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. 2023 Feb;17(1):76-85.
doi: 10.14444/8386. Epub 2022 Nov 22.

C1-C2 Facet Joint Penetration by C2 Pedicle Screws: Influence of Local Anatomy, Bone Mineral Density, and Screw Length

Alexander Rosinski  1 , Cristian Balcescu  1 , Ian Singleton  1 , Ashish Mittal  1 , Khalid Odeh  1 , Victor Ungurean  2 , Jeremi Leasure  2 , Dimitriy Kondrashov  3   4
Affiliations

C1-C2 Facet Joint Penetration by C2 Pedicle Screws: Influence of Local Anatomy, Bone Mineral Density, and Screw Length

Alexander Rosinski et al. Int J Spine Surg. 2023 Feb.

Abstract

Background: A challenge of C2 pedicle screw placement is to avoid penetration into the C1-C2 facet joint, as this may alter normal biomechanics and accelerate joint degeneration. Our objective was to clarify how local anatomy and surgical technique may relate to C2 pedicle screw penetration into the C1-C2 facet joint.

Methods: C2 pedicle screws were inserted using a fluoroscopically assisted freehand technique. Independent fellowship-trained spine surgeons blindly reviewed intraoperative fluoroscopic and postoperative computed tomography (CT) images for evidence of facet joint penetration (FJP). C2 pedicle morphometry, the sagittal angle of the facet joint, axial and sagittal pedicle screw angles, and screw length were measured on the relevant CT images.

Results: A total of 34 patients fulfilled the study criteria, and a total of 68 C2 pedicle screws were placed. Eight screws (16%) penetrated the C1-C2 facet joint. The mean sagittal angle of the C1-C2 facet joint was significantly lower in the FJP group compared with the non-FJP group. The mean sagittal angle of the screws was significantly higher in the FJP group compared with the non-FJP group. The mean screw length was significantly greater for screws causing FJP compared with the non-FJP group. The mean axial screw angle was significantly lower in the FJP group compared with the non-FJP group. Pedicle width, length, height, and transverse angle were not significantly associated with FJP. Independent reviewers were able to identify FJP on intraoperative fluoroscopic imaging in 2 out of 8 cases.

Conclusion: Lower sagittal angle of the facet joint, higher sagittal angle of the pedicle screw, and screw length >24 mm are associated with higher risk of C1-C2 FJP. When placing C2 pedicle screws under these conditions, caution should be taken to avoid FJP.

Clinical relevance: Several anatomical and technical factors may increase the risk of C1-C2 FJP during placement of C2 pedicle screws using a fluoroscopically assisted freehand technique, underscoring the importance of preoperative planning and limiting screw length.

Keywords: C2 pedicle screws; cervical fusion; cervical spine surgery; facet penetration.

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Conflict of interest statement

Declaration of Conflicting Interests: The authors declare that the study was performed in the absence of any commercial or financial relationships that could be considered a potential conflict of interest.

Figures

Figure 1
Figure 1
Sagittal computed tomography image of C1-C2 facet joint penetration.
Figure 2
Figure 2
A wine cork placed in the mouth to help visualize the C2 pedicles on the intraoperative open mouth view.
Figure 3
Figure 3
Measurement of the sagittal angle of the C1-C2 facet joint. The inferior endplate of C2 represents the reference line (A). A second line approximates the slope of the C1-C2 facet joint (B). The sagittal screw angles were measured using a similar method.
Figure 4
Figure 4
The axial angle of each pedicle screw was measured relative to a line bisecting the C2 vertebra and aligned with the spinous processes to account for any vertebral rotation.
Figure 5
Figure 5
Computed tomography images demonstrating a lower sagittal facet joint angle in the facet joint penetration (FJP) group (B) compared with the non-FJP group (A).
Figure 6
Figure 6
Computed tomography images demonstrating a higher sagittal screw angle in the facet joint penetration (FJP) group (B) compared with the non-FJP group (A).
Figure 7
Figure 7
Computed tomography images demonstrating increased screw length in the facet joint penetration (FJP) group (B, 38 mm) compared with the non-FJP group (A, 26 mm). Both patients had similar sagittal facet joint angles, sagittal screw angles, and axial screw angles (19° vs 21°, 51° vs 53°, and 20° vs 21°, respectively).
Figure 8
Figure 8
Intraoperative fluoroscopic open mouth view demonstrating C1-C2 facet joint penetration.
See this image and copyright information in PMC

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