A study in The Spine Journal, comparing posterior transarticular screw (PTS) fixation with percutaneous anterior transarticular screw (ATS) fixation for atlantoaxial subluxation, has indicated that the ATS technique may be associated with a lower risk of vertebral artery injury than the PTS technique.
According to Hui Xu, Department of Spinal Surgery, The Second Affiliated Hospital of Wenzhou Medical College, Wenzhou, China, and others, transarticular screw fixation (whether using posterior or anterior approach) is a “technically demanding procedure” that carries a potential risk of iatrogenic vertebral artery injury, which they described as being rare but a “serious and potentially fatal complication”. They added that, at present, there is no data to show which approach to transarticular screw fixation carries the greatest risk of vertebral artery injury.
Using 3D CT images, including those of the C1–C2 complex, Xu et al examined data for 60 patients with atlantoaxial subluxation. They measured the maximum diameter of percutaneous ATS and PTS trajectories and reported: “We defined the placement of the screws where the maximum possible diameter was ≤3.5mm as ‘risky’.” They added that they deemed the maximum diameter to be “unacceptable” if it was ≤3mm.
Overall, Xu et al found that the mean maximum isthmus height diameter was 4.72±1.12mm and the mean maximum isthmus width diameter was 5.18±1.41mm for 120 percutaneous PTS fixations compared with a mean maximum screw path diameter of 8.32±1.99mm for 120 percutaneous ATS fixations—these values were significantly different (p<0.001). They noted: “There were 23 (19.2%) screw trajectories using the percutaneous posterior transarticular technique judged as risky. Six (5%) were judged as unacceptable. None of the screw trajectories using the percutaneous anterior transarticular technique were judged as risky or unacceptable.”
Xu et al noted that radiological and anatomic studies of the atlantoaxial joint have suggested that up to 20% of the population may have anomalous positioning of the vertebral artery, which they said would “preclude safe bilateral PTS placement in these cases.” They added: “From the anatomic standpoint, percutaneous ATS may have more extensive indications and greater security than percutaneous PTS.”
However, the authors said that a limitation of their data was that they were based on “anatomical rather than clinical” findings and reported: “Thus, the next steps of the research should be to expand the sample size, continue to improve iconography measurements, and collect additional clinical data.” Concluding, Xu et al commented, “As alternative surgical therapy for atlantoaxial subluxation, compared with percutaneous PTS fixation, percutaneous ATS fixation may have more extensive indications and greater security, especially for patients with anomalous vertebral artery.”
