Index terms:Jaws

abnormalitiescomputed tomography

Correlative thin sectiontemporomandibularjoint anatomyand computed tomography

Edwin L. Christiansen, D.D.S.*

Joseph R. Thompson, M.D.t

Anton N. Hasso, M.D.t

David B. Hinshaw Jr., M.D4

The author believes That multiplanar CT imaging serves todistinguish the articular disc from other tissues of similardensity and Is necessary for a detailed temporomandib-ularjolnt survey.

Introduction

The purpose of this exhibit is to present correlative anatomic sectionsand multiplanar CT images ofthe temporomandibularjoint (TMJ). This willafford the reader an opportunity to determine the efficacy of CT in dem-onstraling the articular disc in normal and abnormal situations. The colortissue sections were obtained in various planes through thejoints of unem-balmed, frozen cadavers, with the jaws closed.

OTimaging was performed on either the General Electric 8800 or9800w scanner. Using the Arrange#{174}1program, vertically reformatted im-ages were made from the scan data of I .5 mm thick transaxial sectionsobtained with a 0.5 mm overlapping in accordance with our standardclinical scanning protocol (1,2,3,45,6).

Selected correlative CT sections obtained by direct coronal or sagittalscanning have been included for comparison with the reformatted im-ages. CT number highlighting has been used in most cases in order to ac-centuate tissues of disc attenuation. To asslstthe reader, all reformattedimages were filmed with the same coronal, sagittal and axial orientation(Diagram 1).

1General �ectricCompany, Medical Systems Group, Milwaukee, WI.

Volume 6, Number 4 ‘ July, 1986 #{149}RadioGraphics 703

THIS EXHIBIT WAS DISPLAYED AT THE71ST SCIENTIFIC ASSEMBLY AND AN-NUAL MEETING OF THE RADIOLOGI-

CAL SOCIE1Y OF NORTH AMERICANOVEMBER 17-22. 1985. CHICAGO,

ILLINOIS. IT WAS RECOMMENDED BYTHE GENERAL AND NEURORADIOL-OGY PANELS. AND WAS ACCEPTEDFOR PUBLICATION AFTER PEER REVIEWON FEBRUARY17, 1986.

From the School of Dentis-

try, Department of Endodonticsand School of Medicine (*), De-

partment of Radiation Sciences,Sections of Neunonadiology (t),and Magnetic Resonance Imag-

ing (t)� Loma Linda University.Supported in part by a

grantfnom the Medical Systems

Group of General Electric Com-

pany, Milwaukee, and a grant

from the Foundation for Ortho-

dontic Research, Pacific

Palisades, California.

Address reprint requests to

EL. Chnistiansen, D.D.S., Depart-

ment of Endodontics, Section of

TMJ/Onofacial Pain, School of

Dentistry, Loma Linda University.Loma Linda, CA 92350.

C0

U

:1

CORONAL

AXIAL

c�9�17

TMJ anatomy and CT Christlans#{149}n#{149}tal.

7 04 RadioGraphics #{149}July, 1986 #{149}Volume 6, Number 4

SAGITTAL

Normal JoInt

The normal relationships of the TMJ bone and soft tissues are clearlyshown in the nightTMJ of cadaver #1 in Figures 1-3. Ofthe 16 cadaverjoints scanned and sectioned by the authors using this method, only onewas normal.

z0

a

03

Christianson et al. TMJ anatomy and CT

Volume 6, Number4 #{149}July, 1986 #{149}RadioGraphics 705

Figure IASagittal section, lateral aspect This sec-tion shows the articular disc (arrow), condyle,C, temporal bone, T,and external auditorymeatus, EAM.

Figure lBThe planes ofthe coronal and sagiffal sectionsare shown bythe cursor lines on the transaxialimages. The sagiffal image represents thesame plane as the colon section (IA).

C

0

a

0z

r�, .�

rj #{149}�: �

TMJ anatomy and CT Christlansen et al.

706 RadloGraphics #{149}July, 1986 #{149}Volume #{243},Number 4

Flgure2ASagittal section, central aspect The pos-tenor disc band (arrow) rests atthe 12 o’clockposition on the mandibular condyle. The thinportion of the disc is the functional jointinterval.

