Lunotriquetral dissociation

Original Editor - Roselien Pas

Top Contributors - Roselien Pas, Laura Ritchie and Simisola Ajeyalemi  

Definition 

Lunotriquetral dissociation (LTD) is the second most common ligamentous cause of carpal instability and is classified by Mayo ‘s well-known Classification of Carpal instabilities as an example of dissociative carpal instability (CID). The intrinsic meaning of dissociation is the separation of a concrete substance. CID, used in this context, is the compound term to describe an injury to one of the major interosseous ligaments of the wrist, which is in case of LTD an injury of the lunotriquetral ligament. [1]

Clinically relevant atonomy

The lunotriquetral (LT) ligament is an intrinsic ligament of the wrist, more particular an interosseous carpal ligament which provide stability to the proximal carpal row. This ligament has a thin, horseshoe- shaped structure and can be divided into three parts: a dorsal, a proximal and a volar one. The volar and dorsal portions attach directly to the bone, while the proximal portion attaches to the hyaline articular cartilage of the joint. The volar portion is the most substantial one of the three parts because it ensures the functional stability within the lunotriquetral compartment. [2]     

Fig 1. Deep volar wrist ligaments. [3]

Deep volar wrist ligaments.png

Epidemiology/ Etiology

LTD is a complex injury and is difficult to apprehend. It can occur as an isolated rupture of the LT ligament, which is very uncommon and seldom causes symptoms. When a tear of the LT ligament appears in combination with injury of adjacent extrinsic ligaments (volar radiolunotriquetral ligament, ulnotriquetral ligament and dorsal radiolunotriquetral ligament) it produces complete lunotriquetral instability. This situation causes pain at the ulnar side of the wrist and a motion- associated click phenomenon. Due to the modified classification of Watson et al., LTD is divided into different stages ( Fig 2). [4]


Fig 2. The stages of lunotriquetral dissociation (Watson et al.)

I Pre- dynamic  Partial tear of the LT ligament
II Dynamic Complete rupture of the LT ligament
III Static  Complete tears of the LT ligament and other extrinsic ligaments
IV Osteoarthrotic Complete tears of the LT ligament and other extrinsic ligaments, which results in signs of articular degeneration in the midcarpal joint.


Typical for LTD is the ‘ volarflexed intercalated segment instability’ (VISI) configuration. In this formation, the lunate is abnormally rotated in flexion. An isolated LTD should theoretically result in this deformity. Nevertheless a lot of studies showed that the dorsal radiocarpal ligament must also be torn to allow this VISI configuration. [4]

LT ligament tears may occur due to the following movements: a fall onto the outstretched hand in pronation, extension and radial deviation, or from lifting injuries with the hand in forced pronation. [5]


Diagnostic procedures

Complaints related to LTD are generally a combination of ulnar sided wrist pain that is worsened by power gripping and a movement-dependent click phenomenon. Clinically there is tenderness over the lunotriquetral joint and an increased mobility of the triquetrum in relation to the lunate.

Physical Examination

[6]


During the examination of LTD, the following tests should be taken:


  1. The LT ballottement test by Reagan, Linscheid and Dobyns.This test, also called Reagan's test, involves translating the lunate in an anterior- posterior direction while stabilizing the triquetrum by placing your index finger on one side and your thumb on the other. Examine for pain, laxity, and crepitus, which are positive signs for this test. [3]
  2. The Kleinman’s shear test
    This test is similar to the previous one; the examiner’s thumb applies dorsal translation to the pisiform and volar translation to the lunate to reproduce symptoms. Compare this examination test again with the contralateral wrist. [3]
  3. The ulnar snuffbox test
    This test is performed by applying lateral pressure to the triquetrum between the flexor carpi ulnaris and the extensor carpi ulnaris tendons. Pain is considered a positive test result. [3]
  4. Click provocation
    A click with neutral to ulnar deviation with the wrist pronated and under axial compression has been reported to be a predictable finding in patients with dynamic lunotriquetral injury. [3]


Imaging

The following imaging technics should be used to diagnose lunotriquetral dissociation:

  • Arthroscopy is the most definitive modality for the evaluation of lunotriquetral injuries and has become the gold standard for diagnosis. [1][7]
  • Arthrography can demonstrate leakage or pooling of the contrast medium at the lunotriquetral interspace. ( Fig. 3) [5][4]
    Fig 3. Arthrography synoptically show tears of the LTL (arrow). [4]

    Arthrography tear LTL.png












  • Postero-anterior radiography should be taken to reveal the increase of the lunotriquetral joint space, as well as lateral views, which may show palmar flexion of the lunate. ( Fig. 4) [5]
    Fig 4. (A) PA radiograph and (B) lateral radiograph of LT dissociation. 

    Radiograph A.png
    Radiograph B.png


  • MR imaging, using coronal images can also evaluate injury to the intrinsic ligaments. (Fig. 5) [7]
    Fig. 5. Proximal intrinsic ligaments. Coronal cry microtome section of a cadaveric wrist (a) and corresponding fast spin-echo ‘12-weighted MR image from a normal volunteer (b) show the proximal intrinsic ligaments. [7]

    MR.png

Management

We must consider several factors when deciding on the optimal treatment plan for a patient with LTD. Stage of instability, time elapsed since injury, associated injuries and demands of the patient will all affect treatment choice.

Non-operative treatment

The first step in treatment of acute LT ligament injuries is immobilization during 6 weeks. Either a cast or a wrist splint will help to maintain optimal placement as ligament healing advances and inflammation diminishes. Steroid injection can be helpful in the diagnosis en symptomatic relief of this injury, especially in injuries that present more than 3 to 4 weeks after the inciting event. The injury may require 3 to 6 months of conservative treatment for complete resolution of symptoms. This will be curative in the majority of patients. [5]

Operative treatment

We must investigate the indications for medical treatment, including VISI deformity, if symptoms do not significantly improve within 6 weeks. The goal of medical management is to re-establish the lunocapitate alignment and to restore the integrity of the proximal carpal row. Options to achieve these goals include lunotriquetral arthrodesis, ligament reconstruction and ligament repair. [5]

References

  1. 1.0 1.1 Carlsen B.T. , Shin. A.Y. (2008). Wrist instability. Scandinavian Journal of Surgery, 97, 324-332. (1A)
  2. Doyle, J.R. (2006). Hand and wrist. Philadelphia: Lippincott Williams & Wilkins. (169-174).
  3. 3.0 3.1 3.2 3.3 3.4 Butterfield, W.L., Joshi, A.B., & Lichtman, D. (2002). Lunotriquetral injuries. Journal of the American Society for Surgery of the Hand. (4), 195- 203. (5)
  4. 4.0 4.1 4.2 4.3 Schmitt, R. , Froehner, S. , Coblenz, G. , & Christopoulos, G. (2006). Carpal instability. Eur Radiol, 16(10), 2161- 78. (1A)
  5. 5.0 5.1 5.2 5.3 5.4 Watanabe, A., Souza, F., Vezeridis P.S., Blazar, P., & Yoshioka,H. (2009). Ulnar-sided wrist pain. II. Clinical imaging and treatment. Skeletal Radiol, (39), 837-857. (1A)
  6. Physical Therapy Nation. Reagan's Ballot Test. Available from: http://www.youtube.com/watch?v=gFM25GC-Llc [last accessed 14/12/13]
  7. 7.0 7.1 7.2 Timins, M.E., Jahnke, J.P., Krah, S.F., Erickson, S.J., & Carrera, G.F.(1995). MR imaging of the major carpal stabilizing ligaments: normal anatomy and clinical examples. Radiographics, 15(3), 575-87. (2C)
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