Analysis and treatment of hemifacial microsomia in childhood.

Hemifacial microsomia (HFM) is not a fixed dysmorphic deformity, but rather a progressive, complex deformation, involving the soft tissues and skeletal structures derived from the first and second branchial arches. Secondary growth distortion is seen particularly in the failure of midface growth, because of inadequate mandibular vertical growth on the involved side. Based on this concept of a dysfunctional matrix, we treat HFM in childhood according to the severity of the mandibular hypoplasia. In the type I and type IIA children seen in the deciduous stage, we recommend use of an activator or functional appliance. The more severe type IIB and type III children with absent structures need early construction of the mandibular ramus, glenoid fossa, and temporomandibular joint. In so doing, we convert the severely hypoplastic mandible into a more symmetric and functional type IIA status. Correction of the mandible appears to maximize potential growth and minimize the documented secondary distortion in the maxilla. Preliminary study confirms that early correction minimizes the need for maxillary and orbital osteotomies as these patients enter adulthood. We have briefly outlined our approach to soft-tissue hypoplasia and neuromuscular deficiency in HMF. Further refinements are needed in these areas.