The anatomical suitability of the C1–2 complex for transarticular screw fixation

Abstract

Posterior transarticular screw fixation of the C1-2 complex has become an accepted method of rigid internal fixation for patients requiring posterior C1-2 fusion. The principal limitation of this procedure is the location of the vertebral artery, because an anomalous position may prohibit screw placement. In this study, a consecutive series of computerized tomography (CT) scans was reviewed, and the suitability of each patient for transarticular screw fixation was evaluated. All of the fine-slice axial C1-2 CT scans and reconstructions performed on a spiral scanner over 2 years were reviewed. A novel screw trajectory reconstruction was designed to visualize the potential path of a transarticular screw in the plane of the reconstruction. Scans were reviewed for bone anatomy and the position of the transverse foramen. Seventeen (18%) of 94 patients had a high-riding transverse foramen on at least one side of the C-2 vertebra that would prohibit the placement of transarticular screws. The left side was involved in nine patients and the right in five. Three patients had bilateral anomalies. The mean age of the group with anomalies (35.9 years, range 10-76) was not significantly different from the overall mean age (35.7 years, range 6-94). An additional five patients (5%) were considered to have anatomy in which screw placement was feasible but risky. On the basis of these data, it is postulated that 18% to 23% of patients may not be suitable candidates for posterior C1-2 transarticular screw fixation on at least one side.

Risk of vertebral artery injury: comparison between C1–C2 transarticular and C2 pedicle screws

“…Placement of either C1-C2 transarticular or C2 pedicle screws has a potential risk of vertebral artery injury [1][2][3][4][5][6][7][8][9][10][11][12][13][14]21]. The risk of vertebral artery injury by these two techniques needs to be carefully analyzed so as to allow the surgeon to choose the appropriate screw insertion method.…”

“…Vertebral artery injuries commonly occur if a drill, tap, or screw perforates or occludes the vertebral artery in the vertebral artery groove of C2, which is located on the lower surface of C2 and lateral to the pedicle ( Fig. 1) [1][2][3][4][5][6][7][8]. It has been suggested that C2 pedicle screw combined with C1 lateral mass screw placement is inherently safer than C1-C2 transarticular screw fixation in view of the risk of vertebral artery injury at C2, as the medially directed trajectory of the C2 pedicle screw carries the screw away from the vertebral artery, which normally is located lateral to the screw [9][10][11].…”

“…Two anatomic variations have been suggested to be associated with vertebral artery injury. First, it is well known that the risk of vertebral artery injury during C1-C2 transarticular screw placement increases with a high-riding vertebral artery [2,5,6,15,16]. However, we are unaware of any reports comparing the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw in those with a high-riding vertebral artery, and no references on the topic could be found in a computerized search using MEDLINE.…”

Treatment of pediatric atlantoaxial instability with traditional and modified Goel–Harms fusion constructs

“…First, the vertebral arteries have to have a particular anatomy to allow safe placement of C1-2 transarticular screws. If the artery has an unusual course, as has been shown to occur in 10-20% of adult patients, then a screw can not safely be placed on that side [26,31,32,37]. In one study on pediatric patients, the authors found that the anatomy of the vertebral artery prevented safe placement of a transarticular screw in 11% of joint spaces [6].…”

Plasmocitoma de base craneal con inestabilidad cráneo-cervical

“…El trayecto de la arteria vertebral a este nivel es, por lo tanto, variable en forma, tamaño, localización y simetría. Estudios radiológicos y en cadáveres sugieren que existe una anatomía desfavorable para la colocación de estos tornillos, por lo menos en un lado, en el 18-23% de los casos debido al trayecto de la arteria vertebral 1,10,14,18 . En concreto, se ha estimado el riesgo de lesión de la arteria vertebral durante la inserción de los tornillos trasarticulares C1-C2 en 4-8% 10,14,24,25 .…”