Perilunate/Lunate Dislocation

Scenario

A 45 Year old female presents with pain in the wrist after falling onto an outstretched hand from a horse.

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This is an AP and Lateral plane film radiograph of a skeletally mature individuals wrist. The most obvious abnormality is that there is a trans-scaphoid perilunate dislocation. 

Three lines that can be join on a Poster-anterior radiograph of the wrist.

  1. Proximal joint surfaces of the proximal row of the carpal bones
  2. Distal joint surfaces of the proximal row of the carpal bones
  3. Proximal joint surfaces of the distal row of the carpal bones

Foreshortened appearance of the distal pole of the scaphoid rotated on its axis.

Refers to an abnormal triangular appearance of the lunate on a PA image of the wrist representing a perilunate or lunate dislocation.

  • Perilunate: Represents a Mayfield 3 injury. The lunate is dislocated at the mid-carpal joint (capitate dislocated from the lunate) but remains congruent at the radiocarpal joint.
  • Lunate dislocation: Represents a Mayfield 4 injury. The lunate is dislocated at both the Radiocarpal and mid-carpal (luno-capitate) joints.

Lesser arc injury: purely ligamentous injury

Greater arc injury: ligament injury with one of more fractures; typically radial styloid, scaphoid, capitate, hamate, triquetrum +/- ulnar styloid

 

Mayfield classification. Classify the ligamentous component.

 

I

Failure of the scapholunate ligament (Terry Thomas’ sign)

II

Failure of the scapholunate and capitoluate ligament (Peri-lunate dislocation)

III

Failure of the luno-triquetrial and dorsal mid-carpal dislocation (peri-lunate dislocation)

IV

Palmar dislocation of the lunate at the radiocarpal joint (lunate dislocation)

 

I would take a detailed history including hand dominance, occupation, mechanism of injury, co-morbidities, allergies and time since last meal.

I would examine carefully for abnormal wrist contour, pain/swelling and pulses, capillary refill and signs of median nerve compression (Sensation component: over palmar aspect of the radial 3.5 digits. Motor component: opponens polisis and abductor polisis brevis)

I would document relevant findings.

Initial management

  • Exclude other injuries
  • Provide analgesia, NV observations
  • Keep NBM
  • Splintage e.g. padded plaster of Paris + loose bandages
  • Chinese finger traps
  • Explain severity of the injury to the patient
  • Prepare and consent patient for theatre
  • Minimal initial intervention requires closed (+/-) open reduction using II +/- carpal tunnel decompression + POP slab stabilisation