November 15, 2010

Bennett's Fracture Dislocation


Facts:
  • Most frequent fracture at the base of the first metacarpal
  • Fracture dislocation resulting from axial loading to a partially flexed thumb (i.e., in a fist fight)
  • Oblique fracture involves the carpometacarpal joint, resulting in a volar fragment attached to the trapezium and the distal metacarpal fragment displacing proximally/radially/dorsally by pull of abductor pollicis longus
  • First CMC joint is a saddle-shaped bone, any minor malalignment results in substantial articular incongruity. This fracture dislocation frequently requires open reduction and fixation
Imaging
  • Oblique fracture line with a triangular fragment at the first metacarpal base
  • Proximal displacement of the metacarpal
  • Important to note the size of the triangular volar fragment and the degree of displacement of the metacarpal fragment

References:
1. Robinson P. Essential Radiology for Sports Medicine, 2010.
2. Bennett's Fracture Dislocation. Wheeless' Textbook of Orthopedics

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