Atlantoaxial dislocation

Area of Science:

• Neurosurgery
• Orthopedic Surgery
• Radiology

Background:

• Atlanto-axial dislocations (AADs) present diverse classifications based on displacement and surgical reducibility.
• Reducible AADs (RAADs) are typically managed with posterior fusion, often utilizing transarticular screw fixation and sub-laminar wiring for stability.
• Irreducible AADs (IAADs) pose unique challenges, sometimes stemming from dynamic X-ray findings or muscle spasms, necessitating advanced diagnostic and therapeutic approaches.

Purpose of the Study:

• To delineate the classification and surgical management strategies for various types of atlanto-axial dislocations.
• To clarify diagnostic criteria for reducibility, emphasizing the role of imaging modalities like X-ray, CT, and MRI.
• To address misconceptions regarding specific entities like 'dolichoodontoid' and differentiate them from true pathologies such as basilar invagination.

Main Methods:

• Classification of AADs into anteroposterior, rotatory, central, and mixed types, with further surgical categorization into reducible (RAADs) and irreducible (IAADs).
• Utilizing dynamic X-ray studies, flexion/extension cervical spine imaging, and computerized tomography (CT) scans to assess joint integrity and reducibility.
• Evaluating congenital anomalies and chronic post-traumatic conditions, including Type II odontoid fractures with malunion or nonunion.

Main Results:

• Posterior fusion with transarticular screw fixation and sub-laminar wiring is the preferred treatment for RAADs.
• IAADs may be reducible with cervical traction or intraoperative joint mobilization if the C1-C2 facet surfaces are anatomically normal.
• The entity 'dolichoodontoid' is identified as an artifact of C2-C3 fusion, not a distinct pathology. Transoral odontoidectomy requires adequate decompression for congenital IAADs.

Conclusions:

• Accurate diagnosis through advanced imaging is crucial for determining the appropriate surgical strategy for AADs.
• Distinguishing between reducible and irreducible dislocations guides treatment, with posterior fusion for RAADs and comprehensive decompression for IAADs.
• Understanding the nuances of AADs, including differentiating congenital anomalies and post-traumatic sequelae, is essential for successful patient outcomes.