Transarticular Screws for C1-2 Fixation

Indications for C1-2 transarticular screw fixation, also known as Magerl’s method, are atlantoaxial instability, tumor formation, ligamentous abnormality, acute fracture, os odontoideum such as nonunion, rheumatoid arthritis with severe pain resistant to conservative treatments, or congenital abnormality such as incomplete ossification or previously unrecognized fracture. Trauma and rheumatoid arthritis are the two most common indications for C1-2 fixation.

C1-2 transarticular screws can also be used in patients with atlantoaxial instability who have failed external orthosis treatment, including more conservative approaches (halo vest, neck collar, traction, etc.), and patients who develop pseudarthrosis after undergoing C1-2 fixation and fusion with other techniques such as wiring.

For elderly patients, it should be noted that a posterior approach like this is preferred, especially if the individual is also experiencing osteoporosis. Furthermore, studies have shown that nonsurgical treatments tend to fail early for a greater percentage of elderly patients, albeit without additional complicating comorbidities.

Biomechanical studies in cadavers show that C1-2 transarticular screws provide slightly better fixation than C1 lateral mass/C2 pars screws in cases of rotary subluxation and dislocation of C1 relative to C2. In adults, transarticular screw fixation results in a fusion rate of approximately 95%. In children, the fusion rate is even more favorable, at approximately 100% according to some studies.

The anatomic relationship between the C2 foramen transversarium and the C1-2 facet joint must be studied carefully preoperatively, because 18% to 23% of patients have a high-riding foramen transversarium (and vertebral artery) on at least one side that would prevent safe placement of a C1-2 transarticular screw. Thin-cut CT scans of the cervical spine with sagittal reconstruction generally offer sufficient detail to analyze the course of the vertebral artery through C2. In addition, special care should be given to avoid using screws of too long a length, as this correlates with risk for injury to the vertebral artery.

The procedure is relatively contraindicated in polytrauma patients with severe injury to other organ systems, elderly patients with other significant comorbidities, and patients who may be unable to tolerate a prone procedure.