Procedure 10 C2 Translaminar Screw Fixation
Figures 10-4 through 10-7 and 10-9 through 10-12 redrawn with permission from Leonard JR, Wright NM. Pediatric atlantoaxial fixation with bilateral, crossing C-2 translaminar screws. Technical note. J Neurosurg 2006;104:59-63.
Indications
Examination/Imaging
CT imaging is critically important to determine the suitability of the C2 laminae to accept a 3.5-mm diameter screw. In this image the right laminae (arrow) is too narrow to safely place a laminar screw (Figure 10-1).
Treatment Options
• C1-C2 transarticular screw fixation: Magerl technique (if vertebral artery anatomy favorable)
• C1 lateral mass to C2 pedicle screw fixation: Harms technique (if vertebral artery anatomy favorable)
• Posterior C1-2 wiring techniques
Surgical Anatomy
Intact posterior elements of C2 are crucial to the placement of translaminar screws. The spinous process of C2 is typically bifid. The laminae thickness needs to be evaluated preoperatively by computed tomography (CT), and the screw length should be measured. Screw length is determined from the axial CT slice that shows the thickest portion of the laminae of C2 (Figure 10-2).
Positioning
Similar to positioning for C1 lateral mass screws and other fixation techniques for C2, the patient is prone in a Mayfield headholder. The neck is placed in a neutral position.
Hair is shaved as needed to expose the inion rostrally down to the midcervical spine.
Positioning Pearls
• Although it is tempting to place the neck in a flexed position to facilitate surgical exposure, this should be avoided.
• It is important to place the neck in an anatomically neutral position.
• Gently taping the shoulders can facilitate radiographic visualization of the C1-2 complex.
• Gently taping the upper back can reduce redundant neck folds in the more obese patient, facilitating skin opening and closure.
Positioning Pitfalls
• Placing the patient in a flexed position, while facilitating exposure, will result in stabilizing the atlantoaxial complex in a flexed position, resulting in permanent difficulty with swallowing and high patient dissatisfaction.
• Placing the patient in an overly extended position will make surgical exposure more difficult.
Portals/Exposures
A skin incision is made from the inion down to approximately the C3 level.
After dividing the dorsal fascia in the midline, the paraspinal muscles are reflected from the suboccipital skull, the dorsal arch of C1, and the spinous process and laminae of C2 (Figure 10-3).
Portals/Exposures Pearls
• The electrocautery can be safely used to reflect the paraspinal muscles off of the spinous process and laminae of C2, but this should not be used to expose the lateral aspects of the dorsal C1 laminae to avoid possible vertebral artery injury.
• Frequent repositioning of the retractors to tension the paraspinal muscles facilitates exposure.
