Aesthetic guidelines in genioplasty: the role of facial disproportion.

It has been demonstrated previously that many individuals requesting chin enlargement have small or retruded mandibles. A weak chin may be only one aspect of this particular class II skeletal deformity, the other components being a procumbent, retrusive lower lip, excessive labiomental fold depth, and decreased to normal lower face height. To avoid unaesthetic results, the chin should not be advanced beyond the retrusive lower lip, the only component over which osseous genioplasty has no control. This may result in residual sagittal "weakness" of the lower face, for which visual compensation can be achieved by vertical overelongation of the chin. Thirty-two patients requesting chin enlargement presented with the aforementioned class II deformity. Twenty patients had decreased lower face height and 12 patients had normal lower face height. Preoperative soft-tissue cephalometric analysis documented physical findings. The extent of sagittal chin movement was planned to advance the soft-tissue pogonion no further than the lower lip. Vertical chin movement was intentionally designed to overelongate the lower face relative to the midface in all patients. Radiographs were repeated at a mean 8.2 months following surgery to document skeletal displacements. Mean chin advancement was a modest 4.2 mm (2- to 7-mm range), and chin vertical displacement was a mean 7.9 mm (5.5- to 9-mm range). All patients had residual sagittal disproportion of the pogonion relative to the subnasale (-7.6 mm mean) and newly created vertical disproportion with mean lower face heights of 69.8 mm compared with mean midface heights of 64 mm.(ABSTRACT TRUNCATED AT 250 WORDS)