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Year : 2022  |  Volume : 9  |  Issue : 1  |  Page : 2-5

Address the cause, not the effect: C1-2 joint manipulation and not odontoidectomy in congenital atlantoaxial dislocation and basilar invagination

Department of Neurosurgery, PGIMER, Chandigarh, India

Date of Submission25-Dec-2021
Date of Acceptance26-Dec-2021
Date of Web Publication9-Mar-2022

Correspondence Address:
Pravin Salunke
Department of Neurosurgery, PGIMER, Sector 12, Chandigarh - 160 012
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/joss.joss_40_21

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The C1-2 joints in cases of congenital atlantoaxial dislocation are often oblique in both sagittal and coronal planes giving rise to anteroposterior and vertical slip of C1 over C2. Asymmetry on either side gives rise to coronal/lateral angular tilt along with rotational component. The dislocation is a dynamic process though it may appear to be fixed. The compressing dens is effect of dislocation and not the cause. The treatment should be directed towards C1-2 joint manipulation that would realign the joints as well as the dens. The facetal osteotomies coupled with manipulation for realignment in all planes provides a composite solution for even the complex lateral dislocation or complete spondyloptosis with severely deformed C1–2 joints, obviating the need for transoral decompression.

Keywords: C1-2 joint manipulation, congenital atlantoaxial dislocation, odontoidectomy

How to cite this article:
Salunke P. Address the cause, not the effect: C1-2 joint manipulation and not odontoidectomy in congenital atlantoaxial dislocation and basilar invagination. J Spinal Surg 2022;9:2-5

How to cite this URL:
Salunke P. Address the cause, not the effect: C1-2 joint manipulation and not odontoidectomy in congenital atlantoaxial dislocation and basilar invagination. J Spinal Surg [serial online] 2022 [cited 2022 May 27];9:2-5. Available from: http://www.jossworld.org/text.asp?2022/9/1/2/339275

The treatment of any disease is most effective when the underlying cause is addressed. Congenital atlantoaxial dislocation (CAAD) is no exception. It is imperative to understand what causes the atlantoaxial dislocation so as to provide the most rational and effective treatment.

The atlas is a ring-shaped vertebra that pivots around the odontoid process of C2 and is held in position with a strong transverse ligament. However, this atlanto-dental joint is not a weight-bearing joint. The weight of the cranium is transmitted to cervical spine through the lateral C1-2 joints. The C1-2 joints provide six degrees of freedom. Rotation as well as translation is possible in sagittal, coronal, and axial planes.[1] The normal C1-2 joints are flat in sagittal plane and inclined to about 25 degrees in the coronal plane.[1]

C1-2 dislocates either due to incompetent ligaments or due to abnormal disposition of facets. The facets are abnormally disposed in those with complex dislocations.The joint may dislocate in any of the 3 planes and may have components of translation and rotation. No patient is born with a dislocated atlantoaxial joint. They may be born with deformed joint. The disposition of the C1-2 facets in these deformed joints decides the plane of dislocation.[2],[3],[4] With sagittal obliquity the C1 dislocates anteriorly over C2, while the coronal obliquity leads to vertical dislocation or the so called basilar invagination.[2],[3],[4] Asymmetric C1-2 obliquity leads to lateral tilting and rotation.[4],[5] It is a glacial phenomenon and the C1 dislocates over C2. Initially, the patient may be able to correct it with extension or with a particular neck movement. The slipping of C1 over C2 continues and the dislocation cannot be reduced with simple maneuvers. The dens intrudes into the spinal canal, compressing the cord leading to neurological deficits.[2],[3] The vertebral arteries may be stretched beyond physiological limits causing vertebro-basilar insufficiency.[6] The intrusion of dens with cord compression is the effect of dislocation and not the cause.

The traditional way to treat CAAD was decided upon its reducibility with traction.[2] Those irreducible were treated with transoral decompression. The dens appears to be compressing the cord and hence its removal would bring about reversal of neurological deficits. However, removal of dens destabilizes the joint further mandating fixation, often carried out through the posterior route. Such a procedure is not without challenges and complications. The transoral route provides the shortest and the most direct access to the compressing element. Unfortunately, the route passes through a potentially infected cavity. Besides, severe vertical dislocation may require splitting of palate that may worsen the outcome. Finally, the root cause of dislocation is not addressed and the “glacial slipping of C1 over C2” is likely to continue.[7]

