1 Principles topenlarge
A thorough knowledge of the anatomy is mandatory to perform the correct placement of the K-wires. All important neurovascular structures run in the posterior half of the cross section.
Wires should be positioned as proximal as possible but not through the joint. The most proximal wire should be at least 14 mm below the articular surface because of the distal capsular insertion.
2 Patient preparation topenlarge
This procedure is normally performed with the patient in a supine position.
3 Reduction of the articular surface topenlarge
Generally, the medial plateau is reduced first because it is usually less comminuted and allows the surgeon, once reduced, to reestablish normal length, rotation, and alignment of part of the articular surface.
It is then provisionally fixed and one turns one’s attention to the lateral side which is accessed through an anterolateral parapatellar incision. After elevation and reduction of the depressed articular surface, bone graft (autologous, allograft, or bone substitute) the defect in the metaphysis to prevent future collapse of the reduced articular surface, reduce the metaphysis, secure provisional fixation with K-wires, check radiographically and if satisfactory complete the fixation with a lateral buttress plate.
Ligamentotaxis helps to achieve preliminarily reduction of the main fracture fragments and helps to maintain length during the operation. It is also used preoperatively to maintain provisional reduction.
Use of distractors and external fixators
In order to reduce these complex fractures one may need to use two femoral distractors one on the medial and one on the lateral side. To do this, place the knee in slight flexion.
One can also achieve the same with the use of two external fixators or one distractor and one external fixator. The use of the external fixators makes intraoperative adjustments almost impossible because they do not allow for rotational or angular correction.
Distractors, because they apply the force directly to the bone, are very powerful and make distraction easy. Use the distractor on the side with more comminution. Usually, the medial side can be managed with an external fixator because it is usually less comminuted. If only external fixators are available, place one on the medial and one on the lateral side or span the knee joint anteriorly with a unilateral frame.
Open book technique
Hinge the main fragments back on their soft-tissue attachments and visualize the depression of the articular fracture. Reduce the impaction by gentle elevation. Once this is completed, reduce the metaphyseal fracture by indirect or direct manipulation. The metaphysis, if possible, should be reduced anatomically to restore inherent stability.
A pointed reduction forceps is a very useful tool in securing reduction of the main fragments and their provisional fixation.
In these complex fracture patterns, arthroscopy is not helpful.
In multifragmentary proximal bicondylar articular fractures, be careful when you insert lag screws so as not to narrow the width of the proximal tibia.
The same holds true when one is using the pointed reduction clamps for provisional fixation.
Once the fracture is reduced, provisional fixation of the fragments is achieved with K-wires. The accuracy of the reduction should be checked with an image intensifier.
After elevation and reduction of the depressed articular surface, bone graft (autologous or bone substitute) the defect in the metaphysis to prevent future collapse of the reduced articular surface.
4 Proximal ring application topenlarge
As wires go through both cortices, good knowledge of anatomy is mandatory (see the safe zones). Carefully choose wire corridors. At least two wires have to be used.
For intraarticular fractures needing compression choose spade-point reduction wires with an “olive”. At least two wires have to be inserted.
Connect wires with ring
Connect the wires with the ring and tighten clamps. Thereby, the articular fracture component is fixed.
After the wires are tightened, the pointed reduction forceps can be removed.
5 Inserting pins into tibial shaft topenlarge
Mid shaft level
The neurovascular bundle (the anterior tibial artery and vein together with the deep peroneal nerve) run anterior to the interosseous membrane close to the posterolateral border of the tibia.
They are at risk if the pin is inserted in the direction as indicated by the red dotted line approximately half way between the anterior crest and the medial edge of the tibia.
Distal shaft level
When inserting pins in the distal zone take into account the position of the anterior tibial artery and vein. Percutaneous insertion of pins in this area is dangerous. A minimal incision will allow preparation and safe insertion.
The peroneal bundle is located very close to the posterolateral border of the tibia and therefore at risk if pins are inserted in this direction.
Pins at this level should be inserted as shown in the illustration from anteromedial to posterolateral. A second pin can be inserted from medial to anterolateral, ventral to the fibula.
Standard Schanz screws
Drill through both cortices with a 3.5mm drill bit.
Use measuring device to determine diameter of bone.
Insert Schanz screw.
Pin insertion depth
Make sure that the Schanz pins are not penetrating excessively through the far cortex, so as to avoid injury to either the neurovascular structures or soft tissues.
Image intensification control in two planes is recommended.
Insert four pins into the tibia two at each level.
Place the proximal Schanz pins as close as possible to the fracture. The second Schanz pin pair must be positioned as distally as possible. The further the pin pairs are apart, the more stable the construction will be.
6 Finalizing the external fixator topenlarge
Connect the Schanz screws with the two rings. Then, interconnect all three rings with tubes. The clamps are left loose to allow manipulation.
Use the rings to reduce the fracture by manipulation under image intensification.
Before manipulation, loosen the distractors.
After successful reduction, tighten clamps.