Factors affecting long-term results in hemifacial microsomia.

: Mandibular malformations in patients with hemifacial microsomia are described and six phases of treatment outlined. Growth of the malformed mandibular ramus in response to functional appliance treatment was studied in 15 subjects with type I mandibular malformations. It was found that length increase of the affected side during the treatment period was not significantly different from the growth of the other side. Changes in length of the affected side of the mandible following surgical repositioning and bonegrafting was assessed in 25 consecutive cases. In 10 of these subjects, the surgical procedure was done during the growth period and in 15 of them after growth had ceased. In the still growing subjects, there was additional length increase of the reconstructed mandibular ramus, but on an average, less than on the side which had normal temporomandibular joint structures. In seven cases, the length increase was similar on the two sides ( +/- 2 mm) or greater on the affected side, and the established symmetry was maintained. In three subjects, there was recurrence of asymmetry, which in two individuals was corrected by a second surgical lengthening of the mandible. There was minimal loss in length of the reconstructed mandibular ramus in the nongrowing subjects and the established mandibular position was maintained.