Also called atlantoaxial rotatory fixation, atlantoaxial rotatory subluxation is a condition where there is a fixed rotation of C1 over C2. This condition occurs when normal motion between the atlas and axis becomes limited or fixed either spontaneously or following minor trauma [which usually is the case]. It can also or follow an upper respiratory tract infection.
The cause of this subluxation is not completely understood. It is related to increased laxity of ligaments and capsular structures caused by inflammation or trauma.
Atlantoaxial rotatory subluxation is a common cause of childhood torticollis. Both the subluxation and torticollis usually are temporary. but rarely they persist and become atlantoaxial rotatory fixation.
Classification of Atlantoaxial rotatory subluxation [Fielding and Hawkins]
Simple rotatory displacement without anterior shift of C1
Rotatory displacement with an anterior shift of C1 on C2 of 5 mm or less
Rotatory displacement with an anterior shift of C1 on C2 greater than 5 mm
Rotatory displacement with a posterior shift.
Type I atlantoaxial rotatory subluxation is the most common and occurs primarily in children. Type II atlantoaxial rotatory subluxation is less common but carries a higher risk for neurological damage.
Presentation of Atlantoaxial Rotatory Subluxation
The child usually presents with torticollis following trauma or upper respiratory tract infection. The sternocleidomastoid muscle on the side opposite to tilt is in spasm as there is an attempt to correct this deformity. Head movements may cause pain in acute situations.
When the subluxation is acute, attempts to move the head cause pain.
With time, as the muscle spasms subside, and the torticollis becomes less painful, but the deformity persists. Neurological examination should be carried to find compression.
Radiographic Findings in Atlantoaxial Rotatory Subluxation
Anteroposterior and odontoid views of the cervical spine should be done.
In open-mouth odontoid view, the lateral mass that is rotated forward appears wider and closer to the midline, and the opposite lateral mass appears narrower and further away from the midline. Apparent overlapping may obscure one of the facet joints of the atlas and axis.
On the lateral view, the anteriorly rotated lateral mass appears wedge-shaped in front of the odontoid. The posterior arch of the atlas may appear to be assimilated into the occiput because of the head tilt.
Flexion and extension views in lateral position are done to find atlantoaxial instability.
CT reveals the deformity better and CT with the head rotated as far to the left and right as possible can confirm the loss of normal rotation at the atlantoaxial joint.
This loss of normal rotation at atlantoaxial joint confirms the diagnosis of rotatory subluxation.
Treatment of Atlantoaxial Rotatory Subluxation
Nonoperative treatment should be used only if no significant anterior displacement or instability is seen on radiographic evaluation.
- If rotatory subluxation has existed less than 1 week, immobilization in a soft collar, analgesics, and bed rest for 1 week. If reduction does not occur spontaneously, hospitalization and traction are indicated.
- If rotatory subluxation is present for longer than 1 week, hospitalization and cervical traction [Head-halter traction but if duration > 1 month, skeletal traction] may be required. Traction is maintained until the deformity corrects, then a cervical collar is worn for 4 to 6 weeks.
Operative treatment is indicated in the following situations
- Neurological involvement
- Anterior displacement
- Failure to achieve and maintain correction and deformity > 3 months
- Recurrence of the deformity after an adequate trial of conservative management
A preoperative traction for 2 to 3 weeks to correct the deformity is recommended as much as possible.
Fusion is carried out with the head in a neutral position. Six weeks of traction/ immobilization after surgery is recommended to maintain correction while the fusion becomes solid. Immobilization is continued until there is radiographic evidence of fusion.
Image Credit: Behrang Amini