A bone plate may be placed so that it may be utilized for one of the following kinds of structural support:
- Compression Mode
- Neutralization Mode
- Buttress plate
- Antiglide plate
- Bridge plating or span plating
- Tension band
Plates are available in various shapes and sizes depending on the bone size and its anatomical shape. Similarly, Bone Screw size is dependent on the size & type of plate used. A small plate will typically be used for a small bone, which allows space only for the screw of smaller size.
Depending upon the fracture type and location, a plate can be used in any one of the following methods
Compression Mode
The word compression in fixation of a fracture means bringing the two fragments closer to one another so that the fragments oppose well.
When the plate is utilized to achieve compression with the fracture fixation, it is said to be utilized in compression mode. This mode is utilized on oblique and transverse fractures.
Neutralization Mode
In this kind of plating, a lag screw is utilized to neutralize shear, bending and rotational forces. The goal of this kind of plating is not to attain compression (this has already been attained by the lag screw).
This type of plating is also utilized as an adjunct where bone screws are used alone in long bones an accurate reconstruction with interfragmentary compression can be attained, but screws are not strong in resisting twisting or bending forces. Addition of a bone plate offers further resistance to such forces.
The fibular fracture normally seen in ankle injuries is usually fixed with lag screws protected by a neutralization plate.
The orthopedic plate is put on the tensile surface of the bone, but it is not pre-bent.
Buttress Plate
A buttress is an architectural structure built against or projecting from a wall which helps to reinforce or support the wall.
A buttress plate is utilized to prevent collapse in fracture patterns which are unstable under compressive forces.
A buttress plate is very thin in comparison to compression plate and is usually applied on the compressive surface of the bone.
This is the most commonly used plates around joints.
Here there is a comparatively soft cancellous bone core enclosed by a thin layer of cortical bone. Correct osteosynthesis may be attained by lag screws alone but under load, there may be a risk of screws cutting out of the bone or bending.
The addition of a bone plate will prevent such deformity under axial load. The plate should be located where the maximum load is predicted to be. Proximal tibia, for example, plates may be needed on one side or another to protect a fixation of tibial plateau fracture.
For the most common anatomical buttressing needs, there are specially shaped plates.
Antiglide Plate
In antiglide plating, the plate is fixed to the bone in such a manner that it prevents the distal fragment from overriding when force is applied along the long bone axis.
The distal fragment is firmly impacted between the plate and the fracture surface of the proximal plane.
This principle is generally applied in distal fibula fracture. It can be termed as a variation of compression plating.
