3-D sonography for diagnosis of disk dislocation of the temporomandibular joint compared with MRI

Ultrasound in Med. & Biol., Vol. 32, No. 5, pp. 633– 639, 2006 Copyright © 2006 World Federation for Ultrasound in Medicine & Biology Printed in the USA. All rights reserved 0301-5629/06/$–see front matter

doi:10.1016/j.ultrasmedbio.2006.02.1401

● Original Contribution 3-D SONOGRAPHY FOR DIAGNOSIS OF DISK DISLOCATION OF THE TEMPOROMANDIBULAR JOINT COMPARED WITH MRI CONSTANTIN A. LANDES,* WOJCIECH A. GORAL,* ROBERT SADER,* and MARTIN G. MACK† *Department of Oral Maxillofacial and Plastic-Facial Surgery; and †Department of Diagnostic and Interventional Radiology, Frankfurt University Medical Centre, Frankfurt, Germany (Received 19 September 2005, revised 31 January 2006, in final form 10 February 2006)

Abstract—This study determines the value of three-dimensional (3-D) sonography for the assessment of disk dislocation of the temporomandibular joint (TMJ). Sixty-eight patients (i.e.,136 TMJ) with clinical dysfunction were examined by 272 sonographic 3-D scans. An 8- to 12.5-MHz transducer, angulated by step-motor, was used after picking a volume box on 2-D scan; magnetic resonance imaging followed immediately. Every TMJ was scrutinized in closed- and open-mouth position for normal or dislocated disk position. Fifty-three patients had complete data sets, i.e., 106 TMJ, 212 examinations. Sonographic examination took 5 min, with 74% specificity (62% closed-mouth; 85% open-mouth); sensitivity 53% (62/43%); accuracy 70% (62/77%); positive predictive value 49% (57/41%); and negative predictive value 77% (67/86%). This study encourages more research on the diagnostic capacity of 3-D TMJ sonography, with the advantage of multidimensional joint visualization. Although fair in specificity and negative predictive value, sensitivity and accuracy may ameliorate with future higher-sound frequency, real-time 3-D viewing and automated image analysis. (E-mail: [email protected]) © 2006 World Federation for Ultrasound in Medicine & Biology. Key Words: 3-D ultrasound, Temporomandibular joint, Temporomandibular dysfunction, MRI, Disk dislocation, 3-D sonography, Four-dimensional sonography.

tablished comparing postmortem cryosections to previous TMJ-MRI (Westesson et al. 1985; Tasaki and Westesson 1993), whereas arthrography shows merely 83% accuracy combined with videofluoroscopy (Westesson and Bronstein 1987) and is associated with radiation exposure, invasive and may be complicated by allergy, infection and pain. Rapid MRI sequences permit reconstructed, yet not real-time, motion cycles (Eberhardt et al. 2000). MRI as diagnostic aid is limited by the costs and low availability (variable according to country, investigator and clinical setting). Therefrom results limited repeatability; moreover, reduced patient comfort and considerable duration of the examination occur. Sonography allows dynamic real-time visualization of the TMJ (Landes et al. 2000), yet so far only conventional sonography in two dimensions has been reported (Stefanoff et al. 1992; Emshoff et al. 1997; Hayashi et al. 2001; Uysal et al. 2002; Emshoff et al. 2002). Twodimensional (2-D) sonography allows fast reliable assessment of condylar translation, considerable information of disk position, yet without three-dimensional (3-D) viewing (Landes and Sterz 2003a,b; Landes 2004). TMJ examinations are comfortable for the patient. There is no

INTRODUCTION Temporomandibular joint dysfunction (TMD) is a common disorder and is clinically classified (Helkimo 1976) because it presents with an array of symptoms: pain, joint sounds, headaches, tinnitus and irregular jaw movements (Eversole and Marchade 1985; Dworkin and LeResche 1992). Magnetic resonance assessment evidenced disk dislocation, degeneration, perforation and fibrosis (Westesson et al. 1985; Lundh and Westesson 1989; Truelove et al. 1992) to be associated with TMD. Disk dislocation is the most obvious pathology and, therefore, a new sonographic diagnostic technique should in the first place become evaluated here with defined parameters against the standard diagnostics. Magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) today is widely used and can reliably depict anatomic details of the disk-condyle alignment. A diagnostic accuracy of 95% has been es-

