Comparison of skeletal and soft-tissue changes following unilateral mandibular distraction osteogenesis

Background: The purpose of this study was to investigate the relationship between soft-tissue and underlying skeletal structures before and after unilateral mandibular distraction osteogenesis. Methods: The sample consisted of 11 patients (three girls and eight boys) with an average age of 4.6 years at the time of treatment. All patients had unilateral craniofacial microsomia (four right-sided and seven left-sided unilateral craniofacial microsomia) and all underwent unilateral mandibular distraction osteogenesis. Measurements were performed on frontal medical photographs and posteroanterior cephalograms at predistraction (time 1) and postdistraction (time 2) periods. Left and right ramus heights, skeletal midline deviation, and transverse occlusal plane were measured on the posteroanterior cephalograms and compared with the linear distances between the lip commissures and the orbital plane, the circumference of both sides of the faces, and the angulation of the oral commissure plane as recorded on the medical photographs, respectively. To reduce magnification error, ratios of affected to less affected sides of the mandibles and soft-tissue facial structures were selected and studied. Results: A similar relationship was observed between soft-tissue and skeletal components. However, there was no 1:1 relationship between the changes in ramus height and improvement in parallelism of lip commissures to the orbital plane. Conclusions: A significant improvement in soft- and hard-tissue anatomy has been observed following unilateral distraction osteogenesis of the mandible. The relationship between the soft-tissue and skeletal correction was different for all patients because of the large range in severity of the craniolacial malformation. Greater skeletal deficiency requires more correction to achieve symmetry of both hard and soft tissue.