Scapholunate Ligament

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

Description

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

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

Scapholunate ligaments - S, scaphoid; L, lunate; T, triquetrum; SLId, dorsal portion of scapholunate ligament; SLIpx, palmar and intermediate portion of scapholunate ligament; SLIp, palmar segment of scapholunate ligament

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.

Attachments

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.

Function

SLL connects the scaphoid bone and the lunate bone to together, providing stability to the proximal carpal row of the wrist. 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.

Clinical relevance

Scapholunate ligament is the most commonly injured ligament in the hand. A rupture or a tear of this ligament will lead to instability of the wrist. Scapholunate dissociation is the frequent carpal instability of the wrist. About 13.4% of distal radius fractures are associated with scapholunate dissociation. Eventually, untreated scapholunate instability will lead to wrist osteoarthritis and Scapholunate Advanced Collapse (SLAC).

Assessment

History:

• Acute FOOSH injury
• Degenerative rupture

Symptoms:

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

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

Treatment

Treatment of SLL injuries varies depending on the degree of injury. They can range from conservative management for non displaced SLL injuries to surgical intervention for more severe injuries.