Digits and Hand Radiographic Positioning Flashcards

DIGITS and HAND by Brey

Second to Fifth Digit Radiography

Radiography of the fingers typically uses an 8 x 10 IR size, either lengthwise or crosswise, depending on the number of images. The patient is usually seated at the end of the radiographic table.

PA Projection

  • Part Position: 

    • Digits extended with the palmar surface down, slightly separated.

    • The PIP joint of the affected digit is centered to the IR.

    • Gonads should be shielded.

  • Central Ray (CR): Perpendicular to the PIP joint of the affected digit, with collimation to the digit under examination.

  • Evaluation Criteria:

    • No rotation of the digit.

    • Concavity of phalangeal shafts and equal soft tissue on both sides.

    • Entire digit from fingertip to distal metacarpal.

    • No soft tissue overlap from adjacent digits.

    • Open interphalangeal (IP) and metacarpophalangeal (MCP) joint spaces without bone overlap.

Lateral Projection (Lateromedial or Mediolateral)

  • Part Position: The digit to be examined is extended, while other digits are closed into a fist. The elbow is supported.

    • For the 2nd to 3rd digit: Hand rested on the lateral/radial surface.

    • For the 4th to 5th digit: Hand rested on the medial/ulnar surface.

    • Elevate the 3rd and 4th digits to be parallel with the IR.

    • The PIP joint is centered to the IR. The extended digit should be immobilized (e.g., with tape, tongue depressor). Shield gonads.

  • Central Ray (CR): Perpendicular to the PIP joint of the affected digit, with collimation to the digit under examination.

  • Evaluation Criteria:

    • Entire digit in a true lateral position.

    • Concave, anterior surfaces of the phalanges.

    • No rotation of the phalanges.

    • No obstruction of the proximal phalanx or MCP joint by adjacent digits.

    • Open interphalangeal joint spaces.

PA Oblique Projection (Lateral Rotation)

  • Part Position: 

    • Forearm on the table, hand pronated. Rotate the hand externally until digits are separated and supported on a 45-degree foam wedge. 

    • Shield gonads. 

    • For the second digit, some radiographers may rotate it medially from the prone position for better detail and fracture visibility.

  • Central Ray (CR): Perpendicular to the PIP joint of the affected digit, with collimation to the digit under examination.

  • Evaluation Criteria:

    • Entire digit rotated at a 45-degree angle, including the distal portion of the adjoining metacarpal.

    • No superimposition of adjacent digits over the proximal phalanx or MCP joint.

    • Open IP and MCP joint spaces.

    • Clear soft tissue and bony trabeculation.

First Digit (Thumb) Radiography

AP Projection

  • Patient Position: Seated at the end of the table with the arm internally rotated.

  • Part Position: 

    • Rest the thumb on the IR. 

    • Extended digits are held back with tape or the opposite hand.

    • The long axis of the thumb is parallel with the long axis of the IR.

  • Central Ray (CR): Perpendicular to the MCP joint.

PA Projection

  • Patient Position: Seated at the end of the table with the hand resting on its medial surface.

  • Part Position: 

    • The elevated and abducted thumb rests on a radiographic support or is held by a radiolucent stick, leading to magnification. 

    • The dorsal surface of the digit is parallel with the IR. The MCP joint is centered to the IR.

  • Central Ray (CR): Perpendicular to the MCP joint.

Evaluation Criteria (AP/PA Projection - Thumb)

  • No rotation (concavity of phalangeal and metacarpal shafts).

  • Area from distal tip of thumb to trapezium.

  • Open IP and MCP joint spaces without bone overlap.

  • Overlap of soft tissue profile of the palm over the midshaft of the first metacarpal.

  • Clear soft tissue and bony trabeculation.

  • PA projection of the thumb is magnified compared to AP.

Lateral Projection

  • Patient Position: Seated at the end of the table, hand relaxed on the IR.

  • Part Position: 

    • Hand in natural arched position, palmar surface down, fingers flexed or resting on a sponge. 

    • The IR is centered to the MCP joint. Adjust hand arching for a true lateral position of the thumb.

  • Central Ray (CR): Perpendicular to the MCP joint.

  • Evaluation Criteria:

    • First digit in a true lateral projection.

    • Concave, anterior surface of the proximal phalanx.

    • No rotation of the phalanges.

    • Area from distal tip of thumb to trapezium.

    • Open interphalangeal and MCP joint spaces.

    • Clear soft tissue and bony trabeculation.

