Os Odontoideum Mimicking Acute Odontoid Peg Fracture

Abstract

The atlantoaxial complex is a common site for cervical spine injuries, of which fractures of the axis (C2), occur most frequently. Over half of these fractures involve the odontoid process. Numerous developmental anomalies of the axis, although rare, can also occur and may simulate trauma. Specifically, os odontoideum is a cranial-vertebral junction anomaly in which the odontoid remains separate from the body of the axis as an independent ossicle. We report a case of a 53-year-old incarcerated male who was found by his five cellmates hanging partially suspended by a bed sheet. Emergency personnel re-established a pulse for a short time, and the patient was transferred to the hospital. Imaging of the cervical spine pointed to an avulsion fracture of the odontoid process of the axis, raising the possibility of trauma and foul play. Postmortem lateral radiographs revealed a smooth ossicle with a circumferential cortical rim superior to the axis, and a posterior neck dissection failed to reveal evidence of an acute injury. Contrary to the diagnosis of an isolated odontoid fracture, this is a case of os odontoideum. This case emphasizes the importance of a thorough dissection with direct visualization, accompanied by a complete investigation and radiographs. An overview of the development of the axis is discussed, including descriptions of various anomalies of the odontoid that may be encountered during postmortem cervical spine examination. Failure of the forensic pathologist to recognize the developmental anomalies of the axis could lead to improper certification of death, resulting in devastating medicolegal consequences.