Characterization of Posterior Disc Displacement of the Temporomandibular Joint on Magnetic Resonance Imaging.
OBJECTIVES Posterior disc displacement (PDD) of the temporomandibular joint (TMJ) is an uncommon condition that remains that remains poorly documented in the literature. This study aimed to characterize the magnetic resonance imaging features of PDD and assess their distribution according to sex, age, and selected imaging variables. MATERIAL AND METHODS In this retrospective study, 1,266 TMJ MRI examinations from a private radiology service were screened. Sixty-two patients with unilateral or bilateral PDD were identified, comprising 91 affected TMJs analyzed individually. MRI scans were reviewed in consensus by two experienced radiologists. The assessment included displacement extent, reduction status, degenerative bone changes, condylar shape or size alterations, TMJ mobility, and the presence and location of joint effusion on T2-weighted sequences. Statistical analysis was performed using the chi-square test and Fisher's exact test. RESULTS No statistically significant differences were observed in the overall distribution of PDD between sexes, and no associations were found with age, degenerative/morphological condylar alterations, or hypomobility. However, female patients presented a significantly higher frequency of displacement with reduction (p = 0.006). Only one TMJ exhibited degenerative changes, and no joint effusion was observed. CONCLUSIONS PDD showed a particular MRI pattern in this sample, especially regarding reduction status in female patients, the low occurrence of degenerative bone changes, and the absence of joint effusion. This MRI-based characterization may support more consistent recognition and reporting of this uncommon finding, although its clinical relevance should be further investigated in studies with standardized symptom correlation.