Study design: Retrospective analysis of collected data and operative experiment on human cadavers.
Objective: To describe a novel technique of the anterior atlantooccipital (AC) transarticular screw fixation, and to analyze the pertinent anatomy with cadaveric and radiographic assessment of the feasibility, safety, and general applicability of this technique.
Summary of background data: In some situations, the posterior AC fixation techniques may not be possible, or may require supplemental fixation, which include the congenital hypoplasia, absence of the bony elements, and even revision surgery. However, an anterior screw fixation technique may add stability to further attempts at obtaining an arthrodesis.
Methods: A detailed description of the surgical technique was presented. Three-dimensional (3D) CT reconstruction of the cranioverteral region of 30 patients were performed 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 C1 superior facet joint in line with the medial third of the C1 superior facet. The ideal screw is directed 41.7° posteriorly in the sagittal plane and 11.6° laterally in the coronal plane with a length around 30.4 mm. The feasibility of anterior AC screw fixation was 92% (35/38 cases). There is a risk of injury to the vertebral artery and the hypoglossal nerve.
Conclusion: Anterior AC transarticular screw fixation is feasible and can be considered as a salvage technique or an alternative for the posterior AC fixation, as well as the supplement to the anterior occipitocervical fixation.
Level of evidence: 3.