A device for three-dimensional quantitative assessment and alignment of C1-2 vertebrae during posterior distraction and fusion technique for atlantoaxial dislocation and/or basilar invagination.

The most common type of congenital C1-2 dislocation is a combined type in which atlanto-axial dislocation (AAD) and basilar invagination (BI) are often associated with a rotational dislocation and coronal tilt. An optimal surgical treatment involves reduction of AAD and BI with simultaneous correction of the rotation and coronal tilt to achieve an optimal cervical canal decompression, sagittal and coronal realignment and bony fusion. The most acceptable technique to facilitate this correction is the C1-C2 distraction technique, which is accomplished by the manual joint manipulation. In this study, the authors describe an instrument that accomplishes distraction of the C12 joint space along with its quantitative assessment, permits the easy installation of a joint spacer without damage to the articular surfaces, brings about reduction of AAD and BI, while simultaneously also helping in the correction of the coexisting coronal tilt and rotational dislocation. This distractor not only achieves a multi-planar three-dimensional correction of the displacements at the C1-2 vertebral level, but may be used for the quantitative assessment of the correction and is compatible with the related surgical instruments of all standard companies utilized in this operative procedure.