Short Radiolunate Ligament: Anatomy, Function, MRI & CT Imaging

Topic

Short radiolunate ligament

The short radiolunate ligament (SRL) is a strong, intrinsic palmar (volar) radiocarpal ligament that connects the anterior surface of the distal radius to the palmar surface of the lunate bone. It is one of the key stabilizing ligaments of the wrist, located on the ulnar side of the wrist’s volar aspect, deep to the flexor tendons.

The SRL is crucial for stabilizing the radiolunate joint and maintaining normal carpal alignment during wrist motion. It functions synergistically with the long radiolunate, radioscaphocapitate, and ulnolunate ligaments, forming part of the volar radiocarpal complex that prevents volar translation of the lunate.

Synonyms

Volar short radiolunate ligament
Anterior radiolunate ligament
Palmar radiolunate ligament

Origin, Course, and Insertion

Origin: Anterior (palmar) margin of the distal radius, just ulnar to the radioscaphocapitate ligament.
Course: Short, thick, and oblique fibers pass distally and medially across the radiocarpal joint capsule.
Insertion: Palmar surface of the lunate, near its midportion.

Relations

Anteriorly: Flexor digitorum profundus and flexor pollicis longus tendons, covered by the flexor retinaculum.
Posteriorly: Radiocarpal joint cavity and anterior lunate surface.
Laterally: Radioscaphocapitate ligament.
Medially: Long radiolunate ligament and ulnolunate ligament.

Structure

Thick, short band of dense collagenous tissue.
Oriented obliquely from proximal-lateral to distal-medial direction.
Integrates with the volar capsule of the wrist.
Often blends distally with the long radiolunate ligament.

Function

Primary stabilizer of the radiolunate articulation.
Prevents volar translation and excessive motion of the lunate on the radius.
Acts in synergy with adjacent volar ligaments to maintain carpal stability during wrist flexion and extension.
Resists rotational and shearing stresses within the proximal carpal row.
Contributes to smooth load transmission from the hand to the radius during grip and weight-bearing.

Clinical Significance

Ligament tears: May occur in lunate dislocation, perilunate instability, or radiocarpal fracture-dislocation.
Degeneration: Common in chronic carpal instability or post-traumatic arthritis.
Injury patterns: Frequently involved with scapholunate dissociation or lunotriquetral instability.
Imaging importance: Assessment of SRL integrity is vital in diagnosing midcarpal and radiocarpal instability syndromes.
Surgical relevance: Repair or reconstruction of the SRL may be required during volar ligamentous stabilization procedures.

MRI Appearance

T1-weighted images:

Normal ligament: low signal (dark linear band) connecting the distal radius and lunate.
Surrounding fat: bright, enhancing ligament visualization.
Disruption or partial tear: intermediate-to-bright signal gap or irregularity in the ligament.
Adjacent bone marrow: bright on T1 due to fatty content in normal adults.

T2-weighted images:

Intact ligament: low signal throughout its course.
Partial or complete tear: bright hyperintense signal within or replacing the ligament.
Joint fluid or synovitis: bright signal outlining ligament margins.
Lunate and radial cartilage appear intermediate-to-bright relative to ligament.

STIR:

Normal ligament: dark (low signal intensity).
Pathology: bright hyperintensity in cases of acute strain, tear, or inflammatory thickening.
Periligamentous edema and joint effusion easily detected.

Proton Density Fat-Saturated (PD FS):

Normal SRL: dark linear structure with clear margins.
Tears: bright focal signal indicating disruption or mucoid degeneration.
Best for evaluating partial tears and adjacent soft-tissue changes.

T1 Fat-Sat Post-Contrast:

Normal ligament: minimal enhancement.
Inflamed or torn ligament: enhancing thickened segment or rim enhancement at attachment sites.
Postoperative or chronic scarring: mild heterogeneous enhancement.

CT Appearance

Non-Contrast CT:

Ligament not directly visualized due to its small size and soft-tissue density.
Indirect findings include:
- Widening of radiolunate joint space
- Lunate malalignment or volar tilt
- Cortical avulsion fragments near radial or lunate attachments.
High-resolution CT shows adjacent bony landmarks and secondary degenerative changes.

Post-Contrast CT (standard):

Ligament remains poorly differentiated.
Periligamentous enhancement or adjacent soft-tissue swelling may indicate inflammation or scarring.
CT arthrography (if performed) demonstrates contrast leakage into the radiolunate interval, confirming ligament disruption.

MRI images

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