Traumatic lateral atlantoaxial dislocation combined with a type II odontoid fracture in a patient with ankylosing spondylitis: A case report

Rationale: Traumatic lateral atlantoaxial dislocation (AAD) combined with an odontoid fracture is extremely rare. The standards applicable to management of the traumatic lateral AAD are still in flux due to the infrequency of this injury. Patient concerns: We present a unique case of traumatic lateral AAD combined with a type II odontoid fracture in a patient with ankylosing spondylitis (AS). Diagnosis: Spinal computed tomography showed ankylosis of the entire spine from the sacroiliac joint to the cervical spine. On the cervical X-ray the head was rotated to the right with anterior subluxation of the C1 and odontoid tip relative to C2. The coronal computed tomography (CT) scan also revealed left lateral dislocation of C1 on C2 with a horizontal translation of the odontoid tip. On the axial and sagittal CT scan, the left C1 lateral mass was displaced anteriorly and locked by C2 body Interventions: We performed occipito-cervical fusion (OCF) after successful manual reduction under general anesthesia. Outcomes: The patient's recovery from surgery was uneventful and without complication. At the 3 year follow-up the patient was asymptomatic and reportedly satisfied with the surgery. Lessons: Traumatic AAD with an odontoid fracture is an exceedingly uncommon cervical spine injury. A lateral subluxation with a type II odontoid fracture in a patient with AS is rarer still, so much so that this type of subluxation was not classifiable using any of the previously developed classification systems. In this patient with AS, posterior OCF with internal fixation was necessary to avoid hardware failure, particularly in light of the intensive stress caused by AS.