The surgical management of CAAD has undergone a significant change in the past two decades. The compressing dens is the effect and not the cause of dislocation. With a better understanding of pathophysiology, the management has now shifted to the C1-2 joints which is the cause of dislocation in most of the cases.[8],[9],[10],[11],[12] These joints are usually approached posteriorly and opened. This is followed by distraction and manipulation of joints to reduce the dislocation, and finally, fuse it as first described by Goel.[11],[12]

As described earlier, the C1-2 joints are deformed in many cases of CAAD. Deformity correction is likely to aid reduction in all planes as well as to prevent redislocation. The C1-2 joints are opened and drilled comprehensively in both coronal and sagittal planes to make it near-normal. In the sagittal plane, the posterosuperior wedge of C2 and the anteroinferior wedge of C1 are drilled. In the coronal plane, the medial wedge of C2 and the lateral wedge of C1 are drilled.[5],[8],[10] This corrects the deformity and converts a deformed trapezoid lateral mass to a near-normal cuboidal structure. Such drilling, however, leads to bone loss that needs to be compensated with metallic spacers.[5],[8],[10]

Further manipulation can be achieved using the facetal screws by holding them together with a loosely fastened rod and then manipulating them using a long stout rod holder. The long rod holder acts as a lever.[9],[10] Anteroposterior correction can be achieved by turning the rod holder caudally, whereas lateral tilt and translation can be corrected by turning the lever clockwise or anticlockwise. Thus, multiplanar alignment can be achieved.[9],[10] Finally, the tulips need to be compressed a bit to jam the spacers in the realigned position to prevent any movement.

Alternatively, the same can be achieved using an osteotome insinuated in the joint, which acts as a lever, as described by Goel and Shah.[11],[12] Using the Goel's plate, the anteroposterior dislocation can be corrected and the lateral masses can be compressed together. Whatever the technique, the final goal is to achieve multiplanar realignment and to avoid redislocation till the joints fuse.

The opening of joints is usually carried out posteriorly. One needs to be aware of anomalous vertebral artery. However, it is not a deterrent to posterior C1-2 joint manipulation and fixation. The aberrant artery can be mobilized and joints can be drilled comprehensively and realigned.[13],[14],[15] The screw insertion points may be changed if deemed necessary. Similarly, the c2 nerve root may be preserved to avoid complications of neuropathic ulcers.[16] Pseudofacets should not be confused with the true C1-2 joints.[17] The identification of true joints is necessary so as to address the cause of dislocation. The direction of these joints helps in differentiating the same.

The opening and drilling of C1-2 joint becomes difficult in cases of extreme obliquity. However, with experience, the joints can be addressed appropriately. Apart from this, when the deformity of C1-2 is asymmetrical, the more inclined joint would dislocate faster and to a greater extent.[5] With coronal asymmetry, the more vertical joint dislocates earlier and the dens tilts to the opposite side leading to lateral angular dislocation.[5] This is further exaggerated by the presence of bifid C1 that splays and allows further angular dislocation. Asymmetry of sagittal inclination leads to the anterior dislocation of one joint more as compared to the other. This adds rotational component to the dislocation.[5] Some surgeons believe that rotation, angular tilts, severe basilar invagination is a relative contraindication for joint manipulation and needs transoral decompression. It is important to understand these are a result of deformed joints. With experience, the joints can be addressed appropriately and the most complex CAAD can be treated with joint manipulation obviating the need for transoral decompression. [Figure 1], [Figure 2], [Figure 3] show scans of patients with severe C1-2 dislocation that were operated successfully with joint manipulation alone.
Figure 1: (a) Mid Sagittal section showing anteroposterior and vertical AAD. The C1 arch is free. (b and c) Parasagittal sections showing bilateral C1-2 joint dislocation. Notice the complete listhesis. (d) Three-dimensional computed tomography image to show the dislocation. (e-g) Mid and para-sagittal cuts showing the complete realignment of C1-2 joints without the need for transoral decompression

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Figure 2: (a) Mid Sagittal section showing anteroposterior and vertical AAD. The C1 arch is assimilated. (b and c) Coronal sections showing the lateral angular dislocation. (d and e) Parasagittal sections showing extremely oblique/vertical C1-2 joints. (f-k) Showing complete reduction and realignment in all planes. The C1-2 joints have been drilled flat to aid reduction

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Figure 3: (a) Mid Sagittal section showing anteroposterior and vertical AAD. The C1 arch is free. (b) Parasagittal sections showing C1-2 joint with complete listhesis. (c and d) Axial images through C1 and C2 showing rotational dislocation. (e) Lateral tilt noticed on coronal section. (f-g) Complete realignment in all planes with manipulation of C1-2 joints

