Unilateral External Fixators

Ahmed Thabet, M.D.
Texas Tech Health Science Center at El Paso


What are unilateral external fixators?
Unilateral external fixators are a type of fixation to stabilize broken bones to allow healing to happen. They may be used when the bone is broken in a trauma (fracture) or when your surgeon performs a bone cut (osteotomy) to correct a deformity (crooked bone). External fixators sit outside the bone and are connected to the bone by metal pins. This is in contrast to the more commonly seen types of internal fixation which reside under the skin and are not seen by patients, such as plates and screws or nails on the inside of the bone.

The pins in an external fixator are attached together using special clamps. The clamps are attached together with connecting bars. The external fixators can be used to fix the bone through different orientation in different planes. The external fixators can be attached to the bone from the front or from side or both. Unilateral external fixation is when essentially all the pins are connected to the bone coming from the same direction.

How does the surgeon decide to use unilateral fixators vs internal fixator implant? Why does my surgeon recommend a unilateral external fixator?
This depends on may factors:

1- The surgeon might decide to use external fixation if there is a severe open wound connected to your fracture site. These open fractures are at increased risk of osteomyelitis (infection of the bone). This can be a temporary measure until complete wound healing as a first stage, followed by a second stage usually with conversion to internal fixation.
2- Unilateral external fixation is used in certain fractures involving joint surfaces (intra-articular fractures) around the knee and ankle joints. These fractures are commonly associated with severe swelling and blood-filled blisters. External fixation is used when the surgeon is concerned that immediate surgical intervention might lead to severe complications including wound breakdown and infection.
3- Unilateral external fixators are used for deformity correction and gradual bone lengthening. When your bone is crooked or short, your surgeon may opt to used external fixators to straighten your bone and or make your bone longer.
4- Children with decreased blood flow to hip joint (the ball of hip joint) may benefit from joint distraction (stretching the joint apart) to increase the blood flow to the ball of their hip joint. This procedure called arthrodiastasis.

How do the surgeons apply unilateral external fixators?
External fixators are most commonly applied in the operating room (OR) when the patient is fully asleep. There are some situations in which patients are too sick or unstable to go to the OR and an external fixator may be applied in an intensive care setting.

External fixators are applied by drilling holes into the bone followed the insertion of pins to the bone above and below a fracture or osteotomy.

1- The clamps are then attached to the pins
2- Then the connecting rods are attached to the clamps
3- All these steps are followed by bone reduction from its displaced position and then tightening all the connections
4- Special X-ray machines called fluoroscopy are used during application of external fixators pins and to check restoration of bone alignment

What are the benefits of unilateral external fixators?

1- Unilateral external fixators can be applied quickly, and they are useful for critically ill patients who are not healthy enough to tolerate a longer procedure
2- They reduce the risk of deep infection especially in the setting of open fractures and infected implants
3- They can be used for bone lengthening and deformity correction
4- They are useful as a temporary reduction tool (to help align and hold bone segments) in the operating room

What are the risks of the unilateral external fixators?
There are multiple risks of using unilateral external fixators

1- Infection of the pins sites is the most common complication associated with unilateral external fixators. This is generally treated successfully with pin care and antibiotics
2- Joint stiffness due to tethering the muscles and tendons
3- Loss of reduction and delayed fracture healing. In these circumstances either modification of the external fixator or conversation to a different implant is generally necessary.
4- Bone fracture after frame device removal. The bone is generally protected with decreased activity levels or casting/bracing after frame removal.
5- Deep infection of the internal fixation implant after conversion to internal fixation

Your surgeon will review with you the particular risks associated with each particular injury or surgery.