Introduction: Congenital atlanto-axial dislocation (CAAD) is often seen as abnormal antero-posterior or axial rotational. The focus in such cases has shifted to c1-2 joints. The c1-2 joints have six degrees of freedom of movement and caad is often multiplanar rather than the commonly described antero-posterior or rotational. The purpose of this study is to objectively assess CAAD in each plane.

Methods: CT CVJ of 100 patients with irreducible congenital aad was studied in axial, coronal, and sagittal planes. The relationship of c1-c2 along with the c1-c2 joint inclination was studied in each plane. Newer indices were described to assess dislocation in each plane both pre and postoperatively. Japanese orthopaedics association score (JOAS) was used objectively assessing clinical status and was compared with the plane of dislocation.

Results: The dislocation could be antero-posterior, lateral translation, lateral angular, rotation (axial), vertical (traditionally known as basilar invagination). The commonest variety was a combination of anteroposterior (AP) and vertical c1-c2 dislocation (65 patients). Five patients had predominant ap, 6 vertical, 4 axial rotational, 10 lateral angular tilt, and 3 had lateral translational. Seven patients had a combination of dislocation in AP, vertical, and rotational planes. AP dislocation was seen with sagittal inclination of c1-c2 joints and vertical dislocation with coronal inclination. Asymmetry in the joint’s sagittal inclination added to a rotational component, whereas asymmetry in the coronal angulation caused lateral angular tilt. Pure rotational or lateral translation dislocation had near normal c1-c2 orientation. Preoperative JOAS was worst in the lateral tilt and the lateral translation. Correction in all planes was achieved in nearly all patients.

Conclusions: The newer indices assess c1-c2 dislocation and joints in each plane and compare it postoperatively. Studying the radiology in all three planes is important to plan the surgery and achieve multiplanar correction.

Patient Care: Surgery is the best option for patients with CAAD. Good surgical correction improves the quality of life to great extent. It is important to assess dislocation in each plane to achieve a multiplanar correction.

Learning Objectives: By the conclusion of this session, participants should be able to discuss 1) Identification of C1-2 dislocation in each plane and objectively assess them. 2) The type of dislocation and the orientation of C1-2 joints would help in planning the management by facetal drilling and maneuvering the lateral masses 3) The facetal drilling and realignment using screws can correct C1-2 dislocation in all planes. Furthermore the effectiveness of any new technique can be assessed using the indices described

References: 1. 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 Apr;131:47-53. 2. 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 Sep;23(3):294-302. 3. Salunke P, Sahoo SK, Deepak AN, Khandelwal NK. Redefining Congenital Atlantoaxial Dislocation: Objective Assessment in Each Plane Before and After Operation. World Neurosurg. 2016 Nov;95:156-164. 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 Apr;25(4):1098-108. 5. Salunke P, Sahoo SK, Deepak AN, Garg R. Congenital C1-2 Lateral Translational Dislocation: Case Illustration with Pre- and Postoperative Imaging. Pediatr Neurosurg. 2016;51(4):218-20..