Placement of lag screw
The placement of the lag screw or screws used to achieve absolute stability of the articular surface is determined by the fracture pattern. Ideally, these screws should be inserted at right angle to the fracture plane.
The buttress plate, once properly contoured, is inserted on top of the periosteum deep to the muscle envelope. The most proximal screw if it fits with the fracture morphology may be a lag screw.
Click here for a detailed description of the lag screw technique.