Anatomie et imagerie de l’articulation temporo-mandibulaire

Temporomandibular joint (TMJ) is a bicondylar synovial joint containing an articular disc between the carnial basis and the mandible. The osseous conditions of this joint constituted by two condyles makes it very unstable. Stability of these two convex articular surfaces (temporal and mandibular), is constituted by the articular disc, which is a biconcave lens, with a thin center and a thick peripheric labrum, made of fibrocartilage. The capsule-ligamental system participates to the TMJ stability. Among TMJ motor muscles, some of them are elevators and diductors of the mandible, innervated by the mandibular nerve (masseter, temporal medial and lateral pterygoid muscles) and others are depressors of the mandible (platysma, digastrics, mylohyoïd and geniohyoïd muscles). TMJ can be studied by conventional Xrays as the orthopantomogram, which allows XRays focused on the TMJ with mouth opening and mouth closed positions. A CT-scanner of the TMJ is useful in bony trauma or illness (fracture of the condylar process, tumor, tempormandibular ankylosis, arthrosis…). The gold standard exam for the TMJ is MRI which allows a multiplanar and dynamic study using acquisitions at different degrees of mouth opening.