Odontoideum Bone Revealed by c1-c2 Dislocation of the Cervical Spine during a Diving Accident

INTRODUCTION: Odontoideum bone or the mobile odontoid process is one of the rarest malformations of the cervico-occipital hinge. It exposes to the atlo-axial instability and to the risk of bulbo-medullary compression threatening then the vital and functional prognosis. We report the case of a 16-year-old patient who was the victim of a raod accident resulting in acervical spine injury. Radiological investigation found an odontoideum bone malformation associated with C1C2 dislocation. CASE REPORT: A 16-year-old patient with no medical history had a road accident. Clinical evaluation found an incomplete tetraplegia.The imaging has revealed an atlo-axoidal dislocation with aspinal cord compression. Furthermore, radiological exams relvealed an odentoideum bone. A transcranial traction by a Gardner stirrup was set for 15 days to obtain a progressive reduction of the displacement. A full neurological recovery (FB-FD) was obtained.The patient was then operated to stabilize the reduction. A C1-C2 posterior zygapophyseal arthrodesis was performed. An autograft harvested from the iliac crest was used. Complementary open reduction and fixation of the cervico-occipital hinge was made using lamellar hooks and compression rods. At the 18-month follow-up, the clinical examination found no neurological deficiency and the plain radiography showed a complete fusion of the arthrodesis. CONCLUSION: Odontoideum bone is a rare and potentially life-threatening malformation. It is most often asymptomatic but symptoms could occur any time after a benign trauma. The prognosis mainly depends on the precocity of the management. Preventive surgery is recommended byseveral authorsin case ofinstability.