1 Principle topenlarge
B3-type fractures are intraarticular, therefore they need anatomical reduction.
The plate in this procedure acts as a buttress to neutralize the axial forces on the tibial plateau.
Lateral versus medial condylar fractures
The operative procedures for lateral condylar fractures (B3.1 fractures) and medial condylar fractures (B3.2 fractures) are comparable, except the medial fractures are more difficult.
In medial condylar fractures, the position of the plate is determined by the principle fracture line. Therefore, the plate may be anteromedial, posteromedial or posterior.
The B3.3 fracture is a special subtype. It is sustained usually as a result of a high velocity axial compression which is directed posteromedially. The result is a posteromedial fracture dislocation of the knee. The difficulties in dealing with this fracture arise in restoring the medial tibial condyle which is frequently split in the coronal plane as well, with the impaction and fragmentation of the medial portion of the lateral plateau and the intercondylar eminence, and fragments of bone caught in the major fracture line.
A lateral condylar fracture treatment (B3.1-type fracture) is shown here.
2 Reduction topenlarge
Window in the metaphyseal area
Approach from below through the fracture. The reduction of the articular surface is checked directly through a standard submeniscal articular exposure. Reduction of the articular surface is always accomplished by elevating the fragments from below.
Temporary fixation with K-wires may be helpful.
Filling of defect
The metaphyseal defect, which results when the articular fragments are reduced, must be filled with cancellous autograft or a corticocancellous block to support the elevated fragments. Alternatively bone substitutes may be used.
3 Fixation topenlarge
Once reduction of the articular fragments is achieved and the metaphyseal defect has been bone grafted the lateral condylar fragment is reduced. Now, temporary K-wire fixation helps to maintain reduction. Large clamps may help to keep large metaphyseal fragments reduced prior to definitive plate fixation either from the lateral or medial side.
Plate osteosynthesis represents the standard treatment concept for these fractures. The position of the plate is determined by the location of the fracture. The plate acts as a buttress plate and compression of the articular fragments and of large metaphyseal fragments is achieved by means of lag screws. Angular stable plates may be used, but are rarely necessary in monocondylar fractures except in osteoporotic bone.
After the preliminary fixation with K-wires prior to plate fixation, a clamp, if used for preliminary fixation, may have to be removed, but one must be very careful not to lose the reduction.
If the articular surface is very comminuted one must be careful not to overtighten the lag screws so as not to narrow and deform the articulation. Click here for a detailed description of the lag screw technique.
Usually three screws are necessary to achieve adequate fixation of the buttress plate to the distal fragment. The number of screws in the proximal fragment will depend on the fracture pattern and the degree of comminution. Lag screw fixation of the articular surface is usually achieved by passing the lag screw outside the plate but may also be through the most proximal hole of the plate. This will depend on the fracture configuration because lag screws should be inserted at a right angle to the principle fracture plane. If one is using a plate with angular stability then fewer number of screws may suffice distally unless the bone is osteoporotic.
This image shows the final result with the use of a locking proximal tibia plate. Remember that a screw which locks in the plate will not act as a lag screw. Therefore, the first proximal screws one inserts do not lock in the plate and if partially threaded will exert compression. One then removes these screws one at a time and replaces them with fully threaded locking screws. The advantage of this is that one is able to maintain interfragmentary compression while also achieving angular stability and stronger purchase in the proximal fragment.