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 young patients login to view 1 more bullet elderly patients login to view 2 more bullets children login to view 1 more bullet Etiology Pathophysiology mechanism displacement may be anterior (hyperflexion) or posterior (hyperextension) login to view 4 more bullets biomechanics a fracture through the base of the odontoid process severely compromises the stability of the upper cervical spine Associated conditions os odontoideum etiology login to view 2 more bullets imaging login to view 1 more bullet treatment login to view 1 more bullet Anatomy Osteology axis has an odontoid process (dens) and body contains a transverse foramen that the vertebral artery travels through embryology develops from 5 ossification centers login to view 2 more bullets secondary ossification center login to view 1 more bullet Arthrology C1-dens anterior dens articulates with the anterior arch of C1 C1-2 articulation diarthrodial joint C2-3 joint participates in subaxial (C2-7) cervical motion Ligaments occipital-C1-C2 ligamentous stability provided by the odontoid process and its supporting ligaments login to view 7 more bullets Blood supply a vascular watershed exists between the apex and the base of the odontoid apex login to view 1 more bullet base login to view 1 more bullet the limited blood supply in this watershed area is thought to affect healing of type II odontoid fractures 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 worse with motion, especially rotation dysphagia may be present when associated with a large retropharyngeal hematoma Physical exam neurologic deficits very rare due to large cross-sectional area of spinal canal at this level Imaging Radiographs required views AP, lateral, open-mouth odontoid view of the cervical spine login to view 1 more bullet optional views flexion-extension radiographs are important to diagnose occipitocervical instability in type I fractures and os odontoideum login to view 5 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 indications login to view 2 more bullets hard cervical orthosis indications login to view 5 more bullets technique login to view 1 more bullet halo immobilization indications login to view 1 more bullet contraindications login to view 2 more bullets technique login to view 1 more bullet Operative posterior C1-2 fusion indications login to view 4 more bullets anterior odontoid screw indications login to view 5 more bullets outcomes login to view 1 more bullet transoral odontoidectomy indications login to view 3 more bullets Techniques Halo immobilization complications pin site infection login to view 1 more bullet C1-2 posterior fusion approach posterior midline cervical approach stabilization technique sublaminar wiring techniques (Gallie or Brooks) login to view 1 more bullet posterior C1-2 segmental fixation login to view 7 more bullets posterior C1-2 transarticular screws construct login to view 1 more bullet outcomes C1-2 fusion will lead to 50% loss of neck motion Higher fusion rate in the elderly compared to anterior fusion Anterior odontoid screw approach anterior approach to the cervical spine technique single screw adequate advantages preservation of atlantoaxial motion disadvantages higher failure rate than posterior C1-2 fusion Transoral odontoidectomy technique usually combined with posterior stabilization procedure Complications Nonunion overall incidence 33% (as high as 88% in some studies) risk factors type II fractures with login to view 7 more bullets Mortality overall patients >80 y/o do poorly with operative or nonoperative treatment especially with halo orthosis