Elbow

ELBOW

INRODUCTION

Optimum projections of the elbow joint are obtained when the upper arm is in the same plane as the forearm.

For many examinations, the patient will be seated at the table with the shoulder lowered, so that the upper arm, elbow and forearm are on the same horizontal level.

Elbow

To gain the patient’s confidence, the lateral projection is taken first, because the patient will find it easier to adopt this position.

The humerus must be rotated through 90° to make sure that two projections at right-angles are obtained of the humerus as well as the ulna and radius.

Alternatively, if the limb cannot be moved, two projections at right-angles to each other can be taken by keeping the limb in the same position and moving the tube through 90° between projections.

If the patient cannot extend the elbow fully, modified positioning is necessary for the antero-posterior projection.

Note

Special care should be taken with a child suspected of having a supracondylar fracture of the humerus.

Modified projections must be obtained without moving the arm from the collar and cuff that should be used to immobilize the arm.

1.LATERAL

• Position of Patient and Image Receptor

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

The elbow is flexed to 90 degrees and the palm of the hand is rotated so that it is at 90 degrees to the tabletop.

The shoulder is lowered so that it is at the same height as the elbow and wrist, such that the medial aspect of the entire arm is in contact with the tabletop.

The image receptor is placed under the patient’s elbow, with its centre to the elbow joint.

The limb is immobilized using sandbags.

Direction and Centring of X-ray Beam

The vertical central ray is centered over the lateral epicondyle of the humerus.

Essential Image Characteristics

The central ray must pass through the joint space at 90 degrees to the humerus, i.e. the epicondyles should be superimposed.

The image should demonstrate the distal third of humerus and the proximal third of the radius and ulna.

Notes

Care should be taken when a supracondylar fracture of the humerus is suspected. In such cases, no attempt should be made to extend the elbow joint, and a modified technique must be employed

RADIOGRAPHIC ANATOMY -LATERAL

2.Antero-posterior

• Position of Patient and Image Receptor

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

The arm is extended fully, such that the posterior aspect of the entire limb is in contact with the tabletop and the palm of the hand is facing upwards.

The image receptor is positioned under the elbow joint.

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

The limb is immobilized using sandbags.

Direction and Centering of X-ray Beam

The vertical central ray is centered through the joint space 2.5 cm distal to the point midway between the medial and lateral epicondyles of the humerus.

Essential Image Characteristics

The central ray must pass through the joint space at 90 degrees to the humerus to provide a satisfactory view of the joint space.

The image should demonstrate the distal third of humerus and the proximal third of the radius and ulna.

RADIOGRAPHIC ANATOMY-AP

Notes

When the patient is unable to extend the elbow to 90 degrees, a modified technique is used for the antero-posterior projection.

If the limb cannot be moved, two projections at right-angles to each other can be taken by keeping the limb in the same position and rotating the X-ray tube through 90 degrees.

MODIFIED TECHNIQUE ELBOW

These projections may be useful in cases of trauma when the patient is unable to extend the elbow joint.

These are ;

• Forearm in contact with image receptor fosuspected radial head and olecranon fractures.
• Upper arm in contact with image receptor for suspectedsupracondylar fractures.

Axial projection when the patient cannot extend their arm to any extent.

1.Antero-posterior – partial flexion

Adaptation of technique

If the patient is unable to extend the elbow fully, the positioning for the AP projection may be modified.

For a general survey of the elbow, or if the main area of interest is the proximal end of the radius and ulna, then the posterior aspect of the forearm should be in contact with the image detector.

If the main area of interest is the distal end of the humerus, however, then the posterior aspect of the humerus should be in contact with the image detector.

If the elbow is immobilized in the fully flexed position, then an axial projection must be used instead of the AP projection.

Notes

In both of the above cases, some superimposition of the bones will occur. However, gross injury and general alignment can be demonstrated.

a.Antero-posterior – forearm in

• contact
• Position of patient and image receptor

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

The posterior aspect of the forearm is placed on the table, with the palm of the hand facing upwards.

The image receptor is placed under the forearm, with its centre under the elbow joint.

The arm is adjusted such that the medial and lateral epicondyles of the humerus are equidistant from the image receptor.

The limb may be supported and immobilised in this position.

Direction and location of X-ray beam

The collimated vertical beam is centered in the midline of the forearm 2.5 cm distal to the crease of the elbow.

Essential image characteristics

The image should demonstrate the distal 1/3 of humerus and the proximal 1/3 of the radius and ulna

b.Antero-posterior – upper arm in

• contact
• Position of patient and imaging receptor

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

The posterior aspect of the humerus is placed on the table, with the palm of the hand facing upwards.

• The image receptor is placed under the forearm, with its centre under the elbow joint.
• The arm is adjusted such that the medial and lateral epicondyles
• of the humerus are equidistant from the image receptor.
• The limb may be supported and immobilised in this position.

Direction and location of X-ray beam

The collimated vertical beam is centered midway between the epicondyles of the humerus.

Essential image characteristics

The image should demonstrate the distal 1/3 of humerusand the proximal 1/3 of the radius and ulna.

2.Antero-posterior – full flexion

When the patient’s elbow is immobilized in full flexion, an axial projection may be substituted for the AP projection.

