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