Fingers

FINGERS

SESSION: 04

Clinical indications

Fractures and dislocations of the distal, middle, and proximal phalanges; distal metacarpal; and associated joints Pathologic processes, such as osteoporosis and osteoarthritis

BASIC PROJECTION/VIEWS

• Two projections are routinely taken,
• a postero-anterior

a lateral.

The adjacent finger is routinely imaged unless the injury is very localized, e.g. a crush injury to the distal phalanx.

Each image is acquired using an 18cm × 24 cm

Dorsi-palmar (DP)- postero-anterior

Position of patient and image receptor The patient is positioned seated alongside the table as for a postero-anterior projection of the hand.

The forearm is pronated with the anterior (palmer) aspect of the finger(s) in contact with the image receptor.

• The finger(s) are extended and separated.

A sandbag may be placed across the dorsal surface of the wrist for immobilization.

Direction and location of X-ray beam

The collimated vertical beam is centered over the proximal interphalangeal joint of the affected and adjacent finger

PA OF SECOND DIGIT

PA OF FOURTH DIGIT

Essential image characteristics

The image should include the fingertips, including soft tissue, and distal 3rd of the metacarpal bone(s).

It is necessary to include adjacent finger(s), i.e. the 2nd and 3rd or 4th and 5th to aid in identifying the relevant anatomy.

If this is the case, then care should be taken to avoid superimposition, particularly in the lateral projection, by fully extending one finger and partly flexing the other.

PA OF THE FOURTH FINGER

Radiological considerations

The image should include the fingertip and the distal 3rd of the metacarpal bone.

Lateral- index and middle fingers

Position of patient and image receptor The patient is seated alongside the table with the arm abducted and medially rotated to bring the lateral aspect of the index finger into contact with the image detector.

The raised forearm is supported.

The index finger is fully extended and the middle finger slightly flexed to avoid superimposition.

The middle finger is supported on a non-opaque pad.

The remaining fingers are fully flexed into the palm of the hand and held there by the thumb.

Direction and location of X-ray beam

The collimated vertical central ray is centred over the proximal interphalangeal joint of the affected finger.

Essential image characteristics

The image should include the fingertip and the distal 3rd of the metacarpal bone.

Thumb

• Basic projections/VIEWS
• Two projections are routinely taken,
• a lateral
• an antero-posterior.
• Occasionally a postero-anterior may be undertaken
• if the patient is unable to get into position because of a painful fracture

18 × 24 CM CASSETES

Lateral

Position of patient and image receptor The patient is seated alongside the table with the arm abducted, the elbow flexed and the anterior aspect of the forearm resting on the table.

The thumb is flexed slightly and the palm of the hand is placed on the image receptor.

The palm of the hand is raised slightly with the fingers partially flexed and may be supported on a non-opaque pad, such that the lateral aspect of the thumb is in contact with the image receptor.

Direction and location of X-ray beam

The collimated vertical beam is centered over the 1st MCPJ.

Essential image characteristics

The image should include the fingertip and the distal 1/3 of the metacarpal bone.

Where there is a possibility of injury to the base of the 1st metacarpal, the carpo-metacarpal joint must be included on the image.

Antero-posterior (AP)

Position of patient and image receptor The patient is seated facing away from the table with the arm extended backwards and medially rotated at the shoulder.

The hand may be slightly rotated to ensure that the 2nd, 3rd and 4rth metacarpals are not superimposed on the base of the 1st metacarpal.

The patient leans forward, lowering the shoulder so that the 1st metacarpal is parallel to the tabletop.

The image receptor is placed under the wrist and thumb and oriented to the long axis of the metacarpal.

Direction and location of X-ray beam

• The collimated vertical central ray is centred over the

1st MCPJ.

Postero-anterior foreign body

Position of patient and image receptor With the hand in the postero-anterior position, the palm of the hand is rotated through 90° to bring the medial aspect of the hand in contact with the table and the palm vertical.

The image receptor is placed under the hand and wrist, with its long axis along the line of the thumb.

The fingers are extended and the hand is rotated slightly forwards until the anterior aspect of the thumb is parallel to the image receptor.

The thumb is supported in position on a non-opaque pad.

Direction and location of X-ray beam

The collimated vertical beam is centered over the base of the 1st metacarpal.

Note

The use of the postero-anterior projection maintains the relationship of the adjacent bones, i.e. the radius and ulna, which is essential in cases of suspected foreign body in the thenar eminence.

When undertaking a PA projection there is an increased object to detector distance. This will lead to magnification of the image and any associated unsharpness.

To prevent this, increase the focus receptor distance (ffd).

Radiological considerations

Fracture of the base of the 1st metacarpal through the joint surface may be associated with dislocation due to the pull of the abductor and extensor tendons of the thumb. This is known as Bennett’s fracture and may cause functional impairment and early degenerative disease if not corrected.

In contrast, a fracture that does not transgress the articular surface does not dislocate and does not have the same significance (Rolando fracture).