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.
There is also a disruption of the dorsal radiolunotriquetral ligament complex.
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.
Closed reduction is a preliminary to operative treatment and has three benefits:
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
The anchor suture is inserted into the torn end of the ligament.
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.
The anchor sutures in the ligament are then tied.
If there is a mid-substance tear of the ligament, suture it directly.
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.
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.
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.
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.
The midcarpal joint is irrigated. Loose bodies or subchondral flakes are removed, and the tears are repaired with interrupted sutures.
After final confirmation, using image intensification, cut and bend over the K-wires, so that they do not protrude through the skin.
Immobilize the wrist with a well-padded below-elbow splint for 2 weeks.
While the patient is in bed, use pillows to keep the hand elevated above the level of the heart to reduce swelling.
For ambulant patients, put the arm in a sling and elevate to above the heart.
After 14 days remove the sutures, check the skin over the K-wires, and apply a below-elbow scaphoid cast.
Immediately postoperatively begin active, controlled digital range-of-motion exercises.
Load bearing through the splinted wrist must be avoided. The cast is renewed and the skin regularly checked every 2 weeks in the outpatient clinic.
Cast immobilization is usually continued until 8-10 weeks postoperatively, when the K-wires are also removed with appropriate pain control.
At this stage, start with range-of-motion exercises of the wrist. A removable wrist splint may be used for patient comfort for a few more weeks.
The importance of mobilization must be emphasized to the patient and rehabilitation should be supervised by a physical therapist.