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 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.
This procedure may be performed with the patient in one of the following positions:
Remove the intraarticular hematoma and rinse the joint thoroughly with
Ringer lactate solution.
Reduce the fragment by the gentle use of a periosteal elevator and a
ball-spiked pusher (illustrated), or a dental pick.
Skin incision for large pointed reduction forceps placement
Make a lateral skin incision for the insertion of a large pointed reduction
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.
Check of reduction
Check the reduction in two planes using image intensifier control.
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
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
Screw length determination
Determine the appropriate screw length using the dedicated measuring
Manually insert the screws of appropriate lengths over the guide-wires.
Partially countersink the most proximal screw head for better plate
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
To enhance the stability and to avoid displacement of the fracture fragment
by axial load (especially in osteoporotic bone), a buttress plate is
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
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.