Magnetic resonance imaging of temporomandibular disorders: classification,prevalence and interpretation of disc displacement and deformation

Aim: To analyse the prevalence of disc displacements and deformations from MRI of symptomatic temporomandibular disorders (TMD). Methods: The study was conducted retrospectively on 192 joints of 9X patien ts (67 females, 31 males, mean age 29 years), who had undergone bilateral M RI (except for four who had unilateral) in the sagittal (both open and clos ed mouth) and coronal (closed mouth only) planes. These displacements were subdivided into static (complete anterior and posterior, partial anterolate ral and anteromedial, sideways lateral and medial, anterolateral and antero medial rotational) and dynamic (with reduction, without reduction, with inc omplete reduction; non-determinable). Disc deformations were subdivided int o: enlargement of the posterior band, reversed biconcave shape, biplanar (f lattened) and biconvex shape. Results: Eighty per cent of patients had bilateral displacement, 15% unilat eral and 5% a normally positioned disc. Complete anterior displacement was the commonest and sideways the rarest. Reduction was present in 58% of disc displacements, no reduction in 26%, incomplete reduction in 4%, while in t he remaining 12%, it could not be determined. Rotational displacement was t he most likely to feature reduction and sideways the least. Temporomandibul ar joints with no reduction were closely correlated with bone lesions. The most frequent deformation was biplanar and the rarest enlargement of the po sterior band. Conclusions: There was a high prevalence of displacements and deformations. While they do not appear to be significant in inducing pain, they can pred ispose to the onset of osteoarthrosis.