Unintelligent manipulations of the structures of the region of the upper cervical spine may result in undesired sequelae, such as have occurred in the three cases here presented. A forward dislocation of the atlas on the axis has been a consequence in each of the cases, one with fracture of the odontoid process; all of the cases were apparently the result of chiropractic treatments. One of them resulted in death, the second in constant dull pain and limitation of motion, with a material loss in efficiency of the patient, while the third appears to be progressing satisfactorily in spite of the dislocation of the atlanto-axial joint, although there is a marked reduction in the movements of the head.
The articulation of the atlas with the axis is a joint of complicated nature, as it is made up of four distinct parts or joints. These are: (1) a pivot