Authors of section


Florian Gebhard, Phil Kregor, Chris Oliver

Executive Editor

Chris Colton, Richard Buckley

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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.

mio lag screws

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.

mio cannulated lag screws

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.

mio lag screws

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.

mio cannulated lag screws

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.

mio dynamic condylar screw dcs

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

mio dynamic condylar screw dcs

5. Cannulated screw insertion

Screw length determination

Determine the appropriate screw length using the dedicated measuring device.

mio cannulated lag screws

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.

mio cannulated lag screws

Completed osteosynthesis

Illustration showing the completed osteosynthesis.

partial articular fracture lateral condyle sagittal simple

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

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.