Case of Atlantoaxial Dislocation with Assimilated C1, Absent Posterior C2, Butterfly C3, and Fused Subaxial Cervical Spine: Management Dilemma with Multiple Segmentation and Formation Defects.

Segmentation defects are often seen with congenital atlantoaxial dislocation (AAD) though an associated absence of posterior arch of C2 and butterfly C3 is rare. Apart from rarity, the combination of formation and segmentation defects adds to the management dilemma. We report a case of AAD with assimilated atlas, absent C2 posterior arch, C3 butterfly vertebra with floating posterior elements, and fused C4-C6. The child was managed by C1-C2 fusion alone with immediate symptomatic improvement. The presence of formation defects such as adjacent butterfly vertebra and absent posterior elements does not alter the management of AAD. Fusing the C1-C2 joints appears to be a balanced approach.

'Split and splayed C3'-traumatic lateral C2-3 dislocation without neurological deficits: unique case and its management.

BACKGROUND: Traumatic C2-3 dislocation has been often described in the antero-posterior plane but is extremely rare in the lateral plane. Such dislocations have been described in thoraco-lumbar and C1-2. The need to study the imaging in multiple planes has been highlighted to plan proper realignment. METHODS: A young male presented with neck pain alone following a train accident. The imaging showed a fracture of C3 splaying it. The C2-3 showed lateral dislocation in the lateral plane with locked C2-3 facets on one side and C3-4 facets on the other. Through the posterior approach, the dislocation was corrected by manipulating (distraction and rotation) the lateral mass screws and rods. Curvilinear rods helped to maintain realignment after reduction. Residual lateral rotation was corrected by subsequent anterior approach. RESULTS: Compression, distraction and lateral force possibly resulted in such fracture dislocation. Using the technique, the fracture fragments could be realigned perfectly and the reduction was maintained. CONCLUSION: The saddle shape of the sub-axial cervical spine prevents such lateral dislocations. It is imperative to study the radiology in multiple planes to assess the 'multiplanar dislocation'. Correction is possible with proper planning and manipulation of facets and bodies using the available instrumentation. Though not obtained in this case, a preoperative MRI and a CT angiogram are important in surgery planning.