Screws are inserted at least two or three segments above and below the tumor.
In tumor patients achieving optimal screw purchase is even more important than in trauma patients to minimize risk of pullouts and reduce the number of levels involved.
Optimal pedicle screw purchase will, in order of importance, be achieved by:
Selecting the largest possible screw diameter
Selecting the longest possible screw
Positioning of the screw under the cranial endplate
Cement augmentation of the screw.