The essence of atlantoaxial rotational dislocation fixation is chronic dislocation. Fielding (1977) referred to the state of atlantoaxial rotational subluxation that occurs spontaneously or after grade I trauma as atlantoaxial rotational fixation. Later (1983), he termed it rotational dislocation. Atlantoaxial joint rotational dislocation and fixation are conditions characterized clinically by idiopathic torticollis, neck stiffness, and limited rotation, with radiographic features showing changes in the corresponding joints of the dens and the lateral mass of the atlas. These conditions are often misdiagnosed due to clinical oversight.

bubble_chart Etiology

Infection Theory

Upper respiratory tract infections can cause hyperemic decalcification of the atlantoaxial joint, leading to the loosening of the associated ligaments from their attachments and resulting in dislocation.

Trauma Theory

Most minor traumas do not cause bony injury but can lead to tears in the transverse ligament of the atlas and the alar ligaments, resulting in atlantoaxial joint instability.

Whether due to trauma or infection, the joint capsule experiences synovial effusion, swelling, and muscle contracture. Prolonged failure to restore normal anatomical alignment leads to contracture of the ligaments and joint capsule, forming rotational dislocation and fixation.

bubble_chart Clinical Manifestations

1. Idiopathic Torticollis: The characteristic of torticollis is a 20° tilt to one side with grade I flexion, presenting as the "male robin" posture. Long-term torticollis leads to asymmetric development of the head and face.

2. Neck Stiffness: The patient has significantly limited head and neck rotation.

4. Restricted Movement: The head and neck are fixed.

This condition is rarely accompanied by spinal cord or nerve root compression.

X-ray Findings and Classification

X-ray plain films indicate disruption of the anatomical relationship between the odontoid process and the lateral mass of the atlas, with changes in the atlanto-dental interval. Fielding classified atlantoaxial joint rotation and fixation into four types:

Type I: Rotation and fixation without anterior dislocation of the axis (displacement distance ≤ 3mm), indicating no injury to the transverse ligament of the atlas and normal range of atlantoaxial rotation.

Type II: Rotational fixation with displacement between 3mm and 5mm, possibly combined with transverse ligament injury. One lateral mass is displaced, while the corresponding lateral mass remains unchanged. Atlantoaxial movement exceeds the normal range.

Type III: Severe displacement, with the atlas displaced anteriorly by more than 5mm, and the ADI exceeding the normal range.

Type IV: Posterior displacement of the atlas, possibly with displacement of only one lateral mass, which is clinically rare. X-ray plain films may have difficulty identifying these changes, especially on lateral views. Open-mouth views can show the lateral mass positioned anteriorly and closer to the midline, with the spinous process deviating to one side. Open-mouth views may also reveal the "winking sign" on the uninjured side of the small joint and overlapping interlocking of the injured joint at cervical levels _1-3. The degree and direction of rotation can be determined from anteroposterior tomograms and CT scans.

bubble_chart Treatment Measures

The choice of treatment method should be based on the condition of the lesion. Traction reduction and gypsum fixation are suitable for the acute phase. Occipitomandibular traction is sufficient to achieve reduction, and skull traction is only considered for those who fail. Atlantoaxial fixation is performed for those who are stable after traction reduction.