Upper Extremity Radiography: Hand, Wrist & Forearm Positioning
Introduction
Upper extremity radiography of the hand, wrist, and forearm is a high-frequency topic on the ARRT Radiography exam. These studies require precise positioning, appropriate low-kVp technique, and attention to evaluation criteria to demonstrate fine bony detail and open joint spaces.
Definition: Upper extremity radiography refers to non-grid, detail-screen imaging of the hand, wrist, and forearm using low kVp technique to maximize contrast and resolve fine trabecular bone structure.
Key exam priorities for this topic include:
- Correct central ray (CR) placement for each projection
- Recognizing positioning errors such as rotation and improper centering
- Selecting appropriate technical factors for small-part extremity imaging
- Identifying fracture patterns and special projections tested on the ARRT exam
Exam Tip: Extremity radiography does not require a grid due to small part size. Always use a detail (extremity) screen or digital direct capture to maximize spatial resolution.
Technical Factors & Equipment
Definition: Technical factors for extremity imaging are optimized for high-contrast, high-resolution images of small bones with minimal soft tissue thickness.
Standard technical parameters:
| Parameter | Value |
|---|---|
| SID | 40 inches (102 cm) |
| kVp range | 50–65 kVp |
| Grid | Not required (small part size) |
| Receptor | Detail (extremity) screen or digital direct capture |
| Collimation | Tight to area of interest |
Using low kVp (50–65 kVp) increases subject contrast, which is essential for visualizing fine trabecular bone patterns and subtle fracture lines. Proper bone trabecular pattern visualization on the image confirms correct exposure.
Radiation Protection: Apply tight collimation to the area of interest on every extremity study. Use gonadal shielding when the gonads are within 5 cm of the primary beam edge.
Common Errors:
- Using a grid unnecessarily — increases dose without benefit for small extremities
- Selecting kVp above 65 kVp — reduces contrast and obscures fine bone detail
- Inadequate collimation — increases scatter and patient dose
Hand, Wrist & Forearm Positioning
Definition: Hand radiography routinely includes PA, oblique, and lateral projections to demonstrate the phalanges (proximal, middle, distal), metacarpals, and carpal bones in multiple planes.
PA Projection — Hand
- Patient seated at table; hand placed flat (pronated) on the IR with fingers extended
- Central ray (CR): perpendicular, directed to the third metacarpophalangeal (MCP) joint
- Evaluation criteria: all phalanges and metacarpals visualized without rotation; joint spaces open; soft tissue included
Oblique Projection — Hand
- Hand rotated 45 degrees from the PA position (lateral oblique)
- CR directed to the third MCP joint
- Demonstrates the metacarpals and phalanges free of superimposition
Lateral Projection — Hand
- Hand in true lateral position; fingers extended or fanned
- CR directed to the second MCP joint
- Used to assess anterior/posterior displacement of fractures
Positioning Trap: On the PA hand, if the hand is not fully flat and pronated, the metacarpals will appear rotated and joint spaces will be closed — a common ARRT-tested error.
Special Projection — Ball-Catcher View (Norgaard Method)
- Both hands in 45-degree oblique position, palms up, fingers slightly flexed (as if catching a ball)
- Used for early detection of rheumatoid arthritis — demonstrates erosions at the radial aspect of the proximal phalanges
Definition: Wrist radiography demonstrates the eight carpal bones — scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, and hamate — as well as the distal radius and ulna.
