Perilunate and lunate dislocations

Background

• Perilunate Dislocation
  • Dorsal displacement of capitate in relation to lunate
  • Note that radius, capitate, lunate, and 3rd metacarpal form straight line on lat x-ray
• Lunate Dislocation
  • Volar dislocation of the lunate in relation to the radius, spilled teacup
    

Clinical Features

• FOOSH injury with excessive hyperextension, ulnar deviation, and intercarpal supination
• On exam, decreased range of motion with focal swelling
  • Dorsal swelling with mass in perilunate dislocation
  • Volar swelling with palpable mass in lunate dislocation
• Median nerve compression possible, perform thorough neurovascular exam
• Scaphoid fractures and scaphoid rotary subluxation are common
• Degenerative arthritis is very common, 60% incidence

Workup

• X-ray: wrist series, minimum of three views
• Perilunate dislocation
  • Lateral view, dorsal dislocation of capitate when an imaginary line is drawn through radius, luante, and capitate
  • PA view, capitate and lunate overlap
• Lunate dislocation
  • Lateral view, lunate displaced and tilted volarly
  • PA view, lunate is triangular in shape

DDX

1. Fractures of the distal radius
2. Fractures of the carpal bones, the scaphoid being the most common
3. Scapholunate dissociation
4. Ligamentous injury
5. Septic arthritis

Treatment

1. Immediate orthopedic consult for closed vs open reduction
   1. Longer the dislocation is left unreduced, the lower the likelihood of reduction
2. In ED, volar splint in neutral position

Source

• Emergency Orthopedics, The Extremeties
• Radiopaedia.org

File:PL 1.jpg

Perilunate lateral

File:PL 2.jpg

Perilunate AP

File:Lun 1.jpg

Lunate