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Authors

Florian Gebhard, Phil Kregor, Chris Oliver

Executive Editor

Chris Colton, Richard Buckley

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ORIF - cannulated lag screws with buttress plate

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.

Completed osteosynthesis

Buttress plate

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.

Buttress plate counteracting vertical shear forces

2. Patient preparation

3. Approach

For this procedure a medial parapatellar approach is used.

medial parapatellar approach

4. Joint debridement

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

Removing intraarticular hematoma

5. Reduction

Temporary reduction

Reduce the fragment by the gentle use of a periosteal elevator and a ball-spiked pusher (illustrated), or a dental pick.

Reducing the fragment

Skin incision for large pointed reduction forceps placement

Make a lateral skin incision for the insertion of a large pointed reduction forceps.

Skin incision for 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.

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

Securing the reduction with temporary K-wires

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.

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

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.

Insert the appropriate guide-wires for cannulated screws

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.

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

7. Cannulated screw insertion

Screw length determination

Determine the appropriate screw length using the dedicated measuring device.

Determine the appropriate screw length

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.

Manually insert the screws over the guide-wires

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.

Inserting of an additional cannulated screw over a K-Wire

8. Insertion of buttress plate

Principle

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

To enhance the stability and to avoid displacement, 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 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.

Applying the buttress plate to the medial aspect of the distal femur

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.

Completed osteosynthesis

9. 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.

10. Aftercare following screw (and plate) fixation of partial articular fractures

Introduction
Impediments to the restoration of full knee function after distal femoral fracture are fibrosis and adhesion of injured soft tissues around the metaphyseal fracture zone, joint capsular scarring, intra-articular adhesions and muscle weakness.

Continuous passive motion is a low load method of restoring movement and is a useful tool n the early post operative phase. It must be used in combination with muscle strengthening programs. With stable fracture fixation, the surgeon and the physical therapy staff will design an individual program of progressive rehabilitation for each patient.

The regimens suggested here are for guidance only and not to be regarded as proscriptive.

Functional treatment
Unless there are other injuries, or complications, joint mobilization may be started immediately postoperatively. Both active and passive motion of the knee and hip can be initiated immediately postoperatively. Emphasis should be placed on quadriceps strengthening and straight leg raises. Static cycling without load, as well as firm passive range of motion exercises of the knee, allow the patient to regain optimal range of motion.

mio dynamic condylar screw dcs

Weight bearing
Touch-down weight bearing (10-15 kg) may be started immediately with crutches, or a walker. This will be continued for 6-8 weeks postoperatively. After that, touch-down weight bearing progresses to full weight bearing gradually over a period of the next 2 to 3 weeks. In general, patients are full weight bearing without devices (e.g., cane) by 10-12 weeks.

Follow up
Wound healing should be assessed at 2 to 3 weeks postoperatively. Subsequently 6 week, 12 week, 6 month, and 12 month follow-ups are usually made. Serial x-rays allow the surgeon to assess the healing of the fracture.

Implant removal
Implant removal is not essential, unless there are implant-related symptoms after consolidation.

Thrombo-embolic prophylaxis
Consideration should be given to thrombo-embolic prophylaxis, according to local treatment guidelines.