MIDFACIAL GROWTH AFTER COSTOCHONDRAL GRAFT CONSTRUCTION OF THE MANDIBULAR RAMUS IN HEMIFACIAL MICROSOMIA

Purpose: The purpose of this study was to document vertical midfacial growth after costochondral graft mandibular ramus construction in chil dren with type IIB and type III hemifacial microsomia (HFM). Methods: This is a retrospective study of 33 children who underwent costochondr al graft (CCG) construction for mandibular type LIE (abnormal, small, and medially displaced ramus, n = 19) and mandibular type III (absent ramus and glenoid fossa, n = 14) HFM, between 1980 and 1990. Types I a nd IIA patients were not included because their milder mandibular defo rmities were lengthened by osteotomy. Mean age at operation was 6.2 (2 to 10) years, and the mean follow-up period was 5.5 (1 to 13.5) years . Occlusal cant, piriform angle, and intergonial angle were measured o n the most current posteroanterior CPA) cephalogram. The ratio of unaf fected to affected ramus length was determined on the most current pan oramic radiograph. Patient outcomes were classified based on the occlu sal cant at the latest follow-up: group 1, successful result with a sy mmetrical maxilla (occlusal cant of <5 degrees); group 2, acceptable r esult (occlusal cant greater than or equal to 5 degrees but <8 degrees ), and Group 3, failure (occlusal cant greater than or equal to 8 degr ees). OMENS scores were calculated for each patient: each of the five major anatomic deformities of HFM (orbital, mandibular, auricular, neu ral, and soft tissue) were graded 0 to 3 and summed. The mean differen ces in age at operation and OMENS scores between groups were calculate d (ANOVA). Results: At the end of follow-up, patients defined as havin g a successful result (group 1) had a mean occlusal cant of 2 degrees, a mandibular length ratio of 1.0, and an intergonial angle of 2 degre es. However, the final piriform angle was 7 degrees, indicating less v ertical midfacial growth than maxillary alveolar growth. These patient s were older at the time of operation (mean age, 6.7 years), and their mean OMENS score (6.3) was significantly lower(P = .004) than in pati ents in group 2 (mean age at operation, 6.3 years; mean OMENS score, 6 .8) and group 3 (mean age at operation, 5.8 years; mean OMENS score, 7 .8). In group 2, the occlusal cant, mandibular length ratio, and inter gonial and piriform angles did not improve. In group 3, the occlusal c ant and piriform angle became worse during the follow-up period. Concl usions: The results of this study indicate that after construction of the ramus and condyle in type IIB and III HFM patients, vertical midfa ce growth is secondary to a combination of midfacial and alveolar grow th. Patients operated on at an older age were more likely to have a su ccessful long-term result. Finally, the severity of the overall deform ity, as reflected in a higher OMENS score, appeared to be an important factor in the response to early correction.