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

Evaluation

Perilunate Dislocation

Lunate Dislocation

Perilunate Dislocation

• Lateral view
  • Capitate displaced dorsal to lunate
  • Lunate retains its normal contact with radius
• PA view
  • Capitolunate joint space is obliterated as the bones overlap one another

Lunate Dislocation

• Lateral view
  • Lunate is pushed off the radius into the palm ("spilled teacup" sign)
• PA view
  • Lunate has triangular shape ("piece-of-pie sign")

Differential Diagnosis

Carpal Dislocations

• Lunotriquetral ligament instability
• Scapholunate dissociation
• Perilunate and lunate dislocations

Carpal fractures

AP view

• Scaphoid fracture
• Lunate fracture
• Triquetrum fracture
• Pisiform fracture
• Trapezium fracture
• Trapezoid fracture
• Capitate fracture
• Hamate fracture

Treatment

• Closed reduction and long-arm splint
  • Likely requires emergent ortho consultation (very difficult to reduce)

See Also

• Carpal dislocations

References

• Emergency Orthopedics, The Extremeties
• Radiopaedia.org