MRI characteristics of anterior disc displacement with and without reduction

Objectives: The aim of this study was to investigate the differences between magnetic resonance imaging (MRI) characteristics of anterior disc displacement with reduction (ADDR) and without reduction (ADDWR). Methods: A clinician and a radiologist, blinded to the results of the clinical examination, independently evaluated the MRI scans of 100 subjects with symptoms of temporomandibular joint (TMJ) disorders. The final sample included 88 subjects in whom there was consensus of disc displacement both between observers and between MRI and clinical examination. There were 130 joints with ADDR and 45 joints with ADDWR in the study. The MRI characteristics such as position, signal intensity and morphology of the disc, degenerative changes, effusion, scar tissue, osteonecrosis and condylar hypermobility were evaluated in the cases of ADDR and ADDWR. The chi(2) test was used to determine the differences between ADDR and ADDWR for these MRI characteristics. Results: There were no significant differences between ADDR and ADDWR for effusion and degenerative changes. There were significant differences between ADDR and ADDWR for sideways displacement, disc deformation, signal intensity changes, scar tissue, osteonecrosis and condylar hypermobility. Conclusions: Degenerative changes and effusion did not appear to be markers of either ADDR or ADDWR. However, the severity of these abnormalities may be correlated with the type of internal derangement. The prevalence of sideways displacement, disc deformation, signal intensity changes, scar tissue, and osteonecrosis was greater in ADDWR than ADDR. These conditions may be considered to be indicators of more advanced and complicated stages of internal derangement. Because the percentage of subluxation was greater in ADDR, localized joint laxity and internal derangement may be correlated.