Transarticular screw and C1 hook fixation for os odontoideum with atlantoaxial dislocation.

OBJECTIVE: To introduce a fixation device composed of C1-2 transarticular (TA) screws and C1 hooks and explore its indication and clinical outcome for os odontoideum with atlantoaxial dislocation (AAD). METHODS: From January 2004 to December 2008, 12 patients with os odontoideum (5 men and 7 women, average age 37.7 years [range 14-62 years]) were treated in the authors' hospital. All patients had AAD with local symptoms, and 10 had myelopathy. All patients underwent a posterior atlantoaxial fixation with C1-2 TA screws and C1 hooks. Clinical and radiographic analyses were performed at 3, 6, and 12 months postoperatively and annually thereafter. RESULTS: The follow-up period was 12-66 months (average follow-up period 35.5 months). No neurologic or vascular complications occurred in these cases, and the device was placed well with no loosening or breakage. Plain radiographs and three-dimensional reconstruction of computed tomography (CT) images revealed solid bony fusion with a good alignment of C1 and C2 at 3 months postoperatively. No hardware failure, pseudarthrosis, or instability was noted during the follow-up period. All patients had relief of pain within 3 months, and neurologic symptoms were substantially improved. CONCLUSIONS: When appropriate patients are selected, C1-2 TA screws combined with C1 hooks can be used to treat os odontoideum with AAD effectively with a relatively simple procedure resulting in excellent biomechanical strength and high bone fusion rate. Preoperative planning is crucial for the management of os odontoideum with AAD.