Establishing Safe Surgical Parameters for Placement of C2 Pedicle Screws: A Retrospective Study.

Abstract

The study aimed to evaluate the safety and feasibility of transpedicular instrumentation for the C2 vertebra and to establish the precise anatomical parameters and boundaries within which this procedure can be safely and effectively performed. This retrospective study analyzed 66 patients who underwent C2 transpedicular screw fixation. Preoperative and postoperative axial, sagittal, and coronal computed tomography (CT) scans were examined. Anatomical measurements were taken to determine the horizontal and vertical distances from the C2 pedicle projection to the vertebral foramen using CT images. Based on the anatomical location of the vertebral artery within the C2 vertebral foramen, the patients were divided into four subgroups using the horizontal pedicle width (HPW) and vertical pedicle width (VPW) of the C2 spine. The average age of the patients included in the study was 46.48 years. The patient population comprised 32 (48.5%) males and 34 (51.5%) females. Based on the anatomical measurements, the distribution of C2 vertebra types was as follows: type 1 accounted for 68.9%, type 2 for 3.8%, type 3 for 16.7%, and type 4 for 10.6%. Significantly narrower pedicle widths were observed in types 2 and 4 compared to other vertebra types. Type 2 had the largest medial angle (MA), while type 4 had the narrowest MA. In terms of the sagittal plane, type 4 exhibited the widest MA and type 3 had the narrowest MA, but these differences were not statistically significant. Among the cases, 12 (18.1%) involved the vertebral foramen, with 1 case (8.3%) showing screw-related vertebral artery injury (0.75% of all screws). No vertebral artery injuries were observed with the other transpedicular screws. Preoperative anatomical measurements for patients undergoing transpedicular instrumentation on the C2 vertebra should include planning CT images on three planes: axial, sagittal, and coronal.