Mandibular elongation by gradual distraction in patients with hemifacial microsomia is a simple and effective procedure to correct facial asymmetry. The two-pin system joined by a softer distracting screw achieves elongation in vertical and sagittal directions as well as medial rotation.
The changes in mandibular shape result in changes in dental occlusion. These are minimal in children because of the rapid growth of the maxilla and can be corrected easily with minor orthodontic work.
Mandibular distraction in adults with hemifacial microsomia, who usually have stable dental occlusion, produces good aesthetic results but also severe alterations in the occlusion requiring complex orthodontic treatment over a long period. To avoid this problem, an incomplete Le Fort I osteotomy is done simultaneously with the mandibular corticotomy. Intermaxillary fixation is done on the fifth postoperative day, and distraction is initiated.
In a series of seven patients, the maxilla was distracted simultaneously with the mandible, preserving the preexisting stable occlusion. Preoperative deviation of the occlusal plane from the horizontal varied from 12 to 18 degrees. The plane became horizontal in four patients, and deviation of 2 degrees persisted in three. The distance from the inferior orbital rim to the occlusal plane on the affected side was increased in all patients, achieving 100 percent correction (compared with the normal side) in four patients and 95, 96, and 97 percent in the other three.