1 Principles topenlarge
In cases of very small posterior fragments, the indirect lag screw technique from anterior is not applicable as the thread will be too long and will not achieve compression of the fragment.
In addition, in small fragments, it is difficult to aim the K-wire from anterior into the fragment.
For this procedure, 3.5 mm cannulated headless compression screws are preferable. Standard 3.5 mm lag screws can be used in larger fragments.
Similar principles apply if both condyles are fractured (B3.3-type fractures).
None of the implants is allowed to project above the articular surface. This
can be achieved by countersunk lag screws (A) or headless compression screws
At least two screws should be used, in order to prevent fragment rotation.
2 Reduction topenlarge
Reduce the fracture using a small ball-spiked pusher and secure it temporarily with a K-wire.
Note: patient is lying prone.
3 Fixation topenlarge
Insert two guide wires. Make sure not to penetrate the far cortex.
Check guide-wire insertion
Check the guide-wire position under image intensifier control, in the lateral and oblique views.
If standard partially threaded lag screws are used, countersink manually prior to screw length measurement.
Do not perform countersinking when planning headless compression screws.
Pitfall: countersinking too deeply
Be aware of countersinking too deeply into the cancellous bone, which often happens using a power tool.
Screw length measurement
Determine the appropriate screw lengths over the guide wires, making sure that the measuring device enters the countersunk holes.
Fixation – sunken screw
Insert the screws using the manual, not powered, screw driver. Tighten judiciously, as the denser subchondral bone can be fractured by over-tightening.
Illustration showing the completed osteosynthesis using standard partially threaded lag screws.
Alternative: headless compression screws
Insert headless compression screws, using the cannulated screw driver, and check under image intensifier control in the lateral view to confirm that the screw length was chosen appropriately.