Study design: A case report of anterior screw fixation from the axis to the occiput is described, as is the surgical technique. The pertinent anatomy is described with a radiographic assessment of the feasibility, safety, and general applicability of this technique.
Objectives: To describe a novel technique of anterior occipitocervical fixation and the pertinent anatomy.
Summary of background data: In unique clinical situations where posterior fixation techniques may not be possible or may have already failed, an anterior screw fixation technique may add stability to further attempts at obtaining a posterior arthrodesis.
Methods: A case report is presented, followed by a detailed description of the surgical technique. Ten normal cervical spines had radiographs and computed tomography scans with reformats reviewed to determine screw entry points, target points, and proposed screw trajectories. Following screw insertion in eight fresh frozen human cadaver spine specimens, dissection verified screw location relative to structures at risk.
Results: The ideal entry point is located caudal to the C2 superior facet joint in line with the medial third of the C2 superior facet. The screw is directed 25 degrees posteriorly in the sagittal plane and 15 degrees laterally in the coronal plane. The screw tip is located in the posterolateral third of the occipital condyle. Anatomic variation is considerable and makes this technique inadvisable in up to 20% of cases. Structures at risk include the vertebral artery and the hypoglossal nerve.
Conclusions: This new technique of anterior fixation of the atlas to the occiput is feasible and safe if meticulous surgical planning is performed.