RESUMO
The aim of this study was to investigate whether anaesthesia and contrast medium injection alter the biomechanics of the TMJ, thus influencing the arthrographic diagnosis in patients with anterior disc displacement with reduction. Opening and closing movements were recorded in nine patients by means of an opto-electronic motion recorder (Jaws 3D) before anaesthesia, after anaesthesia and after arthrography. The system computed the trajectories of a condylar point in the sagittal, frontal and horizontal plane. Data were analysed for changes in the position of the clicks, for the amount of condylar translation and for changes of the trajectories between recording conditions. The results indicated that arthrography had a significant effect on the position of the opening clicks in all nine patients. After injection, the clicks occurred on average 1.6 mm later than before injection. This was probably due to the excursive movements required for defusion of the contrast medium in the joint. The other parameters examined were not affected by the joint anaesthesia and the arthrographic procedure. The interventions influenced the shape and the incline of the sagittal condylar movement in three of the nine patients. In conclusion, arthrography altered the joint biomechanics, but not sufficiently to invalidate the arthrographic diagnosis.