Dens fracture or odontoid bone

Introduction During the embryological development the axis is formed from the proatlas, the C1 sclerotome and the C2 sclerotome. Failure of the odontoid process (C1 sclerotome) to fuse with the body of the axis (C2 sclerotome), or failure of the apex of the odontoid process (proatlas) to fuse with the main portion of the odontoid process has been advocated. The etiology of os odontoideum remains unsettled; both acquired and congenital mechanisms have been suggested [1].In 1863, separation of the odontoid process from the body of the axis was first described in a postmortem specimen. In 1886, Giacomini coined the term os odontoideum for this condition [2]. This entity is clinically important because a mobile or insufficient dens renders the transverse atlantal ligament ineffective at restraining atlantoaxial motion. Sliding of the atlas on the axis may compress the spinal cord or injure the vertebral arteries. Os odontoideum is a rare lesion, and its pathogenesis has been extensively debated in the literature. Some authors have argued that it is congenital and represents the centrum of atlas. However, most authors believe that it is a result of trauma leading to a chronic non-united fracture of the odontoid process [3]. Patients with this condition may be asymptomatic or they may have neck pain, torticollis, or neurological symptoms that may develop either acutely or chronically from repeated spinal cord injury or involvement of the vertebral artery [4]. Os odontoideum has been noted to have a round or oval shape and a smooth margin. On the radiographs, os odontoideum is marked by a small corticated ossicle separated from the base of the odontoid [1]. In this paper, we present a case of os odontoideum that was diagnosed in a trauma patient.