When there is a fracture in the distal half of the shaft of Radius, AO Compression plate is applied to the Volar surface, which is contrary to the the Principle of "applying the Plate to the tension side of the bone".
I agree, it is easier to apply the Plate in the volar surface because the bone contour is flat and the soft tissue coverage is better.
But can it be applied against the principle ??
And if we achieve satisfactory result even if we apply against the principle, Can it be applied in other bone fractures ??
Dear Ashok
Very good question.When the plate is applied in the tension area of bone it has the function of tension band : this principle of tension band is obligatory when the plate is applied in the femur - absolute stability (antero lateral side) because the femur carry load but we can apply a plate in the volar face of forearm and in the humerus (not necessary apply in tension surface -posterior) because these bones don't carry load and this against the law is permitted. Best regards
Plates can be applied and used in a number of configurations and modes. Compression can be achieved by pretbnd of the plate and therefore it doesn't actually matter where the plateis applied as long as it I used correctly. The benefits of easy access, easy placement and soft tissue cover are not outweighed by advantage of dorsal application. Traditional distal radius fixation was applied dorsally for the lassie dorsally displaced fracture in a buttress mode but now the major approach is volar using locking plated to support subchondral bone plateis buttress mode. Locking plates have extended the options for long bone fixation in the same way.
There are some exceptions to the AO rule for chosing the tension side of bone for plating. One of them is if the "compression" side is severely comminuted. In similar cases one should act against the rule in striving to ensure stable fixation. The other one is when the soft-tissue on the tension side is severely damaged and the coverage of plate is problematic.
The described principle is not taking in considatration pre-bending of the plate and compression of the opposite cortex. This is giving the "absolute" compression in both corteces. The usual approach of the forearm is volar due to the bone formation and also the soft tissue cover. There are the surgeons who are placing the plate dorsally but they are the exception. The forearm is not a "monodirectional" concept as the tibia and femur with well defined tension and compression areas as the two bones are forming an "atypical joint" as they are working according to the rotation of the bones. The fixation is done to support this understanding treating the bones as "intra-articular" concept. AO teaching is recognising this. The new locking plates are more or less acting as "static" plates, controlling the length of the bone; that is why they can be used for dorsal defects on the volar side and without the initial teaching of dorsal compression. These two principles must not be mixed.
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