Surgical. . Radiologlc Anatomy
8urg Radiol Anat (1987) 9 : 217-223
9
Springer-Verlag 1987
CT-anatomic correlations of the normal capsulo-ligamentous bands of the extrinsic joints of the thoracic spine JL Burguet ~, H Sick 2 and A Wackenheim l t Service de Radiologie I, l-t6pital Civil, 1, place de l'H6pital 67000 Strasbourg Codex, France 2 Institut d'Anatornie Normale, H0pital Civil, 1, place de I'H6pital, F 67000 Strasbourg Cedex, France
~Ummary. Five anatomic specimens were studied in an attempt to visualize by high-resolution computed tomography (HRCT) the ligamentous bands of the costotransVerse and costovertebral joints. HRCT-anatomic comparison is presented to relate the CT views to the anatomic structures. The authors demonstrate that axial, sagittal and, to a lesser extent, coronal HRCT views perfectly ~utline the ligamentous structures, although these are flattened, short, deep and free from calcium deposit. The method may be valuable in disease states such as ankylosing spondylitis.
COnfrontation anatomo-scanographique ties ~l~ments capsulo-ligamentaires normaux ties articulations extrins~ques du rachis thoracique
R~.sum#,. Les auteurs
&udient cinq pi~ces anatomiques aftn de visualiser en tomodensitom6trie de hauter6solution les tractus ligamentaires des articulations e~ et costo-vert6brales. La confrontation anatomo-scanographique s'av~re fort.ement corr61er les rues tomodensitom6triques et los ~16ments anatomiques r6els. Les auteurs montrent ainsi que les vues Scanographiques haute-r6solution axiales, sagittales et -"- rnais dans une mesure moindre - - frontales, d61imitent parfaitement los structures ligamentaires en d6pit de leur faible 6paisseur, de leur bri~vet6 et de 1cur Profondeur. l~ey Words : Thoracic spine - Ligaments - CostotransVerse joint - Costovertebral joint - CT
OffPrint requests : Pr H Sick
The extrinsic joints of the thoracic spine include the costovertebral and costotransverse joints. The ligamentous bands of these small deep joints are thin, complex and imbricated. Even with such unfavorable anatomic factors, high-resolution computed tomography (HRCT) is a successful method of visualizing the articular ligaments. Only the normal appearance of these tracts will be dealt with in this paper.
Material and method All HRCT views were performed with a CE 10,000 total body scanner (CGR). Eviscerated thoracic cages were used for axial, sagittal and coronal HRCT views. Shoulders and arms were previously removed for axial and coronal studies in order to prevent attenuation of the X-ray beam and resulting artifacts, thus allowing lesser slice thickness. The following parameters were choosen in the light of our previous experience in this field [1] : scanning time 6.8 seconds with 120 kV and 80 mA, 130 mt~ field of view; slice thickness 1 mm; systematic high resolution 512 • 512 matrix, image filtering favoring spatial resolution rather than density discrimination. Once the examination had been performed, intramuscular needles were implanted through the skin of the cadaveric specimens along the reference plane of CT section. Then the specimens were frozen in order to obtain anatomic 5 mm thickness slices along and parallel to the plane thus marked out. In vivo axial HRCT views were performed in patients undergoing scanographic examination for various thoracic or thoracic spinal pathologic conditions. The same imaging parameters were used in all cases.
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JL Burguet et al. : CT Anatomic correlations of the capsulo-ligamentous bands
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Fig. 1 1 Radiate ligament 2 Costotransverse ligament 3 Lateral costotransverse ligament 1 Lig. rayonn6 2 Lig. costo-transversaire 3 Lig. costo-transversaire lat6ral