Address correspondence to: Dr. C. Landes, Oral Maxillofacial and Plastic-Facial Surgery, The Frankfurt University Medical Centre, Theodor-Stern-Kai 7, 60596 Frankfurt, Germany. E-mail: [email protected] 633

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need for intraoral examination at low cost and high availability. Transducer position lateral to the condyle, disk and joint capsule gives a frontal (Emshoff et al. 1997) or axial (Landes et al. 2000) section view. However, 2-D sonography does not show the complete 3-D lateral joint architecture, which might be helpful for better differentiation of lateral vs. anterior disk dislocation. The validity of 3-D TMJ sonography for assessment of disk dislocation is assessed by this study. PATIENTS AND METHODS From July 2002 to May 2003, 68 consecutive TMD patients (44 females, 24 males; mean age 32 y, range 14 to 77 y; 136 TMJ examinations) were referred to the TMJ Clinic at our department for static 3-D sonography. As their primary complaint, all patients reported pain and dysfunction of the temporomandibular area. Informed consent was obtained and sonography was performed in single-blind manner, i.e., sonograms were analyzed without knowledge of the MRI results. The first author’s examination results with regard to disk position were reported to the second examiner for statistical analysis. The results were compared with those assessed by the radiologist who assessed the MRI pictures from the identical joint. MRI examination was performed directly after the sonographic examination. To maintain comparable jaw position, the closed-mouth and maximum opening positions were used for comparison. All 3-D sonographic trials were performed with Voluson 530 equipment (General Electric-Kretz, Solingen, Germany). The transducer was an 8- to 12.5-MHz linear array, moved by a step motor. Initially, a 2-D positioning of the target-volume over the joint and mandibular condyle was performed, first tilting the transducer to obtain optimum visualization. The transducer was oriented in the standard planes of head and neck sonography, parallel-inferior to the zygomatic arch (Siegert 1987). Therefore, the transducer intersected axially the lateral superior and inferior joint compartment. Sections parallel to the route of condylar translation were obtained by positioning the transducer in anterioposterior orientation parallel to the zygomatic arch (Fig. 1). The static examination was held in occlusion and maximal mouth opening. The disk was seen as a hypoechogenic band overlying the lateral condylar pole (Figs. 2 and 3). The disk position was considered to be normal when overlying the condyle between the most anterior-superior point and lateral pole. The MRIs were judged independently by an experienced radiologist. A 1.5-T MRI (Magnetom Vision, Siemens, Erlangen, Germany) with a dedicated surface TMJ coil was used to acquire simultaneous bilateral sagittal oblique and coronal oblique images. The

Fig. 1. Showing the standard closed-mouth and open-mouth positions of the transducer parallel and inferior to the zygomatic arch (parallel to the Camper-line).

imaging protocol included sagittal oblique and coronal oblique T1-weighted spin echo (SE) sequences (450/15 [repetition time ms/echo time ms], imaging matrix 256 ⫻ 256, field of view 128 mm, pixel size 0.5 ⫻ 0.5 mm, slice thickness 3 mm) and sagittal oblique T2- and proton density-weighted turbo spin echo (TSE) sequence (2840/ 103 to 15, matrix 512 ⫻ 512, field of view 128 mm, pixel size 0.3 ⫻ 0.3 mm, slice thickness 3 mm). All sagittal oblique sections were orientated perpendicular to the long axis of the condyle in transverse plane. The patient was positioned in supine position. Sequential bilateral images were obtained in the closed-mouth and maximum opening position. The MR images were interpreted without knowledge of the findings at sonography. The disk position was considered to be normal if the posterior band of the disk was located in a 12 o’clock or superior position relative to the condyle. Disk displacement was diagnosed in patients in whom the posterior band of the disk was situated anterior, anteromedial, anterolateral, medial or lateral relative to the condyle. The functional disk-condyle relationship of the TMJ was diagnosed as normal (grade 0), displacement with reduction (grade I) or displacement without reduction (grade II). This classification depended on whether disk displacement was found in situ in the closed-mouth position or the disk was absent between the condyle and articular eminence in the open-mouth position. The statistical parameters—sensitivity, specificity, accuracy, positive and negative predictive value of 3-D sonography—were compared with MRI. The results were moreover compared by ␹2 testing. RESULTS The datasets of 53 patients (106 joints) were complete. Nine (14% of the total of 68 joints) MRI exami-

3-D TMJ-sonography for disk dislocation ● C. A. LANDES et al.