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In a nutshell, the compressing dens and its orientation in the canal is the effect of C1-2 joint dislocation. Therefore the optimal treatment is realigning the joints and not removing the dens.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Salunke P. Congenital atlantoaxial dislocation: Nature's Engineering gone wrong and surgeon's attempt to rectify it. J Pediatr Neurosci 2018;13:1-7.  Back to cited text no. 1
[PUBMED]  [Full text]  
Salunke P, Sharma M, Sodhi HB, Mukherjee KK, Khandelwal NK. Congenital atlantoaxial dislocation: A dynamic process and role of facets in irreducibility. J Neurosurg Spine 2011;15:678-85.  Back to cited text no. 2
Salunke P. Orientation of C1-2 joints in congenital atlantoaxial dislocation. J Spinal Surg 2014;1:115-20.  Back to cited text no. 3
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Salunke P, Sahoo SK, Deepak AN, Khandelwal NK. Redefining congenital atlantoaxial dislocation: Objective assessment in each plane before and after operation. World Neurosurg 2016;95:156-64.  Back to cited text no. 4
Salunke P, Sahoo SK, Futane S, Deepak AN, Khandelwal NK. 'Atlas shrugged': Congenital lateral angular irreducible atlantoaxial dislocation: A case series of complex variant and its management. Eur Spine J 2016;25:1098-108.  Back to cited text no. 5
Sawlani V, Behari S, Salunke P, Jain VK, Phadke RV. “Stretched loop sign” of the vertebral artery: A predictor of vertebrobasilar insufficiency in atlantoaxial dislocation. Surg Neurol 2006;66:298-304.  Back to cited text no. 6
Salunke P, Sahoo SK, Sood S, Mukherjee KK, Gupta SK. Focusing on the delayed complications of fusing occipital squama to cervical spine for stabilization of congenital atlantoaxial dislocation and basilar invagination. Clin Neurol Neurosurg 2016;145:19-27.  Back to cited text no. 7
Salunke P, Sahoo SK, Deepak AN, Ghuman MS, Khandelwal NK. Comprehensive drilling of the C1-2 facets to achieve direct posterior reduction in irreducible atlantoaxial dislocation. J Neurosurg Spine 2015;23:294-302.  Back to cited text no. 8
Salunke P, Sahoo S, Khandelwal NK, Ghuman MS. Technique for direct posterior reduction in irreducible atlantoaxial dislocation: Multi-planar realignment of C1-2. Clin Neurol Neurosurg 2015;131:47-53.  Back to cited text no. 9
Salunke P, Sahoo SK. Comprehensive drilling of C1-2 facets and multiplanar realignment for atlanto-axial dislocation and basilar invagination: 2-dimensional operative video. Oper Neurosurg (Hagerstown) 2019;16:55-7.  Back to cited text no. 10
Goel A. Atlantoaxial joint jamming as a treatment for atlantoaxial dislocation: A preliminary report. Technical note. J Neurosurg Spine 2007;7:90-4.  Back to cited text no. 11
Goel A, Shah A. Atlantoaxial facet locking: Treatment by facet manipulation and fixation. Experience in 14 cases. J Neurosurg Spine 2011;14:3-9.  Back to cited text no. 12
Salunke P, Sahoo SK. Safeguarding the anomalous vertebral artery while dissecting, drilling, and instrumentation of c1-2 joint for congenital atlantoaxial dislocation: 2-dimensional operative video. Oper Neurosurg (Hagerstown) 2018;15:E57.  Back to cited text no. 13
Salunke P, Futane S, Sahoo SK, Ghuman MS, Khandelwal N. Operative nuances to safeguard anomalous vertebral artery without compromising the surgery for congenital atlantoaxial dislocation: Untying a tough knot between vessel and bone. J Neurosurg Spine 2014;20:5-10.  Back to cited text no. 14
Parthiban JK. Aberrant vertebral artery and screw placement in lateral mass of C1 in atlantoaxial fixation. J Spinal Surg 2021;8:1-3.  Back to cited text no. 15
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Puneeth S, Karthigeyan M, Salunke P, Panchal C, Kataria MS. C2 nerve root preservation during posterior fixation for instability secondary to congenital craniovertebral junction anomalies: Feasibility factors and related outcomes. World Neurosurg 2022;157:e94-101.  Back to cited text no. 16
Salunke P, Futane S, Sharma M, Sahoo S, Kovilapu U, Khandelwal NK. 'Pseudofacets' or 'supernumerary facets' in congenital atlanto-axial dislocation: Boon or bane? Eur Spine J 2015;24:80-7.  Back to cited text no. 17


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