Anatomic data (Figs. 1, 2) Each rib articulates with the thoracic spine b y two different j o i n t s : the j o i n t of the head of the rib (costovertebral) and the costotransverse joint. The head of the rib articulates with the facets situated on the lateral aspects o f the bodies o f 2 adjacent thoracic vertebrae and with the intervertebral disc b e t w e e n them. The first, tenth, eleventh and twelfth ribs are exceptions to the rule and articulate with a single vertebra. In each of the other j o i n t the intra-articular l i g a m e n t divides the j o i n t into 2 distinct parts; this short l i g a m e n t is attached laterally to the crest separating the 2 articular facets on the head of the rib and m e d i a l l y to the intervertebral disc and the adjacent vertebrae. The radiate l i g a m e n t is attached laterally to the head of each rib; its fibers then fan out m e d i a l l y to be attached to the sides of the bodies
Fig. 2 1 Radiate ligament 2 Costotransverse ligament 3 Lateral costotrans" verse ligament 4 Superior costotransverse ligament 5 Intraarticular ligament lLig. rayonn6 2 Lig. costo-transversaire 3 Lig. costo-transversaite lateral 4 Lig. costo-transversaire sup6fieur 5 Lig. interosseux of 2 adjacent vertebrae and the intervertebral disc b e t w e e n them (Fig. 1). At the first rib, the radiate l i g a m e n t is c o n n e c t e d to the body of the 7th cervical vertebra as well as the first thoracic vertebra. In the J
Figs. 3-6 3 a Axial CT view and b corresponding anatomic section passing through the intervertebral disc T4-T5 (X). The interosseous ligament is quite -,veil individualized (long black arrow) (see also Fig. 5). Comparison may be made between the CT view of the left interosseous ligament in Fig. 3-a ~d the anatomic appearance of the fight interosseous ligament in Fig. 4-b (long black arrow) : same streaked aspect. The thick white arrow indicateS the lateral costotransverse ligament just behind the costotransverse joint (short black arrow). The lateral portion of the costotransverse liganae~t (black arrowhead) appears as a homogeneous hyperdensity along the medial border of the costal neck. ~ spinous process of T4 4 a CT view and D corresponding anatomic section passing at mid-thoracic intervertebral level. The transverse insertion of the superior costotransverse ligarrierlt appears as a thick hyperdense strip at the inferior border of the transverse process (black arrow). Note the intra-articular ligament (short black arrow) and the posterior ligamentous plane of the left costovertebral joint (black arrowhead) 5 CT view at T3-T4 level providing excellent visualization of the intraarticular ligament (arrow), fibers of which are in continuity with the fibers of the annulus fibrosus of the intervertebral disc 6 CT view in vivo showing the intraarticular ligament (black arrow). Arrowhead : ventral longitudinal ligament 3 Vue TDM axiale (a) et coupe anatomique correspondante (b), passant par le disque intervert6bral T4-T5 (x). Le ligament interosseux est bielt individualis6 (fl~che noire longue) (of. aussi Fig. 5). Le m6me aspect stri6 du ligament interosseux se retrouve sur l'image TDM du ligament
JL BUrguet et al. : (?T Anatomic correlalions of the capsulo-ligamenlous hands
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inlerosseux gauche de la Fig. 3a et sur la coupe anatomlque du ligament interosseux 'a droite (Fig. 4b, Iongue fl~che noire). La fleche blanche Pointe le ligament costo-transversaire [at6ral justc en arri~zre de I'articulation costoqransversaire (courte fl~:che noire). La pax-tie latdrale du ligament ~st~ (t~te de fl~che noire) apparait comme une hyperdensitd homog6ne le long du bord mddial du col costal. ~ : apophyse dpineuse ~, Vue TDM (a) et coupe anatomlque (b) correspondante, passant entre 2 vertebres du rachJs thoramque moyen. L msemon transversalre du 'gatnent costotransversaire supdrieur apparatt comme une bande hyperdense 6paisse au bord infdrieur de I'apophyse transverse (fleche noire). Notez le ligament intra-articulaire (petite fleche noire) ainsi que le plan ligamentaire posldrieur de l'articulation costo-vertebrale gauche (pointe de fl~che naire) 5 Vne TDM passant au niveau T3-T4 fournissant une excellentc visualisation du ligament interosseux intra-articulaire (fl~ehe) dont les fibres Slant en Continuitd avec celles de l'annulus intervertdbral 6 Coupe TDM obtenue in vivo et montrant Ie ligament interosseux intra-articulaire (fl~che noire). Pointe de I'Rzche noire : ligament longitudinal ventral 4.
