Significance of arthrography and computed tomography in the assessment of internal derangement of the temporomandibular joint

J. Cranio-Max.-Fac. Surg. 15 (1987) I. Cranio-Max.~Fac. Surg. 15 (1987) 265-269 © Georg Thieme Verlag Stuttgart • New York

Significance of Arthrography and Computed Tomography in the Assessment of Internal Derangement of the Temporomandibular Joint Irene Jend-Rossmann I, Hans-Holger Jend2, Ralf SiegertI 1Departmentof Maxillofacia[Surgery,NordwestdeutscheKieferklinik (Head: Prof. G. Pfeifer,M.D., D.M.D.)and 2Departmentof Radiology(Head.Prof.Dr. E. Bticheler,M.D.),University HospitalHamburg(UKE),Hamburg,W-Germany Submitted 24. 6. 86; accepted 20. 8. 86

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Summary Arthrography was performed on 56 joints of 47 patients presenting with symptoms of pain and dysfunction of the temporomandibular joint. The diagnosis could be confirmed in 53 joints. In addition, there was evidence of 13 perforations and 7 joints with adhesions. In 51 of the affected joints, computed tomography (CT) was also performed to compare both methods. The same CT procedure was performed on 12 joints of patients without any joint problem. Almost consistently (88 %), an arthrographically anteriorly dislocated disc was detectable in the axial CT scans, 92 % of the healthy joints showed normal soft tissue structures. For CT visualization of a displaced disc sagittal reformations or primary sagittal scans are not necessary. Confirmation of possible perforations or adhesions cannot be made by CT. Comparing the advantages and disadvantages, arthrography must still be regarded as superior to CT. In some cases, however, CT is a valuable tool in assessing an internal derangement.

Key-Words Introduction Internal derangement of the temporomandibular joint has been recognized as a reason for functional disturbances in many cases of so-called myoarthropathy. It can usually be described as anterior or anteromedial displacement of the joint disc relative to the condylar head. In developing the present concept of the underlying pathology (Farrar, 1971), arthrography has played a major part. Its va!ue in assessing and confirming the different stages of internal derangement is undeniable (Fig. 1-3). On the other hand, there is still some opposition to arthrography, it being an invasive technique, and efforts to replace it by a non invasive method seem justifed. Computed tomography (CT) - having much improved in its spatial resolution - has been reported as being capable of depicting the TMJ meniscus by various techniques (Helms et al., 1984; Manzione et al., 1984; Sartoris et al., 1984). Having developed our own standardized method which permits evaluation of axial scans, we had a series done in a group of patients who also underwent arthrography, in order to compare the results of both methods.

Temporomandibular joint - Arthrography - Computed tomography

In all 47 patients computed tomography was intended, but not done for some reason in 4 (51 affected joints of the remaining 43 patients). Positioning of the patient was as for cranial CT. The patient was asked to open the mouth near to the point where the click would appear. In a second series the patient opened the mouth maximally. If no sounds were audible or palpable, the scans were performed with the mouth maximally opened. A bite block stabilized the mandible in the desired position. The investigation was done on a SOMATOM 2 (Siemens Corp.). On a digital radiograph the scan level and gantry tilt were determined by selecting a plane cranial to the condylar head and parallel to Camper's line (meatus acusticus - spina nasalis

Material and Method In a period of 12 months 47 patients appeared at the Pain Outpatient Clinic of the Nordwestdeutsche Kieferklinik with clinical signs and symptoms of internal derangement of the temporomandibular joint. Evidence of internal derangement was based on the diagnostic criteria described in the literature (Farrar and McCarthy, 1979; Jend et al., 1986). All 47 patients underwent arthrography of the affected joints (n=56). Lower joint space arthrography was performed and interpreted with regard to dislocation with or without reduction (closed locking), perforation or a°dhesions according to the literature (Dolwick et al., 1979 Farrar and McCarthy, 1979; Katzberg et al., 1980; Ioannides and Scar 1985; Jend et al., 1987) (Fig. 1-3).

Fig. 1 Arthrography in an anterior disc displacement with reduction ("reciprocal clicks"): note widening of anterior recess.

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Fig. 2 Arthrography in a "closed locking" situation: characteristic upward pointing spike of the contrast medium in the anterior recess.