Figure 2BIn this multiplanar panel, the coronal imagerepresents a plane through the anterior as-pect of the condyle. The sagittal section con-respondsto the plane ofthe color section (2A).

z

0

a

03

Christianson #{149}tal. TMJ anatomy and CT

Volume 6, Number 4 #{149}July, 1986 #{149}RadioGraphics 707

Figure 3ASagittal section, medial aspect The ten-dinous insertion ofthe lateral pterygoid mus-cle (arrowhead) isseen inferiorto the anteriordisc band (arrow).

Figure 3BIn this multiplanar panel, the plane of thecoronal image is located anteriorto the con-dyle. The sagittal image corresponds to theplane of the color section (3A). In this sagiffalsection, the tendinous insertion ofthe lateralpterygoid muscle cannotbe differentiatedfromthe anterior disc band (arrow). Multipleimages in multiple planes are necessary toavoid confusing the disc with other tissues ofsimilar density.

LI�

TMJ anatomy and CT Christianson ot al.

708 RadioGraphics #{149}July, 1986 #{149}Volume#{243},Number 4

Slippage of the disc foundin the IeftTMJ ofcadaver #1and illustrated in Figures 4-6, isnotto be confused with disc dis-location, though it may be aprerequisite to it. Discs thathave slipped either medially orlaterally present a radiologicdiagnostic problem. Arthro-grams or tomoarthrograms, insuch cases, usually appear un-remarkable owing to the ab-sence of an anterior compo-nent to the disc dislocation.

Flgure4ACondylar axis coronal section, an-tenor aspect The disc (arrow), con-dyle, C, and temporal bone, T,areshown.

Flgure4BCoronal and sagittal reformattedimages orientedtothe axis ofthe con-dyle The plane ofthe coronal sec-tion is the same as thatofthe colorimage.

MedIal Disc Slippage

Christianson ot aI. TMJ anatomy and CT

aa

00U)

‘U‘Uaia0

- ;�:-� �:.3 ,...,,- --, =.

lip

Volume 6, Number 4 #{149}July, 1986 #{149}RadioGraphlcs 709

Figure5ACondylar axis coronal section, central as-pect The posterior disc band (arrow) issuperior to the condyle. Thinned and redun-dantlateral disc can also be seen (arrow-head).

Figure SBCoronal and sagiffal reformaffed imagesrepresentthe planes through the central as-pectofthe condyle. The plane ofthe coronalsection is the same as thatofthe color image.

0

aa.

U)

U00a

Figure 6ACondylar axis coronal section, posterIor as-pect The vasculanized retrodiscal tissuescan be seen (arrow).

TMJ anatomy and CT Christianson et al.

7 1 0 RadioGraphics #{149}July, 1986 #{149}Volume 6, Number 4

Figure 6BCoronal and sagiffal reformaffed imagesrepresent planes through the posterior andmedial aspects ofthe condyle. The plane ofthe coronal section isthe same as that of thecolor image (OA).

Anteromediai Disc Dislocation

‘...(

Christianson et ai. TMJ anatomy and CT

Volume 6, Number 4 #{149}July, 1986 #{149}RadioGraphics 7 1 1

Anteromedial dislocationsof the articular disc are re-ported most frequently. An-teromedially dislocated discsare variously reported to ac-count for from 57 to 95% of discdislocations (7,8). Figures 7-9 ofthe left TMJ of cadaver #2 illus-trate anteromedial dislocation.

Figure 7ACoronal section atthe plane of thearticular eminence This sectionshows the anterior disc band (arrow)dislocated forward, the mandible, M,and thetemporal bone, T.

Figure 7BThis direct coronal scan corresponds tothe plane of the color section (7A).

C

0

a

TMJ anatomy and CT Christianson ot al.

7 1 2 RadloGraphics #{149}July, 1986 #{149}Volume 6, Number 4

Figure8ACoronal section, central condylar aspectThe temporal articular surface (arrowhead)conforms to the shape ofthe antenomediallydislocated disc. The posterior disc band(arrow) is shown, as are the thinned and re-dundantlatenal disc tissues.

Figure 8BThis direct coronal scan corresponds to theplane of the color section (8A). Note the nan-rowed supenionjoint space (arrows).

030a.a

00

I

Christianson et al. TMJ anatomy and CT

Volume #{243},Number 4 #{149}July, 1986 #{149}Radiooraphics 713

Figure 9ACoronal section, posterior aspectofthe con-dyle The retnodiscal tissues (arrow)occupy the joint space, which should containthe posterior disc band.

Figure9BThis direct coronal scan corresponds to theplane of the color section (9A).

