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.
Retropatellar surface Check the retropatellar surface for lesions.
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. Patient preparation
This procedure may be performed with the patient in one of the following positions:
Osteochondral fractures of the medial, or lateral, ridge of the patellar groove of the femur will usually require 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.
4. Reduction and temporary fixation
Achieve reduction by manipulating the fracture with an elevator. Small ball-spiked pushers, or a dental pick, may also be used.
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.
Insert a K-wire to secure the reduction. Make sure that it does not interfere with the intended implant position.
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.
Place the guide wires as perpendicularly as possible to the fracture plane.
Check correct guide-wire placement under image intensifier control.
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.
In screw fixation the lag screw principle is followed. Use partially threaded lag screws so that no gliding hole need to be drilled. It is imperative to countersink for the screw head.
This illustration shows the completed osteosynthesis using sunken screws.
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.
This illustration shows the completed osteosynthesis using headless compression screws.
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.
This illustration shows the completed osteosynthesis using absorbable pins.
6. Aftercare following screw 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.
Weight bearing Touch-down weight bearing (10-15 kg) may be started immediately with crutches, or a walker. This will be continued for 6 weeks postoperatively. After that, touch-down weight bearing progresses to full weight bearing gradually over the next 2 weeks. In general, patients are full weight bearing, without devices (e.g., cane), by 8 weeks.
Follow up 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.
Implant removal Implant removal is not recommended as all implants are buried, or absorbed.
Thrombo-embolic prophylaxis Consideration should be given to thrombo-embolic prophylaxis, according to local treatment guidelines.