C2 Screws (3) 

Anatomy and VA 

Pars Screw 

• Why? 
  • If pedicle screw not possible 
• Start point: 
  • flat part 
  • Lower than pedicle screw start point 
• Trajectory 
  • Sag – straight 
  • Cor – straight 
• Length – 16mm 

Pedicle Screw 

• Preferable to pars 
• Above where the VA exits 
• No high riding vertebral artery 
• Start point 
  • Line on upper 50% of lamina 
  • Line along midpoint of pars 
• Trajectory 
  • Sag – 45 
  • Cor – 45 
• Length – 20mm + 

Translaminar