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

Abstract

OBJECTIVE: 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. MATERIALS AND METHODS: This retrospective study analyzed 66 patients who underwent C2 transpedicular screw fixation. Preoperative and postoperative axial, sagittal, and coronal cervical computed tomography (CT) scans were examined. Anatomic measurements were taken to determine the horizontal and vertical distances from the C2 pedicle projection to the vertebral foramen using cervical 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. RESULTS: The average age of the patients included in the study was 46.48 years. Among the patients, 32 (48,5%) were male and 34 (51,5%) were female. Based on 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 Type 2 and Type 4 compared to other 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 one 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. CONCLUSION: Preoperative anatomic measurements for patients undergoing transpedicular instrumentation on the C2 vertebra should include planning cervical CT images on three planes: axial, sagittal, and coronal.