Forearm Radiography

FOREARM

Two projections are routinely taken, an antero-posterior and lateral.

The projections must be at right-angles to each other and demonstrate the full length of the radius and ulna including both the elbow and the wrist joint.

The antero-posterior projection with the forearm supinated demonstrates the radius and ulna lying side by side.

Poor quality images have superimposition of the radius and ulna and this may obscure pathology(pronation of the fore arm).

24 × 30 cm image receptor is recomended

Antero-posterior

• Position of patient and image receptor

The patient is seated alongside the table, with the affected side nearest to the table.

The arm is abducted and the elbow joint is fully extended, with the supinated forearm resting on the table.

The shoulder is lowered to the same level as the elbow joint.

The image receptor is placed under the forearm to include the wrist joint and the elbow joint.

The arm is adjusted such that the radial and ulnar styloid processes and the medial and lateral epicondyles are equidistant from the image receptor.

The lower end of the humerus and the hand may be immobilized using sandbags.

Direction and Centring of X-ray Beam

The vertical central ray is centred in the midline of the forearm to a point midway between the wrist and elbow joints.

Essential Image Characteristics

Both the elbow and the wrist joint must be demonstrated on the radiograph.

Both joints should be seen in the true antero-posterior position, with the radial and ulnar styloid processes and the epicondyles of the humerus equidistant from the image receptor.

Note

The postero-anterior projection of the forearm with the wrist pronated is not satisfactory because, in this projection, the radius is superimposed over the ulna for part of its length

Radiation protection

Careful technique and close collimation will assist in reducing the patient dose.

Lateral (MEDIAL PROJECTION)

• Position of Patient and Image Receptor

From the antero-posterior position, the elbow is flexed to 90 degrees.

The humerus is internally rotated to 90 degrees to bring the medial aspect of the upper arm, elbow, forearm, wrist and hand into contact with the table.

The image receptor is placed under the forearm to include the wrist joint and the elbow joint.

The arm is adjusted such that the radial and ulnar styloid processes and the medial and lateral epicondyles are superimposed.

The lower end of the humerus and the hand are immobilized using sandbags.

Direction and Centering of X-ray Beam

The vertical central ray is centred in the midline of the forearm to a point midway between the wrist and elbow joints.

Essential image characteristics

Both the elbow and the wrist joint must be demonstrated on the image.

Both joints should be seen in the true lateral position, with the radial and ulnar styloid processes and the epicondyles of the humerus superimposed.

Note

In trauma cases, it may be impossible to move the arm into the positions described, and a modified technique may need to be employed to ensure that diagnostic images are obtained.

• If the limb cannot be moved through 90°, then a horizontal beam should be used
• Both joints should be included on each image.

No attempt should be made to rotate the patient’s hand.

Radiological considerations

When two or more bones such as the radius and ulna form a ring, fracture of one of the bones is often associated with fracture or dislocation elsewhere in the ring, especially if the fracture is displaced or the bone ends overlap.

In Galeazzi fracture there is a fracture of the radius with dislocation of the distal ulna, while in Monteggia fracture there is fracture of the ulna with dislocation of the head of the radius.

In forearm fracture, therefore, both ends of both bones, as well as the proximal and distal radio-ulnar joints, must be demonstrated.

Basic forearm projections do not give adequate views of the elbow and should not be relied upon for diagnosis of radial head injury.

If an elbow joint effusion is shown, formal projections of the elbow joint will be required.