Summary Odontoid fractures are relatively common fractures of the C2 (axis) dens that can be seen in low energy falls in elderly patients and high energy traumatic injuries in younger patients Diagnosis may be made with standard lateral and open-mouth odontoid radiographs; however, some fractures may be difficult to visualize on radiographs and require a CT scan to diagnose. MRI is rarely indicated, as these fractures are usually not associated with neurologic symptoms Treatment may be nonoperative or operative depending on the Anderson and D'Alonzo type and risk factors for nonunion. Patients older than 80 have a high morbidity and mortality regardless of nonoperative or operative treatment Epidemiology Incidence most common fracture of the axis account for 10-15% of all cervical fractures most common cervical spine fracture in the elderly Demographics occur in bimodal distribution in young and elderly patients login to view 7 more bullets Etiology Pathophysiology mechanism login to view 5 more bullets biomechanics login to view 1 more bullet Associated conditions os odontoideum login to view 7 more bullets Anatomy Osteology axis has an odontoid process (dens) and body contains a transverse foramen that the vertebral artery travels through embryology login to view 5 more bullets Arthrology C1-dens login to view 1 more bullet C1-2 articulation login to view 1 more bullet C2-3 joint login to view 1 more bullet Ligaments occipital-C1-C2 ligamentous stability login to view 8 more bullets Blood supply a vascular watershed exists between the apex and the base of the odontoid login to view 5 more bullets Kinematics Normal Cervical Kinematics Flexion/Extension Rotation Lateral Bending Occipitocervical joint (OC) 50 4 8 Atlantoaxial joint (C1-2) 10 50 0 Subaxial spine (C3-7) 50 50 60 Total motion (degrees) 110 100 68 Classification Anderson and D'Alonzo Classification Type I Oblique avulsion fracture of the tip of the odontoid Due to an avulsion of the alar ligament Although rare, atlantooccipital instability should be ruled out with flexion and extension films Type II Fracture through waist High nonunion rate due to interruption of the blood supply Type III Fracture extends into cancellous body of C2 and involves a variable portion of the C1-2 joint Grauer Classification of Type II Odontoid Fractures Type IIA Nondisplaced/minimally displaced with no comminution Treatment is external immobilization Type IIB Displaced fracture with a fracture line from anterosuperior to posteroinferior Treatment is with an anterior odontoid screw (if there is adequate bone density) Type IIC Fracture is from anteroinferior to posterosuperior or a fracture with significant comminution Treatment is with posterior stabilization Presentation Symptoms neck pain login to view 1 more bullet dysphagia login to view 1 more bullet Physical exam neurologic deficits login to view 1 more bullet Imaging Radiographs required views login to view 2 more bullets optional views login to view 6 more bullets CT study of choice for fracture delineation and to assess stability of fracture pattern CT angiogram required to determine location of vertebral artery prior to posterior instrumentation procedures MRI indicated if there are neurologic symptoms present Treatment Treatment Overview Type I Collar Type II (<40 y/o) Halo vest Type II (40-80 y/o) Surgery Type II (>80 y/o) Collar Type III Collar Nonoperative observation alone login to view 3 more bullets hard cervical orthosis login to view 8 more bullets halo immobilization login to view 7 more bullets Operative posterior C1-2 fusion login to view 5 more bullets anterior odontoid screw login to view 8 more bullets transoral odontoidectomy login to view 4 more bullets Techniques Halo immobilization complications login to view 2 more bullets C1-2 posterior fusion approach login to view 1 more bullet stabilization technique login to view 12 more bullets outcomes login to view 2 more bullets Anterior odontoid screw approach login to view 1 more bullet technique login to view 1 more bullet advantages login to view 1 more bullet disadvantages login to view 1 more bullet Transoral odontoidectomy technique login to view 1 more bullet Complications Nonunion overall incidence login to view 1 more bullet risk factors login to view 8 more bullets Mortality overall patients >80 y/o do poorly with operative or nonoperative treatment login to view 1 more bullet