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

Reference:

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