Influence of setback and advancement osseous genioplasty on facial outcome: A computer-simulated study.

The aim of this virtual study was to investigate the influence of angular deviation and displacement distance on the overlying soft tissue during chin genioplasty. Computed tomography data from 21 patients were read using ProPlan CMF software. Twelve simulated genioplasties were performed per patient with variable osteotomy angles and displacement distances. Soft-tissue deformations and cephalometric analysis were compared. Changes in anterior and inferior soft-tissue of the chin along with resultant lower facial third area were determined. Maximum average changes in soft-tissue were obtained anterior after 10-mm advancement about 4.19 SD 0.84 mm and inferior about -1.55 SD 0.96 mm. After 10-mm setback anterior -4.63 SD 0.56 mm and inferior 0.75 SD 1.16 mm were deviations found. The anterior soft tissue showed a statistically significant change with bony displacement in both directions independent of osteotomy angle (p < 0.001) and only after a 10-mm advancement with an angle of -5 degrees significant differences at inferior soft-tissue were noted (p = 0.0055). The average area of the total lower third of the face was 24,807.80 SD 4,091.72 mm(2) and up to 62.75% was influenced. Advanced genioplasty leads to greater changes in the overlying soft tissue, whereas the affected area is larger after setback displacement. The ratio between soft and hard tissue movements largely depends on the displacement distance.