Approach to WRIST radiograph

Standard Views:

• Posteroanterior (PA) View: Best for evaluating carpal height, alignment, and the relationship between the distal radius/ulna and the proximal carpal row.

  
  

• Lateral View: Crucial for assessing carpal alignment, specifically the scapholunate and capitolunate angles, and the relationship between the radius, lunate, and capitate.

• Essential for diagnosing carpal instability patterns - DISI and VISI

  
  

• Oblique View: Typically used to better visualize the trapezium and trapezoid, and to assess the pisotriquetral joint.

Wrist PA view :

• What to look for in a PA Wrist radiograph:

  • Positioning

  • Joints

  • Carpal arcs - Gilula's arc

Check the positioning. The Extensor Carpi Ulnaris grove (yellow arrow) should be radial to the ulnar styloid (red arrow).

The arcs of Gilula:

• Gilula's arcs are three smooth, continuous curves drawn on the PA View.

  
  

• Any break or step-off in these arcs is a highly sensitive sign of ligamentous injury or carpal fracture/dissociation.

1. Arc I: The smooth curve connecting the proximal convexities of the scaphoid, lunate, and triquetrum.

2. Arc II: The smooth curve connecting the distal convexities of the scaphoid, lunate, and triquetrum.

3. Arc III: The smooth curve tracing the proximal outline of the capitate and hamate.

Joint spaces:

1. Joint spaces at carpal and carpometacarpal joints <= 2 mm

Joint Space	Normal Measurement	Significance of Widening
Scapholunate (S-L) Interval	<3 mm	>3 mm (The "Terry Thomas Sign" or "David Letterman Sign") is pathognomonic for Scapholunate Dissociation.
Capitolunate (C-L) Interval	<2 mm	Disruption of the surrounding intercarpal ligaments.
Carpometacarpal (CMC) Joints	Smooth and equal	Widening/step-off suggests CMC subluxation/dislocation.

Alignment Check - The Lateral View

The most important step is ensuring normal bony alignment. This is primarily assessed on the Lateral View by drawing three distinct lines.

A. The R-L-C Alignment (Lateral View)

1. Radio-Lunate Alignment: The lunate should sit directly in the cup of the distal radius.

   
   

2. Lunate-Capitate Alignment: The concave distal surface of the lunate should articulate perfectly with the convex head of the capitate.

   
   

3. Capitate-3rd Metacarpal Alignment: The head of the capitate should be aligned with the third metacarpal.

Lunate dislocation	Perilunate dislocation

B. Carpal Angles (Lateral View)

Two angles are critical for assessing stability:

Angle	Normal Range	Significance of Abnormality
Scapholunate Angle	30∘ to 60∘ (Average 47∘)	Increased (>60∘): Suggests Scapholunate Dissociation (DISI).
Capitolunate Angle	Typically <30∘ (Should be 0∘±15∘)	Increased (>30∘): Indicates dissociation (Lunate tilted) - either DISI or VISI.

DISI (Dorsal Intercalated Segmental Instability)	VISI (Ventral Intercalated Segmental Instability)

Fractures of the Hand:

Systematically inspect every carpal bone and the distal forearm for subtle fracture lines, sclerosis, or cortical irregularities.

Focus Areas:

• Scaphoid: The most commonly fractured carpal bone.

  • Inspect the waist (most common), proximal pole, and distal pole.

  • A subtle fracture may only be visible as a sclerosis or a small fat pad sign initially.

    
    

• Triquetrum: Second most common carpal fracture, often seen on the Lateral View as a small dorsal chip fracture (avulsion from the dorsal radiotriquetral ligament).

  
  

• Distal Radius & Ulna: 

  • Check for Colles' (dorsal angulation/displacement) or

  • Smith's (volar angulation/displacement) fractures.

  • Check the ulnar styloid for a fracture, which is often associated with a distal forearm fracture.

    
    

• Capitate/Hamate: 

  • Inspect the hook of the hamate (difficult to see on standard views, requires a carpal tunnel view) and the body of the capitate.

    
    

• Kienböck's Disease:

  • Sclerosis and eventual collapse of the lunate bone are indicative of avascular necrosis (Kienböck's disease).

  • Evaluate for ulnar minus variance (shortening of the ulna relative to the radius), which is a common predisposing factor.

Soft Tissues

Finally, check the surrounding soft tissues for secondary signs of injury.

• Fat Pads: Look for displacement or bulging of the pronation fat stripe (distal radius) or the scaphoid fat stripe. Displacement suggests occult fracture or severe soft tissue swelling.

  
  

• Swelling: Note any generalized soft tissue swelling, which correlates with the severity of trauma.