Traumatic atlantoaxial anteroinferior subluxation with dens and Hangman fractures

Rationale: Traumatic atlantoaxial anteroinferior subluxation associated with a dens fracture and a Hangman fracture is a very rare and complex injury. Therefore, appropriate surgical strategy is not established. Patient concerns: An 85-year-old female presented with posterior neck pain and atypical neck position caused after rolling down a hill. Although neurological examinations for motor, sensory, gait, and reflex tests were normal, the patient complained of an abnormal neck posture. Diagnoses: Radiological examinations revealed an atlantoaxial anteroinferior subluxation with kyphosis, a type IIA dens fracture (Anderson and D’Alonzo classification) with an anterolateral rotatory angulation of type IIA dens fracture fragment, and a type I Hangman fracture (Levine and Edwards classification). Nevertheless, the transverse atlantal ligament was intact. Interventions: We considered that the intact transverse atlantal ligament and kinking of the type IIA dens fracture fragment into the left lateral mass of C1 prevented a spinal cord injury by blocking a further displacement of C1 to C2. Due to the patient's osteoporosis and the anterolateral rotatory angulated type IIA dens fracture fragment, a forceful reduction of the atlantoaxial anteroinferior subluxation with kyphosis could pose a high risk of fixation failure and spinal cord injury. Therefore, we performed in-situ posterior C1-2 fusion using a C1 lateral mass screw and C2 lamina screw fixations. Outcomes: At 1 year after surgery, the bone union of all fractures was achieved in the kyphosis state. Furthermore, the patient's clinical symptoms were improved with no neurological deficit. Lessons: A thorough radiological examination and appropriate surgical strategy are important for successful diagnosis and treatment of a complex C1-2 injury.