1 Preliminary considerations topenlarge
Fracture characteristics of 43-B1 fractures
B1 type fractures of the distal tibia are usually caused by low energy traumas with rotational or pure bending forces. In some cases it is difficult or even impossible to distinguish between a malleolar and B1-type pilon fracture (“pilonoid” fracture). The larger the fractured piece is, the more likely it is classified as a pilon fracture.
Depending on the mechanism of injury, the split fracture is placed in the frontal or sagittal plane, or in between. Usually, the soft-tissue injury is minimal and therefore, these fractures can often be fixed in one stage. Even then, the timing can be crucial. Optimal time is either in the first six hours after injury, or after 4-6 days depending on the soft-tissue swelling.
As in any pilon fracture, the fibula can be intact or not. Additional injury of the syndesmotic ligaments has to be detected during the operation. It might be necessary to address these injuries as well by suture and/or syndesmotic fixation.
2 Fracture orientation and choice of approach topenlarge
Many 43-B1 fractures can be approached minimally invasive using stab incisions for the application of reduction forceps and screw fixation. Depending on the fracture pattern, a smaller open approach for the insertion of an antiglide plate might be a good option.
This latter approach has to be placed in relation to the position of the proximal end of the fracture and can be placed wherever the fracture ends proximally.
In general, interfragmentary lag screws should be inserted from the small fragment to the large fragment, providing optimal compression force by the long threaded hole. In the illustrated cases with smaller fractured fragments, plate and screws are inserted from the same direction. With a large fragment, it might be necessary to insert the lag screws at the joint level from the opposite direction of the plate, as shown in the following example.
The split fracture in type B1 fractures may be placed in the frontal or sagittal plane, or in between. Our example shows a fracture with a large posteromedial fragment of the distal tibia, involving more than 80% of the articular surface. There is a moderate displacement with shortening, resulting in a small intraarticular step and a larger gap. The fracture plane is located between the frontal and sagittal planes and therefore has to be classified as 43-B1.1/B1.2.
It is combined with a proximal fibular fracture...
...and with a rupture of the anterior syndesmotic ligament.
3 Approach topenlarge
Since the proximal end of the illustrated tibial fracture is posteromedial, this is where an incision is required. A small posteromedial approach is performed.
After dividing the subcutaneous fat preserving the greater saphenous vein and nerve, the posteromedial tibial crest is exposed by a small longitudinal incision of the fascia of the deep flexor compartment.
Distal anterolateral approach
A separate small, distal anterolateral approach is helpful to apply a reduction forceps close to the joint and to insert separate lag screws.
Care has to be taken to the superficial peroneal nerve which crosses this approach in a slightly oblique direction.
4 Reduction topenlarge
After cleaning of the fracture line, reduction is achieved by fixation of a one-third tubular plate. Place the four-hole plate at the level of the proximal end of the fracture, through the posteromedial approach. This plate aids reduction and acts in an antiglide mechanism. Tightening the first screw which is placed just proximal to the fracture, will reduce the fracture by pushing the fractured fragment distally.
Reduce the remaining distal gap with percutaneously applied large pointed reduction forceps. Add temporary K-wires if necessary.
It is crucial that the reduction of this large articular piece (red) is absolutely anatomical. This can best be assessed visually at the proximal end of the fracture and by using fluoroscopic control at the joint level. See also assessment of reduction.
5 Insertion of lag screws topenlarge
When anatomic position of the fractured fragment is confirmed, lag screws are inserted above the articular surface and perpendicularly to the fracture plane.
In smaller fractured fragments, plate and screws may be inserted from the same side, through a slightly enlarged approach.
Fracture stabilization is finished with a lag screw through the antiglide plate to prevent a secondary displacement of the proximal end of the large fragment.
6 Assessment of ankle mortise stability topenlarge
Now the stability of the ankle mortise (syndesmotic ligaments) has to be checked under fluoroscopic control using the pronation/external rotation test as shown in the illustration. Alternatively, depending on the location and size of the anterolateral approach, the hook test can be performed.
If a syndesmotic disruption is present, there will be rotational instability of the distal fibula with widening, under stress, of the syndesmosis in the anterior part.
Since this is present in the illustrated case, a suprasyndesmotic fibulotibial positioning screw will be added.
Intraoperative x-rays or image intensification are advised to conﬁrm the position of the screw and the distal tibiofibular joint.
7 Fixation of the syndesmotic complex topenlarge
After reduction of the fibula at the syndesmosis using either manual compression or percutaneously applied large reduction forceps, introduce the positioning screw through a separate stab incision obliquely from posterior to anterior at an angle of 25–30° and parallel to the tibial plafond. The ankle should be neutral or dorsiflexed during the insertion of this screw.
Place a 3.5 mm cortex screw just proximal to the tibiofibular joint. As this screw is not intended to act as a compressive lag screw, the thread must be tapped in both ﬁbula and tibia.
In complete disruption of the syndesmosis with high instability, two screws are advisable.
Intraoperative x-rays or image intensification are advised to conﬁrm the position of the screw and the distal tibiofibular joint. See also assessment of reduction.