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Authors

Florian Gebhard, Phil Kregor, Chris Oliver

Executive Editor

Chris Colton

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ORIF - 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, 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

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.

Screws should be inserted parallel to the patellofemoral and femorotibial joint planes

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.

The buttress plate prevents proximal displacement of the fragment

2. Patient preparation

3. Approaches

For this procedure the following approaches may be used:

The lateral parapatellar incision gives better joint access for reduction, in cases of multiple joint fragments. With lesser joint comminution, the lateral/anterolateral approach can give satisfactory joint access.

4. Joint debridement

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

Rinsing the joint thoroughly with Ringer lactate solution

5. Reduction

Temporary reduction

Reduce the main fragment using a periosteal elevator and a ball-spiked pusher (illustrated) first. Then insert the smaller fragment using a dental pick. Take care to reduce it anatomically to ensure smooth joint surface.

Reducing the fragment

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

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.

Securing the reduction with a K-wire

Option: absorbable pins

Optionally, the small intermediate fragment may first be fixed by absorbable pins, before final reduction of the main condylar fragment.

Optionally, the small intermediate fragment may first be fixed by absorbable pins

Check of reduction

The quality of the reduction is confirmed radiographically.

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 (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.

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 to 4 screws are necessary.

Inserting the appropriate guide-wires

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 tips of the guide wires just penetrate the far cortex

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 distal femur tapers from the posterior to the anterior

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

mio dynamic condylar screw dcs

7. Lag screw insertion

Drill screw hole

Make a small 1.2 cm incision over the lateral femoral condyle. The incision should go through the iliotibial band.

Create a pilot hole using a 3.2 mm drill bit in the direction of the eventual screw insertion.

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 medial cortex.

Determining the appropriate screw length

Tapping

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.

Tap for the cancellous bone screw

Screw insertion

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.

Insert the bone screw and fully tighten

Additional screw insertion

Insert 1 or 2 additional screws in a similar manner, and remove the K-wire.

Inserting additional screws and removing the K-wire.

8. Insertion of buttress plate

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.

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

Insertion of first screw

All types of 4.5mm plates can be applied. Although a condylar LCP could 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.

Applying the plate to the lateral aspect of the distal femur

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.

Securing the plate with at least 2 more bicortical cortical screws

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.

Distal partially threaded cannulated cancellous screws can be inserted

Check of implant position

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

9. Wound closure

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.

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.