[Os odontoideum: clinical and radiological aspects]

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.

Dynamic CT scan of the craniovertebral junction: a role in the management of os odontoideum

Os odontoideum is an uncommon abnormality of the cranio-vertebral junction (CVJ) that exists as a separate ossicle apart from a hypoplastic dens. Its genesis and natural history have been debated, and its proper treatment remains uncertain. A 48-year-old woman complained of persistent upper neck pain and paraesthesia of her left side. Magnetic resonance imaging of the CVJ demonstrated an os odontoideum. Dynamic computed tomography scan of the CVJ showed a reduction of the space available for the spinal cord to 50% from extended to flexed position. The patient underwent posterior spinal fusion of C1-C2 using a sublaminar titanium hook and rods fixed in moderate extension. We discuss the usefulness of the dynamic computed tomography (CT) scan in the evaluation of atlantoaxial motion and the management of this pathology.