1 Note on illustrations topenlarge
Throughout this treatment option illustrations of generic fracture patterns are shown, as four different types:
A) Unreduced fracture
B) Reduced fracture
C) Fracture reduced and fixed provisionally
D) Fracture fixed definitively
2 Principles of modular external fixation topenlarge
The modular external fixator is optimal for temporary use. It is rapidly applied without need for intraoperative x-rays and can be adjusted later.
Details of external fixation are described in the basic technique for application of modular external fixator.
Specific considerations for the forearm shaft are given below.
3 Patient preparation topenlarge
This procedure is normally performed with the patient in a supine position.
4 Pin insertion (forearm shaft) topenlarge
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
Blunt dissection is performed using an instrument such as a small artery clip. This should displace important anatomic structures, which may then be retracted with small Langenbeck retractors. It is important to be aware of the anatomic structures at each level so that care can be taken to avoid damaging them (see Safe zones for pin placement in the forearm).
5 Sequence of fixation (forearm shaft) top
In both bone fractures, it is usually more straightforward to apply the first external fixator to the less complex fracture. In this illustrative series external fixation of the ulna before radius is presented.
To keep the illustrations clearer, the external fixator on the first bone is omitted from the illustrations of fixation of the second bone.
6 Frame construction on the ulna topenlarge
The posterior border of the ulna is subcutaneous, so this usually offers the best access.
The pin should be inserted in the first cortex and through the center of the bone into the far cortex. Care should be taken to avoid the tip of the pin protruding significantly through the far cortex to avoid damage to neurovascular structures.
The proximal ulnar pins are inserted through the subcutaneous cortex of the posterior border of the ulna between the extensor and flexor muscle masses.
The distal ulnar pins are inserted through the posteromedial cortex.
The subcutaneous posteromedial cortex is most safely accessible with the forearm in supination.
7 Frame construction on the radius topenlarge
The pins need to be inserted under direct vision using retractors down to the bone to avoid the superficial branch of the radial nerve.
In the distal third of the forearm, the track for the pin passes between the extensor pollicis longus (EPL) and the radial wrist extensors.
Great care is required during the manual insertion of the proximal radial pins.
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.
8 Bridging the radial and ulnar frame top
In special cases the two external fixators may be bridged temporarily or definitively if the rotation of the forearm needs to be blocked in neutral position of the hand e.g. instability of the distal or proximal radioulnar joints.
9 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.
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.
This is repeated with the wrist in full supination and full pronation.
In order to test the stability of the distal radioulnar joint, the ulna is compressed against the radius...
...while the forearm is passively put through full supination...
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.