1 Principles topenlarge
The B2-type distal femoral fractures are characterized either by a simple, or complex, fracture line into the articular surface. As with any articular injury, anatomical restoration of the joint surface must be obtained. This is generally best done under direct vision, with clamp application, provisional fixation and then lag screw fixation.
The surgeon must bear in mind that the strong axial loading forces, as well as varus/valgus stress in the knee joint can tend to displace fragments. With vertical fracture lines, in particular, screw fixation alone may not be sufficient, and a buttress plate should be added.
In B2-type fractures with a vertical fracture line, a buttress plate is necessary to counteract the vertical shear forces. The buttress plate prevents proximal displacement of the fragment.
The buttress plate is added to enhance the stability and to counter axial load on the fracture, especially in osteoporotic bone.
2 Joint debridement topenlarge
Remove the intraarticular hematoma and rinse the joint thoroughly with Ringer lactate solution.
3 Reduction topenlarge
First reduce the main fragment using a periosteal elevator and a ball-spiked pusher (illustrated). Then reposition the smaller fragment using a dental pick. Take care to reduce it anatomically, to ensure smooth joint surface.
Skin incision for large pointed reduction forceps placement
Make a lateral skin incision for the insertion of a large pointed reduction forceps.
Temporary fixation with K-wire insertion
Hold the final reduction using a large pointed reduction forceps. Make sure not to place the pointed reduction forceps too posteriorly, as compression across the intercondylar notch would tend to tilt the fragment.
Secure the reduction with one, or more, temporary K-wires. Make sure that the K-wire does not conflict with the planned screw track.
Option: absorbable pins
Optionally, the small intermediate fragment may first be fixed by absorbable pins, before final reduction of the main condylar fragment.
Check of reduction
Check the reduction in two planes using image intensifier control.
4 Insertion of K-wires for cannulated screws topenlarge
In general, the screws are inserted at points along the midshaft axis of the femur (dotted line). The area distal to the Blumensaat’s intercondylar roof line must be avoided in order not to violate the notch. In addition, the area of the medial knee recess should be avoided.
If you need to insert a screw in the area distal to the Blumensaat’s intercondylar roof line make sure to direct the screw anteriorly, in order to avoid the intercondylar notch.
Insertion of guide-wires
Insert the appropriate guide-wires for 7.3 mm cannulated screws, or alternatively 4.5 mm, cannulated screws. Depending on the size of the fragment 2-4 screws are necessary.
In good bone stock, you may now remove the pointed reduction forceps. Otherwise, leave the pointed reduction forceps until all the screws have been inserted.
Guide-wire position check
Use image intensifier to make sure that the tips of the guide-wires just penetrate the far cortex. Because of the 10° slope of the lateral condylar cortex, slightly externally rotate the femur for a true profile image, to check for overpenetration.
5 Cannulated screw insertion topenlarge
Screw length determination
Determine the appropriate screw length using the dedicated measuring device.
Manually insert the screws of appropriate lengths over the guide-wires. Partially countersink the most proximal screw head for better plate seating.
Predrilling is usually not necessary.
The temporary K-wire can now be removed.
Pearl: use temporary K-wire for further screw insertion
If you have used an appropriate K-wire size for temporary fixation of the fracture, you can insert an additional cannulated screw over it, to enhance stability.
6 Insertion of buttress plate topenlarge
To enhance the stability and to avoid displacement of the fracture fragment by axial load (especially in osteoporotic bone), a buttress plate is needed.
Insertion of first screw
All types of 3.5mm plates can be used. A 5-hole standard 3.5 mm plate is
sufficient. The plate must be contoured with a light prebend, that is, there
should be a 1 mm gap between the central part of the plate and the bone.
Apply the buttress plate to the medial aspect of the distal femur. To press the plate firmly to the femur a standard cortical screw is necessary. The best position for this screw is in the proximal hole, closest to the fracture. Perform drilling, screw length measurement and tapping, as usual, according to the selected implant.
Final screw insertion
Secure the buttress plate with two more bicortical cortical screws in the remaining proximal screw holes. Use standard bicortical cortical screws.
Check of implant position
Check the osteosynthesis using the image intensifier in at least in two planes.
7 Wound closure top
Irrigate all wounds copiously. Insert an intraarticular suction drain. Close the joint using absorbable sutures. The use of suction drains in the extraarticular tissues may be considered. Close the skin and subcutaneous tissue in the routine manner.