Pooping duck sign
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The "Pooping Duck" Sign
Modality: Plain radiograph - lateral wrist X-ray
Diagnosis indicated: Dorsal triquetral chip (avulsion) fracture
What It Is
The pooping duck sign is a radiological sign seen on a lateral wrist radiograph that indicates a dorsal cortical avulsion fracture of the triquetrum - the second most common carpal fracture after scaphoid fractures, accounting for up to ~15% of all carpal injuries.
How It Gets Its Name
On the lateral wrist view, the overlapping silhouettes of the wrist bones create a duck-like shape:
- The scaphoid and lunate (superimposed on the volar/palmar side) form the beak and body of the duck
- The triquetrum (on the dorsal side) forms the rear/tail of the duck
- The small avulsed bone fragment sitting dorsal to the triquetrum resembles poop being ejected from the duck's rear end
Hence: a "pooping duck."
Clinical Context
| Feature | Details |
|---|---|
| Fracture type | Dorsal cortical chip / avulsion fracture |
| Bone involved | Triquetrum (proximal carpal row, ulnar side) |
| Mechanism | Fall on outstretched hand (FOOSH); forced palmar flexion with ulnar deviation |
| Ligament avulsing | Radio-lunato-triquetral ligament (dorsal radiocarpal ligament) |
| Symptoms | Dorsal ulnar wrist pain, swelling, tenderness |
Imaging
- Best view: Standard lateral wrist radiograph (may need a pronated oblique view)
- A small fleck of bone is visible dorsal to the triquetrum
- CT or MRI can confirm occult fractures or assess ligamentous injuries
As described in Rosen's Emergency Medicine: "Dorsal triquetral chip fractures are best seen on the standard lateral view of the wrist as a small dorsal avulsion fragment, although a more oblique pronated view may be necessary for visualization." - Rosen's Emergency Medicine
Classification (Garcia-Elias)
| Type | Description |
|---|---|
| 1 | Non-displaced (most common) |
| 2 | Partially displaced at proximal end |
| 3 | Partially displaced at distal end |
| 4 | Completely displaced fragment |
| 5 | Multiple completely displaced fragments |
| 6 | Coronal plane fracture with dorsal displacement |
Management
- Dorsal chip fractures: Benign course - immobilize in a short arm volar splint; routine orthopaedic referral within 1-2 weeks
- Triquetral body fractures (non-displaced): Short arm immobilization; urgent orthopaedic follow-up in 5-7 days
- Displaced body fractures: ORIF + ED orthopaedic consultation
- Always assess for associated perilunate/lunate dislocation and ligamentous injuries, especially with body fractures
The sign is a useful and memorable teaching tool because the avulsed fragment is easily overlooked on a busy lateral wrist film - recognizing the "duck" helps radiologists and clinicians avoid missing this subtle but important finding, as reported in the Annals of Medical Science & Research case report.
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