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Dorsal scapholunate ligament

The dorsal scapholunate ligament (DSLL) is the strongest and most functionally important component of the scapholunate interosseous ligament (SLIL) complex, which connects the scaphoid and lunate bones in the proximal carpal row of the wrist. It plays a critical role in stabilizing the scapholunate joint, maintaining synchronous motion between the two bones during wrist flexion and extension.

The ligament is essential for maintaining carpal alignment, and its injury is a major cause of scapholunate dissociation and dorsal intercalated segment instability (DISI) deformity.

Synonyms

  • Dorsal portion of the scapholunate interosseous ligament

  • Dorsal scapholunate intercarpal ligament

Origin, Course, and Insertion

  • Origin: Dorsal ridge of the scaphoid bone

  • Course: Runs obliquely dorsally and slightly radially across the scapholunate joint

  • Insertion: Dorsal surface of the lunate bone, blending with dorsal wrist capsule fibers

Structure

  • Composed of dense collagen bundles arranged obliquely and transversely, providing strong resistance to distraction and rotation.

  • Average thickness: 2–3 mm; length: approximately 4–5 mm.

  • The dorsal band is thicker and stronger than the palmar or proximal portions of the scapholunate ligament complex.

  • It merges with the dorsal radiocarpal and dorsal intercarpal ligaments, forming part of the dorsal capsuloligamentous network of the wrist.

Relations

  • Superficial: Dorsal wrist capsule and extensor tendon sheaths (mainly extensor carpi radialis brevis and longus).

  • Deep: Scapholunate joint space and articular cartilage.

  • Radial side: Scaphoid bone.

  • Ulnar side: Lunate bone.

  • Proximal: Radiocarpal joint.

  • Distal: Capitate and dorsal intercarpal ligaments.

Attachments

  • Proximal: Fibrocartilaginous integration into dorsal capsule.

  • Distal: Anchors into the dorsal ridges of the scaphoid and lunate.

  • Blends with: Dorsal intercarpal and dorsal radiocarpal ligaments.

  • Connective fibers: Extend into the dorsal capsule and occasionally into interosseous septa of the wrist.

Nerve Supply

  • Supplied by small articular branches of the posterior interosseous nerve, which provide proprioceptive feedback to wrist ligaments.

Function

  • Primary stabilizer of the scapholunate articulation.

  • Controls motion between scaphoid and lunate, preventing pathological separation or rotation.

  • Resists dorsal translation of the scaphoid during wrist extension.

  • Synchronizes carpal motion during radial and ulnar deviation.

  • Proprioceptive role: Provides sensory input for wrist position and coordination.

Clinical Significance

  • Scapholunate ligament tear: Most common cause of carpal instability following wrist trauma.

  • Scapholunate dissociation: Widening of the scapholunate interval (“Terry Thomas sign”) on radiographs.

  • Dorsal intercalated segment instability (DISI): Caused by loss of tethering between scaphoid and lunate, leading to dorsal tilt of lunate.

  • Chronic instability: May result in scapholunate advanced collapse (SLAC wrist).

  • Arthroscopy and imaging: DSLL integrity is key in staging scapholunate injury and planning surgical repair.

MRI Appearance

  • T1-weighted images:

    • Ligament appears as a thin, low-signal (dark) band connecting dorsal scaphoid and lunate.

    • Adjacent fat planes and marrow are bright, aiding contrast.

    • Disruption, thickening, or signal heterogeneity indicates partial or complete tear.

  • T2-weighted images:

    • Normal ligament: low signal (dark), sharply defined margins.

    • Partial tear: focal intermediate or bright hyperintensity with fiber continuity.

    • Complete tear: discontinuity or fluid-filled gap between scaphoid and lunate.

    • Associated findings: increased scapholunate space, marrow edema in adjacent bones, and joint effusion.

  • STIR:

    • Ligament: normally dark to intermediate signal.

    • Pathology: bright hyperintense areas indicating edema, inflammation, or fiber disruption.

    • Highlights periligamentous fluid and bone marrow edema around scapholunate articulation.

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligament: low signal band with smooth contour.

    • Partial tear: focal bright signal within ligament substance.

    • Complete rupture: gap with bright fluid signal replacing ligament fibers.

    • Sensitive for subtle intercarpal soft-tissue injury.

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: minimal enhancement.

    • Injured ligament: focal or diffuse enhancement of torn fibers and adjacent capsule.

    • Synovitis or granulation tissue in chronic tears shows irregular enhancement.

CT Appearance

Non-Contrast CT:

  • Ligament not directly visible but inferred from bony relationships between scaphoid and lunate.

  • Indirect signs: scapholunate interval widening (>3 mm), cortical irregularity, subchondral cysts, or sclerosis.

  • Useful for evaluating associated fractures or degenerative changes.

Post-Contrast CT (CT Arthrography):

  • Contrast outlines scapholunate joint and ligament region.

  • Normal ligament: smooth contour with no intra-articular contrast communication.

  • Partial tear: small focal contrast extension into the scapholunate space.

MRI images

Dorsal scapholunate ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Dorsal scapholunate ligament mri coronal image

MRI images

Dorsal scapholunate ligament sagittal mri image