Executive Editor: Chris Colton

Authors: Matej Kastelec, Renato Fricker, Fiesky Nuñez, Terry Axelrod

Carpus - Complete dislocation of the lunate

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Glossary

1 Introduction top

Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

In complete dislocations of the lunate, the displacement is usually in a palmar direction. The greater force required to produce this injury is responsible for massive disruption of both the dorsal and palmar ligaments.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

There is also a disruption of the dorsal radiolunotriquetral ligament complex.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

“Spilled teacup” sign

The capitate displaces proximally towards the distal radial articular surface. A lateral radiograph shows the “spilled teacup” configuration of the lunate.
On the AP view, the displaced lunate has a triangular profile, rather than its normal quadrangular image.

2 Reduction top

Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Closed reduction of the lunate

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

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

Reduction of the displaced lunate is achieved by distracting the wrist and applying direct thumb pressure over the lunate from palmar to dorsal.
The hand is then gently flexed, and once reduction has occurred, the distraction is gently relaxed.
After emergency reduction, the wrist is immobilized in a plaster splint, or cast (Colles), in a position of about 10 degrees of palmar flexion.
 
If closed reduction is not successful, open reduction via a palmar approach is necessary, as soon as possible (due to the risk of median nerve compromise, of pain, and to preserve blood supply to the lunate).


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Open reduction of the scapholunate joint

At the definitive operation, a joystick K-wire is inserted into each of the scaphoid and the lunate. These are used to reduce the scapholunate joint.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Assessment of dorsal and proximal ligament remnants

In most of the cases, the scapholunate (SL) ligament is avulsed from the scaphoid, and remains attached to the lunate.

The avulsion site is freshened to improve contact and healing.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Anatomical reduction (dorsal approach)

A joystick K-wire is inserted into each of the scaphoid and the lunate. They are used to complete the closure of the scapholunate diastasis.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Use the two joysticks to extend the scaphoid, flex the lunate, and then close the gap.

A pointed reduction clamp helps to secure the reduction temporarily.
Confirm reduction using image intensification in two planes.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

On the lateral view, with the wrist neutral, check that the radius, lunate and capitate are in line, that the scapholunate angle is < 60 degrees, and that there is no dorsal tilt of the lunate.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Both bones are secured by transfixation with two K-wires inserted percutaneously from scaphoid to lunate.
Again, confirm the position of both wires using image intensification.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Pearl: Alternative K-wire insertion
The transfixation K-wires can be inserted into the scaphoid from inside outwards, prior to the reduction, and then advanced into the lunate, across the scapholunate articulation, once reduction has been achieved.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Anatomical reduction (dorsal approach)

Assessment of dorsal and proximal ligament remnants

In most of the cases, the dorsal scapholunate (SL) ligament is avulsed from the scaphoid, and still attached to the lunate.
The avulsion site is debrided for better contact and healing.

3 Suture anchors top

Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

The anchor is inserted dorsally into the debrided area of the scaphoid (or in the lunate, if the ligament is avulsed from that bone).
The entry point for the anchor must be placed in such a position that the line of pull of the suture is slightly oblique, in order to resist rotational forces between both bones.
Often, one anchor will be sufficient, but occasionally two anchors will be needed.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

The anchor suture is inserted into the torn end of the ligament.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Option: Transosseous ligament refixation

If bone anchors are not available, the avulsed ligament is attached using sutures which are passed through small tunnels drilled into the proximal pole of the scaphoid, as illustrated.

4 Ligament repair top

Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

The anchor sutures in the ligament are then tied.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

If there is a mid-substance tear of the ligament, suture it directly.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Lunotriquetral ligament repair

In most cases, the lunotriquetral ligament is torn from the lunate.
Usually, reduction and temporary fixation of the lunotriquetral relationship is all that is possible from the dorsal aspect.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

K-wire fixation

The lunotriquetral (LT) relationship is reduced, and two 1.4 mm K-wires are inserted percutaneously from the triquetrum into the lunate.
Confirm the reduction using image intensification.

Pearl: Alternative K-wire insertion
These transfixation K-wires can be inserted into the triquetrum from inside outwards, prior to the reduction, and then advanced into the lunate, across the LT articulation, once reduction has been achieved.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

Lunotriquetral ligament repair

In the rare instance when there is sufficient ligament remnant, repair with a bone anchor is possible after holding the reduction with 2 transfixion K-wires.
A suture anchor is inserted into the debrided area of the avulsion.

If there is a bony avulsion of the lunotriquetral ligament from either bone, the fragment can be fixed with fine K-wires or a small screw.

5 Palmar approach top

Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

A palmar approach demonstrates characteristic disruptions of the extrinsic palmar ligaments, which start in the space of Poirier (as illustrated), and expose the midcarpal joint.


Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

The midcarpal joint is irrigated. Loose bodies or subchondral flakes are removed, and the tears are repaired with interrupted sutures.

6 Final result top

Carpus – Complete dislocation of the luante – ORIF – Open reduction internal fixation enlarge

After final confirmation, using image intensification, cut and bend over the K-wires, so that they do not protrude through the skin.

v1.0 2008-11-08