Perilunate and lunate dislocations

Background

• Occur via high-energy FOOSH injury (fall from height, MVC)
  • Perilunate Dislocation = Lunate stays in place, capitate is displaced
  • Lunate Dislocation = Capitate stays in place, lunate is displaced
• Must rule-out median nerve injury
• Must rule out carpal bone fractures

Clinical Features

• Perilunate dislocation: dorsal swelling with palpable mass
• Lunate dislocation: volar swelling with palpable mass

Diagnosis

• Perilunate Dislocation
  • Lateral view
    • Capitate displaced dorsal to lunate
    • Lunate retains its normal contact w/ radius
  • PA view
    • Capitolunate joint space is obliterated as the bones overlap one another
• Lunate Dislocation
  • PA view
    • Lunate has triangular shape ("piece-of-pie sign")
  • Lateral view
    • Lunate is pushed off the radius into the palm ("spilled teacup" sign)

DDX

1. Fractures of distal radius, carpal bones (esp scaphoid)
2. Scapholunate Dissociation

Treatment

1. Both dislocations require emergent ortho consultation (very difficult to reduce)
2. Closed reduction and long-arm splint

Images

• Perilunate Dislocation

• Lunate Dislocation

Source

• Emergency Orthopedics, The Extremeties
• Radiopaedia.org
• Tintinalli