There are several advantages to a locking plate/screw system:
Locking plates 2.0
Locking plates 2.0 are available in four thicknesses, with or without center space:
They are also available in multiple shapes to meet a variety of clinical applications.
The threaded head of the 2.0 mm locking head screws is conical. It is therefore possible to insert locking head screws at small angles. A threaded drill guide is not necessary.
Locking reconstruction plate (LRP) 2.4
There is only one thickness of the locking reconstruction plate 2.4. However, there are multiple plate configurations to meet a variety of clinical applications.
The threaded head of the 2.4 mm locking head screws is cylindrical. Therefore, a threaded drill guide is mandatory to assure the correct perpendicular insertion of 2.4 mm locking head screws. Angulation is not possible.
Locking head screws
The locking plate has a corresponding threaded plate hole.
During insertion the locking head screw engages and locks into the threaded plate hole.
Conventional screws
If necessary the threaded plate hole also accepts nonlocking screws, which permit greater angulation.
Conventional screws
With the conventional technique, the tightening of the screws presses the plate against the bone. This pressure generates friction, which contributes significantly to primary stability.
Loading forces are transmitted from the bone to the plate, across the fracture and back into the bone. Friction between plate and bone is necessary for stability using conventional screws.
Locking head screws
However, with the locking head screws engaged in the plate, the plate is not pressed onto the bone. This reduces interference to the blood supply to the bone underlying the plate.
Loading forces are transmitted directly from the bone to the screws, then onto the plate, across the fracture and again through the screws into the bone. Friction between plate and bone is not necessary for stability.
The plate and screws provide adequate rigidity and do not depend on the underlying bone (load bearing osteosynthesis) when using a locking reconstruction plate 2.4.
On each side of the fracture, the screws are locked into the plate as well as into the bone. The result is a rigid frame construct with high mechanical stability (internal external fixator).
Conventional plate system
When using conventional plates and screws it is essential to contour the plate precisely to the bone surface.
When using conventional plate and screws the plate must be precisely adapted to the bone, otherwise the tightening of the screws will lead to a primary loss of reduction.
Note: in the top illustration the plate is not well adapted to the outer cortex. The lower illustration shows that when the screws are inserted, the bone will be pulled to the plate, causing malreduction of the fracture.
Locking plate system
When using a locking plate/screw system, the plate does not have to be precisely adapted to the bone. When tightening a locking head screw, the screw will not cause a primary loss of reduction as it tightens into the threaded plate hole and will not draw the bone fragments to the plate.
Conventional plate system
In conventional plate systems, screw loosening may lead to loss of reduction.
X-ray shows the clinical situation described above.
Locking plate system
In a locking system, screw loosening rarely occurs because the screw head is locked to the plate.