Causes / typical injury mechanism:

• A triquetral fracture of the wrist is almost always caused by a fall onto an outstretched hand with the wrist in extension and ulnar deviation.
• Excessive load across the wrist with the wrist in extension can lead to impaction of either the ulnar styloid or the hamate into the triquetrum.

Classic history and presentation: Ulnar-sided wrist pain after a fall onto an outstretched hand with the wrist in extension is the typical presentation.

Prevalence: The triquetral is the second most commonly fractured carpal bone, and triquetral fractures comprise 15%-18% of all carpal fractures.

Risk factors:

• Falls
• A prominent ulnar styloid

Pathophysiology: The triquetrum is a proximal row carpal bone that sustains fracture by direct impact from adjacent carpal bones, most commonly the ulnar styloid or hamate, or avulsion via attaching ligaments, most commonly the dorsal radiotriquetral or dorsal scaphotriquetral ligaments.

Grade / classification system: There are 3 types of triquetral fractures:

1. Dorsal cortical – Seen in 93%-95% of cases. Avulsion fracture off of the dorsal cortex from disruption of the dorsal radiotriquetral or dorsal scaphotriquetral ligaments. The Garcias-Elias classification of dorsal cortical fractures may be used:
   • Type 1: nondisplaced (most common)
   • Type 2: partial displacement proximally
   • Type 3: partial displacement distally
   • Type 4: completely displaced fracture fragment
   • Type 5: multiple / comminuted completely displaced fracture fragments
   • Type 6: coronal fracture line with displacement of the dorsal component
2. Body (3% of cases) – Associated with perilunate fracture dislocations.
3. Volar cortical (not quantified) – Result of volar ulnotriquetral and lunotriquetral ligament avulsion.