Perilunate, dissociation

Perilunate dislocations are pure ligamentous injuries. They result from high-energy trauma. They may lead to severe disruption of carpal anatomy, leading to profound changes in wrist biomechanics.

The pathoanatomy is sequential disruption of carpal ligaments, passing from the radial side to the ulnar side of the wrist. This leads to progressive perilunar instability. The first event is scapholunate dissociation. The final expression is complete displacement of the carpus around the lunate.

Rupture of the scapholunate ligament is the first event in any sequence of perilunar ligament ruptures. It is the most common cause of wrist instability.

The essential elements of the injuries are dissociation of the scaphoid and the lunate, flexion of the scaphoid, and extension of the lunate.

Restoration of rotational stability between scaphoid and lunate is key to restoring normal wrist kinematics.

In this more advanced stage of perilunar dislocation, both the scapholunate (SL) and lunotriquetral interosseous ligaments fail. A rupture of the palmar extrinsic ligaments also occurs.

Closed reduction is a preliminary step to operative treatment and has three effects:

• it restores carpal alignment
• improves the patient’s comfort and
• facilitates surgical repair.

Nonoperative treatment is so frequently followed by redisplacement and later carpal derangement, that ligament repair is strongly indicated.
Combined surgical approaches facilitate comprehensive repair of the multiple ligament disruptions.