Rotational Anterior DIsc DislocatIon

TMJ anatomy and CT Christianson ot al.

7 14 RadioGraphics #{149}July, 1986 #{149}Volume 6, Number 4

The gross changes in discshape and loss ofjoint space,seen inthe lateral portion of the

right TMJ of cadaver #3 (Figure10), are due to a partial, rota-

fional disc dislocation. Movingfrom lateral to medial In thejoint (Figures 1 1 and I 2), it is ob-vious that only laterally Is thedisc clearly dislocated.

Figure IOASagiftal section, lateral aspectThis section showsthe dislocated andmisshapen disc (arrow),the condyle, C,the temporal bone, 1,and externalauditory meatus, EAM. The condylar sun-face has articulated on the thinnedretrodisctissues (arrowhead).

Figure lOBThe coronal reformaffed image repre-sents the plane ofthe articular emi-nence; the sagittal image correspondsto the plane of the color section (bA).

I

Christianson et al. TMJ anatomy and CT

Volume #{243},Number 4 #{149}July, 1986 ‘ Radioraphics 715

Figure hASagittal section, central aspect Carfilag-inoustransformation offhe refrodisc tissuescan be seen superiorto the condyle (arrow).

Figure hIBDirectsagittal, bone detail scans representingplanesfrom the Iateralto the medial aspectsofthe TMJ showthe decreased superior jointspace and the increased space anterior tothe condyle. The disc shadows are faintly visi-ble on each image (window 4000 H, level 80).

C

0

a

TMJ anatomy and CT Christianson ot al.

7 16 RadioGraphics #{149}July, 1986 #{149}Volume 6, Number 4

Figure 12ASagiftal section, medial aspect The disc(arrow) remains malpositioned and mis-shaped but not so dramatically as in the lat-eral portion ofthejoint (Figure bOA).

Figure l2BThe coronal reformaffed image representsthe anterior plane ofthe condyle; the sagiffalimage corresponds to the plane ofthe colorsection (12A).

Anterolateral Disc Dislocation

Christianson ot al. TMJ anatomy and CT

Volume 6, Number 4 ‘ July, 198#{243}#{149}RadioGraphics 717

It has been reported thatthe lateral fascial fat plane ofthe lateral pterygoid musclemay be obscured, on CT Im-ages, by an anterolaterally dis-located disc (9). This is illustra-ted in the left TMJ of cadaver#3 in Figures 13-15.

Figure 13ATransaxial section nearthe plane ofthe articular eminence (large arrow)This section shows the condyle, C, theexternal auditory meatus, EAM, and theposterior disc band (arrow).

Figure h3BThese are successively more inferiortransaxial scans highlighted throughthe left TMJ. The upper left image isslightly superior to the plane of thecolor section (b3A).

C0

TMJ anatomy and CT Christianson #{149}tal.

7 1 8 �a�io�rapi�ics #{149}July, 1986 #{149}Volume #{243},Number 4

Figure 14ATransaxial section atthe plane ofthe supe-nor aspect of the insertion of the lateralpterygoid muscle(large arrow), as seen frombelow One can clearly see the deformed,anterolaterally dislocated disc (arrow) with awidened inferiorjointspace, i, and a promi-nentsuperiorjoint space laterally, s.

Figure l4BThese transaxial scans were generated usinga softtissue window (GE9800). The lower leftimage corresponds tothe plane ofthe colorsection (b4A).

aa

aD

0

I

�. �

� ,,‘i � .‘�; ‘

Christianson ot ai. TMJ anatomy and CT

Volume #{243},Number 4 #{149}Ju� 1986 #{149}RadioGraphics 719

Figure ISATransaxial section through the insertion ofthe lateral pterygoid muscle A portion ofthe disc (arrow) occupiesthe lateral fascialfat plane.

Figure ISBThesetransaxial scans were generated usinga soft tissue window (GE8800). The lower rightimage correspondsto the plane ofthe colorsection (b5A).

Anterior Disc Dislocation with Thinning

TMJ anatomy and CT Christianson of al.

720 RadioGraphics #{149}July, 1986 #{149}Volume 6, Number 4

CT, while sensitive for thedemonstration of the normal orthickened disc is insensitive forthe demonstration of a thinneddisc. A thinned disc may beidentified indirectly, however,by joint space narrowing. Athinned and dislocated discfound in the nightTMJ ofcadaver #5 is illustrated in Fig-ures l#{243}-18.

