Prevalence of High-Riding Vertebral Artery and Morphometry of C2 Pedicles Using a Novel Computed Tomography Reconstruction Technique

Abstract

Study DesignCross-sectional, matched-pair comparative study.PurposeTo determine whether a thin-sliced pedicular-oriented computed tomography (TPCT) scan reconstructed from an existing conventional computed tomography (CCT) scan is more accurate for identifying vertebral artery groove (VAG) anomalies than CCT.Overview of LiteraturePosterior atlantoaxial transarticular screw fixation and C2 pedicle screws can cause vertebral artery (VA) injury. Two anatomic variations of VAG anomalies are associated with VA injury: a high-riding VA (HRVA) and a narrow pedicle of the C2 vertebra. CCT scan is a reliable method used to evaluate VAG anomalies; however, its accuracy level remains debatable. Literature comparing the prevalence of C2 VAG anomalies between CCT and TPCT is limited.MethodsA total of 200 computed tomography scans of the upper cervical spine obtained between January 2008 and December 2011 were evaluated for C2 VAG anomalies (HRVA and narrow pedicular width) using CCT and TPCT. The prevalence of C2 VAG anomalies was compared using these two different measurement methods via a McNemar's test.ResultsOf the 200 patients studied, 23 HRVA (6.01%; 95% confidence interval [CI], 3.61%–8.39%) were detected with CCT, whereas 66 HRVA (16.54%; 95% CI, 12.85%–20.23%) were detected with TPCT (p<0.001). Sixty-two narrow pedicles (15.58%; 95% CI, 11.99%–19.15%) were detected with CCT, whereas 90 narrow pedicles (22.83%; 95% CI, 18.58%–26.87%) were detected with TPCT (p<0.001).ConclusionsVAG anomalies are commonly observed. A preoperative evaluation using TPCT reconstructed from an existing CCT revealed a significantly higher prevalence of C2 VAG anomalies than did CCT and showed comparable prevalence to previously published studies using more sophisticated and higher risk techniques. Therefore, we propose TPCT as an alternative preoperative evaluation for C2 screw placement and trajectory planning.

Differences in fixation strength among constructs of atlantoaxial fixation

“…In the published literature, the incidence of HRVA in the normal population ranged from 10.1% to 32%. 6,13,[24][25][26] However, the incidence increased enormously to 50%-70% in patients with AA subluxation, rheumatoid arthritis, or congenital skeletal anomalies (e.g., os odontoideum, Down syndrome, basilar invagination, and Klippel-Feil syndrome). 2,15,31,32 The issue of HRVA was particularly concerning in candidates for AA fixation, because these diseases frequently coincided with AA subluxation.…”

Can c2-pars interarticularis screw be an alternative in atlanto-axial stabilization? a biomechanical comparison of established techniques

“…Given the anatomical history of VA, there are two anatomic variations associated with VA injury: the first is high-riding VA (HRVA), which increases the risk of VA injury during C1-2 transarticular screw fixation, (1,3,9,13); and the other is a narrow pedicle that increases VA injury risk in C2 pedicle screwing (27).…”

“…C2 pedicular screw placement has a more superior and medial trajectory according to transarticular screw placement, which decreases the risk of VA injury (18,27); however, several studies have also found that the anatomical risk of VA injury does not significantly differ between these two techniques…”

A Review of the Historical Evolution, Biomechanical Advantage, Clinical Applications, and Safe Insertion Techniques of Cervical Pedicle Screw Fixation

“…Following the above-mentioned data, Roy Camille et al successfully used C2 pedicle as an insertion point without any neurovascular deficit 39) . However, the vertebral artery (VA) injury with C2 pedicle screw is 5.3%-21% 40,41) .…”

“…The two anatomic variations associated with VA injury are high-riding VA and narrow C2 pedicle, and the chances of VA injury are more in the latter. The prevalence of high-riding VA is 16.54% 41) . Stanescu et al, in their cadaveric study, mentioned that there is a slight increase in the pedicle height width and length and a decrease in the transverse angle of 4°-6°between adjacent C5-C7 vertebral levels 42) .…”