Authors of section

Authors

Andrew Howard, Theddy Slongo, Peter Schmittenbecher

Executive Editor

James Hunter

General Editor

Fergal Monsell

Open all credits

External fixation

1. Principles of modular external fixation

Modular external fixator

The versatility of a modular external fixator is an advantage in the management of children’s fractures and can accommodate age specific variations in fracture biology and anatomy.

An external fixator may be used for definitive management of forearm fractures in children due to the short healing time.

Practical considerations are illustrated in detail in the Basic technique for application of modular external fixator in children.

Specific considerations for the forearm shaft are given below.

Modular external fixator
Note on illustrations

Throughout this section generic fracture patterns are illustrated as:

  1. Unreduced
  2. Reduced
  3. Reduced and provisionally stabilized
  4. Definitively stabilized
Generic fracture patterns

Other types of external fixator

Alterative configurations are available and include monolateral or ring systems.

Disadvantages of these systems in children include:

  • Fixed distance of pin insertion defined by the clamp
  • Excessively stiff construct
Other types of external fixator

Pin size in forearm fractures

External fixation is suitable for all ages, but the pin diameter must be appropriate to the size of the bone.

Pins with a thread diameter of 2.5-4.0 mm are suitable for forearm fractures and should be about 1/3 of the bone diameter.

Sequence of pin insertion

Determined by:

  • Fracture morphology
  • Personal preference

Safe zones for pin placement

The forearm anatomy is complex due to the presence of three major neurovascular bundles. Pin placement should avoid these structures.

Read more about Safe zones for pin placement in the radius.

external fixation

2. Patient preparation

This procedure is normally performed with the patient in a supine position.

esin

3. Frame construction on the radius

Distal pin insertion

In the distal 1/3 of the forearm, the pin is inserted via a dorsolateral incision with blunt dissection to bone. Pins are inserted under direct vision, using retractors to avoid the superficial branch of the radial nerve. The pin passes between the extensor pollicis longus (EPL) and the extensor carpi radialis or more laterally between extensor carpi radialis and the tendon of brachioradialis.

Distal pin insertion

Make an 8-10 mm skin incision over the site of pin insertion.

Use an artery clip for blunt dissection down to the bone protecting important anatomical structures.

Distal pin insertion

Insert the pin in the near cortex and through the center of the bone into the far cortex.

Take care not to advance the tip of the pin beyond the far cortex to avoid damage to adjacent neurovascular structures.

Pins should not be placed within 1 cm of the physis.

Distal pin insertion

Proximal pin insertion

The most critical anatomical consideration in the proximal 1/3 of the radius is the position of the posterior interosseous nerve, a continuation of the deep branch of the radial nerve, which perforates the supinator.

The dissection for the pin must be distal to the radial tuberosity and pass between the extensor carpi ulnaris and the mobile wad, penetrating the supinator muscle near its ulnar insertion.

Proximal pin insertion

A longer incision and blunt dissection to the bone is recommended to avoid damage to the posterior interosseous nerve.

Make a 1-2 cm skin incision over the site of pin insertion.

Use an artery clip for blunt dissection down to the bone, protecting important anatomical structures with small retractors.

Depending on the length of the proximal fragment, the distal pin may be positioned distal to the insertion of the supinator. This pin should also be inserted under direct vision.

Proximal pin insertion

Insert the pin in the near cortex and through the center of the bone into the far cortex.

Take care not to advance the tip of the pin beyond the far cortex to avoid damage to adjacent neurovascular structures.

Pins should not be placed within 1 cm of the physis.

Proximal pin insertion

4. Assessment of forearm rotation

Once the fracture is reduced and stabilized, the position may be checked with an image intensifier.

The rotation of the forearm is also assessed clinically. Pronation and supination may be limited by the injury and fixator configuration.

If there is important radiological malalignment or functional restriction, the external fixator may be adjusted.

Assessment of forearm rotation

5. Aftercare following external fixation

Pin-site care

There is no universally agreed protocol for pin site care.

The following points are however recommended:

  • Pin site care should continue until removal of the external fixator.
  • The pin sites should be kept clean.
  • Crusts or exudates should be removed.
  • The pins may be cleaned with water, saline, disinfectant solution or alcohol. The frequency of cleaning varies from daily to weekly.
  • Ointments or antibiotic solutions are not recommended for routine pin site care.
  • Pin sites do not need to be protected whilst showering or bathing with clean water, but should be dried immediately.

Pin site infection
Initial management is with oral anti-staphylococcal antibiotics.

In case of pin loosening or unresponsive pin site infection, the following steps should be taken:

  • Remove all involved pins and place new pins in a healthy location.
  • Debride the pin sites in the operating theater, using curettage and irrigation.
  • Take specimens for microbiological culture to guide appropriate antibiotic treatment.

Internal fixation following an infected external fixator pin has a high risk of infection and should be avoided unless no reasonable alternative is available.

See also the additional material on postoperative infection.

Compartment syndrome

See the additional material on compartment syndrome.

Mobilization

Elevation is useful in the initial stages. A sling is helpful if fixator configuration allows its application.

The patient should be encouraged to move the wrist and elbow, within the limits of comfort.

Follow-up

The patient should be seen 7-10 days after surgery for a wound check.

X-rays are taken to check stability and alignment.

See also the additional material on healing times.