*4-7% of all cervical spine fractures & dislocation
*hyperextension with axial compression
l       forced hyperflexion with compression    →　motor vehicle accidents / falls
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*Additional fractures
l         fractures of C1; Jefferson fractures, avulsion fractures of the anterior lip of C1
l                                   fractures through the posterior ring of C1 only
l         compression fracture of anterosuperior C3,
l         fracture of the lateral mass of C6
*Neurologic injuries
l        more frequent with type Ⅱand Ⅲ
*Prevertebral soft-tissue swelling
l        infrequently seen on the initial radiograph
l
l
*Anterior displacement
l        measured by the distance from the posterior margin of the body of C2
l        to the posterior margin of C3 at the level of the C2-3 disk space.
*
*Angulation
l        assessed by measuring the angle subtended by lines drawn along the
l        inferior end plates of C2 and C3.
l
l
l