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?
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, 7e New York, NY: McGraw-Hill; 2014.
