Carpal Fractures

Basics

Description

  • Carpal bones make up the eight bones of the wrist between the radius and ulna proximally and the metacarpals distally:
    • Proximal carpal row: Scaphoid, lunate, triquetrum, pisiform
    • Distal row: Trapezium, trapezoid, capitate, hamate
  • Most commonly injured region of upper extremity:
    • Most commonly fractured carpals are the scaphoid (68%) and triquetrum (18%)
    • Fractures of the trapezium, hamate, capitate, and trapezoid follow in prevalence (2–4%)
  • Carpal bone fractures commonly occur with other wrist injuries:
    • 90% of scaphoid fractures are isolated, while a significant proportion of all other carpal bone fractures involve multiple carpal bones
    • Capitate fractures along with scaphoid (scaphocapitate syndrome) sometimes occur with perilunate dislocations
    • Lunate and triquetrum fractures are also associated with perilunate dislocations
    • Hamate fractures are associated with injuries to fourth and fifth CMC and metacarpals concurrent with distal radius fractures

Etiology

  • Fall on outstretched hand (FOOSH) with a hyperextended or hyperflexed wrist
  • Mechanisms of injury for all fractures commonly include FOOSH
  • Scaphoid fracture:
    • FOOSH with fall onto extended and radially deviated wrist
  • Lunate fracture:
    • Typically fall onto extended wrist
  • Triquetrum fracture:
    • Divided into avulsion (93%) fractures and body fractures
    • Hyperextension → dorsal avulsion fracture
    • Hyperflexion → volar avulsion fracture
    • Body fracture: Typically results from direct blow and high-energy forces
      • 12–25% a/w perilunate dislocation
  • Trapezium fracture:
    • Typically fall onto extended wrist
  • Capitate fracture:
    • Fall onto clenched fist
  • Trapeziod fracture:
    • Axial loading of second metacarpal
  • Pisiform fracture:
    • Direct impact against hard surface
  • Hook of hamate fracture:
    • Forceful swing of a racquet or club

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