Distraction Osteogenesis of the Hypoplastic Midface using a Rigid External Distraction System: The Results of a One- to Six-Year Follow-Up

The purpose of this study was to evaluate the long-term stability of maxillary distraction osteogenesis by use of a rigid external distraction device, based on a 7-year experience. Nine patients with severe cleft maxillary hypoplasia were treated between January of 1998 and August of 2003. Their ages at the time of surgery ranged from 13 to 19 years. Distraction was started at 5 days after a Le Fort I osteotomy at a rate of 1 mm per day for 10 to 15 days. All patients used the Rigid External Distraction I system. After distraction was completed, the device was left in place for another 5 to 6 weeks for bony consolidation. When this was completed, an orthodontic face mask was used with elastic traction for 5 to 6 weeks. The follow-up period ranged from 1 to 6 years. The mean distraction length was 13.6 mm immediately after distraction, 10.8 mm at 6 months after distraction, and 10.4 mm between the 1- and 6-year follow-up period, resulting in relapse rate of 23.0 percent. In three children with mixed dentition, the ANB angle ranged from 7.1 to 8.5 degrees immediately after distraction, from 2.8 to 4.0 degrees 6 months postoperatively, and from 0.4 to 1 degree 5 years postoperatively. Therefore, the growth rate of the distracted maxilla was lower than that of the mandible in those three children. The results suggest that greater anterior overcorrection of the hypoplastic maxilla is needed in the growing child than in adults to compensate for a partial relapse and growth deficit.