1 Note on illustrations topenlarge
Throughout this treatment option illustrations of generic fracture patterns are shown, as four different types:
A) Unreduced fracture
B) Reduced fracture
C) Fracture reduced and fixed provisionally
D) Fracture fixed definitively
2 Principles of joint-bridging modular external fixation topenlarge
The modular external fixator is optimal for temporary use. It is rapidly applied without need for intraoperative x-rays and can be adjusted later.
The joint-bridging modular external fixator for fractures of the malleoli consists of two partial frames, one along the tibia and one medial on the calcaneus or calcaneus and talus.
Details of external fixation are described in the basic technique for application of modular external fixator.
Specific considerations for joint-bridging modular external fixation, the distal tibia and the foot are given below.
3 Patient preparation topenlarge
This procedure is normally performed with the patient in a supine position.
4 Safe zones for pin placement topenlarge
Inserting percutaneous instrumentation such as pins or transfixion wires through safe zones reduces the risk of damage to neurovascular structures.
For safe pin placement make use of the safe zones and be familiar with the anatomy of the lower leg and the foot.
5 Pin insertion (tibia and foot) topenlarge
Choice of tibial pin placement
Drilling a hole in the thick tibial crest may be associated with excessive heat generation and there is a risk the drill bit may slip medially or laterally damaging the soft tissues. As the anteromedial tibial wall provides adequate thickness for the placement of pins, this trajectory is preferable. A trajectory angle (relative to the sagittal plane) of 20-60° for the proximal fragment and of 30-90° for the distal fragment is recommended.
Alternatively, to avoid the frame catching on the opposite leg, the pins may be placed more anteriorly. The drill bit is started with the tip just medial to the anterior crest, and with the drill bit perpendicular to the anteromedial surface (A). As the drill bit starts to penetrate the surface, the drill is gradually moved more anteriorly until the drill bit is in the desired plane (B). This should prevent the tip from sliding down the medial or lateral surface.
Pin placement in the foot
For the construction of the partial frame of the foot the following three options are used most frequently:
- one pin in the calcaneus (green circle) and one in the talus (brown circle)
- two pins in the calcaneus (green and orange circle)
- one pin in the calcaneus (green circle) and one in the cuboid (blue circle)