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 Lag screw insertion 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, direct the screw anteriorly, in order to avoid the intercondylar notch.
Drill screw hole
Make a small 1.2 cm incision.
Create a pilot hole using a 3.2 mm drill bit in the direction of the eventual screw insertion.
Determine appropriate screw length
Insert a depth gauge into the hole, to determine the appropriate screw length. Generally, a screw is chosen which is 5-10 mm short of the lateral cortex.
Remove the depth gauge and tap for the 6.5 mm cancellous bone screw under image intensifier control. In all but the densest cancellous bone of young athletes, tap only the near fragment – the screw itself will normally create its own thread in the cancellous bone of the far fragment
Insert the 6.5 mm partially threaded cancellous bone screw and fully tighten. In the case illustrated, the partially threaded screw will have 32 mm of thread, as opposed to 16 mm of thread.
Note: a washer may be used, particularly in osteoporotic patients.
Additional screw insertion
Insert 1 or 2 additional screws in a similar manner, and remove the K-wire.
5 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 inserted into the proximal hole, closest to the fracture. Perform drilling, screw length measurement and tapping, as usual.
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.
6 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.