Stability of sagittal split advancement osteotomy: single- versus double-jaw surgery.

The effect of Le Fort I maxillary impaction on the stability of the sagittal split advancement osteotomy is debatable. The aim of this study was to compare the stability of mandibular advancement in two groups of patients: those that had simultaneous Le Fort I maxillary impaction and sagittal split advancement osteotomy and those that had only sagittal split advancement osteotomy. Lateral cephalograms taken immediately after surgery, 6 months postoperatively, and at 1-year follow-up were used in the assessment. In addition to routine cephalometric analysis, the Euclidean Distance Matrix method was also used. The magnitude of mandibular relapse was similar in both groups in the form of mandibular clockwise rotation and posterior settling. The mandible rotated by 2.2 degrees in the single-jaw surgery group and 2.5 degrees in the bimaxillary osteotomy group. The mandible settled posteriorly by 1.0 degree in the single-jaw surgery group and 1.2 degrees in the bimaxillary osteotomy group. The differences were not statistically significant. In all the patients, Le Fort maxillary osteotomy was more stable than was mandibular advancement. The counter-clockwise rotation of the distal mandibular segments and the distraction of the condylar segments during surgery were responsible for mandibular relapse.