[Acute torticollis and its roentgen analysis].

It has hitherto been assumed without exception that A-P films of acute torticollis demonstrate neither malposture nor subluxation or (worse still) luxation of the atlas. In contrast, there is ventral subluxation of the atlas in all cases, although in about one-half of them this only become manifest in ventral flexion, with a tendency to form an angle between the odontoid process and the first cervical vertebra. In conformity with the head posture in acute torticollis, X-ray findings in the head joints are normal on A-P films. Fundamental to acute torticollis is that when the head is held in certain positions -- lateral inclination with rotation, sometimes combined with tilting of the head -- spontaneous, occasionally gradual obstruction of rotation of the atlas (and more rarely of the axis) occur; as a result, the head has to be held in these positions by force. In attempts to equalize head posture temporarily, lateral shifting of the atlas quite frequently occurs; depending on atlas rotation and the statics of the cervical spine, it may be either physiological or pathologic.