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 uniplanar external fixation topenlarge
The frame of a uniplanar external fixator consists of at least two pins in each main fracture fragment connected with one single rod. A second rod may be added to increase stiffness of the frame.
Details of external fixation are described in the basic technique for application of modular external fixator.
Specific considerations for the uniplanar external fixator in the tibial shaft are given below.
AO teaching video: Uniplanar double-rod frame
3 Patient preparation topenlarge
This procedure is normally performed with the patient in a supine position.
4 Safe zones for pin placement topenlarge
For safe pin placement make use of the safe zones and be familiar with the anatomy of the lower leg.
The pin in the distal tibia should be placed far away from the extensor tendons on the medial side.
5 Reduction (tibial shaft) topenlarge
Apply manual longitudinal traction to leg and maintain reduction.
6 Pin insertion (tibial shaft) topenlarge
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.
7 Frame construction / fixation (tibial shaft) topenlarge
Pin insertion and frame assembly
Insert a pin into each main fragment in one plane.
Connect the pins with one rod to which 4 clamps have been added.
At this point, some correction to the reduction is still possible.
Tighten the clamps.
On both sides of the fracture, add an additional pin close to the fracture zone using the rod-to-pin clamps as guides.
Tighten the clamps.
Subsequent correction of the reduction is now impossible.
If stability is not sufficient, an additional rod can be added. The stiffness of the construct is increased if the rods are closer to the bone, and the further apart from each other the rods are placed.
Pearl: Prevent plantar flexion contracture
In patients with severe soft-tissue involvement, it may be helpful to add a pin in the foot (one of the tarsal or metatarsal bones) to maintain the ankle at a 90° angle. Thereby a plantar flexion contracture can be prevented.
The pin may be inserted in either the navicular bone, in one of the cuneiforms, in the first metatarsal base, or in the first and fifth metatarsal base, and connected to the tibial external fixator. Care should be taken to insert the pin bicortically and to avoid the intra-articular spaces.