Orthodontic and surgical treatment patterns in hemifacial microsomia: a retrospective multi-institutional study in Japan

Hemifacial microsomia is a congenital craniofacial condition characterized by variable facial asymmetry and mandibular hypoplasia. Its management often requires long-term multidisciplinary care, including orthodontic and surgical treatment. However, multi-institutional data on treatment patterns remain limited. This study aimed to describe the severity distribution, associated anomalies, and orthodontic and surgical treatment patterns in a large multi-institutional cohort in Japan. This retrospective, cross-sectional, multi-institutional study included patients with hemifacial microsomia managed or treated at 19 institutions in Japan between April 1990 and March 2018. Anonymized patient-level data were collected from clinical records and panoramic radiographs using a standardized data collection form with predefined variable categories. Demographic characteristics, severity, associated anomalies, and orthodontic and surgical treatment histories were summarized using descriptive statistics. A total of 584 patients were included. The cohort comprised 318 males and 266 females. The affected side was right in 268 patients, left in 263, and bilateral in 53. According to the Pruzansky classification, 219 patients were Grade I, 304 were Grade II, 54 were Grade III, and 7 had an unknown grade. Microtia was recorded in 386 patients, transverse facial cleft in 151, ocular anomalies in 75, and cleft lip and/or palate in 57. Phase 1 orthodontic treatment was commonly initiated during childhood, with objectives including occlusal plane cant correction, arch expansion, growth modification, anterior alignment, and perioperative occlusal management. Among 198 patients with available phase 2 treatment records, surgical orthodontic treatment was performed or planned in 83 and orthodontic treatment alone in 115. For growth-period mandibular distraction osteogenesis, information was available for 377 patients, of whom 73 underwent distraction (19.4%). Patients with hemifacial microsomia treated at participating institutions in Japan showed heterogeneous severity, frequent associated anomalies, and diverse orthodontic and surgical treatment pathways. These findings provide baseline information on treatment patterns observed in this historical multi-institutional cohort and may support standardization of assessment, terminology, data collection, interdisciplinary referral, and outcome reporting while allowing treatment strategies to remain individualized.