Stability following superior repositioning of the maxilla by LeFort I osteotomy.

Cephalometric data from 61 patients who had undergone superior repositioning of the maxilla via LeFort I osteotomy by means of the downfracture technique were analyzed to evaluate stability of skeletal and dental landmarks at various time intervals up to 1 year. None of these patients had concurrent mandibular ramus or body osteotomy except genioplasty and all had at least 2 mm intrusion at the maxillary incisor or molar. In approximately 20% of the patients, there was 2 mm (critical value) or more postsurgical movement of skeletal or dental landmarks. During the first 6 weeks postoperatively, the maxilla showed a strong tendency to move farther upward in the patients in whom it was not stable. The posterior maxilla was vertically stable in 90% of the patients, the anterior maxilla in 80%. Horizontally, skeletal landmarks were stable in 80%, but when changes occurred, there was a tendency for the anterior maxilla to move back when it had been advanced. After the first 6 weeks, the posterior maxilla was stable vertically in all patients, but in 20% anterior maxillary landmarks moved downward, opposite to the direction of movement during fixation. In 11 of the 15 patients who demonstrated vertical changes postsurgery, the movement from fixation release to 1 year follow-up was opposite and approximately equal to the initial change, so that the net movement after 1 year was less than 2 mm. Only 6.5% (four patients) demonstrated 2 mm or greater net vertical movement for any of the variables studied 1 year after surgical treatment. There was no indication that the amount of presurgical orthodontic movement of incisors, the presence of multiple segments at surgery, the age of the patient, the presence or absence of genioplasty, or the presence or absence of suspension wires was a risk factor for instability.