Definition
- superior migration of odontoid into region of foramen magnum
Diagnosis
- Ranawat's < 13 mm (pedicle of C2 to line of axis)
- McGregor's > 4.5 (hard palate to base occiput)
- McCrae's - dens above line of foramen magnum
Congenital / SAD MAN BOOK
SED
Achondroplasia
Downs
Morquio
Atlas Hypoplasia
NF
Bifid posterior arch atlas
Occipitocervical synostosis
OI
Klippel Feil syndrome
Acquired
JRA
Rickets
RA