Plating modalities
Plates may be applied in various modes according to the function required. These include:
Protection (neutralization)
Compression
Bridging
Buttress (antiglide)
Concepts of Plating :
Tension side of the fracture:
when plating a fracture the plate should be applied to tension side of the fracture (which is often the convex side)
ideally when bone is plated, the bone itself carries the majority of the compression load
- optimally when a plate tends to close a fracture, placing the plate under tension, a significant portion of the load is supported by bone, thereby diminishing bending moment on the plate.
In this situation there will be little benefit accued from increasing either, the breadth of the plate or the size of screws, but when plate was increased in length from 3-6 inches, the strength of the assembly was doubled.
Plate contouring
The plate must fit the shape of the bone. The midshaft of many long bones is straight so plates applied to these regions may not need to be contoured.
Most bones show a flare towards the metaphysis, so plates applied in these regions usually need to be contoured.
The use of a flexible template can facilitate plate contouring.
Where locking screws are used, the bone-plate construct remains stable even if the plate is not in direct contact with the bone. Therefore, contouring does not to be so accurate.
Compression plating
Function
The plate produces compression at the fracture site to provide absolute stability.
Application (transverse fractures)
Reduction
If possible, the fracture is reduced and temporarily fixed with clamps. Place the forceps such that they will not interfere with the planned plate position.
Pre-contouring
If the plate is exactly contoured to the anatomically reduced fracture surface, there will be some gapping of the far cortex when the plate is tensioned by tightening the load screw.
The solution to this problem is to “over-bend” the plate so that its center stands off 1-2 mm from the anatomically reduced fracture surface.
The overbend should lie directly over the fracture line.
When the first screw is inserted, slight gapping of the cortex will occur directly underneath the plate. After fixation is complete, the plate will be in contact with the bone throughout its length, but it is acting as a spring, providing compression at the far cortex.
Screw insertion
The prebent plate is fixed to one of the main fragments with a screw in compression mode. Reduction forceps are placed on the opposite fragment to hold it in the reduced position against the plate. The screw is not fully tightened.
A screw is inserted in compression mode in the opposite fragment. To maintain reduction, it is recommended to tighten the screws gradually by alternating between the two sides.
If there remains a fracture gap after insertion of the two compression screws, a third screw can be inserted in compression mode on either side. Before this screw is tightened, the compression screw already placed in the same fragment needs to be loosened. After the third screw is fully tightened, the first screw is re-tightened and additional screws are inserted in neutral mode.
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