Introduction: Fixation of the atlantoaxial complex has traditionally involved transarticular screws combined with posterior wiring techniques and structural bone grafting. Although this does lead to excellent fusion rates, the technique has a potential risk of injury to the vertebral artery. In addition, it cannot be used in fixed subluxation of the C1/2 complex. We describe the use of C1 lateral mass screws in combination with C2 pedicle screws for safe and versatile C1/C2 fixation.

Methods: Over a fifteen month period, (July 2003–October 2004) a total of 10 patients underwent posterior C1/ C2 fixation alone, or as part of a more extensive posterior construct. The average age was 54.25 years, ranging from 20–78 years. There were 7 women and 3 men. The average length of stay was 18.5 days ranging from 5–36 days.

Technique: A midline posterior approach was used in all cases. The C2 roots were mobilized and the C1 lateral masses identified bilaterally. A drill was inserted into the middle of each lateral mass under image intensification. Bicortical polyaxial screws were then inserted. The C2 pedicle screws were inserted under direct vision, as were the other pedicle screws in the more extensive constructs. Contoured rods and posterior iliac bone graft were used in all cases.

Results: Five patients required isolated C1/C2 fusion for instability, two patients had an odontoid fracture non-union, one had an unstable C2 fracture, and the remaining two patients had C1/C2 subluxation secondary to rheumatoid arthritis. More extensive posterior instrumentation was performed for the following cases, these included; occipitothoracic fixation in one patient with rheumatoid arthritis with multi-level cervical subluxation, and occipitocervical fixation in three patients, two who had metastatic disease in the cervical spine, and the remaining patient who had rheumatoid arthritis. The final patient was instrumented from C1–C5 posteriorally following removal of a C3 giant cell tumour. No neurological or vascular complications were observed. One patient, with rheumatoid arthritis and osteoporosis, had a halo applied to protect an occipitothoracic construct. All other patients were discharged in a Miami-J cervical collar. The early follow up data, clinical and radiological, showed fusion in all patients. There were no implant failures.

Conclusion: The combination of C1 lateral mass and C2 pedicle screws allows safe, effective and versatile fixation of the C1/C2 complex.