Perilunate Dislocation Xray

Perilunate Dislocations are devastating closed wrist injuries, non-uncommonly missed on initial imaging. Below are some of the characteristics of this condition and how they’re spotted in readings.

Perilunate Dislocation Xray

Potentially devastating closed wrist injuries

Non-uncommonly missed on initial imaging.

Dislocation of carpus relative to lunate

Lunate remains in normal alignment with the distal radius

NOT to be confused with LUNATE Dislocation = lunate is dislocated volarly and thereofore abnormal radiolunate articulation.

Carpal dislocations –  less than 10% of all wrist injuries.

Perilunate dislocation-

Young adults

High energy trauma

Loading of hyperextended/ulnarly deviated hand

Fall on dorsiflexed wrist

60% of perilunate dislocations associated with ascaphoid fracture which is then termed a trans-scaphoid perilunate dislocation.

X-RAYS

AP View

Triangular orientation of the lunate

Lateral View

Dislocation most easily appreciated on this view

Lunate in anatomic position to Radius

Capitate dorsal to the lunate

CT

Plain film normally sufficient to diagnose dislocation

CT is important to diagnose associated occult fractures

The most common and important associated = scaphoid fracture

Treatment and Prognosis

If Untreated = High risk of:

  • Median nerve palsy
  • Pressure necrosis
  • Compartment syndrome and long-term wrist dysfunction
  • Perilunate dislocation should be reduced ASAP
  • Prompt open reduction with ligamentous repair recommended

Long-term risk of:

Degenerative arthritis is high (~60%).

Dissociative and non-dissociative carpal instability (DISI or VISI)

Higher rate of nonunion of scaphoid fractures when associated with perilunate dislocation

Differential diagnosis

The most important differential diagnosis is that of Lunate Dislocation which can mimic a Perilunate dislocation on AP projection.

Therefore ALWAYS look at the LATERAL XRAY

TAKE HOME MESSAGE:

DO NOT MISS Perilunate Dislocations

Communicate Positive Findings of Perilunate Dislocation ASAP

Look for associated SCAPHOID FRACTURE

The LATERAL VIEW will help DIFFERENTIATE Perilunate from Lunate Dislocations

 

Remember- “The Eyes Will Not See What The Brain Does Not Know”