Traumatic Posterolateral C1-C2 Dislocation Complicated with Locked Lateral Mass and Type II Odontoid Fracture-5-Year Follow-up.

Objective: We sought to document our experience in managing a rare complex of traumatic posterolateral atlantoaxial dislocation combined with locked lateral mass and type II odontoid fracture.

Method: A 30-year-old male patient was referred to the author's department. He complained of a decrease in neck range of motion following a traffic accident. Neurologic examination was normal. Computed tomography and open-mouth radiographs showed a type II odontoid fracture and a posterolateral dislocation with a laterally locked left lateral mass at the C1-C2 level. Considering the difficulty and risk in reduction, due to this rare instability and dislocation, a 2-staged treatment was performed. With up to 11 kg skull traction for 7 days before surgery, the locked lateral mass and the lateral dislocation was finally reduced without any neurologic deficit. And once closed reduction was confirmed by open-mouth and lateral X-ray views in the cervical spine, a second staged C1-C2 surgical fixation and fusion with iliac bone graft was performed to achieve a normal anatomic alignment with a better stability.

Result: The patient showed significant amelioration of neck symptoms postoperatively, and a successful reduction and fixation of the C1-C2 articulation was achieved. At the 5-year follow-up, solid bone fusion was evident on the computed tomography scan.

Conclusion: For traumatic posterolateral atlantoaxial dislocation complicated with type II odontoid fracture, a closed reduction of the lateral dislocation before operation is both useful and safe because surgeons do not need to reduce the extremely rare lateral dislocation during the operation. Posterior atlantoaxial stabilization and fusion, rather than the occipitocervical fusion as reported previously, is biomechanically stable enough to achieve solid fusion in this rare trauma while not sacrificing the occipitoatlantal joint.