Executive Editor: Chris Colton

Authors: Dominik Heim, Shai Luria, Rami Mosheiff, Yoram Weil

Forearm shaft 22-B3 External fixation

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Glossary

1 Principles top

Principles enlarge

Note on illustrations

Throughout the description of external fixation in the forearm illustrations of generic fracture patterns are illustrated, as four different types:

A) Unreduced fracture
B) Reduced fracture
C) Fracture reduced and fixed preliminarily
D) Fracture fixed definitively


Principles enlarge

In general, external fixation is only used as a temporary treatment in forearm shaft fractures.
It is often indicated in the presence of severe soft-tissue injuries (burns, open fractures, etc.) and in polytrauma patients whose definitive treatment may have to be delayed.
The external fixation should be converted later to an internal fixation whenever possible. This should be conducted no later than 3 weeks after injury, and preferably earlier, due to an increased risk of infection at a later stage.


Principles enlarge

Frame design (unilateral and modular)

The preferred frame design is unilateral and modular. The main advantages of such a frame are:

  • Pin insertion can respect the local soft-tissue situation
  • Allows for easier correction of the fracture alignment

Principles enlarge

Placement of threaded pins

In temporary external fixation, the pins should be placed far enough from the fracture site so as to allow room for later plate placement.

2 Safe zones for threaded pin insertion top

Safe zones for threaded pin placement enlarge

Read more about the safe zones.

3 Hardware top

Hardware enlarge

The main components of an external fixator are:

A) Threaded pins (standard, self-drilling/self-tapping with radial preload)
B) Pin-to-bar clamps
C) Bars
D) Bar-to-bar clamps

Note: technically speaking, the components implanted into the bone, being threaded at one end, are screws. Most designs are derived from the classical partially-threaded Schanz screws. However, calling these components “pins” has entered the common lexicon of external fixation. Usually, they will be referred to as threaded pins throughout this publication.

4 Threaded pin insertion and provisional frame construction top

Threaded pin placement and provisional frame construction enlarge

After skin incision and blunt dissection down to the bone retract the soft tissues with Langenbeck retractors. This is done by inserting the retractors layer by layer until the bone is reached.

Drill the pilot hole with the corresponding drill bit, using the appropriate drill guide.

Pitfall: injury to soft tissues
Be aware not to harm the surrounding soft tissues by insufficient soft-tissue protection.


Threaded pin placement and provisional frame construction enlarge

Conventional threaded pins without radial preload should be bicortical. They must not protrude too far since they would endanger the soft tissues.


Threaded pin placement and provisional frame construction enlarge

Threaded pins with radial preload (self-drilling and self-tapping) must not perforate the far cortex (the protruding sharp tip can cause soft-tissue injury if it projects beyond the cortex).


In 22-A3, 22-B3 and 22-C fractures, temporary external fixation is occasionally used in the presence of severe local soft-tissue compromise, or occasionally as part of damage control surgery in the multiply injured.

It is customary, in these circumstances, to apply the first external fixator to the least complex fracture. In this illustrative series external fixation of the ulna before radius is presented.
In the interest of clarity of illustration, the external fixator on the first bone is omitted from the illustrations of the fixation of the second bone.

5 Fixation of the ulnar fracture top

Threaded pin placement and provisional frame construction enlarge

Ulnar threaded pins

Threaded pin insertion must always respect the anatomical safe zones.
The ulna is subcutaneous along its posterior border and offers ease of access as a result.


Threaded pin placement and provisional frame construction enlarge

The proximal pins are inserted through the subcutaneous cortex of the posterior border of the ulna between the extensor and flexor muscle masses.


Threaded pin placement and provisional frame construction enlarge

The distal ulnar threaded pins are inserted through the posteromedial cortex.


Threaded pin placement and provisional frame construction enlarge

The subcutaneous posteromedial cortex is most safely accessible with the forearm in supination.


Threaded pin placement and provisional frame construction enlarge

Frame assembly

Connect the threaded pins in each main fragment to a bar, using pin-to-bar clamps and tighten them. Connect the two bars loosely with an intermediate bar using bar-to-bar clamps.


