9.1 Hand, Wrist & Forearm
Key Takeaways
- Digit series include PA (or AP for thumb), 45° oblique, and true lateral centered at the appropriate MCP or PIP joint with the entire digit and distal metacarpal included.
- Hand PA and oblique use the third MCP as the centering point; fan lateral separates digits for fracture evaluation, while extension lateral superimposes phalanges for foreign-body localization.
- Wrist PA, 45° oblique, and lateral demonstrate carpal relationships; scaphoid work-ups add ulnar deviation and/or PA axial (Stecher-type) projections to elongate the scaphoid waist.
- Forearm AP (hand supinated) and true lateral must include both the wrist and elbow joints on one image whenever patient size and detector length allow.
- High-yield fractures for RTR critique: Boxer’s (5th metacarpal neck), Colles (distal radius, dorsal fragment displacement), Smith (volar displacement), and scaphoid waist with avascular-necrosis risk.
9.1 Hand, Wrist & Forearm
Quick Answer: Upper-limb general radiography for the RTR candidate is mostly about true planes, correct centering, and including the joints that frame the injury. Digits need PA (or AP for the thumb), 45° oblique, and true lateral. The hand is PA and oblique centered at the 3rd MCP, with fan or extension laterals as indicated. The wrist is PA, oblique, and lateral; scaphoid exams add ulnar deviation and/or PA axial angulation. The forearm is AP with the hand supinated and a true lateral that includes both wrist and elbow. Critique stems often hide a Colles, Smith, Boxer’s, or scaphoid fracture—or a positioning error that would mask one.
General radiography — skeletal (upper limb) sits inside the high-weight clinical procedures / image-analysis cluster of the CAMRT Radiological Technology exam (RTR.3–RTR.6). You will not be graded on artistic beauty; you will be graded on whether the projection demonstrates the anatomy the requisition implies, with markers, collimation, and exposure that support a safe diagnostic decision.
Shared Positioning Principles
- Part parallel to the IR for joints and long bones whenever possible; elevation of the proximal or distal end creates foreshortening.
- CR perpendicular to the IR for standard PA/AP and laterals unless a named axial projection specifies angulation.
- SID typically 100–115 cm (about 40 in) for tabletop extremities; follow department protocol and AEC rules if used (many extremities are manual technique).
- Collimate to the skin margins of the part plus the required joints—tight enough for scatter control and ALARA, wide enough not to clip anatomy.
- Lead markers (R/R or L with side) must be in the primary field but not over critical anatomy; electronic annotation alone is not a substitute for correct side marking practice in competency culture.
- Remove jewelry, watches, and rings when possible; explain why so patients cooperate without feeling rushed.
Immobilization (sponges, tape, sandbags, commercial digit holders) is a care-provider skill as much as a positioning skill: pain, tremor, and pediatric non-cooperation are common. Never force a fracture into “textbook” position—adapt with horizontal-beam laterals and support, then document limitations.
Digits (Fingers 2–5)
| Projection | Patient / part | CR & collimation | Evaluation criteria |
|---|---|---|---|
| PA | Hand pronated, digit extended and flat | Perpendicular to PIP of affected digit; include distal metacarpal | Open IP joints; no rotation (equal concavity of phalangeal shafts); soft tissue and trabeculae visible |
| PA oblique (45°) | Digit rotated 45° (lateral rotation commonly for 2–5; medial optional for 2nd) | Perpendicular to PIP | Open joints; 45° evidenced by twice soft-tissue width on one side of digit |
| Lateral | True lateral of digit; adjacent digits flexed out of way | Perpendicular to PIP | True lateral: fingernail in profile, condyles superimposed; open IP joints |
Exam traps: Centering at the MCP instead of the PIP for a finger series clips the distal tuft or misplaces the field. A “lateral” that is still slightly oblique superimposes fracture lines at the head of the middle phalanx. Always separate the injured digit from its neighbors on the lateral so the soft-tissue and bony margins are not double-exposed by an adjacent finger.
Thumb (1st Digit)
The thumb’s natural plane differs from fingers 2–5. A true AP places the posterior surface of the thumb against the IR (extreme internal rotation of the hand, or reverse positioning with the patient leaning). PA of the thumb increases OID and geometric unsharpness—use only when AP is impossible, and note the limitation.
| Projection | Key setup | CR | Must demonstrate |
|---|---|---|---|
| AP (preferred) | Posterior thumb on IR | 1st MCP | Entire thumb + trapezium; open MCP and IP |
| PA oblique | Natural PA hand often yields ~45° thumb | 1st MCP | Oblique phalanges and MCP without superimposition of other digits |
| Lateral | Hand arched/pronated until thumb is true lateral | 1st MCP | Superimposed phalangeal condyles; first metacarpal and trapezium |
Bennett and Rolando fracture–dislocations at the base of the first metacarpal are clinical reasons departments insist on including the trapezium and carpometacarpal joint—not only the tip of the thumb.
