Computed tomographic evaluation of the density of the temporomandibular joint meniscus

Pathologic alteration of the articular disk, including moderate calcification within the meniscus proper, has been reported to occur in many cases of TMJ dysfunction with chronic anterior meniscal displacement. The purpose of this investigation was to measure, by means of direct sagittal computed tomographic scanning technology, the density (x-ray attenuation) of the meniscus. Fifty-two joints, shown to have meniscus displacement with or without reduction (MD/MDR), and 24 symptomatic joints with normal tomograms were evaluated with the use of a GE 8800 CT scanner. Mean attenuation values were extrapolated with the use of a symmetrical (1 to 9 pixels) region-of-interest (ROI) cursor. Density gradients of the masseter muscle, lateral pterygoid fat pad, and lateral pterygoid muscle were also obtained. The results of this study showed that the mean meniscal density values were 116.7 +/- 4.2 Hounsfield units (HU) for MD subjects, 111.3 +/- 4.6 HU for MDR subjects, and 82.4 +/- 2.9 HU for subjects with symptoms. The MD and MDR density group means were significantly different (p less than 0.001) from the normal group means. A relative comparison of the meniscus density with that of the lateral pterygoid muscle, its fat pad, and the masseter muscle showed a consistent mean difference when the paired t test was used. Meniscal displacement was found to be associated with an increase in density gradient, which suggests histologic alteration.