Atlantoaxial Rotatory Fixation
Atlantoaxial Rotatory Fixation is a rare condition occuring more commonly in children than in adults, in which there is fixed rotation of C1 on C2. The fixation may occur within the range of normal rotation, may occur with subluxation, or may occur with dislocation. Clinically the patients will have ipsilateral rotation and contralateral tilt of the head in relation to the lateral mass of C1. The contra-lateral sternocleidomastoid may be spastic. Fielding and Hawkins in 1977 classified atlantoaxial rotatory subluxation into four types basing their classification on the amount and direction of the midsaggital plane anteroposterior atlantoaxial displacement. This classification was presented in a time when more precise imaging tools were not commonly available thus the measurement of the atlas to dens interval as shown on a lateral X-ray is very important.