Indications
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Patients with acute type II odontoid fractures (<6 months) and patients with fractures with either a transverse or an anterosuperior to posteroinferior fracture plane are the most favorable surgical candidates.
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Odontoid screw fixation is indicated for fractures with displacement of greater than 6 mm, which are unlikely to fuse with external immobilization.
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“Shallow” type III odontoid fractures, in which the fracture pattern extends only minimally into the vertebral body, can be treated with odontoid screw fixation.
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Failure to maintain reduction in halo vest or inability to tolerate halo vest immobilization is another indication.
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Elderly patients with type II odontoid fractures represent a treatment challenge because of comorbidities and varying degrees of osteopenia. Fewer treatment failures and less morbidity are associated with surgical management compared with an external orthosis.
Contraindications
Absolute
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Disruption of transverse ligament—requires C1-2 fixation because repairing the odontoid fracture would not address C1-2 instability
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Irreducible odontoid fractures
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C2 body fracture
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Comminuted odontoid fracture
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Oblique odontoid fractures, specifically anteroinferior to posterosuperior plane—lead to misalignment with odontoid screw reduction
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Pathologic fracture
Relative
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A barrel chest can obstruct the needed trajectory for odontoid screw placement.
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Osteoporosis or osteopenia leads to higher rates of pseudarthrosis and screw pullout.
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Fractures more than 6 months old or with documented pseudarthrosis from nonsurgical management have been treated with odontoid screw fixation but with less favorable results. Some authors recommend curettage of the segment with pseudarthrosis and placement of two screws.
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Concomitant cervical stenosis, can lead to neurologic deficit during manipulation of fracture.
Planning and positioning
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Because of the highly mobile nature of type II odontoid fractures, awake fiberoptic intubation is recommended. After the airway is secured, the endotracheal tube should be secured to the side opposite to the surgical exposure. The table is turned 180 degrees away from anesthesia.
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Two fluoroscopy units are positioned for direct lateral and anteroposterior open-mouth views. A roll of gauze sponges, a radiolucent tape, or a large wooden cork is placed into the oropharynx to keep the mouth open and facilitate anterior open-mouth views. The surgeon needs to confirm true lateral and obstruction-free anteroposterior views of cervical extension; additional scapular padding or manual transoral reduction may be necessary to provide adequate alignment.
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Close attention must be paid to patient positioning, especially if intraoperative reduction is necessary. A well-positioned crack at the head of the bed may be adjusted intraoperatively to achieve more extension or flexion.
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Preoperative images such as lateral x-ray and sagittal computed tomography (CT) reconstructed view are used to obtain an approximate length of the screw to achieve bicortical purchase. Sufficient room usually exists at the craniocervical junction to accommodate up to 5 mm additional length to the screw.
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A radiopaque object should be placed in the trajectory of the odontoid screw as an approximation to the drill guide angle and working distance. Assessment of the level of skin incision and any other impediments should be addressed at this time. The typical level of skin incision is at C4-5.
Figure 58-1:
The operative bed is turned 180 degrees from anesthesia, with the neck carefully extended. Two fluoroscopy machines should be positioned for direct lateral view and anteroposterior open-mouth views. Monitors are placed side-by-side for surgeon’s ease of viewing.Related posts:
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