Radiology: Essential Projections of Digits

Essential Projections of the Digits, Thumb, and Hand

• All images should be taken with an 18 x 24 cm image receptor (IR).
• Technical factors: mAs 1.6 – 2.5, kVp: 63 – 70.
• Central ray should be perpendicular to the IR for all images.

Digits 2 to 5

• Essential projections: PA, lateral, PA oblique.
• Collimation: 2.5 cm on all sides of the digit, including 2.5 cm proximal to the MCP joint.

PA Digits 2 to 5

• Part position:
  • Extend the digit with the palmar surface in the center of the IR.
  • Center the requested digit in the middle of the IR.
  • Separate the fingers slightly.
  • Long axis of digit aligned parallel.
• CR:
  • Perpendicular to the IR.
  • Enters patient at the PIP joint.
• Evaluation criteria:
  • Proper collimation.
  • No rotation of the phalanges.
  • All three phalanges (distal, middle, proximal) included.
  • Distal end of the metacarpal included.
  • Open IP and MCP joint spaces.
  • No superimposition of digits.
  • Proper technical factors (clear soft tissue and bony trabeculae).
  • Right or left marker included.

Lateral Digits 2 to 5

• Part position:
  • Separate the digit of interest using cotton swab or tape, and fold other digits into a fist.
  • The digit of interest should be centered on the IR.
  • The long axis of the digit should be parallel with the IR.
• Second and third digits positioning:
  • Extended with the lateral surface in contact with the IR (mediolateral projection).
  • Minimizes object image distance (OID).
• Fourth and fifth digits positioning:
  • Extended with the medial surface in contact with the IR (lateromedial projection).
  • Minimizes OID.
• CR:
  • Directed perpendicular to the IR.
  • Enters patient at the PIP joint.
• Evaluation criteria:
  • Proper collimation.
  • No rotation of the phalanges from a true lateral position.
  • All three phalanges (distal, middle, proximal) included.
  • Distal end of the metacarpal included.
  • Open IP joint spaces.
  • No superimposition of digits from the other fingers.
  • Proper technical factors (clear soft tissue and bony trabeculae).
  • Right or left marker included.

PA Oblique Digits 2 to 5

• Part position:
  • Extend the digit with the palmar surface resting on a 45-degree wedge sponge.
  • Separate the digit of interest to prevent soft tissue overlap.
• CR:
  • Perpendicular to the PIP joint of the affected digit.
• Collimation: 2.5 cm on all sides of the digit.
• Evaluation criteria:
  • Proper collimation.
  • Phalanges should appear obliqued.
  • All three phalanges (distal, middle, proximal) included.
  • Distal end of the metacarpal included.
  • Open IP and MCP joint spaces.
  • No superimposition of digits from the other fingers.
  • Proper technical factors (clear soft tissue and bony trabeculae).
  • Right or left marker included.

Thumb

• Essential projections: Anteroposterior (AP), lateral, PA oblique.
• Collimation: 2.5 cm on all sides of the digit, including 2.5 cm proximal to the CMC joint.

AP Thumb

• Part position:
  • Place the hand in extreme internal rotation.
  • The posterior surface of the thumb should be on the IR.
  • Center the MCP joint to the IR.
  • Align the long axis of the thumb parallel to the IR.
  • Separate other digits from the thumb with tape or the opposite hand.
  • Ensure a true AP projection by checking the thumb's position.
• CR:
  • Perpendicular to the MCP joint.
• Evaluation criteria:
  • Proper collimation.
  • Entire thumb to the trapezium included.
  • Concavity of the phalangeal bodies visible.
  • Open IP and MCP joint spaces.
  • Proper technical factors (clear soft tissue and bony trabeculae).
  • Left or right marker included.

PA Thumb (Alternative)

• Center the thumb and CR appropriately to the IR.
• Evaluation criteria is the same as the AP thumb projection.
• Magnification occurs due to the large OID.

Lateral Thumb

• Part position:
  • Palmar surface on the IR.
  • Align the long axis of the thumb parallel to the IR.
  • Center the MCP joint to the unmasked portion of the IR.
  • Rotate the thumb until the lateral surface is on the IR (mediolateral projection).
• CR:
  • Perpendicular to the MCP joint of the thumb.
• Evaluation criteria:
  • Proper collimation.
  • Entire thumb to the trapezium included.
  • No rotation of the phalanges.
  • Open IP and MCP joint spaces.
  • Proper technical factors (clear soft tissue and bony trabeculae).
  • Left or right marker included.

PA Oblique Thumb

• Part position:
  • Palmar surface of the thumb on the IR.
  • Align long axis of thumb parallel.
  • Place a 45-degree wedge sponge under the thumb.
  • Center the MCP joint to the IR.
  • Rotate the thumb 45 degrees.
• CR:
  • Perpendicular to the IR and the MCP joint.
• Evaluation criteria:
  • Proper collimation.
  • Phalanges should appear obliqued.
  • Open IP and MCP joint spaces.
  • Proper technical factors (clear soft tissue and bony trabeculae).
  • Left or right marker included.