Review Question - QID 211204

The clinical presentation and imaging are consistent with a chronic lunotriquetral (LT) ligament injury. In contrast to the scapholunate (SL) ligament, the volar fibers of the LT ligament are the most robust.

LT ligament tears present with ulnar-sided wrist pain generally after a fall and are notoriously difficult to diagnose. Physical exam can help delineate a LT disruption from more common causes of ulnar sided wrist pain. The LT shuck test is performed by moving the lunate in a palmar/dorsal direction between one’s thumb and index finger. A positive test would elicit pain and clicking. The Kleinman’s shear test involves loading the triquetrium in the dorsal/palmar plane to produce a shear across the LT articulation. A positive test would be noted in the presence of pain or a clunk. In addition to these exam findings, when the LT ligament is disrupted, the scaphoid’s influence on lunate position is unchecked, and the lunate gradually flexes with the scaphoid. This leads to volar intercalated segmental instability (VISI) posture of the wrist (seen in Figure A). While the normal SL angle is on average 47°, a VISI wrist will have a SL angle of <30°. In addition, on an AP X-Ray of a patient with a LT disruption, the triquetrium may migrate proximally, especially in ulnar inclination. The LT ligament has two transverse components (dorsal and palmar) and a fibrocartilaginous membrane proximally. Similarly, the SL ligament has a dorsal, palmar, and interosseous components.

Berger reviewed the yield strength of the SL and LT ligaments of the wrist. He found that the dorsal aspect of the SL ligament (260 Newtons) was stronger than the volar aspect of the SL ligament (118N). In contrast, the LT ligament is thicker and stronger volarly (301 N) as compared to dorsally (121N).

Atkinson and Watson comprehensively review the management options for LT tears. The authors found that cast immobilization was more successful when the injury was treated in the acute setting, and only a minority (37%) of cases were treated surgically. They note that arthroscopic debridement, direct repair, arthrodesis, capsulodesis, and ligament reconstruction are all surgical options. The authors highlight the need for objective, standard definition of complete tear and LT instability.

Figures and Illustrations:
Figure A is a lateral radiographic view of a wrist with a VISI posture, demonstrating a flexed lunate with a decreased SL angle.
Figure B is an AP clenched fist view of the same wrist showing an incongruent LT articulation of the left wrist.

Illustration A is a lateral radiograph of a patient with VISI posture demonstrating how to measure the SL angle between the lunate axis and the scaphoid axis.

Incorrect Answers:
Answer 1: The dorsal fibers of the SL ligament is the stronger portion of the SL ligament, which is not involved in this patient. A SL tear would result in different clinical exam findings, and radiographs with a widened SL interval and DISI posture.
Answer 2: The volar fibers of the SL ligament are the weaker portion of the SL ligament and is similarly not involved in this presentation.
Answer 3: Although the LT is involved in this case, the DORSAL aspect is the WEAKER portion of the LT ligament.
Answer 5. The short radiolunate ligament remains attached to the lunate in perilunate dislocations, but is not involved with LT disruption.