Anatomic basis of Le Fort 1 impaction osteotomy: a radiological study.

PURPOSE: In Le Fort 1 osteotomy when a maxillary impaction is necessary, surgeons have to face different anatomical problems. (1) To determine the best bone resection route, they have to consider the situation of dental roots, infraorbital foramen and maxillary artery. (2) In case of Le Fort 1 osteotomy combined with a mandibular sagittal split osteotomy, the palate has to be replaced in horizontal position although there is no anatomical landmark. (3) In case of Gummy smiles, it can be due to either long face or short upper lip. The main objective was to identify safe bony landmarks to perform a Le Fort I osteotomy and to find a reliable way for repositioning the palate horizontally; the secondary objective was to determine the upper lip normal length. METHODS: The study was based on 178 facial CT examinations. The following parameters have been used: the vertical length of the upper lip, the vertical heights of the anterior nasal spine, the canine and molar roots, the inferior limit of the pterygomaxillary fossa and the vertical height of the infraorbital foramen on both sides. RESULTS: The vertical length from the subnasal point to the upper vermilion was 15.06 ± 3.09 mm, and to the junction of the upper and lower lips was 23.94 ± 3.79 mm. The vertical length from the anterior nasal spine to the incisor alveolar border was 19.70 ± 3.17 mm. The height of the canine root was 17.11 ± 2.60 mm. The height of the highest lateral root of first or second maxillary molars was 11.71 ± 1.83 mm. The vertical length from the inferior limit of the pterygomaxillary fossa (pti point) to the alveolar border of the pterygomaxillary suture was 19.86 ± 3.45 mm. The height from the center of the infraorbital foramen to the alveolar border of the maxilla on a vertical line was not statistically different on right and left sides. CONCLUSIONS: According to our results, in impaction Le Fort 1 osteotomy, the bone resection must pass 20 mm above the alveolar border in canine area, and 15 mm above the alveolar border in molar area. The resection has to end less than 20 mm above the inferior border of the pterygomaxillary suture. The vertical height of the infraorbital foramen is a consistent landmark for repositioning of the palate in a horizontal plane.