Ultrasonic vertical osteotomy of the distal segment for safe elimination of interference between the proximal and distal segments in bilateral sagittal split osteotomy for mandibular asymmetry.

ilateral sagittal split osteotomy (BSSO) is commonly used n the correction of dentofacial deformities. However, in cases f facial asymmetry with a shift of the mandibular midline r occlusal cant, the condyle is displaced laterally by the ulling of the proximal segment medially when there is bony nterference between the proximal and distal segments after he osteotomy. When the gap between the proximal and disal segments is large, the proximal segment will clearly be symmetrical as a lateral bulge on the patient’s cheek, even f a large piece is removed. To overcome these problems, llis reported a vertical osteotomy of the distal segment ehind the terminal molar to passively align the segments f the sagittal ramus osteotomy.1 This procedure can also e used to improve the angle of the occlusal plane and cclusal stability when rotating the maxillomandibular comlex counterclockwise.2 When the inferior alveolar nerve IAN) is exposed, it is retracted laterally and the vertical steotomy made. However, the IAN is not always exposed ecause surgeons seek to minimise its exposure to prevent njury. As there is the potential for such injury during verical osteotomy of the distal segment when a conventional ur or saw is used, we have developed an ultrasonic vertial osteotomy of the distal segment to eliminate interference