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Volar radioulnar ligament

The volar radioulnar ligament (VRUL) is a strong fibrous band that forms part of the triangular fibrocartilage complex (TFCC) in the wrist. It extends between the ulnar head and the distal radius, acting as a primary stabilizer of the distal radioulnar joint (DRUJ). The ligament functions in concert with its dorsal counterpart to maintain forearm stability during pronation and supination.

The volar radioulnar ligament is essential for constraining anteroposterior translation of the radius relative to the ulna and provides proprioceptive feedback for dynamic wrist control. It tightens during supination and relaxes during pronation, working reciprocally with the dorsal radioulnar ligament.

Synonyms

  • Anterior radioulnar ligament

  • Palmar radioulnar ligament

  • Volar DRUJ ligament

Origin, Course, and Insertion

  • Origin: Arises from the volar edge of the sigmoid notch of the distal radius and the anterior border of the triangular fibrocartilage.

  • Course: Runs obliquely and medially across the volar aspect of the distal radioulnar joint capsule, blending with the volar portion of the triangular fibrocartilage disc.

  • Insertion: Attaches to the ulnar styloid process and adjacent volar margin of the ulnar fovea, forming part of the deep and superficial laminae of the TFCC.

Relations

  • Anteriorly: Flexor digitorum profundus tendons and pronator quadratus muscle

  • Posteriorly: Distal radioulnar joint cavity

  • Laterally: Distal radius and sigmoid notch

  • Medially: Ulnar head and triangular fibrocartilage disc

  • Inferiorly: Blends with the capsule of the radiocarpal joint

Structure

  • Composed of dense collagen fibers arranged in parallel and oblique bundles.

  • Divided into superficial and deep fibers:

    • Superficial fibers: Insert into the ulnar styloid process and contribute to capsule stability.

    • Deep fibers: Attach to the ulnar fovea and are key for rotational stability of the DRUJ.

  • Works synergistically with the dorsal radioulnar ligament and interosseous membrane.

Function

  • Joint stabilization: Prevents anterior translation of the radius during pronation and supination.

  • Dynamic tensioning: Tightens in supination to stabilize the distal radioulnar joint.

  • Load transmission: Transfers compressive forces from the radius to the ulna and carpus through the TFCC.

  • Proprioception: Contributes to wrist position sense and movement coordination.

Clinical Significance

  • TFCC injury: Partial or complete tear of the volar radioulnar ligament is common in TFCC lesions, leading to distal radioulnar joint instability.

  • DRUJ instability: May occur from trauma, repetitive pronation-supination, or degenerative changes.

  • Rupture patterns: Typically associated with avulsion from the ulnar fovea or disruption near the radial attachment.

  • Symptoms: Ulnar-sided wrist pain, clicking, decreased grip strength, and reduced forearm rotation.

  • Surgical relevance: Repair or reconstruction of the volar and dorsal radioulnar ligaments is essential in DRUJ stabilization procedures.

MRI Appearance

  • T1-weighted images:

    • Ligament appears as a thin, low-signal (dark) band along the volar aspect of the distal radioulnar joint.

    • Surrounded by bright periligamentous fat, improving contrast.

    • Chronic thickening or fibrosis may appear as slightly intermediate signal.

  • T2-weighted images:

    • Normal ligament: dark low-signal band.

    • Tears: discontinuity or focal hyperintense signal within ligament fibers.

    • Partial injuries: show irregular contour and mild periligamentous bright signal.

    • Adjacent TFCC degeneration: heterogeneous intermediate-to-bright signal near ulnar insertion.

  • STIR:

    • Normal ligament: dark to intermediate signal.

    • Pathology: bright hyperintense signal in surrounding soft tissues indicating edema or synovial inflammation.

    • Excellent for detecting acute TFCC tears and periligamentous effusion.

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligament: dark, well-defined linear band.

    • Partial or full-thickness tears: bright focal signal within or around ligament fibers.

    • Diffuse hyperintensity along ligament course indicates inflammation or microtears.

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal to no enhancement.

    • TFCC tear or synovitis: enhancing periligamentous soft tissue.

    • Chronic injury: thickened, enhancing scar tissue replacing normal low-signal ligament.

CT Appearance

Non-Contrast CT:

  • Ligament not directly visualized due to small size and low density.

  • Indirect signs: soft-tissue thickening or fat plane obliteration around the volar DRUJ.

  • Chronic injuries: may show mild irregularity or calcification along the ulnar attachment.

Post-Contrast CT (standard):

  • Highlights periligamentous enhancement in inflammation or acute injury.

  • Useful for identifying associated ulnar styloid fractures, TFCC calcification, or capsular thickening.

MRI images

Volar radioulnar ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Volar radioulnar ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI images

Volar radioulnar ligament mri coronal image

MRI images

Volar radioulnar ligament mri sagitta image