Question:hard
What is meant by perilunate dislocation?
What is meant by perilunate dislocation?
Show Hint
Which single carpal bone keeps its grip on the radius while the rest dislocate?
Updated On: Jun 24, 2026
- Lower radius, scaphoid, lunate and capitate all in same plane
- Lower radius, scaphoid and capitate in alignment, lunate alone out of plane
- Lower radius, scaphoid and lunate in alignment, capitate alone is out of plane
- Both lunate and capitate are out of plane
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Picture the central carpal column on a true lateral wrist film: distal radius, then lunate, then capitate should sit in a straight line like cups stacked in cups. A perilunate dislocation breaks this stack because the ligaments tethering the carpus to the lunate tear.
Step 2: When the radioscaphocapitate, scapholunate and lunotriquetral ligaments fail, the capitate and the rest of the carpus swing dorsally off the lunate, yet the lunate remains within the radial socket. So the radius, scaphoid and capitate end up aligned together while the lunate is the odd bone left malpositioned relative to them - exactly option B.
Step 3: Reject the rest: all-in-one-plane means a normal wrist; saying only the capitate is displaced inverts the true finding; and both lunate plus capitate being displaced is the more advanced lunate dislocation, a different stage of the same spectrum.
\[\boxed{\text{Radius, scaphoid and capitate aligned; lunate alone out of plane}}\]
Step 2: When the radioscaphocapitate, scapholunate and lunotriquetral ligaments fail, the capitate and the rest of the carpus swing dorsally off the lunate, yet the lunate remains within the radial socket. So the radius, scaphoid and capitate end up aligned together while the lunate is the odd bone left malpositioned relative to them - exactly option B.
Step 3: Reject the rest: all-in-one-plane means a normal wrist; saying only the capitate is displaced inverts the true finding; and both lunate plus capitate being displaced is the more advanced lunate dislocation, a different stage of the same spectrum.
\[\boxed{\text{Radius, scaphoid and capitate aligned; lunate alone out of plane}}\]
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