A case of evaluation of the bony beam structure in a patient with skeletal mandibular prognathism with X-linked hypophosphatemic rickets treated with surgical orthodontic treatment

X-linked hypophosphatemic rickets (XLH) is a rare disease with an estimated annual incidence of 117 cases (95% CI 75-160) in Japan. It is a disease characterized by bone calcification disorders and bone deformities. We report a case of skeletal mandibular prognathism with XLH. The patient is a 24-year-old man. He visited the near dentistry with the complaint of opposite occlusion, and was referred to our department in April 2015 for the purpose of detailed examination and treatment due to skeletal mandibular prognathism. He had a history of XLH, depression, and a fracture of the right articulatio coxae in 2012, and his orthopedic surgeon reported that it took a long time to heal the bone. Therefore, it was necessary to carefully examine and consider the risk of intraoperative abnormal fractures and postoperative bone healing during surgical orthodontic treatment. In January 2018, the sagittal split ramus osteotomy (SSRO) was performed. As he was progressed favourably, we removed plates and performed genioplasty in February 2019. In order to understand the preoperative bone morphology and evaluate the postoperative bone healing, CT was taken and the trabecular microstructure parameters were analyzed with bone analysis software (TRI / 3D-BON). The operation was completed smoothly without any abnormal fracture during the operation, and the progress is good without delaying the postoperative bone healing. We were evaluating objectively bone quality with CT and were able to evaluate the healing condition.