Executive Editor: James Hunter

General Editor: Fergal Monsell

Authors: Andrew Howard, Peter Schmittenbecher, Theddy Slongo

Pediatric forearm shaft 22r-D/4.1

External fixation

1. Note on illustrations

Throughout this section generic fracture patterns are illustrated as:

A) Unreduced
B) Reduced
C) Reduced and provisionally stabilized
D) Definitively stabilized

2. 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.

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
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 .

3. Patient preparation

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

4. 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.

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.

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

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.

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.

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.

5. 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.

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v1.0 2018-11-28