Sonographic evaluation of the ranges of condylar translation and of temporomandibular joint space as well as first comparison with symptomatic joints

Abstract

To assess the normal ranges of condylar translation and width of the lateral temporomandibular joint (TMJ) of a healthy population by sonography and permit comparison of findings made in individual patients using this norm. Fifty non-orthodontically treated, asymptomatic volunteers (100 joints) were subdivided by Angle classes (I = 20, II = 15, III = 15) and evaluated. Reliability was assessed in 15 of those volunteers. The validity was checked in 8 more patients with temporomandibular dysfunction (TMD), all class II with disc dislocation diagnosed by means of MRI. Sonographic assessment of condylar translation from centric occlusion to maximum opening and during protrusion and mediotrusion was performed with a probe positioned parallel to the zygomatic arch. Translation during opening was 12.7+/-3.2 mm in class I, 12.9+/-3.3 mm in class II and 10.9+/-3.6 mm in class III. Protrusive translation was 7.4+/-2.5 mm/10.3+/-4.4 mm/6.8+/-2.1mm, respectively; and mediotrusive translation was 7.9+/-2.6 mm/10.8+/-3.4 mm/6.7+/-2.4 mm, respectively. Class II had longer and class III shorter condylar translations. The lateral joint space in occlusion and protrusion was wider in class II than in classes I and III. Symptomatic patients had shorter condylar translations than asymptomatic volunteers. Patients with class II had a more anteroposterior mobility, class III shorter translation. Significant sonographic differences of condylar translation from the norm did not correspond with clinical findings. This demonstrates the higher sensitivity of sonography for the evaluation of individual condylar translation. It is a sensitive tool for assessing joint function.