A fracture of the odontoid process of the axis (C2) may fail to heal if certain risk factors are present.


Risk factors for nonunion:

(1) age of the patient > 40 years

(2) angulation of the fracture > 10 degrees

(3) posterior displacement

(4) displacement > 4 mm

(5) instability



• Instability can be demonstrated under fluorscopy using flexion-extension stress views.


The presence of one or more of these factors may be associated with nonunion. A patient with one or more of these risk factors may benefit from an operation with fixation.


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