The influence of the osteotomy slope on bony changes after advancement genioplasty.

[PURPOSE] The purpose of this study was to develop a prediction method for advancement genioplasty that would result in accurate preoperative cephalometric planning of the osteotomy slope and that could be transferred to the patient during the surgical procedure.

[PATIENTS AND METHODS] Serial cephalometric tracings of 20 patients who underwent advancement genioplasty were retrospectively analyzed. The osteotomy slope angle was defined as the angle between the osteotomy and a line perpendicular to the occlusal plane. The measured angle was compared with the calculated angle deduced from the horizontal and vertical genial postoperative changes.

[RESULTS] The measured osteotomy slope angle closely resembled the calculated angle.

[CONCLUSIONS] The close similarity between the calculated and measured osteotomy slope angles in this study shows that simple mathematical calculations can be applied clinically to aid surgeons in achieving a more predictable result. The osteotomy slope can be determined early in the prediction stage as a calculated figure based on the desired horizontal and vertical movements of the chin and can be transferred to the patient's chin during the surgical stage.