The screws are inserted in lag fashion. To achieve maximal interfragmentary compression and avoid shear, the screws must be directed perpendicular to the fracture plane.
A glide hole (outer diameter of the screw) is drilled first into the cis (near) cortex followed by the thread hole (core diameter of the screw) in the trans (far) cortex using the appropriate drill bits and drill sleeves. The drill sleeve for the thread hole must be inserted completely through the cis cortex to ensure proper placement and compression.
The screw length is measured with a depth gauge. At least two measurements in opposite directions should be taken. The longest measurement should be used.
The thread hole is tapped, and a screw of appropriate length is inserted. The screw should protrude minimally (1 mm or less) from the patella to minimize interference with the patellar ligament.