Epibasal fractures of the thumb (also called pseudo Bennett's fracture) are two-piece fractures of the proximal first metacarpal bone. They are usually stable, depending on the degree of displacement, and often do not require surgery. It is important to distinguish them from intra-articular fractures (e.g. Bennett's fracture dislocation or Rolando fracture), which are usually unstable and require surgery.
Epibasal fracture of the thumb account for approximately 3% of all hand fractures and 16% of metacarpal fractures, and are mostly (>80%) seen in young men 4.
These fractures usually result from longitudinal axial loading 5.
Plain films are usually sufficient to diagnose and assess epibasal fractures, however if adequate views cannot be obtained or there is suspicion of intra-articular involvement then further assessment with CT is prudent 3.
Epibasal fractures are divided according to the direction of fracture into transverse and oblique and can be variably angulated and displaced.
Treatment and prognosis
The vast majority of epibasal fractures are considered stable and can be treated conservatively with thumb spica immobilisation for 4-6 weeks 2-3. Both oblique fractures and transverse fractures with greater than 30 degrees of angulation usually require closed reduction and Kirschner wire fixation (CRIF) 2-3.
In addition to stating that a fracture is present, one should assess and comment on:
- angulation: > 30 degrees usually requires internal fixation
- intra-articular extension (Bennett or Rolando fractures)
Wrist and hand fractures
- wrist and hand fractures (Amsterdam wrist rules)
- distal radial fracture (Frykman classification)
- distal ulna fractures
- fracture dislocations of the radius and ulna
- carpal fractures
- metacarpal fractures
- phalanx fractures
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