Anatomy
- Digits (Phalanges): Four fingers each contain three phalanges (proximal, middle, distal), while the thumb (first digit) has only two (proximal and distal). Each phalanx has a base, body (shaft), and head.
The interphalangeal (IP) joints connect adjacent phalanges and allow flexion and extension.
- Metacarpals: Five metacarpals (1–5) form the palm of the hand. Each includes a base, shaft, and head, articulating proximally with the carpals and distally with the phalanges at the metacarpophalangeal (MCP) joints. The first metacarpal is shorter and more mobile, forming the first carpometacarpal (CMC) joint that permits thumb opposition.
- Carpals: Eight carpal bones arranged in two rows (proximal and distal):
- Proximal row (lateral to medial): Scaphoid, Lunate, Triquetrum, Pisiform
- Distal row (lateral to medial): Trapezium, Trapezoid, Capitate, Hamate
- Mnemonic: “Some Lions Try Pouncing Toward The Curious Hippo.”
- The scaphoid is the most frequently fractured carpal.
- The hamate has a prominent hook, best seen on oblique or carpal tunnel projections.
- The lunate commonly dislocates anteriorly in wrist trauma.
- The pisiform, a sesamoid bone, overlies the triquetrum on PA views.
- Distal Forearm: The radius (lateral/thumb side) and ulna (medial/little finger side) articulate with the carpals to form the radiocarpal (wrist) joint. The radius articulates with the scaphoid and lunate, while the ulna connects indirectly via the triangular fibrocartilage complex (TFCC), which stabilizes and cushions the wrist.
- Joint Classification:
- Interphalangeal (IP) – hinge (diarthrodial)
- Metacarpophalangeal (MCP) – condyloid (diarthrodial)
- Carpometacarpal (CMC) – saddle for thumb, gliding for digits 2–5
- Intercarpal and radiocarpal joints – gliding and ellipsoidal types respectively
Common Pathologies
- Fractures:
- Boxer’s fracture – transverse fracture of the fifth metacarpal neck, often with volar angulation.
- Bennett’s fracture – intra-articular fracture at the base of the first metacarpal.
- Colles’ and Smith’s fractures – distal radius fractures that may extend into the wrist; both can affect hand alignment.
Exposure adjustment: may require increased mAs to penetrate immobilization materials (casts or splints).
- Arthritis:
- Osteoarthritis – degenerative narrowing of joint spaces with osteophyte formation.
- Rheumatoid arthritis – soft-tissue swelling, periarticular erosion, ulnar deviation of digits.
- Soft-tissue injury:
- Foreign body detection – metal, glass, or wood fragments localized with high-detail, low-kVp techniques.
- Infection (osteomyelitis) – bone destruction or periosteal reaction; requires high contrast for detection.
PA Hand
CR Location & Positioning
- SID: 40″
- Patient position: Seated at table, forearm resting on table.
- Adjustments: Palmar surface flat on IR, fingers slightly spread, MCP joints centered, long axis of hand aligned with IR.
- CR: Perpendicular to 3rd MCP joint.
- Pt. Instructions: Relax hand, remain still.
- Exposure: 55–65 kVp, low mAs; suspend motion.
Evaluation Criteria
- Coverage: Entire hand, wrist, and 1″ of distal forearm.
- Rotation checks: Equal concavity of phalangeal/metacarpal shafts; equal soft tissue margins; equal spacing between metacarpal heads.
- Motion checks: Sharp trabecular detail, open MCP/IP joints.
- Technique checks: Contrast sufficient for bony and soft tissue detail.
- Clinical aim: Baseline view for fractures, dislocations, arthritis, and alignment.
PA Oblique Hand
CR Location & Positioning
- SID: 40″
- Patient position: Seated at table, forearm on table.
- Adjustments: Palm down, rotate hand laterally until MCP joints form 45° angle with IR; use foam wedge for support.
- CR: Perpendicular to 3rd MCP joint.
- Pt. Instructions: Keep fingers extended or supported.
- Exposure: As for PA.
Evaluation Criteria
- Coverage: Entire hand, wrist, and 1″ of distal forearm.
- Rotation checks: Slight overlap of 3rd–5th metacarpal heads; no overlap of 2nd–3rd; minimal overlap of bases; open MCP/IP joints.