PA Projection — Wrist
- Hand pronated, wrist flat on IR
- CR directed perpendicular to the midcarpal region
- Demonstrates all carpal bones, distal radius, and ulna
Lateral Projection — Wrist
- Wrist in true lateral position (ulnar surface down)
- CR directed to the wrist joint
- Landmarks: ulnar styloid and radial styloid are key evaluation structures on the lateral wrist
Scaphoid View (Ulnar Deviation)
- PA projection with the wrist in ulnar deviation
- CR angled 10–15 degrees proximally (toward the elbow) or perpendicular depending on protocol
- Isolates the scaphoid bone by opening the scaphoid waist and reducing foreshortening
- Critical for detecting scaphoid fractures, which may be occult on standard PA
Carpal Tunnel View
- Wrist in extreme dorsiflexion; CR directed through the carpal tunnel at an angle
- Demonstrates the carpal bones in profile (floor of the carpal tunnel)
- Visualizes the pisiform, hamate hook, trapezium, and scaphoid tubercle
Positioning Trap: Failing to place the wrist in ulnar deviation for the scaphoid view will result in foreshortening of the scaphoid — a frequently tested ARRT error. The scaphoid is the most commonly fractured carpal bone.
Definition: Forearm radiography demonstrates the radius and ulna in their entirety, including the radial head, neck, and tuberosity proximally and the styloid processes distally.
AP Projection — Forearm
- Elbow fully extended; forearm supinated (palm up)
- CR directed perpendicular to the midforearm
- Both the wrist and elbow joints must be included on the image
- Demonstrates radius and ulna without superimposition
Lateral Projection — Forearm
- Elbow flexed 90 degrees; forearm in true lateral position
- CR directed perpendicular to the midforearm
- Radius and ulna will be partially superimposed — this is normal and expected
Positioning Trap: On the AP forearm, if the elbow is not fully extended and the forearm is not fully supinated, the radius and ulna will cross, obscuring fractures — a classic ARRT-tested error. The radial head, neck, and tuberosity are important landmarks to confirm proper positioning.
Fat Pad Sign: Elevation of the anterior or posterior fat pad on a lateral elbow/forearm image indicates joint effusion, often associated with an occult fracture. This is a key radiographic sign tested on the ARRT exam.
Fractures & Radiographic Anatomy
Definition: Recognizing classic fracture patterns and their associated projections is a high-yield ARRT exam topic for upper extremity radiography.
| Fracture | Location | Key Feature |
|---|---|---|
| Colles Fracture | Distal radius | Dorsal (posterior) displacement; dinner fork deformity |
| Bennett Fracture | Base of the first metacarpal | Intra-articular fracture at the thumb CMC joint |
| Boxer Fracture | Neck of the fifth metacarpal | Volar angulation of the metacarpal head |
| Scaphoid Fracture | Scaphoid waist | May be occult on initial PA; ulnar deviation view required |
Radiographic Anatomy Landmarks:
- Radial styloid and ulnar styloid: distal landmarks on lateral wrist
- Radial head, neck, and tuberosity: proximal radius landmarks on forearm AP
- Carpal bones (8 total): Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate — mnemonic: "Some Lovers Try Positions That They Can't Handle"
Exam Tip: The scaphoid is the most commonly fractured carpal bone and is at risk for avascular necrosis if missed. Always obtain an ulnar deviation view when scaphoid fracture is clinically suspected.
Key Concepts Summary
KEY CONCEPTS — Test-Ready Recall
- No grid required for hand, wrist, or forearm — small part size eliminates the need; use detail screens or digital direct capture
- Technical factors: 50–65 kVp, low mAs, 40-inch SID for all upper extremity studies
- CR placement: Hand PA → 3rd MCP joint; Wrist PA → midcarpal region; Forearm AP → midforearm
- Oblique hand is taken at 45 degrees; forearm lateral requires elbow flexed at 90 degrees
- Ulnar deviation is required for the scaphoid view — failure to deviate causes foreshortening
- Rotation and failure to fully supinate the forearm on AP will cause radius/ulna crossover — a critical positioning error
- Fractures: Colles = distal radius; Bennett = base of 1st metacarpal; Boxer = 5th metacarpal neck
- Fat pad sign on lateral view = joint effusion, possible occult fracture
- Ball-catcher view (Norgaard) = early rheumatoid arthritis; Carpal tunnel view = carpal bones in profile
- Gonadal shielding when gonads are within 5 cm of the primary beam; tight collimation always
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