We report the first case in Korea of rapid bone formation on a subperiosteal orbital hematoma after trauma.

A 10-year-old boy who was in the intensive care unit after trauma showed proptosis and ocular movement limitation of the right eye associated with subperiosteal hematoma. On ocular examination, 3 mm of proptosis and limitation of right eye movement were observed; however, visual acuity was not decreased. At 1 month after the trauma, orbital computed tomography (CT) showed new bone formation at the margin of the hematoma border although the size of the hematoma decreased. The patient underwent hematoma and bony tissue removal using anterior orbitotomy approach. A new bone was formed between the orbital border and hematoma from the anterior orbital margin to the orbital apex. During pathological examination, woven bone tissue with fibrotic tissue was observed in the hematoma wall. One year after surgery, the patient's proptosis and limitation of ocular movement disappeared without any evidence of new bone formation.

Waiting for spontaneous absorption of orbital subperiosteal hematoma is usually recommended unless there is significant functional impairment. However, as in our case, new bone formation could occur during a short period of less than 1 month; imaging follow-up is necessary in patients having intensive care or showing delayed absorption of a hematoma.