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Jl. Burguct el al. : (7l" Anatomic correlations of the capsulo-ligamenlOUS bal~dS
Fi~s. 7, 8 7 a Axial CT views and b corresponding anatomic section passing through the vmlebral body of T4. Note the good visualization of tile right aild left radiate ligaments (while arrows) between the head of the 4tb rib (long black arrows) and the posterolateral aspect of the vertebral body (T4)' Note too the hyperdense strip of tile right costotransverse ligament (short black arrow). ~ spinous process of T3 eel 2 CT views in vivo shoWi~" good individualization of the radiate ligaments (white arrows) 8 a CT view and b anatomic section ahmg the shaft of the rib. This plane provides al~ excellent view of the superior eostotransverse ligament (thick black arrow) between the neck of the rib and the inferior border of the transverse process of the vertebra situated above. Note also the radiate ligament (short black arrow) and the very thick ventral longitudinal ligament (white arrow). The short white arrow indicate tile lateral costotransverse ligamenl. * head of 5th rib. * body of 4th rib 7 Vue lomodcnsitomdtrique (TDM) axiale (aj et coupe anatomique (h) correspondante passant par le corns vertebral T4 Les ligaments rayOnrl~s dmit et g' ,auche sont bien visualisO.s bl'mcbes) " : ' " . (flecbes . . . entre . a 4". tete .costa .e (lleches no res o l g,ues) ' et l'a face P ostero- ate'a e du corns - vertebra! -'1 T4. Notez ~Sgalemcnt la bandeletle hyperdense du ligament costo-transversaire (flEche notre courte). -'-- : apophyse dpineuse T3 r 2 coupes TI)t~ obtenues sur le sujet vivanl objectivent bien [es ligaments ravonnds (fl,2ches blanches) 8 Vue TOM (a) et coupe anatomique (b) orientees le lol~- ae l'axe du corps de la c6te. Ce plan fournit une vue cxcellente du ligament costo-transversaire supdrieur (l]eche noire ,Spaisse) entre le col costal et le bord inf&ieur de l'.'~pophyse transverse de la vert~:bre sus-jacenle. Nolez aussi le ligamenl rayonnd (petite fleche notre) et le trbs dpais ligalll~~l longitudinal ventral (fl~che blanche). La petite tlbche blanche pointe le ligament costotransversaire latdral. ~ tete de la 5 ~ c6te. * corps de la 4 ~ cole
]L Burguct el al. : CT Anatomic correl~lli~ns t~f the capsulo-ligamentous bands
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Figs, 9-11 9 a Parasagittal CT view and b corresponding anatomic section. The head t~f a rib (short black arrow) al~Jculate.s with the vertebra situated above (single. lbin acrow~ and with the corresponding vertebra below (main a~'licular facet) (twin thi~ arrows). The white curved arrow indicates the ntra-artlcular ga ~lent 10 nb Parasaein~l view lateral 'to that of Fig 9' corresponding CT and anatomic section The fasciculi of the costotransverse ~,~!~ent (white curved arrows) are well-delineated between the sections of the neck of the rib in front (black arrow) and of the transverse process "~:,~nd (black sl'~shed arrow) 11 zb Par~sagittal slices lateral to those of Fig. lO give the best view of the superior costotransvcrse ligament (open cttrved white arrow) directed obliquely upward and backward. --~ neck of rib; -'--* transverse process of vct-tebra. White curved arn)w : c~ ligament fi~rming a step-like aspect with the superior costo-transversc ligament 9 VUe TDM parasaginale (a) ct coupe anatomique corresp~ndante (b). La t6te d'nnc c?)te ~courte fl~che noire) s'articule avecla verl~bre sus-jacertte (petite fl6che simple) ainsi qu'avec I~l venbbre correspo~adante par sa facette articulaire principale {petites fi~:ches doubles). La fleche blanche incurv6e pointe le ligament interosseux (coupe anatornique) tO Vues parasagittales tOg6rement plus latdrales que relic de la Fig, 9: coupes TDM et anatt~tniques c~rrespondantes. Los fascicules du ligamert~ costotransversaire (fleches blanches incurv,Ses) sont bien visibles entre les sections du col costal eu avant (l]~:che zloirc~ el de Fapophyse transverse en arri'Sre (fl6che noirc barr6e) 11 ab Vucs parasagittales ldgbrement plus lat6rales que relies de la l:ig. 10. Ces c~upes montrem au mieux le hgament c~stotran,~versaire sup6rieur (flbehe blanche ajour6e) tendu obliquement en haul et e~ atri~re. ~ col costal; ~ al-~physe transverse de la vert~brc, La fi~che blanche pleine pointe le ligament costoqransversaire qui r6alise un aspect er~ V~arche d'est:aLier avcc Ic ligament ct~sto-transversaire sup6ricur
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JL Burguet et al. : CT Anatomic correlations of the capsulo-ligamentous bands Finally, the inferior costotransverse ligament [2] is constituted by several fasciculi connecting the inferior surface of the neck of a rib and the apex of the corresponding transverse process. This ligament is less important than the others. Results
These different ligamentous tracts are quite well visua" lized in HRCT. We shall review their normal configura" tion in the axial, sagittal and coronal planes. Axial views
Fig. 12
Coronal CT view individualizingthe superiorcostotransverseligament (white arrow) between the neck of the rib (open arrow) and the transverse process (curved arrow) Coupe coronaleTDM rnontrant le ligament costo-transversairesuprrieur (flbche blanche)entre le col costal (fl~cheouverte)et l'apophyse transverse (fl~che courbe)
joints of the 10th, l lth and 12th ribs the radiate ligament is attached to that vertebra and also to the vertebra above. The costotransverse joints are formed by the articular portion of the tubercle of a rib articulating with a corresponding facet on the transverse process of the vertebra to which it corresponds numerically. This articulation is wanting at the T l l and T12 levels. The costotransverse ligament, short and very strong, connects the posterior aspect of the neck of a rib to the anterior surface of the corresponding tranverse process. It may be absent in the case of the 1 lth and 12th ribs. The lateral costotransverse ligament is short, thick and rectangular, and passes obliquely from the posterolateral portion of the tubercle of a rib, immediately lateral to its articular facet, to the apex of the corresponding transverse process. The superior costotransverse ligament, thick and resistant, is attached to the crest of the costal neck below, and ascends towards the inferior border of the transverse process of the vertebra situated above. Laterally, it is continuous with the intercostal membrane and the external intercostal muscle. The first rib has no such ligament.
