Disc displacement without reduction: a retrospective study of a clinical diagnostic sign.

OBJECTIVE: The purpose of this retrospective study is to evaluate a clinical diagnostic sign for disc displacement without reduction (DDWR), the absence of additional condylar translation during opening compared with protrusion. METHOD: Thirty-eight electronic axiographic and magnetic resonance imaging (MRI) examinations of the TMJ were analyzed in order to compare the opening/protrusion ratio of condylar translation between non-painful DDWR and non-DDWR. RESULT: According to the Mann-Whitney U test, the opening/protrusion ratio in non-painful DDWR differs significantly from non-DDWR (p < 0.0001). DISCUSSION: Among non-painful DDWR, there is no additional condylar translation during opening in comparison with protrusion, and this is probably also the case for DDWR without limited opening, which is a subtype that has not been validated by the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Comparative condylar palpation can analyze this sign, and therefore, further comparative investigations between MRI and clinical examination are needed to validate the corresponding clinical test.