Traumatic Atlantoaxial Lateral Subluxation With Chronic Type II Odontoid Fracture: A Case Report.

BACKGROUND: We report a case of an elderly patient who was diagnosed with lateral atlantoaxial subluxation with type II odontoid fracture, an extremely uncommon upper cervical spine injury that has not been previously reported in the literature to the knowledge of the authors. METHODS: An 87-year-old male reported to the emergency room following a syncopal episode after sustaining a fall. He complained of dizziness, fatigue, disruption of vision and audition, and worsening neck pain. Computed tomographic scans were positive of partial dislocation of the C1 relative to C2 and chronic fracture of dens classified as type II according to the Anderson and D'Alonzo classification system. Magnetic resonance imaging further revealed large fracture pannus tissue at the level of the dens, reducing the space in the spinal cord. There was no evidence of spinal cord injury. Atlas-axis fusion with instrumentation was performed to manage the injury. A review of the classification, occurrence, and management of upper cervical spine surgeries was performed. RESULTS: An acute injury to a previously unrecognized type II odontoid fracture with partial C1-C2 dislocation was identified as a rare upper cervical spine injury and classified based on the Anderson and D'Alonzo and Fielding and Hawkins classification systems. The decision was made to perform instrumented spinal fusion by inserting mass screws into C1, pars screws into C2, and locking rods to realign the vertebral bodies and address the atlantoaxial instability. Follow-up scans indicated good postsurgical reduction and fixation, including resolution of the pannus overgrowth without direct intervention. CONCLUSIONS: Lateral atlantoaxial subluxation with chronic type II fracture of the dens constitutes a rare injury of the upper cervical vertebrae. Posterior instrumented spinal fusion was used to effectively manage the injury, leading to reabsorption of retro-odontoid pannus tissue.