I. ]end-Rossmann et al.

Fig. 3 Arthrography of a chronic "closed locking" with perforation: filling of upper and lower joint compartments and delineation of the dislocated disc.

mouth fully opened was interpreted as a sign of disc repositioning (Fig. 5), its remaining, accordingly, was recorded as closed locking (Fig. 6). In addition to a persisting hyperdense crescent the blocked joint could be recognized on the scan from the lack of condylar protrusion. Results Arthrographically, the clinical diagnosis of an internal derangement could be confirmed in 53 joints (95 %). In addition, a perforation was diagnosed in 13 joints. Adhesions were detected in 7 joints (Table 1). CT investigations of 3 joints were eliminated because of different scanning techniques at the beginning of the study. In the affected joints an identical CT diagnosis was made in 42 joints, whereas 6 joints showed no sign of disc dislocation. The sensitivity of CT therefore worked out at 87 %. There were 6 positive diagnoses out of 32 clinically asymp-

Table

Fig. 4 Lateral digital radiograph shows Camper's line for positioning the plane of scanning. Note distance to the orbits.

anterior) (Fig. 4). 2 mm thick "stacked" slices were made until the necks of the mandibular condyles were reached. 760 projections with 460 mas were used. A study was performed on 12 clinically normal joints of patients with problems not related to the TMJ but mostly with brainstem problems. There was no indication for arthrography in this group.

Recognition of Disc Dislocation In pathological conditions the disc would appear as a round crescent-shaped or linear structure in front of the condyle and just below the eminence. The density was sfightty higher than that of the adjacent muscle (Fig. 5 and 6). If this structure was visible, an anteriorly dislocated disc was assumed. Its disappearance in the second series with the

1

Results of arthrography

-Total number: 56 joints (47 patients) - Internal derangement confirmed - Perforations - Adhesions

Table 2

Results of CT

Number CT: dislocated disc visualized negative CT: sensitivity specificity

53 13 7

Affected joints

Asymptomatic contralaterai joints

Joints of patients with no TMJ problems

48

32

12

42

6

1

6

26

t1

(81%)

(92 %)

87 % -

Arthrography and CT in the Assessment of Internai Derangement

Fig, 5 a Mouth opened to pre-click position. Displaced disc is seen as a hyperdense zone in front of the condylar head, Note additional partial obliteration of the fat pad lateral to the musculus pterygoideus lat. Fig. 5

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Fig, 5 b Mouth opened to post-click position. No hyperdensity in front of the condylar head: the disc has reduced.

Axial CT of reducing disc displacement of the right TMJ,

Fig, 6 a Ciosed mouth position. Displaced disc can be suspected from small hyperdense zone in front of the condyle as well as from slightly dislocated pterygoid fat pad. Fig. 6

J. Cranio-Max.-Fac. Surg. 15 (1987)

Fig, 6 b Mouth opened to maximum. Non-reducing displaced disc becomes more prominent due to bulging and folding.

Axial CT of anterior disc displacement without reduction of the right TMJ,

tomatic contraiatera! joints. Assertions about the posterior attachment, perforations, or adhesions could not be made from CT (Table 2). In the patient group with no TMJ problems there was only one joint out of 12 which showed signs consistent with anterior disc displacement. This would account for a specificity of 92 %, judging from the clinical impression.

Discussion

The evaluation of TMJ arthrography has been debated extensively in the literature (Dolwick et al., 1979; Farrar and McCarthy, 1979; Katzberg et al., 1980). Of the different techniques reported (Noergaard, 1947; Lundberg, 1965; Katzberg, et al. 1980; Westesson, 1983) arthrography of the lower joint space is most widely used. In our

