Specific considerations for hybrid external fixation in the distal tibia are given below.
2. Patient preparation
This procedure is normally performed with the patient in a supine position.
3. Safe zones for wire and pin placement
Knowledge of safe zones and anatomy of the lower leg and the foot is essential for safe wire and pin placement.
4. Wire placement
Planning of wire placement
2 mm diameter wires are recommended.
Placement of wires for distal tibial fixation must be carefully planned.
Note: In addition to distal ring and tensioned wires, the proximal pins and frame, and its connection to the ring, must be planned for maximal stability.
Safe wire placement in the distal tibia
Many important structures surround the ankle and must not be injured by the wires. Good knowledge of anatomy is mandatory.
No consistently safe zones for pin or wire insertion in the distal tibia have been identified. A small skin incision is performed. Tissues are spread to expose the bone, avoiding nerves and vessels. If a tendon is impaled, the offending wire must be changed.
Intraarticular placement of the wires should be avoided, if possible, to reduce the risk of joint infection. Pins that are inserted less than 20 mm proximal to the tibiotalar joint may enter the joint capsule.
To improve and reach appropriate stability, it is important to:
Maintain an overall arc of 60-80° between the wires
Add a third wire or a threaded pin
5. Ring placement
Insertion of the first wire
Make a stab incision and use blunt dissection down to the bone.
Insert the protection sleeve until it reaches the bone. Place the wire parallel to the tibiotalar joint under image intensification until it penetrates the far cortex. Finish wire insertion by hand, until the wire extends an equal length on both sides of the tibia. Make sure that the wire does not impale tendons or neurovascular structures.
Option for insertion of first wire
A non-olive wire placed through the fibula to emerge from the anteromedial tibia is often a good first wire. It is inserted from posterolateral (avoiding peroneal tendons) to anteromedial, parallel to the ankle joint.
Attaching ring to first wire
Place a wire-to-ring clamp on either end of the wire and attach these clamps to the ring, keeping the wire straight.
Tighten the clamps to the ring and then provisionally to the wire.
Option: Some surgeons place two wires initially and then attach the ring to both.
Insertion of additional wires
The wire-to-ring clamps may serve as guides for insertion of additional wires. The angle between the first and the second wire should be as wide as possible. Confirm that the articular reduction is satisfactory.
It is advisable to use at least three distal wires, or two with a supplementary threaded pin.
Flexible wires must be under tension for mechanical stability. Generally, a tension of 100 kg force is appropriate.
Pearl: While tensioning the second wire, the tension in the first may decrease due to ring deformation. Both wires should be retensioned to obtain better stability. If two tensioning devices are available, they can be used simultaneously to ensure equal tension in the two wires.
6. Pin insertion (tibial shaft)
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.
7. Ring-to-rod connection
An anteromedial rod is placed and attached to the ring to hold the provisional reduction. Then an anterolateral rod and cross brace is added for mechanical stability, with supplementary diaphyseal pins in multiple planes.
Placement of the first rod
Place an anteromedial proximal pin first. Choose a rod that is long enough to connect the pin to a clamp on the medial side of the ring. Place a rod-to-rod clamp and then a second rod-to-pin clamp on the rod.
Then attach the distal end of the rod to the ring, with a rod-to-ring clamp, with approximate fracture reduction. Angular alignment, length, and rotation must each be restored.
Next, insert a pin in the distal shaft through the rod-to-pin clamp.
8. Reduction and fixation
Loosen the rod-to-ring clamp. Reduce the segments using ring and rod as reduction handles. Restore length, alignment and rotation. Check reduction clinically and with image intensification. If reduction is satisfactory, tighten the ring-to-rod clamp.
9. Frame completion
Second and third rod
Attach the anterolateral rod to the proximal pin and to the ring laterally, using a rod-to-ring clamp. A rod-to-rod clamp is first placed on the rod.
Once the anterolateral rod is positioned, and reduction reconfirmed, connect the two rods with a short cross-brace using the previously placed clamps. If reduction remains satisfactory, tighten all frame clamps.
Additional pin from ring (option)
A pin from the ring may be used for fixation to the distal shaft. This is placed through a ring-to-pin clamp, directed proximally, towards the anteromedial tibial shaft, proximal to the fracture zone. (An alternative supplementary pin must be chosen if comminution extends too far proximally.)
Predrill if necessary for thick cortex. Place the pin, using the previously described technique, and tighten the clamp.
Once again, confirm the reduction. If satisfactory, tighten all the clamps. If necessary, readjust the reduction first.
Bending the wires
Cut and bend the wires. The sharp end can be bent into a space on the clamp. Alternatively, the sharp end can be covered with a protective cap and bent to avoid prominence.
Example of final construct.
10. Aftercare following hybrid external fixation
External fixation of distal tibial fractures is often extended to include the foot, to avoid an equino-varus deformity. Otherwise consider a splint to support the foot and ankle.
Note: Remember the risk of ankle joint infection with intraarticular wires or pins.
Proper pin/wire insertion To prevent postoperative complications, pin/wire-insertion technique is more important than any pin/wire-care protocol:
Correct placement of pins/wires (see safe zones) avoiding ligaments and tendons, e.g. tibia anterior
Correct insertion of pins/wires (e.g. trajectory, depth) avoiding heat necrosis
Extending skin incisions to release soft-tissue tension around the pin/wire insertion (see inspection and treatment of skin incisions)
Pin-site care Various aftercare protocols to prevent pin tract infection have been established by experts worldwide. Therefore, no standard protocol for pin-site care can be stated here. Nevertheless, the following points are recommended:
The aftercare should follow the same protocol until removal of the external fixator.
The pin/wire-insertion sites should be kept clean. Any crusts or exudates should be removed. The pins/wires may be cleaned with saline and/or disinfectant solution/alcohol. The frequency of cleaning depends on the circumstances and varies from daily to weekly but should be done in moderation.
No ointments or antibiotic solutions are recommended for routine pin-site care.
Dressings are not usually necessary once wound drainage has ceased.
Pin/wire-insertion sites need not be protected for showering or bathing with clean water.
The patient or the carer should learn and apply the cleaning routine.
Pin/wire loosening or pin tract infection In case of pin/wire loosening or pin tract infection, the following steps need to be taken:
Remove all involved pins/wires and place new pins/wires in a healthy location.
Debride the pin sites in the operating theater, using curettage and irrigation.
Take specimens for a microbiological study to guide appropriate antibiotic treatment if necessary.
Before changing to a definitive internal fixation an infected pin tract needs to heal. Otherwise infection will result.
Weight bearing is usually avoided with hybrid fixators.
The timing and how much weight may be taken through the fracture will be influenced by:
Stability of the fixator construct
See patient 7-10 days after surgery for a wound check. X-rays are taken to check the reduction.
The fixator is left in place until the fracture is united. A weight-bearing cast is advisable for several weeks after fixator removal.