464 - Anatomic Feasibility of C2 Pedicle Screw Fixation: The Effect of Varia...

#464 Anatomic Feasibility of C2 Pedicle Screw Fixation: The Effect of Variable Angle Interpolation of Axial CT Scans

Oral Posters: Cervical

Presented by: J. O'Brien


L. Burke (1)
A. Ho (1)
T. Wagner (1)
W.D. Yu (1)
J.R. O'Brien (1)

(1) George Washington University, Department of Orthopaedic Surgery, Washington, DC, USA


Introduction: Anatomic morphology of the C2 pedicle poses a challenge for C2 pedicle fixation. The use of multidimensional computed tomography (CT) interpolation is useful and may be an asset in preoperative planning. The purpose of this study is to evaluate the suitability of C2 vertebra for pedicle fixation using virtual gantry angle interpolation of CT angiograms.

Methods: A retrospective review of CT angiograms of the cervical spine from 47 consecutive trauma patients. Standard axial images were reconstructed using virtual variable axis interpolation from (Osirix). Data collection included length and width of the C2 pedicle allowing 94 data points analyzed by 3 independent observers. Statistical analysis was performed.

Results: 20 were female patients and 27 were male. Mean C2 pedicle width and length were 8.3 ±1.3 mm and 27.0 ± 3.5 mm. Gender difference was statistically significant for width (p = .012) but not for length (p = 0.41). All patients could tolerate a 3.5mm or 4.0mm screw, based on width. Only three patients had vertebral anatomy that precluded screw length greater than 14mm. Figure 1 and 2 demonstrate axial and re-interpolated images.

Conclusion: Careful preoperative planning is imperative for instrumentation at C2. Axial CT is a useful tool to delineate anatomy; however, the axis of images is not always along the axis of the area to be instrumented. With variable axis interpolation, this study's data approximated manual anatomic measurements and found that 94% of patients could tolerate 3.5mm or 4.0mm pedicle screw at C2. Only 6% of patients (3 of 47) have vertebral anatomy that precluded the use of screw lengths greater than 14mm.

Figure 1

Figure 2