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DR.JAMAL AL-SAIDY
M.B.CH.B…F.I.C.M.S
LUNATE AND PERILUNATE DISLOCATIONS
A fall with the hand forced into dorsiflexion may tear the tough ligaments that
normally bind the carpal bones.
The lunate usually remains attached to the radius and the rest of the carpus is
displaced backwards (perilunate dislocation).
Usually the hand immediately snaps forwards again but, as it does so, the lunate
may be levered out of position to be displaced anteriorly (lunate dislocation).
Sometimes the scaphoid remains attached to the radius and the force of the
perilunar dislocation causes it to fracture through the waist (trans-scaphoid
perilunate dislocation).
Clinical features
The wrist is painful and swollen and is held immobile.
If the carpal tunnel is compressed there may be paraesthesia or blunting of
sensation in the territory of the median nerve, and weakness of palmar abduction
of the thumb.
X-ray
Most dislocations are perilunate.
In the antero-posterior view the carpus is diminished in height and the bone
shadows overlap abnormally.
One or more of the carpal bones may be fractured (usually the scaphoid and radial
styloid).
If the lunate is dislocated, it has a characteristic triangular shape instead of the
normal quadrilateral appearance.
In the lateral view it is easy to distinguish a lunate from a perilunate dislocation.
The dislocated lunate is tilted forwards and is displaced in front of the radius,
while the capitate and metacarpal bones are in line with the radius.
With a perilunate dislocation the lunate is tilted only slightly and is not displaced
forwards, and the capitate and metacarpals lie behind the line of the radius (DISI)
if there is an associated scaphoid fracture,the distal fragment maybe flexed
Treatment
Closed reduction The surgeon pulls strongly on the dorsiflexed hand; then, while
maintaining traction, he or she slowly palmarflexes the wrist, at the same time
squeezing the lunate backwards with his or her other thumb.
These manoeuvres usually effect reduction; they also prevent conversion of a
perilunate to a lunate dislocation.
A plaster slab is applied holding the wrist neutral. Percutaneous K-wires may be
needed to hold the reduction.
Open reduction Reduction is imperative, and if closed reduction fails, or if a later
x-ray shows that the wrist has collapsed into the familiar DISI pattern, open
reduction is performed.
This injury is frequently accompanied by severe compression of the median
nerve, which should be released.
THANK YOU
DR.JAMAL AL-SAIDY
M.B.CH.B..…… F.I.C.M.S