Table 1.

Atlantoaxial rotatory fixation classification according to Fielding and Hawkins (2)

Type I
Rotatory fixation without anterior displacement of the Atlas	Odontoid acting as the pivot, no anterior displacement
Type II
Rotatory fixation with anterior displacement	One lateral articular process acting as the pivot, anterior displacement 3 to 5 mm
Type III
Rotatory fixation with anterior displacement more than 5 mm	Rotatory fixation with anterior displacement more than 5 mm, displacement of both atlantal lateral masses
Type IV
Rotatory fixation with posterior displacement	Rotatory fixation with posterior displacement