- Motion checks: Sharp trabecular markings, no blur.
- Technique checks: Good contrast to visualize soft tissue and trabecular detail.
- Clinical aim: Detect fractures, pathology of metacarpals, and evaluate joint spaces.
Lateral Hand (Extension or Fan)
CR Location & Positioning
- SID: 40″
- Patient position: Seated at table, forearm on table, ulnar side down (or radial side if needed).
- Adjustments: Hand lateral, fingers extended. For fan lateral, digits spread with support to eliminate phalangeal overlap.
- CR: Perpendicular to 2nd MCP joint.
- Pt. Instructions: Hold position, remain still.
- Exposure: 55–65 kVp, suspend motion.
Evaluation Criteria
- Coverage: Entire hand, wrist, and 1″ of distal forearm.
- Rotation checks:
- Extension lateral: Superimposed phalanges, metacarpals, distal radius/ulna.
- Fan lateral: Superimposed metacarpals, separated phalanges.
- Motion checks: Sharp trabecular markings.
- Technique checks: Adequate detail to evaluate bone and soft tissue.
- Clinical aim: Evaluate displacement of fractures and detect foreign bodies.
Supplemental Projections
Lateral Hand – Lateromedial in Flexion
CR Location & Positioning
- SID: 40″
- Patient position: Seated at table, ulnar side down.
- Adjustments: Digits naturally flexed, superimposed; thumb positioned parallel to IR.
- CR: Perpendicular to 2nd MCP joint.
- Pt. Instructions: Relax hand.
- Exposure: Same as PA.
Evaluation Criteria
- Superimposed phalanges, metacarpals, and distal radius/ulna.
- Thumb free of superimposition.
- Flexed digits show fracture displacement in natural resting position.
AP Oblique Hands – Norgaard Method (Ball-Catcher’s)
CR Location & Positioning
- SID: 40″
- Patient position: Seated, both hands placed together.
- Adjustments: Hands half-supinated, resting on 45° sponges; fingers extended or cupped (“ball-catcher’s” position).
- CR: Perpendicular, midway between both MCP joints.
- Pt. Instructions: Remain still.
- Exposure: Low kVp (60–65) for detail.
Evaluation Criteria
- Both hands from carpals through digits.
- Metacarpal heads and phalangeal bases free of superimposition.
- Excellent bone and soft tissue detail.
- Clinical aim: Early rheumatoid arthritis detection; 5th metacarpal base fractures.
Anatomy
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What carpals articulate with the metacarpals?
The trapezium articulates with the 1st metacarpal, the trapezoid with the 2nd, the capitate with the 3rd, and the hamate with the 4th and 5th metacarpals — forming the carpometacarpal (CMC) joints.
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What type of joint are the MCP joints?
Synovial, condyloid-type joints that allow flexion, extension, abduction, and adduction.
- What type of joints are the interphalangeal (IP) joints?
Synovial hinge joints permitting flexion and extension.
Positioning
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Why is the hand placed flat with fingers spread for PA?
To prevent overlap of soft tissue and to open joint spaces.
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Why is the hand rotated 45° for the oblique?
To demonstrate the metacarpals without superimposition and show fractures/pathology.
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Why is a foam wedge used for the oblique?
To keep fingers parallel to the IR and avoid foreshortening.
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Why is a fan lateral used instead of an extension lateral?
To separate the phalanges for evaluation of fractures.
Technique & Image Evaluation
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How can you tell the PA hand was not rotated?
Equal concavity of shafts of phalanges and metacarpals, equal soft tissue margins, and equal spacing of metacarpal heads.
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How do you know the hand was flat on the IR?
Open IP and MCP joint spaces.
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How can you tell if the oblique rotation is correct?
Minimal overlap of 3rd–5th metacarpals; 2nd and 3rd metacarpals not overlapped.
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How do you confirm true lateral?
Superimposed metacarpals and distal radius/ulna; in fan lateral, separated phalanges.
Clinical Applications
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Why is the Norgaard (ball-catcher’s) view performed?
To detect early rheumatoid arthritis changes before lab tests are positive.
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Why is a lateral hand important in trauma?
It demonstrates displacement of fractures and helps localize foreign bodies.
