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Lunotriquetral Dissociation

- See: Triquetrium

- Lunotriquetral Dissociation:
    - ulnar side carpal instability;
    - involves disruption of lunotriquetral & volar radiolunotriquetral ligaments & attentuation or rupture of dorsal radiotriquetral attachments;
    - w/ a isolated tear of the LT interosseous ligament, there will be only a small amount of increased motion, however, even this is enough to cause symptoms;
    - mechanism:
            - injury occurs w/ forced extension or extension-radial deviation, as scaphoid induces the lunate into a further flexion stance while triquetrum extends;
    - w/ advanced injury, lunotriquetral, volar radiolunotriequetral, & dorsal radiotriquetral ligaments are torn;
            - VISI collapse deformity develops;
    - diff dx: ulnar sided wrist pain
            - ulnar impaction syndrome

- Exam:
    - tenderness to direct pressure localized specifically to lunotriquetral joint;
    - ballottement test (shuck test)
            - triquetrum is displaced dorsally and palmarly on the lunate, demonstrating increase excursion over the normal side and often painful crepitus;
    - compression test: displacement of the triquetrum ulnarly during radioulnar deviation, which is also painful;
    - lunotriquetral shear maneuver involves stabilizing the lunate between thumb and index finger of one hand and the triquetrum between the thumb and index finger of the other;
            - the pisiform and triquetrum are pushed in a volar to dorsal direction;
            - discomfort in this area suggests the possibility of injury to lunotriquetral interosseous ligament;

- X-rays:
    - often radiographs will be unremarkable in lunotriquetral instability;
    - PA View:
         - shows fully developed volar intercalated-segment instability shows scaphoid to be volar flexed and foreshortened;
         - ring sign is present, & distance between the ring & proximal pole of scaphoid is decreased;
         - unlike the case with scapholunate dissociations, lunate is volar flexed and triangular;
         - triquetrum is dorsiflexed and distal in relation to the hamate;
         - on average the ulnar varience is neutral (0);
    - Lateral view:
         - may occassionally show static palmar flexion of the lunate (VISI deformity)
               - normal triquetrolunate angle of approx -16 degrees is converted to neutral or positive angle;
               - VISI deformity occurs in only a minority of cases because for it to occur there must be a tear of the dorsal radiocarpal ligament in addition to a tear of the LT interosseous ligament;

- Arthrography:
    - may accurately detect triquetral-lunate dissociation in the majority of cases;
    - note possible false positive study may be due to age related attritional changes in the LT interosseous membrane;
    - w/ a positive study, expect leakage of dye from the radiocarpal to the midcarpal joint or vice versa;

- Non Operative Treatment:
    - wrist immobilization;

- Operative Treatment:
    - arthroscopy allows the best method of determining whether LT instability is present;
    - lunotriquetral arthrodesis may be indicated for disabling pain after non operative treatment measures have failed;
    - patients may expect good to excellent relief of pain, upto 80% of normal wrist motion and upto 90% maintenance of grip strength;
    - technique:
           - dorsal incision centered over the LT joint (between 4th and 5th compartments);
           - extensor retinaculum is opened in line with the incision, thru the fifth extensor compartment;
           - wrist capsule is opened longitudinally along the LT joint;
           - articular cartilage betweeen these bones is removed, however, the most volar portion of the LT joint is left untouched inorder to preserve joint alignment and the inorder to hold the graft;
           - bone graft is applied between the lunate and triquetrum;
                   - bone graft is obtained either from distal radius or iliac crest;
           - ulnar margin of the triquetral is opened thru a second incision along the ulnar margin of the 6th extensor compartment;
           - arthrodesis is fixed w/ multiple K wires or with Herbert screw;
                   - attempt to place the Herbert screw centrally on both radiographic views;
                   - K wires should be left buried beneath the skin, since they may need to be left in place for several months;
    - post operative immobilization:
           - short arm cast for 6-12 weeks;
           - K wires are removed only after a solid fusion is demonstrated on radiographs

Management of Chronic Lunotriquetral Ligament Tears.

Lunotriquetral Arthrodesis.

Lunotriquetral sprains.

Complications of Intercarpal Arthrodesis.

Chronic Lunotriquetral Instability: Diagnosis and Treatment.

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