A study of atlanto-axial motions using clinical material, a fresh anatomical specimen, and cineroentgenography is presented. The findings in previous studies have been confirmed. Special emphasis was directed to lateral motion of the atlas on the axis since this motion has received little clinical attention and is not well appreciated. It was shown that under normal physiological conditions, lateral movement is possible up to four millimeters. This is, however, a complex motion requiring both lateral bending and rotation at the atlanto-axial joint. From these findings it was concluded that a diagnosis of subluxation of the atlanto-axial joint or injury to the odontoid process cannot be made on the basis of lateral displacement of the atlas with respect to the axis.
Copyright 1964 by The Journal of Bone and Joint Surgery, Incorporated