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Fracture reduction and fixation

Reduce the fracture by external traction, using the proximal and distal bars as “joy sticks”.

The surgeon performs this reduction …


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… while an assistant tightens the clamps.

6 Fixation of the radial fracture top

Fixation of the radial fracture enlarge

Radial threaded pins

Beware of injuries to the neural structures:

  • in the distal fragment: the superficial branch of the radial nerve
  • in the proximal fragment: posterior interosseous nerve

Fixation of the radial fracture enlarge

Radial threaded pins - Manual insertion

Insert the pins manually until they engage properly according to the pin type used.
Insertion should follow strictly the anatomical safe zones.


Fixation of the radial fracture enlarge

This illustration shows the distal third of the forearm. The track for the pin passes between the extensor pollicis longus (EPL) and the radial wrist extensors.

The pins need to be inserted under direct vision using retractors down to the bone in order to avoid the superficial branch of the radial nerve.
A skin incision is made and then progressively deepened by spreading a forceps and advancing the retractors layer by layer until the bone is reached.


Fixation of the radial fracture enlarge

Great care is required during the manual insertion of the proximal radial pins.


Fixation of the radial fracture enlarge

The supinator muscle cloaks the dorsal aspect of the upper 3rd of the radius, with the posterior interosseous nerve running through its substance.

The track for the pin must be distal to the neck of the radius and passes between the extensor carpi ulnaris muscle and the mobile wad. It will penetrate the supinator muscle.

A posterolateral skin incision is made over the gap between the two muscle masses and then progressively deepened by spreading a forceps and advancing the retractors layer by layer until the bone is reached.


Fixation of the radial fracture enlarge

Frame assembly

Connect the threaded pins in each main fragment to a bar, using pin-to-bar clamps and tighten them. Connect the two bars loosely with an intermediate bar using bar-to-bar clamps.


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Fracture reduction and fixation

Reduce the fracture by external traction, using the proximal and distal bars as “joy sticks”.

The surgeon performs this reduction …


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… while an assistant tightens the clamps.

7 Check of reduction top

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Check the reduction using image intensification and if necessary, readjust the reduction and fixation.


Reduction and fixation enlarge

Also check for the correct insertion depth of the threaded pins.

8 Assessment of Distal Radioulnar Joint (DRUJ) top

Before starting the operation the uninjured side should be tested as a reference for the injured side.

After fixation, the distal radioulnar joint should be assessed for forearm rotation, as well as for stability. The forearm should be rotated completely to make certain there is no anatomical block.


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Method 1

The elbow is flexed 90° on the arm table and displacement in dorsal palmar direction is tested in a neutral rotation of the forearm with the wrist in neutral position.

This is repeated with the wrist in radial deviation, which stabilizes the DRUJ, if the ulnar collateral complex (TFCC) is not disrupted.


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This is repeated with the wrist in full supination and full pronation.


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Method 2

In order to test the stability of the distal radioulnar joint, the ulna is compressed against the radius...


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...while the forearm is passively put through full supination...


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...and pronation.

If there is a palpable “clunk”, then instability of the distal radioulnar joint should be considered. This would be an indication for internal fixation of an ulnar styloid fracture at its base. If the fracture is at the tip of the ulnar styloid consider TFCC stabilization.

9 Wound care top

Wound care enlarge

Any skin tension at the threaded pin entry site must be dealt with by appropriately extending the incision. The incisions should be left open and treated locally with antiseptic dressings.

Pitfalls: suturing of stab incisions
Do not suture stab incisions as this increases the risk of pin track infection.

10 Definitive fixation top

Definitive internal fixation

Once the soft-tissue problem, which determined the use of temporary external fixation, has been resolved, it is desirable to remove the external fixator and undertake definitive internal fixation of the fractures.

Any signs of infected pin tracks will demand energetic measures to combat the infection prior to internal fixation. This will involve repeated irrigation of the pin tracks with appropriate bactericidal solution (after microbiological specimens have been taken), consideration of systemic antibiotics and possibly the removal of affected pins.

v2.1 2017-04-03