Hand
| Projection | Setup | CR | Evaluation |
|---|---|---|---|
| PA | Palm flat, fingers slightly spread | 3rd MCP | Entire hand + 2–3 cm of distal radius/ulna; open MCP joints; equal soft tissue either side of 2nd–5th metacarpals |
| PA oblique (45°) | From PA, rotate hand laterally 45°; support with sponge | 3rd MCP | Minimal overlap of metacarpal heads/shafts; 3rd–5th metacarpals largely free; open IP joints |
| Lateral (fan) | Ulnar surface down; digits fanned and parallel to IR | 2nd MCP | Phalanges individually demonstrated; metacarpals largely superimposed; radius and ulna superimposed for true lateral wrist relationship |
| Lateral (extension / foreign body) | Digits extended and superimposed | 2nd MCP | Superimposed phalanges; used for localization of foreign bodies and metacarpal alignment |
Fan lateral is the workhorse for phalangeal and metacarpal trauma. Extension lateral is preferred when the clinical question is a foreign body or when the metacarpals—not the separated fingers—are the priority.
Wrist
| Projection | Setup | CR | Evaluation |
|---|---|---|---|
| PA | Hand pronated; fingers slightly flexed to flatten carpus | Midcarpal area | Proximal metacarpals, carpals, distal radius/ulna; open radiocarpal joint; minimal ulnar/radial styloid rotation |
| PA oblique (45°) | Lateral rotation 45° from PA | Midcarpal | Trapezium and scaphoid more open; carpals on radial side demonstrated |
| Lateral | Elbow flexed ~90°; ulnar side down; true lateral forearm | Wrist joint | Superimposed distal radius and ulna; superimposed metacarpals; palmar tilt of radius appreciated |
Scaphoid (navicular) series
The scaphoid is the most frequently fractured carpal bone. Blood supply enters mainly distal to the waist, so waist and proximal-pole fractures risk avascular necrosis and non-union. Standard PA may superimpose the scaphoid on itself; special projections elongate and free it:
- PA ulnar deviation: From PA wrist, evert the hand toward the ulna without lifting the carpus; CR perpendicular to scaphoid (or angled per protocol). Ulnar deviation reduces foreshortening of the scaphoid.
- PA axial (Stecher-type): Elevate the hand on a 20° sponge or angle the CR 20° toward the elbow with the wrist PA and often in ulnar deviation. Goal: scaphoid parallel to IR and elongated without excessive overlap.
Departments may add clenched-fist, radial deviation (for lunate/triquetrum focus), or carpal tunnel projections—know that scaphoid protocol is not “just three wrist views.”
Forearm
| Projection | Setup | CR | Evaluation |
|---|---|---|---|
| AP | Arm extended; hand supinated; epicondyles equidistant from IR | Mid-forearm | Wrist and elbow joints included; slight superimposition of radial head on ulna is expected; humeral epicondyles in profile |
| Lateral | Elbow flexed 90°; hand and wrist true lateral (thumb up) | Mid-forearm | Superimposed distal radius/ulna; superimposed humeral epicondyles; both joints included; true 90° elbow flexion |
Critical error: Pronating the hand for an “AP” forearm crosses the radius over the ulna and mimics pathology. For trauma when the patient cannot fully extend or supinate, obtain two projections 90° apart that still include both joints—horizontal-beam laterals are acceptable.
High-Yield Fractures & Critique Links
| Injury | Classic radiographic idea | Positioning / critique note |
|---|---|---|
| Boxer’s fracture | Transverse fracture of 5th metacarpal neck with volar angulation of the head | Hand PA + oblique essential; lateral shows angulation |
| Colles fracture | Distal radius fracture with dorsal displacement/angulation of the distal fragment; often ulnar styloid | Lateral wrist is decisive for dorsal vs volar; include distal forearm |
| Smith fracture | “Reverse Colles”—distal fragment displaced volarly | Same series; do not call every distal radius a Colles |
| Scaphoid fracture | Often waist; may be occult on day-of-injury PA | Ulnar deviation / axial views; soft-tissue swelling in snuffbox clinically; follow-up or advanced imaging if negative but suspicion high |
On CAMRT-style stems, match the projection deficiency to the missed diagnosis: a rotated lateral wrist underestimates Colles angulation; a hand series without a true oblique under-calls metacarpal base injuries; a forearm that clips the elbow misses Monteggia-pattern associations (ulnar fracture with radial-head dislocation) even though the formal Monteggia work-up extends into the elbow chapter knowledge.
Technique & Image Quality Reminders
Extremity work is high spatial-resolution territory. Use the small focal spot when loading allows, adequate mAs for noise control on digital detectors, and kVp in the typical extremity range (often ~50–65 for digits/hand/wrist; slightly higher for forearm—follow technique charts). Check exposure index / deviation index against department targets. Motion unsharpness from pain is more common than geometric blur—immobilize and coach a short suspended stillness rather than cranking mA blindly.
CAMRT Application Focus
When an item describes “pain in the anatomical snuffbox after a fall on the outstretched hand,” prioritize scaphoid-inclusive wrist imaging and evaluation criteria that free the scaphoid waist. When the stem shows a distal radius with dorsal angulation on lateral, name the Colles pattern and verify the lateral was truly lateral (superimposed radius/ulna). When a 5th metacarpal neck is impacted, demand PA, oblique, and lateral hand—not a wrist series alone. Positioning knowledge and pathology recognition are one competency chain for RTR.4 / RTR.6, not two separate study silos.
For a PA projection of the 3rd digit, where should the central ray be directed, and which anatomy must be included?
Which statement best describes correct AP forearm positioning for a routine non-trauma examination?
A patient has snuffbox tenderness after a FOOSH injury. Which projection set best targets the structure most at risk?
On a true lateral wrist radiograph, a distal radial fracture shows volar displacement of the distal fragment. Which injury pattern does this describe?