The entry point of the pedicle screw is defined as the confluence of any of the four lines:
Mamillary process (shown)
Lateral border of the superior articular facet
Mid transverse process (shown)
2. Opening of the cortex
Open the superficial cortex of the entry point with a burr or a rongeur.
3. Sagittal plane angulation
A pedicle probe is used to navigate down the isthmus of the pedicle into the vertebral body.
The pedicle probe should be inserted in a trajectory superimposed on the transverse process and parallel to the superior endplate.
4. Transverse plane inclination
It is important to avoid medial penetration of the spinal canal superficially or lateral or anterior penetration of the vertebral body cortex at the depth of insertion.
5. Screw insertion
Once the pedicle track has been created, it is important to confirm a complete intraosseous trajectory by pedicle and body palpation using a pedicle probe. At any point in the process, radiographic confirmation can be obtained.
A screw of the appropriate diameter and length is carefully inserted into the prepared track.