Condylar response to large mandibular advancement combined with maxillary impaction and counterclockwise rotation: A computed tomographic study

BACKGROUND: This study aims to analyze the effectiveness of cone-beam computed tomography (CBCT) in the evaluation of the condylar position, angulation and intercondylar distance and assess the changes in these parameters before and after bimaxillary surgery, preformed with the critical movments of Le Fort I osteotomy (for impaction of the maxilla and conterclockwise rotation of the upper occlusal plane) and Bilateral Sagittal Split Osteotomy (BSSO) for mandibular advancement (> 8mm). MATERIAL AND METHODS: Twenty class II patients successfully treated with BSSO of the mandible, in conjunction with Le Fort I osteotomy, were studied to evaluate the condylar changes before and after surgery. The position of the condyle was classified according to the Pullinger & Hollender’s formula in both phases. A MANOVA analysis followed by post-hoc tests were conducted to ascertain if there were statistically significant differences between pre and post surgical variables under study. The agreement of the condylar position’s classification was evaluated resorting to the Kappa statistics. RESULTS: There were no statistically significant differences between the values of the position and angulation of the condyles and intercondylar distance before and after surgery. There was an increase of the axial angle of the left condyle and the frontal angle of both condyles, while there was a decrease of the axial angle of the right condyle, the sagittal angle of both condyles and intercondylar distance. CONCLUSIONS: The CBCT is a useful method for assessing variations of condylar position in detail. It was verified that the critical movements of maxillary impaction associated with the mandibular advancement do not produce significant alterations in the mandibular condyles, however, these tend to perform a posterior and inferior movement. Key words:Cone-Beam computed tomography, orthognathic surgery, mandibular condyle, osteotomy, le fort, temporomandibular joint.