Scapholunate Ligament

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Original Editor - Sukhi Dhaliwal Top Contributors - Sukhi Dhaliwal, Kim Jackson and Manisha Shrestha


Description[edit | edit source]

The scapholunate ligament (SLL) is one of the two proximal interosseous carpal ligaments of the wrist. The other being the lunotriquetral interosseous ligament.[1][2]

These ligaments cover the dorsal, proximal and palmar aspects of their respective joints. The distal aspect of each joint articulates with the midcarpal joint.

Illustration of scapholunate interosseous ligament anatomy. The drawing depicts a slightly oblique, coronal view of the distal radius (R), scaphoid (S) and lunate (L). The scapholunate ligament has been transected to demonstrate its three distinct parts, which include the dorsal region (arrowhead), palmer region (white arrow) and proximal region (black arrow) components. Note that the dorsal component is the thickest.

Scapholunate ligament regions:

  • Dorsal - thickest region; a true ligament; composed of transversely orientated collagen fibres; Provides most mechanical strength.
  • Palmer - thin region; a true ligament; orientated from palmer to dorsal obliquely progressing from schizoid to lunate; Provides most rotational constraint
  • Proximal - composed of fibrocartilage; no collagen orientation, blood supply or nerves; Covered partially by the radioscapholunate ligament palmarly; Provides minimal mechanical strength.

[2][3]

Attachments[edit | edit source]

SLL is a C shaped ligament that binds the scaphoid bone to the lunate bone of the wrist. The SLL inserts to the most proximal and superior parts of the the articular surface between the scaphoid and lunate bones. [2]

Function[edit | edit source]

SLL connects the scaphoid bone and the lunate bone to together, providing stability to the proximal carpal row of the wrist.[1] During load bearing activities, large forces are transmitted across the wrist joint. The carpal bones in the distal row distribute axial loads relatively evenly, 50% of the axial load is transmitted through the radioschapoid joint and 35% across the radiolunate joint. The SLL connects these two primary load bearing bones, thus, allowing the wrist the strength to withstand axial loads without giving way. [1]

Clinical relevance[edit | edit source]

Scapholunate ligament is the most commonly injured ligament in the hand. SLL injuries, also referred to as ligament sprains are most often due to physical trauma to the wrist. For example, sporting injuries, falls and motor vehicle accidents. The most common mechanism of injury is a fall onto an outstretched hand (FOOSH). SLL injuries can also be a result of chronic conditions such rheumatoid arthritis and pseudogout.[1]

As with other ligament sprains, the severity of the sprain can range from the tearing of a few fibres to a complete rupture of the SLL. A rupture or a tear of this ligament will lead to carpal instability. Scapholunate dissociation is the most frequent carpal instability of the wrist, it refers to the loss of the normal alignment between the scaphoid and lunate bones. About 13.4% of distal radius fractures are associated with scapholunate dissociation.[1] Eventually, untreated SL instability will lead to a progressive form of wrist osteoarthritis referred to as Scapholunate Advanced Collapse (SLAC).[3]

Assessment[edit | edit source]

History:

  • Acute - FOOSH- fall on to extended, ulnar deviated wrist
  • Acute - Motor vehicle accident, patient may report they were holding the steering wheel
  • Chronic - Repetitive heavy loading of the wrist
  • Chronic - Pre-exisitng inflammatory condition resulting in damage over time

[1]

Symptoms:

  • dorsal and radial sided wrist pain
  • pain with increased loading of the wrist
  • clicking or clunking sensation
  • wrist instability or weakness

[1]

Objective Assessment:

  • Inspection - signs of trauma, swelling etc.
  • Palpation - tenderness over anatomical snuff box or the palmer scaphoid tuberosity
  • Provocation tests: Watson's test "scaphoid shift test"
    • Test is performed by the examiner stabilizing the scaphoid with one hand while using the other hand to move the wrist from ulnar to radial deviation.
    • Positive test: The examiner should feel a significant "clunk" and the pt will experience pain.
  • Decreased range of motion due to pain
  • Decreased grip strength
  • Radiography - using static and dynamic radiographs with multiple views
  • MRI
  • Arthroscopy

[1]

Stages of SLL Injuries: :

  1. Predynamic instability
    • The ligament is only partially ruptured, no diastasis on standard or stress views between the scaphoid and lunate.
    • Patient may complain of pain when lifting objects or placing axial load on wrist (push up position).
  2. Dynamic instability
    • The ligament is completely ruptured but the dorsal region of the SLL is repairable, may show diastasis of SL joint on stress radiographs.
  3. Dynamic instabillty
    • The ligament is completely ruptured and irreparable, may show diastasis of the SL joint on stress radiographs.
    • Patient may complain of feeling clunking or weakness with lifting or placing and axial load on the wrist.
  4. Static instability
    • The ligament is irreparable and there is carpal malalignment at rest, scaphoid will be in a flexed and pronated position and the lunate will be in an extended position.
    • Patient may complain of feeling clunking or weakness with lifting or placing and axial load on the wrist.
  5. Scapholunate dissociation
    • The ligament is irreparable and there is carpal malalignment to the point where normal biomechanics of the wrist will never be restored and the cartilage is normal on arthroscopy. Plain radiography will show fixed SL diastasis on a PA view and increased SL angle on a lateral view.
    • The patient may or may not complain of pain.
  6. Scapholunate Advanced Collapse (SLAC)
    • The ligament is irreparable, there is fixed carpal malalignment , biomechanics of the wrist will never be restored and there is cartilage damage and wrist arthritis.
    • The patient may or may not complain of pain.

[1]

Treatment[edit | edit source]

Treatment of SLL injuries varies depending on the degree of injury. Due to insufficient evidence at this time there is no gold standard that can be declared. Currently, conservative options for less severe SLL injuries (predynamic phase) consist of a period of immobilization with casting/splint, activity modification and NSAIDs to manage pain. These patients may also benefit from arthroscopic debridement as they have shown success at reducing pain in patients with partial tears without clinical findings of instability. [4]For more severe SLL injuries for example, complete tears surgical intervention such as pins and wires may be required to hold the scaphoid and lunate bones in place as the ligament heals.[1]

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Konopka G, Chim H. Optimal management of scapholunate ligament injuries. Orthop Res Rev. 2018;10:41-54 https://doi.org/10.2147/ORR.S129620
  2. 2.0 2.1 2.2 Apergis, Emmanuel. Fracture-Dislocation of the Wrist. First Edition. Milan: Springer Verlag, 2013. p19-20.
  3. 3.0 3.1 Duke University. Duke Orthopaedics, Wheeless' Textbook of Orthopaedics. Available from:[1]. (Accessed 27 November 2021).
  4. Kitty, Alison MD, Wolfe, Scott MD. Scapholunate Instability: Current Concepts in Diagnosis and Management. J Hand Surg 2012;37A:2175–2196