The intraarticular-ligament is constantly visible in the view passing through the intervertebral disc. It appears (Figs. 3-6) as a slightly hyperdense short strip between the tip of the head of the rib and the intervertebral disC. Its density is almost the same value as that of invertebral disc so that the 2 structures seem to be in continuity. Sometimes, more hyperdense thin linear strips may longitudinally reinforce the density of the interosseoUS ligament (Fig. 3 a). The radiate ligament is also quite well seen, more particularly in the views passing just above or below the intervertebral disc. It appears as a linear hyperdensity, slightly convex forward, connecting the anterior aspect of the head of the rib to the lateral aspect of the vertebral body (Fig. 7 ad). The costotransverse ligament appears on HRCT scans as a rather isodense or slightly hyperdense zone of tissue occupying the whole interval between the neck of the rib and the corresponding transverse process behind (Fig. 7 ab). The lateral costotransverse ligament is individualized as an hyperdense strip with forward convexity on the posterior aspect of the costotransverse joint (Fig. 3 ab). A particular non classical but very informative plane for HRCT imaging of these ligamentous bands is represented by the section along and parallel to the shaft of the rib, i.e. the gantry has to be craniocaudally tilted. Such a slice passes through 3 different adjacent vertebrae but displays a very good view of all the ligaments of the costovertebral and costotransverse joints and particularly of the superior costotransverse and interos" seous ligaments (Fig. 8 ab). Sagittal views Sagittal and parasagittal HRCT views are not feasible it~ vivo; nevertheless, HRCT study in other planes, thar~ axial allows better comprehension of the axial CT vieWS and also of the images obtained by MRI. Parasagittal slices passing through the costovertebral joint provide an excellent view of the articular inter-
JL Burguet et al. : CT Anatomic correlations of the capsulo-ligamentous bands Space, with its characteristic shape and an axis that is increasingly flat!ened and backwardly oriented at the lower thoracic levels (Fig. 9 ab). The intraarticular ligament lies between the head of the rib and the intervertebral disc (Fig. 9 ab). More lateral slices allow individualization of the faseiculi of the costo-transverse ligament as short, thick, linear hyperdensities between the neck of the rib in front and the transverse process behind (Fig. 10 ab). P'arasagittal slices best show the superior costotransVerse ligament (Fig. 11 ab). This appears as a very hyPerdense, well-delineated strip directed obliquely upward and backward from the superior border of the neck of the rib to the inferior aspect of the transverse Process of the vertebra above. The superior costotransVerse ligaments form with the costotransverse ligaments a characteristic step-like aspect in these parasagittal Views (Fig. 11 ab).
COronal views These were less informative in our study than the other 2 Views. Nevertheless, they allow perfect demonstration of both articular surfaces of the head of the rib. The SUperior costotransverse ligament is also well-shown in the view as a hyperdense strip slightly oblique upward and outward (Fig. 12). Others ligamentous structures are not to be seen in this coronal view because of their frontal general Orientation, more or less parallel to the scanning plane.
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Conclusion The ability of high-resolution computed tomography (HRCT) to demonstrate ligamentous tracts is now well-established. This is true, not only for the ligamentous structures of large joints such as the knee or shoulder, but also for small deep joints such as the extrinsic joints of the thoracic spine. A knowledge of their normal appearance in CT views may be a point of departure for their description in disease states such as ankylosing spondylitis.
References 1. Burguet JL, Sick H, Dirheimer Y, Wackenheim A (1985) CT of the main ligaments of the cervico-occipital hinge. Neuroradiology 27 : 112-118 2. Gray S (1973) Anatomy of the human body 29th Amrricain Ed. Lea & Febiger, Philadelphia 3. Forestier J, Lagier R (1971) Ankylosing hyperostosis of the spine. Clin Orthop 74 9 65-83 4. Meyer PR (1972) Contribution ~t l'rtude des cavitrs articulaires costo-vertrbrales. Arch Anat Hist Embr Norm Exp 55 : 283-360 5. Resnick D, Niwayama G (1981) Diagnosis of bone and joint disorders. WB Saunders Co, 1040-1102 6. Resnick D, Niwayama G (1976) Radiologic and pathologic features of spinal involvement in diffuse idiopathic skeletal hyperostosis (DISH). Radiology 119:559-568 7. Testut, Latarjet (1948) Trait6 d'Anatomie Humaine TL, 9~ Ed. Doin, Paris