Executive Editor: Chris Colton

Authors: Florian Gebhard, Phil Kregor, Chris Oliver

Distal femur Partial articular fracture, lateral condyle, sagittal simple

MIO - cannulated lag screws

1. Introduction

General consideration

These single plane, intraarticular fractures require anatomical reduction and interfragmentary compression, sufficient to allow early joint motion. The perfection of the articular reduction is usually assessed by an open approach, but where the skills and resources are available, arthroscopically assisted reduction and percutaneous fixation may be considered. The surgeon should be prepared to find additional comminution, not evident until fracture exposure.

Note on approaches

Unless full facilities and expertise for an arthroscopic approach are available to check the closed reduction, prior to percutaneous screw insertion, the standard lateral parapatellar approach is used to give an optimal view of the joint fracture reduction.

3. Reduction

General consideration

Closed reduction and internal fixation (CRIF) is used in minimally displaced, or undisplaced simple, lateral sagittal, partial articular fractures.

Preliminary reduction
As simple, lateral sagittal, partial articular fractures usually result from a valgus force, the application of a varus stress may reduce the fracture. If varus stress alone is not sufficient, arthroscopy may be helpful.

Temporary K-wire insertion

Under image intensifier control, make a stab incision over the lateral aspect of the injured condyle and insert a temporary K-wire, to hold the reduction.

Make sure, that the K-wire does not conflict with the planned screw tracks.

Check of reduction
Check the reduction in two planes using the image intensifier.

4. Insertion of guide wires for cannulated screws

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.

Insertion of guide wires

Make a separate stab incision for each screw. Bluntly dissect to the bone, avoiding the lateral recess of the knee.
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.

Correct depth of guide-wire insertion

The depth of guide-wire insertion is crucial. Remember that the cross section of the distal femoral condylar mass is trapezoidal and slopes markedly on the medial side. The tip of the guide wire should just engage the medial cortex, and so will appear short of the medial condylar cortex on the AP intensifier image.

If necessary, internally rotate the femur under AP image intensifier control, to profile the medial cortex and check for over-penetration.

5. Cannulated screw insertion

Screw length determination

Determine the appropriate screw length using the dedicated measuring device.

Screw insertion

Manually insert the screws of appropriate lengths over the guide wires. Washers may be used. Predrilling is usually not necessary if using self-drilling/self-tapping screws.

Then remove the temporarily placed K-wire and guide wires.

Completed osteosynthesis

Illustration showing the completed osteosynthesis.



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v1.0 2008-12-03