1 Principles topenlarge
B1-type fractures are intraarticular, therefore they need an anatomical reduction and absolute stability.
The plate functions as a buttress plate. In osteoporotic bone consider the use of locking compression plates (LCP) which offer greater stability in osteoporotic bone.
Lateral versus medial condylar fractures
The operative procedures for lateral condylar fractures (B1.1-type fractures) and medial condylar fractures (B1.2- and B1.3-type fractures) are similar but have some differences.
In both the position of their respective buttress plates is governed by the direction of the fracture planes. However, on the lateral side because of the fibula, the buttress plate is always positioned antero-laterally and not laterally. If the main split-wedge fragment is either postero-lateral or postero-medial it has to be buttressed postero-laterally or postero-medially respectively. The postero-lateral buttress plate is best applied through a posterior transpopliteal approach. On the medial side, because one is not dealing with a fibula, the plate may come to lie antero-medially, postero-medially, or posteriorly.
A lateral condylar fracture is used here as an illustration.
2 Reduction topenlarge
Indirect reduction may be attempted by percutaneous manipulation of the fractured fragment using a clamp. The reduction should be checked with an arthroscope if no arthrotomy is carried out because frequently the lateral meniscus is caught in a fracture line. In cases where adequate closed reduction is not achieved the joint must be opened to carry out an anatomical reduction.
Pearl: clamp with plate
If you intend to keep the clamp on throughout the whole procedure it is best to slip the plate under the clamp prior to tightening the clamp to maintain reduction. Under these circumstances you determine which screw hole is best for the placement of the tip of the clamp from the pre-operative plan and intra-operative trial.
The plate is temporarily held in place with a K-wire and the clamp.
The positioning of the buttress plate is important as the ideal place is at the tip of the fragment and perpendicular to the fracture plane.
3 Fixation topenlarge
Lag screw through the plate
The first lag screw should be inserted at 90° to the fracture plane. Thus it is best to insert the first lag screw outside the plate unless the fracture plane is oblique and parallel to the position of the plate. Under these circumstances, the lag screw can be inserted through the plate.
Click here for a detailed description of the lag screw technique.
Additional screw insertion
The insertion of the subsequent screws follows your pre-operative plan. Please note that one can insert a second distal lag screw through the plate.
Alternative: lag screw outside the plate
If screw fixation has already been performed and you come now to apply a plate consider a slightly more distal placement for the plate.
In this x-ray, the lag screws were applied first.
The short plate buttresses the fragment.
Remember, that reduction and fixation of the medial plateau fracture, particularly if the fracture plane is oblique and runs antero-medial to postero-lateral may be much more difficult. Reduction particularly if the medial wedge fragment is further split in the coronal plane can only be achieved with the knee in extension. The position of the plate is determined by the direction of the principle fracture plane.