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experience, spot films were sufficient for documentation (Fig. 1-3). In contrast to Ioannides and Scar (1985) we found a higher percentage of perforations. This high percentage of perforations may be due to an accumulation of advanced diseases at our institution when the study was initiated. Computed tomography is a non-invasive method capable of demonstrating both osseous and soft tissues. With improved resolution of 3rd and 4th generation scanners, Helms et al. (1982) first introduced the CT diagnosis of internal derangements by use of the blink mode in sagittal reformations. This procedure is still being used (Thompson et al., 1985). The method has been criticized, however, as being too dependent on the skill of the examiner (Manco et al., 1985). Manzione et al. (1984) therefore suggested direct sagittal CT scans as being more accurate, the disadvantage being, however, that this method requires special equipment for correct positioning, and that both sides need to be done separately. In addition, there can be picture degradation because of dental restorations (Sartoris et al., 1984; Simon et al., 1985). In our opinion, neither of those techniques is necessary, since any kind of information gained by direct sagittal scans, or even sagittal reformations, can be obtained from the axial plane as well. The only advantage of sagittal scans may be seen in the fact that the joint is more easily recognized by the clinician. The method we employed is time saving, easy, and can be carried out by a less experienced investigator. If the disc is small and thin without prominent ridges, the hyperdense zone may hardly be visible, and the diagnosis may then depend on the dislocated lateral pterygoid fat pad (Manzione et al. 1984) (Fig. 5 a, 6 a, b). Our correlation of positive findings between arthrography and CT of 87 % was slightly lower than claimed by Manzione et al. (1984) (94%, n=51), Helms et al. (1984) (97%, n=75) and Thompson et al. (1985) (90%, n = 10). The percentage of correct negative findings in CT was 8 1 % in the TMJ-patient group. We found a very high coincidence of clinical and arthrographic diagnoses of disc displacement. Nevertheless the comparison with the asymptomatic joints of the same group of patients may be deceiving since TMJ disorders very often involve both joints, with one joint predominating in discomfort and pain. It is possible that in some of the "false-positives" of this group, CT had shown early stages of internal derangements which had not yet led to clinical symptoms. Arthrographic study of these joints should be done if surgery is being considered. For the asymptomatic patient group we calculated a specificity of 92 %. These patients also lack the gold standard of arthrography. Looking for a test group we feel there is no indication to perform arthrography on patients without strong evidence of specific TMJ problems. Considering the accuracy of the clinical diagnosis of the disc displacement itself, the calculated specifity seems, however, to be a realistic value. In choosing a method for the diagnosis of an internal derangement, the clinician has to be aware of the specific advantages and disadvantages (Table 3). CT, being noninvasive, is well accepted by the patient, and there are hardly any contraindications. The radiation dose to the lens of the eye (especially if compared with arthrotdmography) is considerably lower (Helms et al., 1984). It is further diminished by our method of investigation. Placing the plane of scanning into Camper's line avoids direct irradia-

L Jend-Rossmann et ai. Table 3

Comparison of arthrography and CT

Advantages of arthrography

- Lower costs General availability - Shows perforations and adhesions - Shows dynamics of function Higher sensitivity -

Advantages of CT -

-

-

Non invasive Lower radiation dose to lens Shows both joints simultaneously

-

tion of the lens and exposes it only to scatter radiation of about 0.005 Gy. In tomography of the joint, irradiation of the lens amounts to at least 0.025 Gy (Jend-Rossmann et al., 1985). In the evaluation of axial scans as described, both joints are seen simultaneously. Some authors point to the simultaneous visualization of bone morphology with respect to arthrotic changes (Thompson et al., 1985). In a CT study which apparently included some patients with not clearlydefined internal derangements, Raustia et al. (1985) found an increased density of the condylar head. Gross structural changes of the TMJ are delineated by CT (Thompson et al., 1985), but can be depicted by conventional radiography as well. A promising feature of CT, however, may be the quantification of subtle changes of mineralization (Hi~Is et al., 1984; Manzione and Katzberg, 1984) correlated with different stages of internal derangement. Arthrography on the other hand costs less, is more sensitive and available with ordinary equipment in most radiology departments. Although invasive, the discomfort to the patient is only mild, and its specific risks can be considered low (Katzberg et al., 1980). Furthermore, it provides additional information about perforations and adhesions and about the dynamics of function which can be recorded on a video tape. Conclusion In summary we must conclude that arthrography is still superior to CT. In patients allergic to contrast media, however, or in those refusing arthrography for some other reason, in cases in which a sound clinical diagnosis needs only documentation, or in monitoring the effect of therapy CT can be a valuable tool in assessing an internal derangement.

References

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Dr. Dr. IreneJend-Rossmann Nordwestdeutsche Kieferklinik Martinistrafle 52 D-2000 Hamburg 20