What are the pathomechanics of the triangular fibrocartilage relevant to ulnar-sided wrist pain?

Updated: Nov 22, 2019
  • Author: David M Lichtman, MD; Chief Editor: Harris Gellman, MD  more...
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Answer

Answer

The triangular fibrocartilage and the dorsal and volar ligaments arise from the ulnar aspect of the lunate facet of the radius. The triangular fibrocartilage continues ulnarly, inserting about the fovea at the base of the ulnar styloid. The fovea is a groove that separates the styloid from the ulnar head (see Clinical Presentation for a brief discussion of the ulnar fovea sign).

From the ulnar styloid, the triangular fibrocartilage extends distally, receiving contributions from the ulnar collateral ligament, which thickens (the meniscus homologue), inserting onto the lunate, the triquetrum, and the fifth metacarpal. The ulnar collateral ligament is a poorly developed thickening of the joint capsule that arises from the base of the ulnar styloid. The ulnolunate and ulnotriquetral ligaments arise from the volar radioulnar ligament and ulnar styloid, extend to the lunate and triquetrum, and then extend to volar aspects of the capitate and hamate. The tip of the ulnar styloid distal to the fovea is covered by hyaline cartilage where it lies within the prestyloid recess.

The sixth dorsal compartment containing the extensor carpi ulnaris (ECU) is a subsheath that is separate from the extensor retinaculum. From the dorsal base of the ulnar styloid, fibers from the subsheath blend and strengthen the dorsal aspect of the triangular cartilage and ligaments. These fibers extend to the fifth metacarpal distally. The actual extensor retinaculum courses over the subsheath; continues volarly without attachment to the ulna; and inserts onto the pisiform, triquetrum, fifth metacarpal, and volar ulnar soft-tissue structures.

At the volar wrist, the ulnar nerve lies lateral to the flexor carpi ulnaris (FCU) and is accompanied by the ulnar artery to its lateral side. Both the ulnar artery and nerve pass through the Guyon canal. The dorsal surface of the Guyon canal is composed of the pisohamate ligament. Forearm fascia and expansions from the FCU tendon (volar carpal ligament) form the volar surface. The canal is bordered by the pisiform medially and the hook of the hamate laterally.


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