A neutralisation plate removes the loading forces across a fracture by transmitting the loading forces through the plate rather than through the fracture site. This allows the primary fracture fixation to be accomplished with other devices such as lag screws.
Neutralisation plates do not have a special design or shape nor do they act to provide compression. They simply hold the position of the bone and act as resistance to compression and torsional forces. The lag screw has provided the inter-fragmentary compression and so additional compression through a plate is not going to be effective or may even be be counter-productive. The plate simply protects the fixation.
Use the lag screw fixation from chapter 4.
Step 1 – Select a plate for 1.5mm or 2 mm screws and ensure it has adequate length (so there are at least 2 screw holes that would get cortical fixation on each side of the fracture). Often a 5 hole plate is adequate with the central hole overlying the fracture and the lag screw.
Step 2 – Ensure that the plate sits accurately on the surface without gaps and the plate may need to be bent slightly to adjust for this.
Note: If accurate plate contouring is not done then, as the screws are tightened, the fracture fixation, despite the lag screw, may slip and distract the fracture.
Step 3 – Fix one end of the plate by its furthest hole. The simplest way of doing this is to hold the plate in place with fracture holding forceps and drill the hole at one end with the neutral or centered drill guide.
Note: The drill guide has a centred and off-centred guide on the same handle. Use the concentric circles (centred) end as shown. The off-centered guide end is used only in compression plates.
Tip: However if the instrumentation is inadequate or the configuration doesn’t lend itself to this easily, then use a marker pen and make a mark where the end hole is, remove the plate, and drill.
Keeping the drill guide still, bring the depth guide adjacent to get the angle and orientation. Remove the drill guide, place the depth gauge accurately first time through both holes and measure the depth. Select the appropriate size screw, put the plate in place and attach.
Step 4 – Apply screw to the opposite most distal screw to get the correct longitudinal alignment. Once these two screws are in place, the intervening screw holes can be fixed. You need at least 4 good cortical fixations on each side of the fracture.