Effect of bilateral sagittal split ramus osteotomy setback on the soft palate and pharyngeal airway space

To evaluate the effect of bilateral sagittal split ramus osteotomy setback on the morphology of the pharyngeal airway, especially the structures of the soft palate and pharyngeal airway space (PAS), lateral cephalograms obtained from 49 women before treatment and 1 year after surgery were traced and compared. All patients underwent this osteotomy to correct mandibular hyperplasia. The data were corrected with the use of regression equations for the PAS, taking into account head posture. On average, the SNB angle decreased by 3.9 degrees, resulting in an increase of 4.1 degrees in OPT/NSL (head posture, defined as the craniocervical angulation at the uppermost part of the cervical spine). The morphology of the PAS and soft palate changed significantly (p<0.01). The mean reduction in the PAS was 2.6mm retropalatinally and 4.0mm retrolingually. On average, the soft-palate length increased by 3.2mm and the soft-palate angle increased by 4 degrees. These results show that mandibular setback surgery markedly decreases the PAS and changes the morphology of the soft palate.