A dorsal triquetral avulsion fracture is a small cortical (chip) fracture off the dorsal surface of the triquetrum. The triquetrum is the second most commonly fractured carpal bone after the scaphoid, and the dorsal cortical pattern makes up roughly 93 to 95 percent of triquetral fractures. It is easily overlooked on the frontal radiograph but has a classic clue on the lateral view – the pooping duck sign. This page covers the mechanism, imaging, Garcia-Elias classification, differentials and management for radiology trainees and clinicians.
Quiz
What is the most common mechanism of this fracture?
- Blunt trauma to the wrist
- Fall from height
- Fall on the outstretched hand
- Penetrating trauma to the wrist
Triquetral avulsion fracture at a glance
| Feature | Detail |
|---|---|
| Frequency | Second most common carpal fracture after the scaphoid (about 15-18% of carpal fractures) |
| Most common type | Dorsal cortical (chip) fracture (about 93-95%) |
| Typical mechanism | Fall on the outstretched hand; dorsal impaction by the ulnar styloid or hamate, or ligament avulsion |
| Classic sign | Pooping duck sign on the lateral radiograph |
| Best radiographic views | Lateral and 45-degree pronated oblique (dorsal); radial deviation view (volar) |
| Usual treatment | Immobilization for 4-6 weeks for stable dorsal cortical fractures |
| Red flag | Volar cortical fracture – lunotriquetral ligament tear and carpal instability |
Pathophysiology and mechanism
- The triquetrum is the second most commonly fractured carpal bone, after the scaphoid.
- The dorsal cortical fracture is the dominant pattern, comprising about 93-95% of triquetral fractures.
- The usual injury is a fall on the outstretched hand with the wrist in extension and ulnar deviation.
- Two mechanisms are proposed: impaction of the dorsal triquetrum by the ulnar styloid or the proximal hamate, and avulsion by the dorsal radiotriquetral and dorsal scaphotriquetral ligaments.
- MRI series show that most dorsal fractures carry associated dorsal carpal ligament tears – dorsal radiocarpal, ulnotriquetral and intercarpal – supporting a mixed impaction-avulsion mechanism rather than a single cause.
- A longer ulnar styloid (higher ulnar styloid process index) has been linked with the impaction mechanism, although this is not universal.
Types of triquetral fracture
Triquetral fractures are grouped into three anatomical types. Recognising the type matters because the volar cortical fracture and the body fracture carry a much higher risk of associated ligament injury and carpal instability than the common dorsal chip fracture.
| Type | Frequency | Mechanism | Key associations |
|---|---|---|---|
| Dorsal cortical (chip) | Most common (93-95%) | Dorsal impaction (ulnar styloid or hamate) or ligament avulsion | Frequent dorsal carpal ligament tears; usually benign |
| Body | Second most common | High-energy trauma; axial load or crush | Perilunate fracture-dislocation in 12-25%; lunotriquetral, scaphoid and distal radius injuries |
| Volar cortical | Least common | Avulsion of the volar ulnotriquetral or lunotriquetral ligaments | Lunotriquetral instability; worse prognosis; often missed on standard films |
Garcia-Elias classification of dorsal cortical fractures
Garcia-Elias described a six-type system for the pattern of dorsal cortical fractures (J Hand Surg Am, 1987). Type 1 is by far the most common.
| Type | Description |
|---|---|
| Type 1 | Nondisplaced fracture (most common) |
| Type 2 | Partially displaced at the proximal end |
| Type 3 | Partially displaced at the distal end |
| Type 4 | Completely displaced fragment |
| Type 5 | Multiple completely displaced fragments |
| Type 6 | Verticofrontal (coronal-plane) fracture with dorsal displacement |
Key imaging features and views
There is no single view that shows every triquetral fracture, so multiple radiographs are read together. Around one in five triquetral fractures are occult on the initial films and need CT to confirm the diagnosis.
| Modality / view | Role |
|---|---|
| PA (AP) radiograph | Baseline view; the triquetrum overlaps the lunate, so the fracture is often hidden and may be mistaken for a lunate fracture |
| Lateral radiograph | Shows the dorsal cortical fragment – the pooping duck sign |
| 45-degree pronated oblique | Best single view for the dorsal cortical fracture |
| Radial deviation view | Best for showing a volar cortical fragment obscured by the hamate |
| CT | Occult fracture with high clinical suspicion, body fractures and fracture-dislocations; may be justified first-line when suspicion is high |
| MRI | Occult fracture and bone marrow oedema, plus extrinsic carpal ligament injury and carpal instability |
Imaging recommendation: start with PA and lateral radiographs (add a 45-degree pronated oblique if a triquetral fracture is suspected). Move to CT for a suspected occult or body fracture, and to MRI when carpal instability or extrinsic ligament injury is a concern.
The pooping duck sign
The pooping duck sign is the classic lateral-radiograph clue. The combined outline of the scaphoid, lunate and dorsal triquetrum resembles a duck, and the avulsed dorsal triquetral fragment projecting behind the carpus looks like a dropping from the duck.
Differential diagnosis
| Entity | Distinguishing features |
|---|---|
| Os triangulare | Well-corticated accessory ossicle between the ulnar styloid, lunate and triquetrum; smooth margins, no bone marrow oedema, often bilateral |
| Pisiform fracture | Volar location; needs a 30-degree supination or carpal tunnel view to see the pisotriquetral joint |
| Lunate fracture | Triquetral fractures are commonly misread as lunate fractures on the PA view – correlate with the lateral and oblique views |
Clinical features
- Ulnar-sided wrist pain, worse on wrist flexion and extension.
- Dorsal wrist swelling with point tenderness over the dorsum of the triquetrum.
- A history of a fall on the outstretched hand is typical.
- Persistent ulnar-sided pain after a normal-looking radiograph should prompt further imaging for an occult fracture or ligament injury.
Associated injuries and complications
- Perilunate fracture-dislocation: triquetral body fractures may be part of a perilunate injury (present in 12-25%).
- Lunotriquetral ligament injury and carpal instability: particularly with volar cortical avulsion fractures.
- Triangular fibrocartilage complex (TFCC) injury and distal radioulnar joint involvement.
- Non-union and pisotriquetral arthritis as late complications.
Treatment
| Scenario | Management |
|---|---|
| Stable dorsal cortical (chip) fracture | Cast or splint immobilization for 4-6 weeks, then hand therapy; good outcomes |
| Significant displacement or fracture-dislocation | Surgical fixation (percutaneous pinning or open reduction and internal fixation) |
| Volar cortical fracture with instability | Directed at restoring carpal stability; may need fixation or ligament repair |
| Symptomatic non-union | Surgical management |
Frequently asked questions
References
- Guo RC, Cardenas JM, Wu CH. Triquetral fractures overview. Curr Rev Musculoskelet Med. 2021;14(2):101-106. PMID: 33483875.
- Garcia-Elias M. Dorsal fractures of the triquetrum – avulsion or compression fractures? J Hand Surg Am. 1987;12(2):266-268. PMID: 3559084.
- Becce F, Theumann N, Bollmann C, et al. Dorsal fractures of the triquetrum: MRI findings with an emphasis on dorsal carpal ligament injuries. AJR Am J Roentgenol. 2013;200(3):608-617. PMID: 23436851.
- Smith DK, Murray PM. Avulsion fractures of the volar aspect of the triquetral bone of the wrist: a subtle sign of carpal ligament injury. AJR Am J Roentgenol. 1996;166(3):609-614. PMID: 8623636.
Case co-authored by TeamGyan member Dr. Mansi.
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