Accuracy of 2D Sagittal Radiological Analysis vs 3D Templating for Pedicle Screw Fixation of C2 Vertebral Body

There are currently no studies that directly compare the previously established 2-dimensional (2D) sagittal technique with 3-dimensional (3D) templating for C2 pedicle screw.

To verify the accuracy of sagittal radiological analysis for safe placement of a C2 pedicle screw by performing a direct comparison between 2D planning with 3D templating methods.

In this retrospective analysis, forty-six sets of computed tomography scans that contained 2-mm bony cuts and 2D reconstructions in the axial, sagittal, and coronal planes of skeletally mature patients were analyzed. StealthStation S7 (Medtronic Surgical Navigation, Minneapolis, Minnesota, United States) trajectory planning was used to plan the ideal placement, maximum diameter pedicle screw into the C2 pedicle. Based on the parameters of ≤3 mm screw diameter as high risk, >3 mm and <5 mm as moderate risk, and ≥5 mm as low risk, frequency and percentage values were calculated for the left, right, and bilateral pedicle screws.

Out of the 46 patients analyzed in this study, only 1 patient (2.2%) was classified as low risk (≥5 mm) bilaterally, 5 were classified as high risk (≤3 mm) bilaterally (10.8%), and 25 patients (54.3%) showed variability in pedicle width between the left and right sides. With analysis of both left and right pedicle, 7 out of 92 pedicles (7.6%) analyzed were classified as low risk (≥5 mm), 67 out of 92 (72.8%) were at moderate risk (>3 mm and <5 mm), and 18 out of 92 (19.6%) were at high risk (≤3 mm).

Both the previously described 2D sagittal planning method and the current 3D templating method allow for accurate preoperative planning for the placement of ≤4 mm C2 pedicle screws, which is important given the limited availability and amount of resources utilized for the 3D templating model. However, the 3D templating method more precisely identifies C2 pedicles where 3.0 to 4.5 mm screws can feasibly be placed.