aka Bone and Joint Bamboozler 005
45 year old male presents to the emergency department with swollen, painful wrist following a fall onto the outstretched hand.
Q1. What does this X-ray show?
This X-ray demonstrates a transcaphoid perilunate fracture-dislocation and oblique ring finger metacarpal fracture.
A fall onto the outstretched hand may displace the hand and most of the carpus backwards, leaving only the lunate in contact with the radius (perilunate dislocation). When the dorsiflexion injury is associated with a fracture of the scaphoid – the proximal half of the scaphoid remains alongside the lunate in whichever position it lies
Q2. What are the potential long term sequele of this type of injury?
Perilunate fracture dislocation is a frequently missed injury. When unrecognized and untreated these injuries lead to a high incidence of long term functional disability and pain.
The majority of the proximal scaphoid blood supply is retrograde. Dorsal vessels enter the scaphoid distal to the waist to perfuse distal and proximal segments. Avascular necrosis may therefore result from untreated proximal third scaphoid fractures secondary to disruption of the proximal supply of blood.
Note: Not all scaphoid fractures are radiographically visible at the time of presentation with perilunate dislocation, but as 90% of such dislocations have an associated fracture they are treated expectantly with scaphoid internal fixation.
Classic avascular necrosis of the lunate (Keinbock disease) has not been demonstrated following perilunate dislocation. However transient vascular compromise with a relative increase in lunate bone radiodensity has been shown, despite the lunates rich dual blood supply.