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Dorsal radioulnar ligament

The dorsal radioulnar ligament (DRUL) is one of the two principal ligaments of the distal radioulnar joint (DRUJ), the other being the palmar (volar) radioulnar ligament. Together, they form the key stabilizing components of the triangular fibrocartilage complex (TFCC).

The DRUL extends between the distal ends of the radius and ulna on the dorsal aspect of the wrist. It stabilizes the DRUJ during pronation and supination, preventing excessive separation or translation of the ulna relative to the radius. It is composed of dense fibrous connective tissue and functions as a crucial static stabilizer for wrist rotation and load transmission.

Synonyms

  • Dorsal distal radioulnar ligament

  • Dorsal component of the triangular fibrocartilage complex

  • Dorsal radioulnar band

Origin, Course, and Insertion

  • Origin: Posterior margin of the sigmoid notch of the distal radius.

  • Course: Fibers pass obliquely dorsomedially across the dorsal aspect of the distal radioulnar joint.

  • Insertion: Attaches to the dorsal margin of the ulnar head and base of the ulnar styloid process.

Structure

  • Composed of dense collagen bundles oriented obliquely and horizontally.

  • Works synergistically with the palmar radioulnar ligament as part of the TFCC.

  • Taut during pronation, relaxed during supination.

  • Receives reinforcement from the dorsal capsule of the wrist joint and extensor retinaculum.

Relations

  • Superficially: Extensor tendons of the wrist (particularly extensor digitorum and extensor digiti minimi).

  • Deeply: Articular surfaces of the distal radius and ulna, along with the TFCC articular disc.

  • Proximally: Posterior border of the distal radius.

  • Distally: Capsule of the distal radioulnar and radiocarpal joints.

  • Medially: Ulnar head and triangular fibrocartilage (articular disc).

Attachments

  • Proximal attachment: Posterior rim of the sigmoid notch of the radius.

  • Distal attachment: Dorsal aspect of the ulnar fovea and base of the ulnar styloid.

  • Associated structures: Merges with fibers of the dorsal capsule and the TFCC disc, contributing to DRUJ stability.

Nerve Supply

  • Branches of the anterior and posterior interosseous nerves (from the radial and ulnar nerves respectively) provide proprioceptive and sensory innervation to the TFCC region.

Function

  • Primary stabilizer of DRUJ: Prevents dorsal displacement of the ulna during pronation.

  • Load transmission: Transfers compressive and shear forces between the radius and ulna during wrist loading.

  • Joint congruence: Maintains alignment of the distal radius and ulna during forearm rotation.

  • Dynamic role: Works with the palmar radioulnar ligament to balance tension through pronation–supination.

  • Proprioception: Contributes sensory feedback for coordinated wrist motion.

Clinical Significance

  • TFCC injury: DRUL is frequently involved in traumatic TFCC tears, especially from pronation and axial loading (e.g., falls on an outstretched hand).

  • DRUJ instability: Partial or complete rupture leads to pain, subluxation, and loss of rotational control.

  • Degenerative changes: Chronic microtrauma can cause thickening or fibrosis.

  • Post-surgical relevance: Critical to evaluate after TFCC repair, ulnar shortening osteotomy, or distal ulna fractures.

  • Imaging importance: MRI is the gold standard for assessing ligament integrity, fiber continuity, and associated TFCC pathology.

MRI Appearance

  • T1-weighted images:

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

    • Adjacent fat planes show bright signal outlining the structure.

    • Disruption or thickening suggests partial tear or scarring.

  • T2-weighted images:

    • Normal ligament remains dark (low signal) against intermediate joint capsule and fluid background.

    • Tear or inflammation: Shows bright hyperintense signal replacing or interrupting normal low-signal fibers.

    • Joint effusion: bright signal separating ligament from TFCC.

  • STIR:

    • Normal DRUL: dark to intermediate signal.

    • Pathologic changes: bright hyperintensity at ligament margins due to edema, sprain, or partial tear.

    • Particularly sensitive for detecting soft-tissue edema around the TFCC.

  • Proton Density Fat-Saturated (PD FS):

    • Ligament: dark linear structure with sharply defined borders.

    • Partial tear or strain: focal bright hyperintensity disrupting continuity.

    • Post-traumatic fibrosis: thickened, irregular, low-to-intermediate signal.

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal or no enhancement.

    • Inflamed or injured ligament: peripheral or diffuse enhancement from reactive synovitis or granulation tissue.

    • Chronic tears: show minimal enhancement with irregular margins.

CT Appearance

Non-Contrast CT:

  • Ligament not directly visualized due to low soft-tissue contrast.

  • Indirect findings: widening of the distal radioulnar joint space or small avulsion fragments from the ulnar fovea.

  • Soft-tissue windows may reveal thickened dorsal capsule or scarring.

Post-Contrast CT (standard):

  • Enhanced visualization of the joint capsule and surrounding synovium.

  • Helps identify peri-ligamentous fibrosis, post-surgical scarring, or chronic inflammation.

  • May detect small avulsion fractures or calcification at ligament attachments.

MRI images

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

MRI images

Dorsal radioulnar ligament mri coronal image

MRI images

Dorsal radioulnar ligament mri sagittal image