Executive Editor: Chris Colton

Authors: Florian Gebhard, Phil Kregor, Chris Oliver

Distal femur Partial articular fracture, medial condyle, sagittal fragmentary

ORIF - cannulated lag screws

1. Principles

General consideration

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.

3. Approach

For this procedure a medial parapatellar approach  is used.

4. Joint debridement

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

5. Reduction

Temporary reduction

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.

6. Insertion of K-wires for cannulated screws

General consideration

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.

7. 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. 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.

8. Wound closure

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.

Appendix

Shortcuts

Contact | Disclaimer | AO Foundation

v1.0 2008-12-03