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  3. Diagnosis
  4. Indications
  5. Treatment

Authors of section


Florian Gebhard, Phil Kregor, Chris Oliver, Markku T Nousiainen

Executive Editor

Chris Colton, Richard Buckley

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Anterior lag screw

1. Principles

General considerations

Anterior and lateral flake fractures may be associated with patellar dislocation/subluxation.

These osteochondral fragments are very often avascular, and their incorporation occurs by “creeping substitution” as vessels grow into the fragment from the living underlying cancellous bone. This requires the abolition of all interfragmentary movement by rigid interfragmentary compression. If this is not achievable, then nonunion and late separation can occur. For this reason, smaller fragments may need to be excised, or washed out of the knee joint.

Osteochondral fractures of the medial, or lateral, ridge of the patellar groove of the femur will usually require open parapatellar approach for reduction and fixation. When full arthroscopic resources, including an expert surgeon, are available, arthroscopic reduction and percutaneous fixation may be considered, but require high levels of skill and expertise.

Check the retropatellar surface for lesions.

Fixation of anterior flake fracture

Pearl: decision making
In these injuries, there may be small osteochondral defects that are not reconstructable. Every reasonable attempt should be made to reconstruct the articular surface. On the other hand, a loose small fragment in the knee joint is clinically worse than a small articular defect. Therefore, surgical judgment must be exercised in determining whether a fragment is reconstructable, or not.
Specialist knee reconstruction surgeons have available advanced techniques to reconstruct the articular surface. Osteochondral autograft and allograft transfer within the knee are possible. Cultured chondrocyte grafting shows promise for the future.

2. Preparation and approach



Osteochondral fractures of the medial or lateral ridge of the patellar groove of the femur will usually require an open medial or lateral parapatellar approach for reduction and fixation.

When full arthroscopic resources, including an expert surgeon, are available, arthroscopic approach and reduction and percutaneous fixation may be considered, but require high levels of skill and expertise.

3. Reduction


Achieve reduction by manipulating the fracture with an elevator. Small ball-spiked pushers, or a dental pick, may also be used.

Reduction of anterior flake using small ball-spiked bushers

Alternative: reduction under arthroscopic view

Achieve reduction by manipulating the fracture with the hook (illustrated) using arthroscopic control. Small ball-spiked pushers may also be used, inserted through separate portals.

Use of arthroscopy

Temporary fixation

Insert a K-wire to secure the reduction. Make sure that it does not interfere with the intended implant position.

If possible K-wires should be inserted outside of the cartilage surface.

Temporary fixation with K-wire

4. Fixation outside of the articular surface

Lag screws are inserted using the standard technique before removing the K-wires.

Fixation outside the articular surface

5. Fixation through articular surface

General consideration

Fixation can be achieved using a small fragment screw system (A or B), or absorbable pins (C). In general screws provide a better compression of the fracture, but need a certain thickness of the osteochondral flake due to the screw head dimension.

Absorbable pins (C) are preferable for thin and small fragments.

Two screws, or pins, should be used in order to prevent fragment rotation.

None of the implants is allowed to project above the articular surface.

Screw types

Guide-wire placement

Place the guide wires as perpendicularly as possible to the fracture plane.

Check correct guide-wire placement under image intensifier control.

Insertion of guide wire


Countersink manually, deep enough to allow for fully buried screw heads.

Pitfall: countersinking too deep
Be aware of countersinking too deeply into the cancellous bone, which often happens using a power tool.


Sunken screws

In screw fixation, the lag screw principle is followed. Use partially threaded lag screws so that no gliding hole needs to be drilled. It is imperative to countersink for the screw head.

Insertion of sunken screws

This illustration shows the completed osteosynthesis using sunken screws.

Compete osteosythesis

Headless compression screw

Insert 3.0 mm headless compression screws with predrilling, or over a guide wire. Neither gliding hole nor countersinking is required. It is imperative to insert the headless compression screw until the screw head has passed the cartilage surface completely.

Headless compression screws

This illustration shows the completed osteosynthesis using headless compression screws.

Complete osteosynthesis using headess compression scews

Absorbable pins

Absorbable pins require predrilling. Use the insertion device to insert the pin with gentle hammer blows. Observe the pin insertion process carefully as the pins might deform during insertion.

In case the pin head does not completely sink into the cartilage use a scalpel to remove the projecting part of the head.

Fixation using absorbable pins

This illustration shows the completed osteosynthesis using absorbable pins.

Complete fixation using absorbable pins

6. Aftercare

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.

Early range of motion helps restore movement in the early postoperative phase. 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 prescriptive.

Functional treatment

Unless there are other injuries or complications, knee 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 progressive 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.

P070 orif anterior screws for large fragments

Weight bearing

Touch-down weight-bearing (10-15 kg) may be performed immediately with crutches, or a walker. This will be continued for 6-10 weeks postoperatively. This is mostly to protect the articular component of the injury, rather than the shaft injury. Touch-down weight-bearing progresses to full weight-bearing gradually, over a period of 2 to 3 weeks (beginning at 6–10 weeks postoperatively). Ideally, patients are fully weight-bearing, without devices (e.g., cane) by 12 weeks.


Wound healing should be assessed at two to three 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.

Thrombo-embolic prophylaxis

Thrombo-prophylaxis should be given according to local treatment guidelines.