Perilunate Dislocations

HPI: Young male presents after a fall while skiing with right shoulder and wrist pain.

PE: Obvious deformity of the right wrist. No abrasions or ecchymosis. Full thumb abduction, able to flex at DIP and PIP joint of all 5 fingers, full abduction of all 4 palmar fingers, 5/5 strength to finger grip. Unable to range wrist, elbow or glenohumeral joint secondary to pain. Normal sensation to pinprick and two point discrimination of all five fingers. 2+ radial pulse with normal cap refill.  

Imaging:

Anatomy:
-    Normal wrist anatomy consists of two rows of bones:
      o   Proximal row: Scaphoid, lunate, triquetrum, pisiform
      o   Distal row: trapezium, trapezoid, capitate, hamate
-    Ligaments of the wrist:
      o   Interosseous ligaments run between the carpal bones and stabilizes proximal carpal bones.
      o   Intrinsic ligaments insert and originate among the carpal bones to internally stabilize them.
      o   Extrinsic ligaments connect radius and ulna to the carpus. 

How to make diagnosis:

• Traumatic high energy mechanism when wrist is extended and ulnarly deviated. 
  
• Can lead to either Perilunate dislocation where lunate stays in position and carpus dislocates or Lunate dislocates by being forced volar or dorsal while carpus remains aligned
  
• Can see median nerve symptoms in ~25% of patients – most common with lunate dislocation into carpal tunnel.
  

Treatment:
o   Require emergent closed reduction and splinting into sugar tong splint. 

• Place hand in finger traps at 90 degrees of elbow flexion with 5-10lbs of traction. 
  
• Wrist traction with one hand and recreate deformity (volar or dorsal dislocation) and pressing with thumb of the non-extending hand onto dislocated carpal bone attempting to press it back into place. 
  
• Reduces median nerve injury and minimizes cartilage damage. 

o   Require open reduction, ligament repair, fixation and possible carpal tunnel release. 

• Even with reduction and operative treatment may still not return to full function with reduced grip strength and stiffness. 
  

Pearls:

• Must obtain a lateral to evaluate for fracture as AP may not reveal obvious carpal misalignment. 
  
• Diagnosis missed 25% of the time. 
  
• Either lunate stays in position and carpus dislocates or carpus stays in position and lunate dislocates. 
  
• Emergent reduction/splinting to reduce incidence of median nerve injury and cartilage damage.