PA Oblique Projection

  • Patient Position: Seated at the end of the table, palm resting on the IR.

  • Part Position: 

    • Thumb abducted with palmar surface in contact with the IR. 

    • Ulnar deviate the hand slightly. 

    • Align the longitudinal axis of the thumb with the long axis of the IR.

  • Central Ray (CR): Perpendicular to the MCP joint.

  • Evaluation Criteria:

    • Proper rotation of phalanges, soft tissue, and first metacarpal.

    • Area from distal tip of thumb to trapezium.

    • Open interphalangeal and MCP joint spaces.

    • Clear soft tissue and bony trabeculation.

Specialized Thumb Projections

Robert Method (1st Carpometacarpal Joint)

This method, originally described by Robert in 1936 and later modified, demonstrates the first CMC joint free of superimposition. It is useful for arthritic changes, fractures (including Bennett's fracture), and displacement. It does not replace initial AP/PA thumb projections.

  • Patient Position: 

    • Seated at the end of the table. 

    • The entire limb must be on the same plane.

  • Part Position: 

    • Limb extended and internally rotated, with the posterior aspect of the thumb against the IR. 

    • Hand hyperextended to prevent soft tissue obscuring the CMC joint. 

    • Patient may hold fingers back.

  • Central Ray (CR) Modifications:

    • Robert Method: Perpendicular, entering the first CMC joint.

    • Long and Rafert Modification: Angled 15 degrees proximally to the long axis of the thumb, entering the first CMC joint.

    • Lewis Modification: 10-15 degrees proximally along the axis of the thumb, entering the first MCP joint.

    • Note: Angulation helps project soft tissue away and open the joint space.

  • Structures Shown: First CMC joint free of superimposition.

  • Evaluation Criteria: 

    • First CMC joint free of superimposition.

    • First metacarpal with the base in convex profile.

    • Trapezium.

Burman Method (AP Projection First Carpometacarpal Joint)

When wrist hyperextension is not contraindicated, this method provides a clearer, magnified image of the first CMC joint, offering a greater field of view of its concavoconvex aspect. Recommended SID is 18 inches.

  • Patient Position: Seated at the end of the table. Forearm approximately parallel to the long axis of the IR.

  • Part Position: 

    • IR under the wrist, centering the first CMC joint. 

    • Hyperextend the hand, holding the position with the opposite hand or a bandage. 

    • Internally rotate the hand and abduct the thumb to be flat on the IR.

  • Central Ray (CR): Through the first CMC joint at a 45-degree angle toward the elbow.

  • Structures Shown: Magnified concavoconvex outline of the first CMC joint.

  • Evaluation Criteria: 

    • First metacarpal.

    • Trapezium in concave profile.

    • Base of the first metacarpal in convex profile.

    • First CMC joint unobscured.

Folio Method (PA Projection First Metacarpophalangeal Joint)

This projection is useful for diagnosing ulnar collateral ligament (UCL) rupture in the thumb's MCP joint (skier's thumb or gamekeeper's thumb).

  • Patient Position: Seated at the end of the table.

  • Part Position: 

    • Both hands placed on the cassette on their medial aspects. 

    • A rubber band is tightly wrapped around the distal portion of both thumbs, and medical tape is placed between the first metacarpals. 

    • Thumbs remain in the PA plane. 

    • Patient instructed to pull thumbs apart just before exposure.

  • Central Ray (CR): Perpendicular to a point midway between both hands at the level of the MCP joint.

  • Structures Shown: MCP joints and metacarpal phalangeal angle bilaterally.

  • Evaluation Criteria: 

    • No rotation of thumbs

    • First metacarpals, diagnostic image of the first MCP joint

    • Correct positioning of rubber band and tape

    • Thumbs centered.

Hand Radiography

PA Projection

  • Patient Position: Seated at the end of the table, forearm resting on the table.

  • Part Position: 

    • Hand pronated. 

    • Center the IR to the MCP joints, aligning the long axis of the IR parallel with the long axis of the hand and forearm. 

    • Fingers are slightly spread.

  • Central Ray (CR): Perpendicular to the third MCP joint.

  • Structures Shown: 

    • PA projections of carpals, metacarpals, phalanges (except thumb), interarticulations, and distal radius and ulna. 

    • Also shows a PA oblique projection of the first digit.

  • Evaluation Criteria:

    • No rotation of the hand.

    • Open MCP and IP joints (hand flat on IR).

    • Slightly separate digits with no soft tissue overlap.

    • All anatomy distal to the radius and ulna.

