ABSTRACT
The goal of this investigation was to identify and quantify nasal morphologic features which predispose to the nasal tip deflection associated with the LeFort I osteotomy. Fifty patients who had undergone LeFort I osteotomies were studied retrospectively from presurgical and postsurgical cephalograms and facial photographs. The magnitude of hard tissue change was measured in the vertical and horizontal planes, and soft tissue nasal change was measured in the vertical plane at two points on the outline of the soft tissue nose. Additional parameters were tested as potential predictors of nasal tip deflection, including the Deflection Resistance Index (DRI), which is a quantitative measure of nasal morphologic features. Data were subjected to a hierarchical multiple regression analysis allowing for multivariate prediction capability. At the supra nasal tip (SNt), magnitude of advancement, magnitude of impaction, and the DRI were all significant predictors (multiple R = 0.86). At the anterior nasal tip (ANt), magnitude of advancement, preoperative columellar angle, magnitude of impaction, the DRI, the interactions of advancement and DRI, and columellar angle and DRI were the significant predictors (multiple R = 0.89). It is concluded that the vertical deflection of the nasal tip resulting from the LeFort I osteotomy is influenced not only by the hard tissue movements but also by nasal structure. The DRI is a quantitative measure that can be used clinically to improve the predictability of vertical nasal tip deflection.
