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Atlantoaxial Rotatory Subluxation With Ankylosis in an 11-Year-Old Girl: A Case Report

Study Design. Report of an 11-year-old girl with a left atlantoaxial rotatory subluxation and ankylosis found 20 months after she sustained a cervical injury. Objective. To describe the radiographic characteristics of this rare deformity assessed with a combination of spiral CT scan with multiplanar three-dimensional reformations and functional CT scan. Summary of Background Data. Atlantoaxial rotatory subluxation is a well-known condition, but its association with lateral C1–C2 ankylosis has not been reported to our knowledge. Methods. For a complete assessment of the dislocation, a combined morphologic volumetric and functional CT study was performed. Results. Spiral CT showed an atlantoaxial rotatory subluxation with lateral C1–C2 ankylosis. CT study also demonstrated a lateral C1–C2 subluxation and an ipsilateral occipitoatlantal subluxation. Cervical MRI showed no spinal cord compression despite the seriousness of the dislocation process. Conclusions. Whereas “classic” spiral study with multiplanar and three-dimensional reformations allows precise assessment of relationships between the upper cervical vertebrae, as well as bony changes, a functional CT study is essential for cervical biomechanic assessment of rotational instabilities of the craniovertebral junction and upper cervical spine.