The Four Fixation Points of the Axis: Technique and Case Report.

Background: Instrumentation of the axis can be accomplished through a variety of techniques including transarticular screw fixation, pars and pedicle screw fixation, translaminar screw fixation, and posterior wiring. We report on the evolution of the axial 4-screw technique.

Methods: Retrospective case review. After exposure of posterior spinal elements, the medial and superior walls of the C2 pedicle were identified from within the spinal canal. A high-speed drill was then advanced under lateral fluoroscopy, which guided craniocaudal angulation. Medial angulation was based on anatomic landmarks and preoperative imaging. This was followed by placement of translaminar screws according to the technique described by Wright. When extending the construct into the subaxial spine or the occiput, lateral connectors are placed in translaminar screws, which are usually more offset. The rod is directly connected to the pedicle screws, which are usually more in alignment with the subaxial/occipital instrumentation.

Results: Two male patients ages 56 and 58 underwent posterior instrumentation of the axis employing a combination of pedicle and laminar polyaxial screws. Indications included multilevel spinal cord compression and deformity in a patient with Down syndrome and cervical meningioma, respectively. Follow-up was 1 year and 5 years, respectively. Medical complications (N = 2) occurred in the patient with Down syndrome resulting in prolonged intubation with tracheostomy placement. Reduction was maintained in both patients at last follow-up. There were no neurologic, vascular, or instrumentation related complications.

Conclusions: The axis serves as a versatile anchor point and offers 4 potential points of fixation. Lateral connectors play a crucial role and allow for incorporation of the C2 screws with the rest of the construct. Local anatomy will dictate the necessity and ability to place instrumentation and detailed preoperative planning is of paramount importance.