"The classification is based upon fracture displacement and instability of the occipitoatlantoaxial (O-C1-C2) joint 1."
"type 2A: with stability of the O-C1-C2 joint"
"type 2B: with instability of the O-C1-C2 joint based on any criteria from radiographic, CT, and/or MRI findings"
"The following criteria for O-C1-C2 instability were proposed:"
">45 degrees of axial rotation of C1-C2 to one side"
">4 mm of C1-C2 translation"
Expected headings
"Classification"
"History and etymology"