TL Pedicle Screws – Dr. Lewis  

Posted bythespinebookadminPosted inTechniques
Level Start Point Trajectory ML Width Pearls 
     
     
T1-T11 Top ridge of TP Lateral 50% of SAP T1 30 degrees medial Linear decrease to straight until T11 straight T4 smallest Transverse and Sagittal increase as lower Funnel concept Bevel away (cord level) 
T12-L1 Mamillary process straight  T12 is the first “lumbar” vertebra as the pars is narrower 
L2-L5 50% TP Lateral edge of pars L23 straight L4 20 degrees L5 30 degrees Transverse width increases as lower Sagittal decreases Lateral edge of pars corresponds with medial wall of pedicle PSIS interferes with L5 instrumentation 
     
     
     

Important Tips 

  • Pedicle Finder (PF) Bevel Direction 
    • 15 degree tip (look at your hand position) 
    • In certain scenarios (ie: concave of scoliosis) point it lateral away from medial cortex so the curve bounces off the medial cortex 
      • Just need to get into body 
      • Then finish with finder 
    • Medial 
      • For medial trajectories can keep hand higher 
    • It’s a tool so be aware of how it works and why there is a curve there on it 
    • DON’T POINT THE BEVEL UP – YOU WILL GET INTO THE ENDPLATE. You have a habit of this 
  • Funnel Concept 

Pedicle Anatomy 

Tuesday, March 30, 2021 

11:39 PM 

  • the bone and just wiggle until you feel the funnel into the pedicle 
    • So basically don’t pick your trajectory until you are in a palpable funnel tip 
    • Push the bone until you can feel the pedicle start 
PF Bevel Direction  

Size 

  • Sagittal Plane 
    • Increases to T12 then decreases 
  • Axial 
    • Increases to T1, then decreases to T4 then increases 

Angulation (Axial) 

  • T1 30 degrees medial 
  • Straightens below 
  • T12 straight 
  • Progressive medialization 
  • L5 is 30 degrees medial 

Lumbar Pedicle Screw 

  • Start Point 
    • TP 50% 
    • Lateral to SAP