Predicting upper lip response to 4-piece maxillary LeFort I osteotomy

The purpose of this retrospective study was to understand and predict the m ultidimensional changes in upper lip. morphologic features after segmental (4-piece) maxillary Le Fort I advancement/impaction with VY closure and afa r base cinch sutures. The study evaluated longitudinal lateral cephalograms of 57 patients (42 women, 15 men) 27.5 +/- 11.2 years of age before surger y. Lateral cephalograms with teeth in occlusion and lips in repose were tak en 2 weeks before surgery and at least 6 months after the operation. Mean p ostsurgical duration was 15.5 months. The upper lip predictably moved anter iorly in a graduated fashion, from 50% (subnasale) to 90% (labrale superius ) the amount of the underlying osseous anterior movement, and showed a slig ht lengthening (0.73 +/- 1.9 mm) from subnasale to upper lip stomion. The u pper lip surface contour was also straightened as a result of the surgical movement. Multiple regression models showed that the anterior changes in th e landmarks prosthion and facial surface of the upper incisor were the most important variables in predicting upper lip response. The prediction equat ions for horizontal movements explained 86% to 94% of the variation, with e rrors of the estimates that range between 1.27 mm and 1.65 mm. The models, when applied to an independent validation sample of 14 subjects, explained between 86% and 94% of the total variation. The conclusion is that upper li p response after 4-piece Le Fort I advancement/impaction (VY closure and al ar base cinch suture) can be accurately predicted.