Decreased disk-eminence ratio is associated with advanced stages of temporomandibular joint internal derangement

Objective : To examine the possible correlation between the stage of intern al derangement and the antero-posterior length of the disk in relation to t he length of the articular eminence. Study design: Twenty asymptomatic volunteers with normal joints and 120 pat ients with TMJ dysfunction underwent MR imaging. The A-P length of the disk in relation to the length of the articular eminence (D/E ratio) was measur ed. Results: The D/E ratio was 0.95 in the asymptomatic volunteers, 0.83 in pat ients with disk displacement with reduction, 0.74 in those with disk displa cement without reduction and 0.57 in the patients with disk displacement an d osteoarthritis. The relationship between the D/E ratio and the stage of i nternal derangement was statistically significant (P<0.01). Conclusion: The D/E ratio decreases with advancing internal derangement. We suggest that it is a reliable numerical method for staging the degree of t he internal derangement.