Figure16ASagittal section, lateral joint aspectThis section shows a thinned and dis-located disc (arrow), the condyle, C,the temporal bone, T,and the externalauditory meatus, EAM.

Figure I6BThe coronal nefonmaffed image repre-sents a plane near the anterior aspectofthe condyle;the sagittal reformattedimage corresponds to the plane of thecolon section (bA).

I0

0U)00U)

00a

03

3.-I3.

33

3(a

Christianson of al. TMJ anatomy and CT

Volume 6, Number 4 #{149}July, 198#{243}#{149}RadloGraphics 721

Figure17ASagittal section, central aspect This sec-tion showsthe monethinned central portion ofthe disc (arrow).

Figure17BThe coronal and sagittal reformatted imagesrepresent planes through the center of thecondyle. Note the narrowed joint space ineach plane (arrows).

CCC

‘C‘U.

‘C

I

TMJ anatomy and CT Christianson et al.

7 22 RadioGraphics #{149}July, 1986 #{149}Volume a,Number 4

Figure18A

Sagittal section, medial aspect This sec-tion shows a flattened temponaljoint surface(arrowhead) . The anterior band of the disc(arrow) rests on top ofthe superior belly of thelateral pterygoid muscle.

Figure 18BThe coronal reformatted image represents aplanethroughthe posterior aspectofthe con-dyle; the sagittal image corresponds to theplane of the colon section (b8A).

Christiansen of al. TMJ anatomy and CT

Volume 6, Number 4 #{149}July, 1986 #{149}RadioGraphics 723

Conclusions

Multiplanar CT imaging is necessary for a detailed temporomandibu-lar joint survey. Without multiplanar views, the articular disc is likely to beconfused with tissues of similar densily, e.g., the tendon of the lateralpterygoid muscle (Figures 3A and B). Temporomandibular joint articulardiscs may become dislocated asymmetrically in various directions (Fig-ures 7-9 and 13-15) leading to serious radiologic diagnostic problems.Some temporomandibular joint discs are relatively thick or opaque andare, therefore, readily seen with CT (Figures 10-1 2). Some temporoman-dibular joint discs, however, with or without dislocation, are less well vis-ualized with CT because ofdegenerative thinning (Figures lo-18).

Ref orences

I . Christiansen EL. Thompson JR. Anteriorly displaced TMJarticular disc: A case diagnosed by computed tomography.

Oral Surg Oral Med Oral Path 1984; 58(3):355-357.2. Thompson JR. Christiansen EL, Hasso AN, Hinshaw DB Jr. Dis-

location ofthe temporomandibularjointdisk demonstratedbyCT.AJNR 1984; 5:115-1 16.

3. Thompson JR. Chnistiansen EL, Hasso AN, Hinshaw DB Jr. Tem-

poromandibular joints: High resolution computed tomo-graphic evaluation. Radiology 1984; 150:105-107.

4. Chnistlansen EL, Thompson JR. Kopp S. HassoAN, Hinshaw DBJr. Radiographic signs of temporomandibularjolnt disease.J Dento-maxillofac Radiol 1985; 14(2)83-91.

5, Thompson JR. Christlansen EL. Sauser DD, HassoAN, HinshawDB Jr. Contnastarthnognaphyvensus computed tomographyfor the diagnosis of dislocation of the temporomandibular

joint meniscus. AJNR 1984; 5:747-750 and AJR 1985;144:171-174.

6. Christiansen EL, Thompson JR. Kopp S.Temponomandibularjoint research: An update. J Cal DentAssoc 1984; 12:157.

7. Thompson JR. Christiansen EL,HassoAN, Hinshaw DB Jr. Nor-mal and abnormal positional relationships of the TMJ disc

demonstrated with CT, anthrography, and tissue photo-

graphs. Proceedings ofthe Thirty-third Annual Meeting ofthe Association of Universily Radiologists, May I 2-1 7. 1985.Abstract #136

8. Anderson QN, Katzberg RW, Helms CA Radiologic imagingofthe temponomandibulanjoint. Radiology 1985; 157(P):20.

9. Manzione JV, Katzberg RW. BrodskyGL. Seltzer SE. Mellins HZ.Internal derangements of the temporomandibular joint:Diagnosis bydirect sagittal computed tomography. Radiol-ogy1984; 150:111-115.

The authorswish to expresstheir sincere thanksto Mr. Roland Rhynus. Chief Technologist.Section of Neunonadiology, for the many hours spent scanning the cadaver joints.