    • Note: AP projection can be used for metacarpals if the hand cannot be extended.

PA Oblique Projection (Lateral Rotation)

  • Part Position: 

    • From pronation, adjust hand obliquity so MCP joints form a 45-degree angle with the IR (using a 45-degree foam wedge). 

    • Rotate hand laterally (externally) until fingertips touch the IR. 

    • Elevating the index finger and thumb on radiolucent material opens joint spaces and reduces foreshortening.

  • Central Ray (CR): Perpendicular to the third MCP joint.

  • Structures Shown: PA oblique projection of hand bones and soft tissues. Used for fractures and pathological conditions.

  • Evaluation Criteria:

    • Minimal overlap of 3rd-4th and 4th-5th metacarpal shafts.

    • Slight overlap of metacarpal bases and heads.

    • Separation of 2nd and 3rd metacarpals.

    • Open interphalangeal and MCP joints.

    • Slightly separated digits with no soft tissue overlap.

    • All anatomy distal to distal radius and ulna.

  • Additional Oblique Projections:

    • Reverse Oblique: 

      • For severe metacarpal deformities or fractures. 

      • Hand rotated 45 degrees medially (internally) from palm-down.

    • Tangential Oblique (Kallen-recommended): 

      • For metacarpal head fractures. From PA position, MCP joints flexed 75-80 degrees, dorsum of digits on IR. 

      • Hand rotated 40-45 degrees toward ulnar surface, then 40-45 degrees forward until affected MCP joint is projected beyond its proximal phalanx. 

      • CR perpendicular, tangential to the MCP joint of interest.

Lateral Projection (Mediolateral or Lateromedial)

In Extension and Fan Lateral Position

  • Patient Position:

    • Seated at the end of the table, forearm resting on the table. 

    • Hand in lateral position (ulnar/radial aspect down).

  • Part Position: 

    • Digits extended, first digit at a right angle to the palm. 

    • Palmar surface perpendicular to the IR. 

    • Extended digit positions result in superimposition; the fan lateral position eliminates superimposition of all but the proximal phalanges.

  • Central Ray (CR): Perpendicular to the 2nd/5th digit MCP joint.

  • Structures Shown: Lateral projection of the hand in extension for localizing foreign bodies and metacarpal fracture displacement

    • Fan lateral superimposes metacarpals but shows individual phalanges (proximal parts may be superimposed).

  • Note: Lewis recommended rotating the hand 5 degrees posteriorly from true lateral for better visualization of 5th metacarpal fractures. The thumb is extended, hand relaxed, and CR angled parallel to the thumb, entering the midshaft of the 5th metacarpal.

Lateromedial in Flexion

  • Patient Position: 

    • Seated at the end of the table, forearm resting on the table. 

    • Hand in lateral position (ulnar aspect down).

  • Part Position: 

    • Digits relaxed to maintain natural arch, arranged for perfect superimposition. 

    • Patient holds thumb parallel with IR (or immobilize).

  • Central Ray (CR): Perpendicular to the second digit MCP joint.

  • Structures Shown: 

    • Lateral image of bony structures and soft tissues of the hand in their normally flexed position. 

    • Demonstrates anterior or posterior displacement in metacarpal fractures.

Norgaard Method (AP Oblique Projection, Medial Rotation)

Also known as the "ball-catcher's position," this method aids in detecting early radiographic changes for rheumatoid arthritis diagnosis, often before laboratory tests are positive. High-resolution screens and low kVp (60-65) are recommended. It's also used for 5th metacarpal base fractures.

  • Patient Position: 

    • Seated at the end of the table. 

    • Norgaard recommended imaging both hands in a half-supinate position for comparison.

  • Part Position: 

    • Rotate hands to a half-supinate position until the dorsal surface rests against 45-degree sponge supports. 

    • Fingers extended, thumbs abducted slightly. 

    • A modified position involves cupping the fingers as if catching a ball.

  • Central Ray (CR): Perpendicular to a point midway between both hands at the level of the MCP joints.

  • Structures Shown: 

    • AP 45-degree oblique projection of both hands

    • Early changes for rheumatoid arthritis include symmetric, indistinct outline of bone at the dorsoradial insertion of the joint capsule on the proximal end of the first phalanx of the four fingers, along with associated demineralization.

  • Example for RA: Normal thumbs show acceptable MCP joints. Increased angulation of the left MCP joint with a 13-degree difference compared to the right, and a partially torn left UCL at 20 degrees (compared to 7 degrees on the uninjured side), indicate pathology.