Fig. 2. (a) Shows the proper closed 3-D sonography in a previously defined volume box in frontal (above left), top (above right) and side view (below left). The scan axially transects the lateral joint. Scrolling permits choosing of deliberate sections within the scanned volume (below right); and (b) depicts the manual cut placed into the volume box and the 3-D volume block (below right). The disk was seen as a hypoechogenic band overlying the hyperechogenic lateral condyle pole. The frontal view informs about lateral-medial disk position, the top view about anterior-dorsal disk displacement and the lateral view transects the disk and lateral pole.

nations and four (6%) sonographs dropped out as the images were lost. Two (3%) patients developed claustrophobia during MRI and interrupted the procedure. One patient had communication problems and did not properly open her mouth on demand. Altogether, 212 of 272 images were analysed (105 in the closed-mouth position, 107 in the open-mouth position). For the diagnosis using 3-D sonography, it proved valuable to cut the data block into several transections because hypoechogenic structures were displayed as transparent and echogenic structures displayed as opaque in proportion to their echogenicity. Initially, an axial cut just transecting the upper condylar pole and disk was preferred. This was later changed to a coronal and sagittal cut (Figs. 4 and 5, or online at www.constantinlandes.net). The latter was the most important for diagnosis

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of disk position because it allowed the easiest determination of anteroposterior disk position. Three-dimensional sonography revealed n ⫽ 29 (62%) of 47 MRI-verified internal derangements (e.g., disk displacements; see Tables 1-4). Three-dimensional sonographic accuracy vs. MRI reached 70% (62% in the closed-mouth, 77% in the open-mouth position). The sensitivity was 53% overall (62% closedmouth/43% open-mouth position); more disk dislocations were correctly discerned in closed position. The specificity reached 74% (62/85%); the openmouth position was more specific for disk dislocation and permitted correct determination of normal disk position. The positive predictive value was 49% (57/41%); the negative predictive value was 77% (67/86%).Therefore, the closed-mouth position was more reliable for disk dislocation assessment and the open-mouth position for normal disk position. Disk displacement grade 0 was correctly diagnosed by 3-D sonography in 36 (62%) of 58 grade-0 TMJ, disk displacement with reduction in 19 (68%) of 28 grade-I TMJ, grade II displacement without reduction was correctly diagnosed in eight (40%) of 20 TMJ. In 18 of 105 available closed-mouth examinations, sonography produced false-negative results, i.e., 17%. In several cases, MRI revealed a medially displaced disk in the closed-mouth position. Comparing positive and negative results, sonography depicted disk dislocation in the closed-mouth position with more precision than in the open-mouth position (29 of 105 examinations were true positive, 22 examinations were false positive. In the open-mouth position, nine of 107 examinations were true positive, 13 examinations were false positive). Grade I reduction was identified more accurately than grade II without reduction (accuracy 68% vs. 40%). Sonography comparably detected grade I and grade 0 (68% vs. 62%). Chi-square testing revealed statistically significant deviation from the expected (MRI) results in the closed-mouth position: p ⫽ 0.04, not in the open-mouth position: p ⫽ 0.8; overall nonsignificant p ⫽ 0.26; at a level of significance of ␣ ⫽ 0.05. DISCUSSION A close association of symptoms of TMD and disk displacements has been repeatedly emphasized, and this study supports this concept. The percentage of disk dislocation of 45% was below the 77% to 89% quoted in other studies (Tasaki et al. 1996), whereas in asymptomatic patient groups, 30% to 33% of dislocated disks were detected (Katzberg et al. 1996). This may be an indication that many patients had TMD

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Fig. 3. Shows the volume block on the left in the sagittal and outlined disk overlying the likewise outlined lateral condylar pole in shape of a beret on the right in (a) closed mouth (on the right is a blueprint of the condyle, disk and capsule); (b) open mouth with normal disk position; (c) shows a closed mouth; and (d) open-mouth position with dislocated, nonrepositioning disk position or dislocation.

