Perilunate and lunate dislocations

Background

• Perilunate Dislocation

  · Dorsal displacement of capitate in relation to lunate

  · Note that the radius, capitate, lunate, and third metacarpal form a straight line on lateral 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

Differential Diagnosis

• Fractures of the distal radius

• Fractures of the carpal bones, the scaphoid being the most common

• Scapholunate dissociation

• Ligamentous injury

• Septic arthritis

Treatment

• Immediate orthopedic consult for closed vs open reduction

  · The longer the dislocation is left unreduced, the lower the likelihood of reduction

• In ED, volar splint in neutral

Sources

• Emergency Orthopedics, The Extremeties • Radiopaedia.org

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