What's the diagnosis? By Dr. Katie Selman

A healthy 22 yo female presents to the ED with left thumb pain.  She was jogging and tripped and used her left hand to break her fall.  An x-ray is shown.  What's the diagnosis?  Scroll down for answer.




Answer: Dislocation of the first metacarpophalangeal joint

  • Occurs with hyperextension injuries, most dislocations occur dorsally
  • Most commonly involves the index finger
  • Simple dislocation
    • More apparent clinical appearance - the MCP joint is in 60-90 degrees of hyperextension
  •  Complex dislocation
    • More subtle appearance - the phalanx is almost parallel to the metacarpal
    • Almost impossible to reduce
  • Reduction technique: further hyperextension with pressure at the base of the phalanx
  • After successful reduction immobilize with MCP flexed at 60 degrees
  • Higher incidence of irreducible dislocations (compared to PIP or DIP joint dislocations)
    • consult hand surgery if unable to reduce





Manthey DE, Askew K. Hand. In: Sherman SC. eds.Simon’s Emergency Orthopedics, 7eNew York, NY: McGraw-Hill; 2014.