A compression plate has holes designed so that insertion of a correctly eccentrically placed screw results in fracture site compression.
A Compression Plate can be used to apply compression across a transverse fracture (usually), as well as providing stable fixation. The plate has to be fixed to one bone fragment first, and the second screw provides the compression.
Once the first screw is in place, subsequent movement of the plate will have a corresponding action on that bone fragment as they are now fixed together. So if the first screw goes into fragment A, then the plate and fragment A move as one as they are fixed together (The plate and the screw shown pi nk in the diagram are all one unit mechanically. Note this is NOT a locking plate).
The second screw is inserted into the other bone fragment (fragment B). Inserting the second screw eccentrically on the side of the hole furthest away from the fracture will exert the compressive effect. (The Medartis
set makes this easy by providing the eccentric drill guide with arrows where the arrow is positioned pointing towards the fracture). As the screw head abuts the edge of the hole the plate is forced away from the fracture sliding over fragment B to allow the screw to centralise into the hole which pulls fragment A into the fracture applying compression.
All subsequent screws are placed in the neutral position, as no further compression is possible unless a screw is loosened first.
Step 1 – Select a compression plate for 2/2.3 mm screws, which will cross the fracture site and allow for four cortical fixations on each side of the fracture.
Step 2 – Fix one end of the plate to the proximal fragment A. Use the drill guide with the concentrically placed circles. The fragment A and the plate now act as one unit.
Step 3 – Align the plate along the axis of the bone and reduce the fracture with the fracture holding clamp.
Step 4 – Using the drill guide with the eccentrically placed holes, line up the drill guide so that the arrow is pointing towards the fracture. This will mean that when a hole is drilled it will be placed away from the fracture site. Measure and select the appropriate sized screw. When the screw is applied to this hole the head will engage with the part of the plate that is furthest away from the fracture and will cause the plate to slide over the bone compressing the proximal fragment against the distal fragment. Once this screw is engaged, the plate is locked and no further plate glide can occur.
Step 5 – Place the remainder of the screws with the centrally placed drill guide.