QUICK TIPS FOR THORACIC PEDICLE SCREWS

*pedicle screw insertional techniques :
freehand
fluoroscopically assisted
computer-aided
open-lamina K-wire assisted

*two trajectories have been described
anatomic trajectory
straight-ahead trajectory

*three anatomic characteristics of the pedicle important before insertion pedicle diameter angle of the trajectory length of the trajectory

*Entry Points:

Proximal thoracic( T-1-4 ) junction of proximal transverse process and lamina medial to lateral pars

Mid-Thoracic ( T-5-8 ) junction of downslope of proximal transverse process and lamina at the base of superior facet, medial to lateral pars

Lower Thoracic ( T-9-12 ) Downslope of bisected transverse process at the junction of transverse process and lamina at the same level as lateral pars.

Freehand technique using straight-ahead trajectory:

* both uni and multiaxial screws can be used
*posterior spine is dissected till exposure of transverse processes
*partial facetectomy done for the inferior facet
*use acorn-tip burr for making the hole, look for a cherry red spot that shows that the tip is in the cancellous bone of the pedicle
*2 mm curved thoracic gearshift pedicle finder is used to make the track for screw
*probe is pointed initially laterally and then near the base of the pedicle medially
*tip of probe should meet the resistance of the cortical bone of body
*signs of screw malposition: screws that overlap screws that are long screws that cross the midline screws that do not line up with the pedicle outline screws that do not follow curvature of spine
*after all screws are passes, stimulate them with EMG to evaluate the potential neurological impingement
*replace loose screw with a screw of bigger diameter