Sanjay Yadla, Benjamin M. Zussman, and James S. Harrop
Introduction
The odontoid process, or dens, is the bony conical projection of the axis (C2), around which the ring-shaped atlas (C1) enables rotational movement of the head. Fractures of the odontoid process constitute approximately 15% of all cervical fractures. They are primarily caused by high-velocity trauma in the young and by falls in the elderly. Odontoid fractures may cause atlantoaxial instability, placing the spinal cord at risk for compressive injury. Fractures may result in progressive neurologic damage or fatality. The goal of treatment is to stabilize or immobilize the atlantoaxial joint and achieve solid fusion of the fractured dens.1Patients with acute odontoid fracture rarely present with severe neurologic injury but commonly complain of axial neck pain subsequent to trauma.
Although evidence-based management recommendations for odontoid fractures are lacking, patient outcomes for the most common conservative and surgical treatments have been reported.1This chapter discusses the emergency management of odontoid fractures with a specific focus on the most commonly performed treatments, including: (1) anterior fusion techniques (odontoid screw) and (2) posterior fusion techniques (C1-C2 transarticular screws; C1 lateral mass/C2 pars/C2 pedicle screws). Contraindications for odontoid screw placement include odontoid fractures with an anteriorly angled tip fragment, osteoporosis, transverse ligament disruption, or accompanying atlantoaxial fractures. Body build or inability to reduce the fracture can be prohibitive with this technique. In these cases, posterior atlantoaxial fusion may be warranted.
Indications
Disruption of the transverse ligament causing atlantoaxial instability.
Type II odontoid fractures with evidence of instability (i.e., greater than 6 mm of displacement).
Movement at the fracture site in halo vest demonstrated on supine and upright X-rays.
Preprocedure Considerations
Radiographic Imaging
Radiological studies—initial films should include anteroposterior, lateral, and open-mouth odontoid views.
Computed tomography (CT) scans with reformatted images may be used to determine the type of odontoid fracture and may provide more detail of bony anatomy than plain films.
Careful preoperative review of CT images with identification of fracture sites, bony anatomy, and vertebral artery course is necessary to determine whether instrumentation can be placed safely.
The Anderson and D′Alonzo classification system, which classifies fracture types I, II, and III, is commonly applied (Figs. 12.1and 12.2; Table 12.1).2
Medication
Perioperative antibiotics are initiated and maintained for 24 hours after incision.
Fig. 12.1 Commonly applied classification of odontoid fractures.
Table 12.1Documented treatment options for odontoid fractures
Type of odontoid fracture
Management
Reported fusion rates
Type 1
Conservative
External immobilization
100%
Type II
Conservative
External immobilization
55-65%
Surgical
Anterior approach, odontoid screw
90%
Posterior approach, atlantoaxial fusion or trans-articular screws
74-87%
Type III
Conservative
External immobilization
50-84%
Surgical
Posterior approach, atlantoaxial fusion
100%
Fig. 12.2a, b (a) Sagittal and (b) coronal preoperative CT images demonstrating a type II odontoid fracture.
FigureFig. 12.3Procedural StepsThe patient is positioned supine on the operating table with the head extended in traction. The patient is intubated. Biplanar fluoroscopy is used to monitor the head and dens during the procedure.Pearls• The anteroposterior (AP) view is obtained transorally using a C-arm fluoroscope, and a radiolucent prop may be used to open the mouth to improve AP visualization. The lateral view is obtained by a second C-arm fluoroscope, oriented horizontally. Using fluoroscopy as a guide, the head and neck are positioned to align the fracture edges. Finally, because blockage of screw insertion due to body obstruction (e.g., barrel chest) or body positioning (e.g., fixed cervical kyphosis) may limit this procedure, a Kirschner wire (K-wire) may be used to estimate screw/instrument trajectory and ensure that the patient′s body will permit clearance during screw placement prior to incision.
Cervical Dissection and Entry Site Preparation (Fig. 12.4a–e)
FigureFig. 12.4Procedural Steps(a) A transverse incision is made at approximately the C4-C5 level similar to an anterior cervical diskectomy. The platysma is incised. (b) Incision of the cervical fascia and plane is developed to the spine. (c) Dissection of the longus colli muscles. (d) Placement of radiolucent retractors. (e) The C3 body is notched and the C2-C3 ventral annulus fibrosis is incised.Pearls• The spine is approached anteriorly at the C4-C5 level using fine dissection between the midline structures and carotid sheath and then blunt dissection from the longus colli muscles to the vertebral bodies.3Radiolucent retractors are used to permit intraoperative fluoroscopy. To prepare the screw entry site, the C3 vertebral body is notched anterosuperiorly, and the C2-C3 ventral annulus fibrosis is incised.
FigureFig. 12.5Procedural Steps(a) A K-wire is advanced through the C2 body to establish the trajectory. (b) A single lag screw is rostrally directed through the entry site, the C2 vertebral body, and the tip of the odontoid process. This compresses the two bony segments together, achieving rigid internal stabilization at the fracture site.Pearls• To establish the trajectory for screw placement, a drill or K-wire is advanced up through the C2 body into the midpoint of the odontoid fragment. Confirmatory visualization of this pilot trajectory is achieved with fluoroscopy. The drill is removed and a lag screw is advanced through the guide hole through the C2 body and through the bony cortex of the odontoid tip. Because the lag screw head is restrained by the C2 body, screw tightening pulls the odontoid fragment inferiorly, internally reducing the fracture.3,4
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