus firosus ppers s peripherl stripe nd thin nd with low signl intensity in ll sequences; the nucleus pulposus shows higher signl intensity, horizontlly crossed y drk line which proly represents the norml intrnucler cleft tht cn e oserved in more thn 94 % of the ptients older thn 30. With dvncing ge, the fluid content of the nnulus firosus nd of the nucleus pulposus progressively decreses, nd therefore, the signl intensity of disc on T2 sequences lso reduces, for dehydrtion nd degenertion process. The ligments, except for the yellow one, hve low signl intensity, similr to the one, in ll sequences ecuse the content hs high collgen levels; they imperceptily merge into the corticl one, with the more externl fires of the nnulus firosus nd the dur mter. The yellow ligment hs intermedite signl intensity in T1- nd T2-weighted sequences nd higher in GE sequences, especilly for its iochemicl composition represented y 20 % of collgen nd 80 % of elstin. The spinl cord hs intermedite intensity signl on T1-weighted sequences nd low intensity signl on T2-weighted nd GE sequences (Fig ); in high-resolution exmintions, performed with high-field, GE, nd T2-weighted sequences, we cn identify the internl rchitecture. This is especilly significnt in xil imges, where you find n H-shped region, corresponding to the centrl grey mtter, with slightly higher signl thn the white mtter cordons. The difference etween the white nd grey mtter is due to three fctors: different fluid content, the presence/lck of myelin, nd, therefore, different relxtion times. Such elements re not visile in SE T2-weighted sequences, where the spinl cord hs n even, intermedite signl.

20 48 M. Crispino nd E. Crispino Fig Lumr spine, CT with one lgorithm. ( ) Axil section. ( ) MPR sgittl reconstruction. L3 spinous pophysis ( curved rrow ), vsculr formen ( empty rrow ), spinous pophysis ( rched rrow ), L3 inferior rticulr process (rrow ) nd the superior one di L4 ( lck rrow ) with the relevnt joint, ri-like process ( rrowhed ) Also the single roots nd nerve rdicles cn e seen through high-resolution imging with highfield MRI system. With ll hevy T2-weighted sequences, cquired with longer repetition times, we cn hve similr myelogrphic ptterns tht highlight the hyperintense cererospinl fluid (Fig ). With FSE sequences, the fluid my e confused with the djcent structures, contining ft, nd it is therefore importnt to suppress the dipose tissue using specific techniques.

21 2 Spine 49 Fig Lumr spine, CT exmintion with soft tissue window. ( ) Axil section. ( ) MPR sgittl reconstruction. The str shows L3 L4 interverterl disc. The interspinous ligments re clerly visile ( rrow ) nd so re the suprspinous ones ( rrowhed ) Fig Lumr rchis CT, with one lgorithm ( ) nd soft tissue window ( ). The corticl one ( rrow ), thin, dense, nd regulr, contining the less dense spongy prt ( str ). The interverterl disc ( circle ) nd the yellow ligments ( rrowhed ) re homogeneous, nd their density is similr to the soft tissues

22 50 M. Crispino nd E. Crispino Fig Sgittl MRI TSE T2-weighted ( ) nd T1-weighted ( ) imges comined for n overll view of the rchis

23 2 Spine 51 Fig MRI, sgittl TSE T2-weighted () nd T1-weighted imges ( ), respectively, of the cervicl rchis nd lumr rchis. The verterl corticl one is hypointense in oth the sequences. Thnks to high resolution, we re le to clerly disply the spinl cord (slightly hyperintense in T2, intermedite in T1)

24 52 M. Crispino nd E. Crispino c Fig Lumr sgittl MRI, sgittl TSE T2-weighted ( ) nd T1-weighted ( ), nd xil T2-weighted imges ( c ). Adipose degenertion of the hemtopoietic one mrrow with multiple ftty nodules ( rrowhed ), hyperintense in ll the sequences; it is prphysiologicl finding ( red mrrow reconversion )

25 2 Spine 53 c Fig Lumr spine, MRI sgittl imging, TSE T2-weighted ( ) nd T1-weighted ( ) nd xil T2-weighted imges ( c ). On T2WI, the interverterl discs re hyperintense nd hypointense on T1WI in connection with their fluid content. The nnulus firosus is hypointense in comprison with the nucleus pulposus ( rrowhed ). (c ) Interverterl disc ( str ), yellow ligment ( rrowhed ), interpophysel joint ( rrow ), spinl gnglion ( empty rrow ), durl sc ( circle ), nd cud equin roots

26 54 M. Crispino nd E. Crispino Fig Spinl cord xil MRI GE T2-weighted sequences. This is good representtion of the medullry ntomicl structures: note the utterfly shpe ( ) or H shpe ( ) of the medullry grey mtter. Anterior nd posterior roots ( rrowheds ) nd spinl gnglion ( rrow )

27 2 Spine 55 c Fig Lumr spine MRI, TSE T2-weighted, xil ( ) nd coronl ( ), nd coronl STIR imges ( c ). The conus medullris ( empty rrow ) is surrounded y the roots of the cud equin ( rrows ) in the cererospinl fluid (hyperintense) inside the durl sc. ( c ) The spinl nerves ( rrowheds ) re depicted

28 56 Biliogrphy 1. Brdley WG, Droff RB, Fenichel GM, Jnkovic J (2007) Neurology in clinicl prctice, 5th edn. Butterworth-Heinemnn Elsevier, Phildelphi 2. Frymoyer JW, Wiesel SW, An S et l (2003) The dult nd peditric spine. Lippincott Willims & Wilkins, Phildelphi 3. Greenerg MS (2010) Hndook of neurosurgery, 7th edn. Thieme Medicl Pulishers, Inc, New York 4. Hg JR, Vikrm SD, Forsting M et l (2008) CT nd MRI of the whole ody. Mosy, St. Louis 5. Hckney DB (1992) Mgnetic resonnce imging of the spine. Norml ntomy. Top Mgn Reson Imging 4: Hrnserger HR, Osorn AG, Ross J et l (2006) Dignostic nd surgicl imging ntomy rin, hed M. Crispino nd E. Crispino & neck, spine. Lippincott Willims & Wilkins, Phildelphi 7. Mnelfe C et l (eds) (1992) Imging of the spine nd spinl cord. Rven, New York 8. Netter FH, Summit NJ (2010) Atls of humn ntomy, 5th edn. Sunders, Phildelphi 9. Pfirrmnn CW, Binkert CA, Znetti M et l (2001) MR morphology of lr ligments nd occipitotlntoxil joints: study in 50 symptomtic sujects. Rdiology 218: Ricci C, Cov M, Kng YS et l (1990) Norml gerelted ptterns of cellulr nd ftty one mrrow distriution in the xil skeleton: MR imging study. Rdiology 177: Ross JS, Brnt-Zwdzki M, Moore KR et l (2004) Dignostic imging: spine. Amirsys Elsevier Sunders, Slt Lke City

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