[Position of the disc in collum mandibulae fractures--a magnetic resonance tomography study].

39 condylar mandibular fractures were examined by magnetic resonance imaging (MRI) within the first 12 hours after trauma prior to therapy. A new classification has been applied on the traumatic disc displacements. Three types A, B, C can be distinguished. Type A means no displacement in relation to the condylar fragment and the fossa. Type B means a displacement in the transversal plane exceeding the physiologic range of movement. Type C means displacement in the sagittal as well as in the transversal plane which exceeds the physiologic range of movement of the disc. The classified type of displacement could not be correlated exactly with dislocation and position of the bony fragments. Therefore the type of displacement cannot be predicted from conventional radiographs. Three cases of evident rupture of the disc in the biconcave zone could be shown by MRI. This kind of displacement has not been represented in the classification yet. In a presented case a rupture of the disc had been depicted preoperatively and the disc could be repaired via an preauricular approach. By means of MRI surgeons in future are able to pay more attention to the traumatology and reconstructive surgery of the temporomandibular disc.