It is preferable for the patient’s upper arm to be in contact with the image receptor for examination of the distal end of the humerus and olecranon process of the ulna, and for the forearm to be in contact with the image receptor if the proximal ends of the radius and ulna are to be examined.

In either of these cases, the bones of the forearm will be superimposed on the humerus. However, gross injury and general alignment can be demonstrated.

a.Axial – upper arm in contact

• Position of patient and image receptor
• The patient is seated alongside the table, with the affected side nearest to the table.

The elbow is fully flexed, and the palm of the hand is facing the shoulder.

The posterior aspect of the upper arm is placed on the image receptor, with the arm parallel to the long axis of the image detector.

The patient’s trunk is adjusted in order to bring the medial and lateral epicondyles of the humerus equidistant to the image detector.

Direction and location of X-ray beam

The collimated vertical beam is centred:

For the lower end of the humerus and the olecranon process of ulna, the vertical central ray is centered 5 cm distal to the olecranon process.

For the proximal ends of the radius and ulna, including the radio-humeral joint, the central ray is directed at right-angles to the forearm and centred 5 cm distal to the olecranon process.

Essential image characteristics

The image will include the olecranon process and the proximal 1/3 of the radius and ulna superimposed on the lower 1/3 of the humerus.

The exposure should be adequate to visualise all three bones.

b.Axial – forearm in contact

• Position of patient and image receptor
• The patient is seated alongside the table, with the affected side nearest to the table.

The elbow is fully flexed, and the palm of the hand is facing the upwards.

The forearm is fully supinated, with the posterior aspect of the forearm resting on the image detector and the arm parallel to the long axis of the image detector.

The patient’s trunk is adjusted in order to bring the medial and lateral epicondyles of the humerus equidistant to the image detector.

Direction and location of X-ray beam

The collimated vertical beam is centered:

For the proximal ends of the radius and ulna and the radiohumeral joint to a point on the posterior aspect of the upper arm 5 cm proximal to the olecranon process.

For the lower end of the humerus and the olecranon process of the ulna to a point at right-angles to the upper arm 5 cm proximal to the olecranon process.

Other elbow views

Lateral head of radius

The elbow is positioned as for the lateral elbow. The hand is then moved through different degrees of rotation, enabling visualization of small fissure fractures through the head of the radius.

Position of patient and image receptor

For the first projection, the patient is positioned as for a lateral elbow projection, with the palm of the hand vertical.

The forearm may be immobilized using a sandbag.

For the second exposure, the upper arm and elbow are maintained in the same position, whilst the hand is rotated medially until the palm of the hand rests on the table.

The forearm may be immobilised using a sandbag.

For the third exposure, the upper arm and elbow are maintained in the same position, whilst the hand is rotated further medially, until the palm of the hand is vertical, facing away from the body.

The forearm may be immobilized using a sandbag.

Direction and location of X-ray beam

The collimated vertical beam is centred to the lateral epicondyle of the humerus for all projections.

Essential image characteristics

The elbow joint should be seen in the true lateral position in each projection.

Sufficient detail of bony trabeculae should be demonstrated to enable fine fractures to be detected.

Proximal radio-ulnar joint – oblique

• Position of patient and image receptor

The patient is positioned for an anterior projection of the elbow joint.

The image receptor is positioned under the elbow joint, with the long axis parallel to the forearm The humerus is then rotated laterally (or the patient leans towards the side under examination) until the line between the epicondyles is approximately 20° to the image receptor.

The forearm may be immobilised using a sandbag.

Direction and location of X-ray beam

The collimated vertical beam is centered 2.5 cm distal to a midpoint between the epicondyles.

Essential image characteristics

The image should demonstrate clearly the joint space between the radius and the ulna.

Ulnar groove – axial

The ulnar groove through which the ulnar nerve passes lies between the medial epicondyle and the medial lip of the trochlear of the humerus and is a possible site for ulnar nerve compression.

A modified axial projection with the elbow joint fully flexed demonstrates the groove and any lateral shift of the ulna, which would lead to tightening of the ligaments overlying the ulnar nerve.

Position of patient and image receptor

The patient is seated alongside the X-ray table, with the affected side nearest the table.

The elbow is fully flexed, and the posterior aspect of the upper arm is placed in contact with the tabletop.

• The image detector is positioned under the lower end of the

humerus, with its centre midway between the epicondyles of the humerus.

With the elbow still fully flexed, the arm is externally rotated through 45° and supported in this position.

Direction and location of X-ray beam

The collimated vertical beam is centred over the medial epicondyle of the humerus.

Essential image characteristics

• The image should be exposed to show the ulnar groove.
• Note

A well-collimated beam is used to reduce degradation of the image

Radiological considerations

An effusion is a useful marker of pathology and may be demonstrated in trauma, infection and inflammatory conditions.

It is seen as an elevation of the fat pads anteriorly and posteriorly and requires a good lateral projection with no rotation.

It may be an important clue to otherwise occult fracture of the radial head or a supracondylar fracture of the humerus.

Radial head fracture may be nearly or completely occult, showing as the slightest cortical infraction or trabecular irregularity at the neck or just a joint effusion.

Avulsion of one of the epicondyles of the humerus may be missed if the avulsed bone is hidden over other bone or in the olecranon or coronoid fossae.

Recognition of their absence requires knowledge of when and where they should be seen.