with a muscular imbalance and merely incipient degenerative joint disease. The accuracy of high-resolution 2-D sonograms compared with MRI, in general, was reported to be 83% to 95% (Landes et al. 2000; Emshoff et al. 2002); even a “perfect agreement” was found (Uysal et al. 2002). This study examined the benefit of 3-D sonography and compared 3-D sonograms with MRI for assessment of disk dislocation. Three-dimensional sonographic examination of the TMJ had an accuracy

Fig. 4. Above left and right show the sagittal cut that is manually placed through the volume block to provide a frontal view of the mediolateral disk position.

Fig. 5. The 3-D view in sagittal (left) and additional frontal (right) viewing mode in (a) closed-mouth; and (b) open-mouth positions.

3-D TMJ-sonography for disk dislocation ● C. A. LANDES et al.

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Table 1. Sonographic result distribution compared with MRI in (a) closed- and (b) open-mouth positions Disk dislocation, mouth closed ⫹ 3-D sonography

–

⫹

29 True positives (TP)

22 False positives (FP)

–

18 False negatives (FN)

36 True negatives (TN)

All with disk dislocation 47 Sensitivity ⫽ TP/(TP⫹FN) ⫽ 0.62

All without disk dislocation 68 Specificity ⫽ TN/(FP⫹TN) ⫽ 0.62

All with positive test Positive predictive value ⫽ 51 TP/(TP ⫹ FP) 0.57 All with negative test Negative predictive value ⫽ 54 TN/(FN ⫹ TN) 0.67 Everyone TP ⫹ FP ⫹ FN ⫹ TN Pre test probability ⫽ (TP⫹FN)/(TP⫹FP⫹FN⫹TN) ⫽ 0.45

(a) Disk dislocation, mouth open ⫹ 3D sonography

⫹ –

–

9 (TP)

13 (FP)

12 (FN)

73 (TN)

All with disk dislocation 21 Sensitivity ⫽ TP/(TP ⫹ FN) ⫽ 0.43

All without disk dislocation 86 Specificity ⫽ TN/(FP ⫹ TN) ⫽ 0.85

All with positive test Positive predictive value ⫽ 22 TP/(TP ⫹ FP) 0.41 All with negative test Negative predictive value ⫽ 85 TN/(FN⫹TN) 0.86 Everyone TP ⫹ FP ⫹ FN ⫹ TN Pre test probability ⫽ (TP ⫹ FN)/(TP ⫹ FP ⫹ FN ⫹ TN) ⫽ 0.20

(b)

of 70% (62% closed-mouth, 77% open-mouth) compared with MRI. This is a value not as significant than previous 2-D studies by other authors; however, this probably indicates investigator and equipment variation. However, specificity and sensitivity could be optimized compared with a previous 2-D study by the author (Landes et al. 2000). Diagnostic capacities may be improved when 7.5-MHz transducers are replaced by 12-MHz transducers (Emshoff et al. 2002). The transducer in this study used 8- to 12-MHz, depending on the focus. Using the high “resolution mode” with enhancement of echoes between 12.5 and 4.5 MHz and

Table 3. MRI and 3-D sonography diagnoses MRI diagnoses 160

144

140 total

120

closed

100 80

86

60

open

71

68

73

58 35

40

right TMJ left TMJ

47 33

21

20 0 Dis loc ation

No dis loc ation

(a) 3-D Sonography Diagnoses

Table 2. Distribution of true/false positives vs. MRI in openand closed-mouth position. True/False-Positive and Negative Distribution 80

73

60 false-positive

36

139 total closed

85

73 51

43 22

open

76

54

63

right TMJ left TMJ

30

Dislocation

true positive

50

30

120 100 80 60 40 20 0

70

40

160 140

No dislocation

(b)

true negative

29 22

20

false-negative

18 9

10

13

0 Closed-mouth

Open-mouth

12

In the a) MRI diagnoses, 68 of 212 examinations showed disk dislocations (32%) and b) 3D TMJ sonography showed 73 of 212 examinations with disk dislocation (34%). Disk dislocation was more frequent in closed mouth position than in open mouth position left and right joint were evenly distributed.

