J Korean Orthop Assoc.  2008 Oct;43(5):572-578. 10.4055/jkoa.2008.43.5.572.

Risk of Vertebral Artery Injury: A Comparison between C2 Subarticular Segmental and C1-2 Transarticular Screws

• Kim SW
• Yeom JS
• Kwon YJ
• You SM
• An YH
• Park KW
• Chang BS
• Lee CK

• KMID: 2186418
• DOI: http://doi.org/10.4055/jkoa.2008.43.5.572

Abstract

PURPOSE: We compared the risk of vertebral artery injury associated with the insertion of C1-2 transarticular screws and C2 subarticular segmental screws using a computer simulation of computed tomography (CT) scans.
MATERIALS AND METHODS
We simulated the placement of C1-2 transarticular screws and C2 subarticular segmental screws using 1-mm interval CT scan images in 166 patients, along with simulation software. We then determined the incidence of violation of the C2 vertebral artery groove. The same determination was performed for high-riding vertebral arteries found among those patients.
RESULTS
Among the 332 C2 vertebral artery grooves (166 patients), C1-2 transarticular screws violated the groove in 33 (9.9%) instances, while C2 subarticular segmental screws violated the groove in 19 (5.7%) instances. The difference in incidence between the two screw types was statistically significant (p=0.001, McNemar test). In the 48 high-riding vertebral arteries, C1-2 transarticular screws led to violation of the C2 vertebral artery groove in 30 (62.5%) instances, while C2 subarticular segmental screws led to violation of the groove in 18 (37.5%) instances. The difference in incidence between the two screw types was statistically significant (p=0.002, McNemar test).
CONCLUSION
Use of C2 subarticular segmental screws is associated with a lower risk of vertebral artery injury than is the use of C1-2 transarticular screws, even for high-riding vertebral arteries.

MeSH Terms

Computer Simulation
Humans
Incidence
Vertebral Artery

Figure

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  Fig. 1 Vertebral artery grooves (arrowheads) are shown in axial (A) and sagittal (B) CT scan images along with the trajectories of the transarticular screws (black lines). Vertebral artery grooves are located lateral (A) and anterior (B) to the transarticular screws.

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  Fig. 2 The trajectory of the transarticular screw is shown. The entry point is set at 3 mm cranial to the caudal edge of the C2 inferior articular process (A) and as medial as possible without penetrating the lateral wall of the spinal canal (B). The upward angulation is afforded as much as possible while maintaining the screw within the posterior boundary of the superior articular surface of C2.

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  Fig. 3 The trajectory of the subarticular segmental screw is shown. Medial angulation is the same as that of the pedicle on the axial CT images (A). The screw is angled toward the antero-superior end of the superior articular process of C2 in lateral fluoroscopy. The entry point is 3 mm caudal to the posterior aspect of the superior articular surface, and the screw is inserted close to the superomedial border of the superior articular process (B).

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  Fig. 4 The two heights that were used to distinguish the high-riding vertebral artery are shown. It is defined by an isthmus height (*) less than 5 mm and/or an internal height (**) less than 2 mm.

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