Executive Editor: Chris Colton

Authors: Florian Gebhard, Phil Kregor, Chris Oliver

Distal femur 33-B1.1/2 ORIF

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Glossary

1 Principles top

Completed osteosynthesis enlarge

General consideration

The B1-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.


The distal femur has a unique anatomical shape enlarge

Anatomy of the distal femur

The distal femur has a unique anatomical shape. Seen from an end-on view, the lateral surface has a 10° inclination from the vertical, while the medial surface has a 20–25° slope. A line drawn from the anterior aspect of the lateral femoral condyle to the anterior aspect of the medial femoral condyle (patellofemoral inclination) slopes approximately 10°. These anatomical details are important when inserting screws. In order to avoid joint penetration, screws should be inserted parallel to the patellofemoral and femorotibial joint planes.


The buttress plate is added to enhance the stability enlarge

Buttress plate

In B1-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 by axial forces.

The buttress plate is added to enhance the stability and to avoid axial load on the fracture, especially in osteoporotic bone.

2 Joint debridement top

Rinsing of the joint with Ringer lactate solution enlarge

Remove the intraarticular hematoma and rinse the joint thoroughly with Ringer lactate solution.

3 Reduction top

Reducing the fragment enlarge

Temporary reduction

Reduce the fragment using a periosteal elevator and a ball-spiked pusher (illustrated), or a dental pick.


Stab incision for the placement of the pointed reduction forceps enlarge

Skin incision for pointed reduction forceps placement

Make a medial stab incision for the placement of the pointed reduction forceps.


Stab incision for the placement of the pointed reduction forceps enlarge

Temporary fixation with K-wire insertion

Hold the final reduction using a large pointed reduction forceps. Make sure to place the pointed reduction forceps not too posterior 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

The quality of the reduction is confirmed radiographically.

4 Insertion of K-wires for cannulated screws top

The screws are inserted at points along the midshaft axis of the femur enlarge

General consideration

In general, the screws are inserted at points along the midshaft axis of the femur (dashed 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 lateral 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.


Inserting the appropriate guide-wires enlarge

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 to 4 screws are necessary.


The tips of the guide wires just penetrate the far cortex enlarge

Guide-wire position check

Use the image intensifier to make sure that the tips of the guide wires just penetrate the far cortex.

In good bone stock, you may now remove the pointed reduction forceps. Otherwise, leave the pointed reduction forceps in place until all screws have been inserted.


The distal femur tapers from the posterior to the anterior enlarge

Pitfall: too long a guide wire

It is important to remember that the distal femur tapers from the posterior to the anterior. Therefore, if a straight AP view is obtained, the guide wire can appear to be inside the bone. If it appears to be outside the bone, it is most likely too long. In order to assess the exact length of the guide wire obtain an AP view with 30° internal rotation of the lower extremity.


The guide wire length was chosen inappropriately enlarge

In this illustration, internal rotation by 30° reveals that the guide wire length was chosen inappropriately.

5 Cannulated screw insertion top

Determining the appropriate screw lengths enlarge

Screw length determination

Determine the appropriate screw lengths using the dedicated measuring device.


Insert the screws over the guide-wire enlarge

Screw insertion

Predrilling is usually not necessary.

If it is planned to use a plate it is helpful to slightly countersink the head of the most proximal screw. Manually insert the screws of appropriate length over the guide-wire.

Washers are helpful if plate application is not planned, and always in osteoporotic bone.

The temporary K-wire can now be removed.


Inserting an additional cancellous screw enlarge

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 now insert an additional cancellous screw further to enhance stability.

6 Insertion of buttress plate top

The buttress plate is needed to prevent cranial displacement of the fragment enlarge

Principle

To enhance the stability and to avoid axial load on the fracture (especially in osteoporotic bone) a buttress plate is needed to prevent cranial displacement of the fragment.


Applying the plate to the lateral aspect of the distal femur enlarge

Insertion of first screw

All types of 4.5mm plates can be applied. Although a condylar LCP can be utilized, a simple slightly undercontoured 4.5 mm narrow plate is sufficient, as shown here.

Apply the plate to the lateral aspect of the distal femur. To press the plate firmly to the femur, insert a standard cortical screw just proximal to the fracture line. Perform drilling, screw length measurement, and tapping, as usual.


Securing the plate with at least 2 more bicortical cortical screws enlarge

Final screw insertion

Secure the plate with at least 2 more bicortical cortical screws proximal to the first screw.

Additional 4.5 mm screws are optionally inserted in the distal aspect of the plate.


Distal partially threaded cannulated cancellous screws can be inserted enlarge

Alternative: lag screws through plate

Distal partially threaded cannulated cancellous screws can be inserted in lag mode through the plate. This is an alternative to inserting independent lag screws outside of the plate.


Check of implant position

Check the osteosynthesis, using the image intensifier in at least two planes.

7 Wound closure top

Irrigate all wounds copiously. Insert an intraarticular suction drain. Close the joint and the iliotibial tract using absorbable sutures. Close the skin and subcutaneous tissue in the routine manner.

Pearl: post-ORIF examination of knee joint stability under anesthesia
With the femur now stable, it is possible to perform a gentle examination of the knee joint to exclude associated ligamentous laxity, but be extremely careful testing with valgus stress.

v1.0 2008-12-03