Anterior transarticular screw (ATS) fixation is a useful surgical option for atlantoaxial stabilization.
Using a standard anterior cervical approach, the vertebral bodies of the middle cervical spine are exposed. Blunt dissection then proceeded cranially along the anterior surface up to the C2-3 intervertebral disc. A Cusco speculum is placed to secure the operative field. Under biplanar fluoroscopy image guidance, a Kirschner-wire is introduced as a guide from the midpoint on the inferior border of the axis to the superior articular process (SAP) of the atlas, following the preoperative planning for the screw trajectories. The depth to the SAP of the atlas has to be measured, and a cannulated full-threaded screw of the same length inserted.
Because wide tissue dissection is unavoidable with this approach, there is latent danger of tissue injury to the throat, trachea, esophagus, pharynx, major vessels, and lower cranial nerves. Advances in posterior instrumentation techniques and the technical difficulty of the anterior retropharyngeal approach have been cited as reasons why ATS fixation is rarely the procedure of choice. Recently, however, there have been a few reports on ATS fixation using minimally invasive techniques, such as microendoscopy and percutaneous screw systems 5) 6).
Although wide tissue dissection is unnecessary for these methods, there seems to be a higher risk of tissue injury during introduction of devices into the unopened operative field.
In Case 1, the patient was diagnosed with an unstable C1 fracture. The clinical features of the case did not allow for any type of posterior atlantoaxial fusion, Halo immobilization, or routine anterior fixation using the Reindl and Koller techniques. The possible manner of screw insertion into the anterior third of the right lateral mass was via a contralateral trajectory, which was performed in this case. Case 2 involved a patient with neglected posteriorly dislocated dens fracture who could not lie in the prone position due to concomitant cardiac pathology. Reduction of atlantoaxial dislocation was insufficient, even after scar tissue resection at the fracture, while transdental fusion was not possible. Considering the success of the previous case, atlantoaxial fixation was performed through the small approach, using the Reindl technique and contralateral screw insertion.
These two cases demonstrate the potential of anterior transarticular fixation of C1-C2 vertebrae in cases where posterior atlantoaxial fusion is not achievable. This type of fixation can be performed through a single approach if one screw is inserted using the Reindl technique and another is inserted via a contralateral trajectory 7).
A patient with an old odontoid fracture and severe degenerative changes of the lateral atlantoaxial joints (LAAJs) who was treated successfully with ATS fixation. The method included the utilization of conventional surgical techniques plus rigid stabilization to attain solid fusion between the atlas and the axis 8).