📌 Sagittal Wrist MRI Anatomy_Ulnar-Sided Stabilizing System

https://youtu.be/kOoXWzWtoYM

 

 

https://youtube.com/shorts/gBfJcQGh48I

 

Concept

On sagittal wrist magnetic resonance imaging,
the triangular fibrocartilage complex should not be read as a single disc.
It represents a continuous ulnar-sided stabilizing system connecting the distal radioulnar joint to the ulnocarpal joint.

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Central Anchor — Articular Disc

• The articular disc lies at the center of the triangular fibrocartilage complex.
• Its dorsal and volar margins are not free edges.
• They blend directly into the dorsal and volar radioulnar ligaments, forming the core stabilizing arms.

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Radioulnar Ligaments

Dorsal Radioulnar Ligament

• Thickened dorsal peripheral margin of the articular disc.
• Extends from the dorsal rim of the distal radius (sigmoid notch)
  to the ulnar styloid and fovea of the ulnar head.
• Consists of:
• Becomes taut in pronation and provides dorsal stability of the distal radioulnar joint.
• Blends dorsally with the floor of the extensor carpi ulnaris tendon sheath.

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Volar Radioulnar Ligament

• Thickened volar peripheral margin of the articular disc.
• Originates from the palmar rim of the sigmoid notch and lunate facet of the distal radius.
• Also composed of superficial (styloid) and deep (foveal) fibers.
• Tightens in supination, acting as the primary volar stabilizer of the distal radioulnar joint.
• Serves as the proximal origin for the major palmar ulnocarpal ligaments.

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Ulnocarpal Ligaments (Distal Continuation)

Ulnolunate Ligament

• Palmar ligament extending from the volar radioulnar ligament region
  and indirectly from the ulnar fovea or styloid base.
• Inserts on the palmar cortex of the lunate.
• Courses distally along the long axis of the forearm.
• Helps suspend the lunate and resist palmar and ulnar translation of the proximal carpal row.

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Ulnotriquetral Ligament

• Palmar ligament arising mainly from the volar radioulnar ligament,
  with partial contribution from the palmar-ulnar aspect of the ulnar styloid.
• Fans out distally to the proximal and ulnar surfaces of the triquetrum.
• Lies just ulnar to the ulnolunate ligament.
• Contributes to ulnocarpal stability and load transmission from the ulnar carpus to the ulna.

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MRI Take-Home Message

On sagittal wrist magnetic resonance imaging:
disc → radioulnar ligaments → ulnocarpal ligaments
should be followed as one continuous stabilizing chain.
Instability rarely comes from the disc alone.

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