A Case of Mandibular Prognathism with Crouzon Syndrome Treated by Application of Maxillary Distraction Osteogenesis and Sagittal Split Ramus Osteotomy

Crouzon syndrome is a type of craniofacial dysostosis characterized by early fusion of certain skull bones, which can affect the shape of the head and face. Signs and symptoms of Crouzon syndrome include bulging eyes, underdeveloped upper jaw and severe mandibular prognathism. This case report describes a patient with Crouzon syndrome who received maxillary distraction osteogenesis using a rigid extraoral distractor (RED) system and sagittal split ramus osteotomy (SSRO). A boy, 10 years and 1 month old, was referred to our clinic to treat mandibular prognathism. He had already undergone cranioplasty at 1 year old, maxillary distraction at 7 years old, and surgical closure of the occipital region at 9 years old at another hospital. He showed a concave profile and also had an abnormal swallowing habit. The overjet and overbite were −1.0mm and 2.0mm respectively. ∠ANB was −10.0°, ∠SNA was 71.0°, and ∠SNB was 81.0°. We applied orthodontic expansion and a maxillary protractive appliance at the first phase of treatment. However, at 17 years and 0 months, overjet became −3.0mm and ∠ANB worsened to −15.8°. Therefore, at the second phase of treatment, we performed alveolar osteotomy with maxillary expansion, maxillary distraction osteogenesis using a RED system for maxillary advancement and SSRO for mandibular setback. As a result, overjet improved to 2.0mm and ∠ANB changed to −4.5°. Although the skeletal discrepancy was not improved enough, his concave facial profile was changed to almost a straight profile by the orthognathic surgery. The active treatment period was 2 years and 5 months and the patient’s occlusal relationship remained stable during the retention period.