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Table 4. Synopsis of 3D-sonographic accuracy, sensitivity, specificity, positive predictive value and negative predictive value in diagnosing disk dislocation grades, fibrosis and perforation vs. MRI Results 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

Total average

Accurracy

Sensitivity

Closed-mouth

Specificity

Open-mouth

Positive predictive value

Negative predictive value

near-field focus did improve the diagnostic efficacy, and this was therefore employed throughout this study. Selecting a second frontal or axial visualization plane in cases where the disk position in the standard sagittal plane was uncertain was the biggest advantage over 2-D sonography. The data block whose acquisition did not take more time than regular 2-D sonography could be cut at any plane, making the diagnosis of lateral, medial disk dislocation feasible; this is not possible with 2-D sonography. Three-dimensional visualization may improve when automated image enhancement is available. The use of “4-D sonography” was explored on a trial basis (see www.constantinlandes.net). A disadvantage of the method is that suboptimal angulation of the transducer may easily cause the correctly positioned disk to disappear from the sonographic picture in the 2-D linear B-scan. This was the major reason for false-negative results in 2-D sonography. If the beam does not intersect the disk at its lateral portion in the axial plane, higher echoes resulting in part from artifactual echoes (multiple reflection echoes) between the osseous surfaces (Malzer 1992) make the disk appear scarred, flat or dislocated. False-negative results were mainly caused by effusion and joint capsule edema that mimicked a disk in regular position. The medial joint is not accessible to 2-D sonography and, thus, a medially dislocated disk cannot be identified (Emshoff et al. 2002). The tissue block obtained by 3-D sonography made the diagnosis of combined dislocations easier and a 3-D in-depth view of the hypoechogenic disk was possible. Cryosections have shown high correlation of MRI findings to postmortem histologic examination and, therefore, it seems justified to correlate to MRI as reference standard in this study (Tasaki and Westesson 1993).

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The observers have been involved with TMJ sonography and MRI for more than 5 y, and the learning curve has entered a steady slope; however, despite this, individual observer variation can influence the result. Retest examinations have shown a 96% concordance. MRI is a somewhat artificial examination setting, and an anxious patient in the prone position may exhibit stronger dislocation as consequence of bruxism. Problems with interpretation of MRI sections have been annotated by Brady et al. (1993) when MRI results only correlated with 71% sensitivity and 91% specificity compared with clinical assessment. The principal advantage of using 3-D sonography was to obtain a complete overview of the condyle and disk, not a transection. This made the interpretation much more feasible. The transducer position and, thus, the insonating angle, were not viewed as keenly as in 2-D sonography. Yet the upper margin of the selected 3-D “box” from the 2-D pilot picture has to be adjusted as a box-cube and cannot follow the slope of the condyle in real-time mode to reproduce the translation of an identical point in motion. An adjustable nonlinear border might enhance the results. The potential of TMJ sonography lies in noninvasive, increasingly reliable diagnosis of TMJ disk dislocation at times where budgetary considerations play an important role in patient management. The high specificity (85%) and negative predictive value (86%) in open-mouth position should exclude a pathologic disk position with about 90% certainty. When the sonographic examination is unobtrusive, it will need to be prospectively combined with higher sensitivity to clearly select TMD patients for splint therapy (Okeson 1988), with the remaining cases submitted to MRI only. Prospectively, real-time 3-D sonography will be compared with rapid MRI sequences. In this report, 3-D-sonography is applied in the first assessment for the diagnosis of disk dislocation of the temporomandibular joint. The proposed measurement takes ⬍5 min and is adequate for a differentiation of normal disk position and partial and full dislocation with repositioning or without. Sonography is fast and comfortable for the patient, setting aside the initial outlay for sonographic equipment; it is an economic and versatile alternative, although only advanced equipment provides 3-D reconstruction. Alternative methods for TMJ diagnosis, such as arthrography or arthroscopy, are invasive; MRI is limited by cost, expense, duration and availability. 3-D sonography should be further enhanced by improved image resolution, automated image enhancement and higher emission frequency. As satisfactory specificity and negative predictive value for a screening instrument were obtained, sensitivity and accuracy may improve with future higher frequency, real-time viewing

3-D TMJ-sonography for disk dislocation ● C. A. LANDES et al.

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