Diagnostic Value of High-Resolution Ultrasound for the Evaluation of Capsular Width in Temporomandibular Joint Effusion

Abstract

Aim: The aim of this study was to evaluate if the increased temporomandibular joint (TMJ) capsular thickness, measured by ultrasound (US), is associated with the presence of effusion, diagnosed using MRI imaging. Materials and Methods: 102 patients with signs and symptoms of temporomandibular disorders were included in the study. Each patient underwent US and MRI examinations, 1 to 5 days following clinical examination. The US was performed with an 8−40 MHz linear transducer operating at 20 MHz. The MRI was performed using a 1.5 T MRI device. The ROC curve was analyzed to identify the optimal cut-off value for capsular distention, which can be interpreted as an indirect sign of TMJ effusion. Results: The capsular width values were found to be between 0.7 and 3.6 mm. The best cut-off value was 2.05 mm with a sensitivity of 55.9% and a specificity of 94.7%. The next optimal cut-off value was 1.75 mm with a sensitivity of 67.6% and a specificity of 82.4%. The area under the ROC curve was 0.78 (95% CI 0.68, 0.87, p < 0.05). Conclusions: Ultrasound-measured capsular width can be interpreted as an indirect sign of TMJ effusion. The critical cut-off for capsular width was 2 mm.

Keywords: effusion; magnetic resonance imaging; temporomandibular joint; ultrasonography.

Figure 1

High-resolution 20 MHz US image (a) of joint effusion detected by direct visualization and abnormal capsular width (2.12 mm). Sagittal oblique T2-weighted TSE with fat suppression image (b) of the same joint with effusion (arrow) posterior to the disc in the closed-mouth position.

Figure 2

High-resolution 20 MHz US image (a) of joint effusion detected by direct visualization and abnormal capsular width (2.46 mm). Sagittal oblique T2-weighted TSE with fat suppression image (b) of the same joint with effusion (arrow) anterior to the disc in the closed-mouth position.

Figure 3

High-resolution 20 MHz US image of an effusion in the left TMJ detected by abnormal capsular width (2.86 mm). 1—mandibular condyle; 2—articular disc; 3—glenoid fossa.

Figure 4

High-resolution 20 MHz US image of a normal TMJ: closed-mouth (a), opened-mouth (b). 1—mandibular condyle; 2—articular disc, situated with the intermediate part between the anterosuperior zone of the mandibular condyle and the posterosuperior part of the articular eminence; 3—glenoid fossa.

Figure 5

Scatterplot chart showing the relation between inter-observation time (MRI and US) and the capsular width, along with locally estimated scatterplot smoothing lines.

Figure 6

High-resolution 20 MHz US image of a TMJ with abnormal capsular width (2.33 mm) (a). Coronal T1 closed-mouth image (b) of the same TMJ with lateral disc displacement (arrow).

Figure 7

Bee swarm plot along with boxplot of the distribution of capsular width with values grouped by joint effusion presence.

Figure 8

The receiver operator characteristic curve (ROC) was plotted for the presence of the joint fluid identified with MRI, using the capsular width (mm) as measured by high-resolution 20 MHz US.