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Year : 2000  |  Volume : 10  |  Issue : 3  |  Page : 175-176
CT demonstration of rotatory atlanto-Axial subluxation


Dept of Radiodiagnosis & imaging, Kasturba Medical College & Hospital, Manipal, India

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Keywords: CT, atlanto-axial rotary subluxation, spine, cervical

How to cite this article:
Rajagopal K V, Lakhkar BN, Banavali S. CT demonstration of rotatory atlanto-Axial subluxation. Indian J Radiol Imaging 2000;10:175-6

How to cite this URL:
Rajagopal K V, Lakhkar BN, Banavali S. CT demonstration of rotatory atlanto-Axial subluxation. Indian J Radiol Imaging [serial online] 2000 [cited 2014 Oct 2];10:175-6. Available from: http://www.ijri.org/text.asp?2000/10/3/175/30590
Rotatory atlantoaxial fixation is a common cause of a spontaneous torticollis in children. The normal rotation of the  Atlas More Details on the axis becomes limited or fixed in rotatory atlantoaxial subluxation [1]. The etiology of this condition is not known, but it may be related to increased laxity of the alar and transverse ligaments and of capsular structures secondary to inflammation or trauma. The importance of recognizing atlantoaxial fixation lies in the fact that it may indicate a compromised atlantoaxial complex with the potential to cause neural damage or even death. Radiologic evaluation of the patient with this condition is difficult because of the patient's rotated head position. Before the advent of CT, radiologic diagnosis required careful functional examination with cineradiography [2],[3]. The advantage of CT over cineradiography is the ease of performance and interpretation.


   Case report Top


A sixteen-year-old girl presented with a history of spontaneous torticollis and neck pain for two weeks. There was no history of trauma or upper respiratory tract infections.

Examination revealed torticollis with the head turned towards the right side. There was markedly diminished neck motion with spasm of the sternocleidomastoid muscle on the left side. The patient was directly referred for CT with clinical suspicion of atlantoaxial fixation.

CT demonstrated rotational displacement of the atlantoaxial complex. The left lateral mass of C1 was displaced anterior to the superior articular surface of C2 [Figure - 1]A. The septal axis formed an acute angle with the transverse axis of the atlas. The odontoid showed a normal relationship with the anterior arch of atlas and was eccentrically placed between the lateral masses of C2 [Figure - 1]B. After trying to turn her head as far as possible to the left side, no change in relationship between the transverse axis of C1 and axis of C2 was evident, confirming rotatory fixation. A 3DCT showed excellent demonstration of the rotatory atlantoaxial subluxation [Figure - 2].

The patient was treated with cervical traction. Post reduction immobilization was advised for six weeks.


   Discussion Top


Atlantoaxial rotatory subluxation is a common cause of childhood torticollis, but the subluxation and torticollis are usually temporary. Rarely do they persist and become what is best described as atlantoaxial rotatory fixation [1]. Most authors now agree that the subluxation is related to increased laxity of the alar and transverse ligament and capsular structures caused by inflammation or trauma.

Fielding and Hawkin's classifies atlantoaxial rotatory subluxation into four types [1] [Figure - 3].

Type I - Rotatory fixation without anterior displacement of the atlas.

Type II - Rotatory fixation with anterior displacement of the atlas - of three to five millimeters.

Type III - Rotatory fixation with anterior displacement of more than five millimeters.

Type IV - Rotatory fixation with posterior displacement.

Interpretation of a plain radiograph of a child who has rotatory atlantoaxial subluxation is often difficult. A plain film in patients whose heads are rotated, whether voluntarily or pathologically, as in atlantoaxial fixation or torticollis, shows a rotated appearance of C1 on C2, with asymmetry of distance between the odontoid and the lateral masses of C1 [2]. Open mouth radiograph of the upper cervical spine can be performed with the patient rotating the head to each side, but these are often difficult to interpret [1] [5]. The lack of cooperation on the part of the patient or diminished active movement of the neck may render it impossible to make these radiographs.

Fielding et al [1] proposed cine radiography, but the level of radiation is relatively high and again cooperation by the patient may be inadequate, due to pain and spasm. Cineradiography of the atlantoaxial joint during turning of the head from side to side has been shown to demonstrate fixation of atlantoaxial joint.

Computed tomography with head rotated as far to the left and right as possible during scanning, can demonstrate the loss of normal rotation at the atlantoaxial joint [4]. Kawalski et al postulated that the demonstration of cervical rotation without movement at C1-C2 is necessary to establish the diagnosis of rotatory fixation [5]. Our patient demonstrated Type I atlantoaxial rotatory subluxation. Dynamic CT performed with the head rotated to the opposite side as far as possible demonstrated no change in relationship between the transverse axis of C1 and the axis of C2 confirming atlantoaxial rotatory fixation. The 3DCT was an additional aid in demonstrating rotatory atlantoaxial subluxation.

Atlantoaxial fixation indicates a compromised atlantoaxial complex with the potential of causing neural damage or even death. Dynamic CT is an excellent method for early diagnosis of rotatory atlantoaxial fixation.

 
   References Top

1.Fielding JW, Hawkins RJ. Atlantoaxial rotatory fixation. The Journal of Bone and Joint Surgery 1977; 59:37-44.   Back to cited text no. 1  [PUBMED]  
2.Fielding JW, Hawkins RJ. Hensinger RN, Francis WR. Atlantoaxial rotatory deformities. Ortho Clin. North America 1978; 9:955-967.   Back to cited text no. 2    
3.Wortzman G, Dewar FP. Rotary fixation of the atlantoaxial joint: Rotational atlanto-axial subluxation. Radiology 1968; 90:479-487.   Back to cited text no. 3  [PUBMED]  
4.William C, Warner JR. Pediatric Cervical Spine. In Campbell's Operative Orthopedics; Ed. S.Terry Canale; 9th ed, Vol 3: 2839-2841.   Back to cited text no. 4    
5.Kowalski HM, Cohen WA, Cooper P, Wisoff JH. Pitfalls in the CT diagnosis of Atlantoaxial rotary subluxation. AJR 1987; 149: 595-600.  Back to cited text no. 5    

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Correspondence Address:
Bhushan N Lakhkar
Dept of Radiodiagnosis & imaging, Kasturba Medical College & Hospital, Manipal
India
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[Figure - 1], [Figure - 2], [Figure - 3]



 

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