Topics

Topic

design image
Triangular fibrocartilage complex (TFCC )

The triangular fibrocartilage complex (TFCC) is a fibrocartilaginous and ligamentous structure located on the ulnar side of the wrist, between the ulna, lunate, and triquetrum. It provides stability to the distal radioulnar joint (DRUJ) and cushions axial loads transmitted through the ulnar carpus.

The TFCC acts as a major stabilizer of the ulnar wrist, enabling smooth forearm rotation and load transfer between the radius and ulna. It is composed of several interconnected components that together form a triangular structure on axial section, hence the name.

Synonyms

  • Ulnar triangular complex

  • Articular disc complex of the wrist

  • Ulnocarpal fibrocartilage

Components

The TFCC is a composite structure that includes:

  • Articular disc (triangular fibrocartilage): Central avascular fibrocartilaginous structure connecting radius and ulna.

  • Dorsal and volar radioulnar ligaments: Stabilize the distal radioulnar joint during pronation-supination.

  • Ulnolunate and ulnotriquetral ligaments: Ulnocarpal ligaments anchoring the TFCC to carpal bones.

  • Meniscus homologue: Fibrocartilaginous band connecting triquetrum to the ulnar styloid process.

  • Extensor carpi ulnaris (ECU) subsheath: Provides dorsal reinforcement and stabilizes ECU tendon.

Origin, Course, and Insertion

  • Origin: From the ulnar notch of the distal radius and base of the ulnar styloid process.

  • Course: Extends transversely across the distal radioulnar joint, covering the ulnar head.

  • Insertion: Attaches to the base of the ulnar styloid, lunate, and triquetrum via ulnocarpal ligaments.

Relations

  • Superiorly: Distal radioulnar joint and ulnar head

  • Inferiorly: Carpal bones (lunate and triquetrum)

  • Medially: Ulnar styloid process and ulnar collateral ligament

  • Laterally: Ulnar aspect of distal radius and sigmoid notch

  • Dorsally: Extensor carpi ulnaris tendon and subsheath

  • Ventrally: Pronator quadratus and volar wrist capsule

Function

  • DRUJ stability: Prevents dorsal and volar displacement of the ulna during rotation

  • Load transmission: Distributes compressive and shear forces between ulna and carpus

  • Shock absorption: Cushions the ulnar side of the wrist during axial loading

  • Rotation coordination: Maintains congruency during pronation and supination

  • Joint lubrication: Assists in smooth articulation of distal radius, ulna, and carpus

Nerve Supply

  • Branches of the anterior interosseous nerve and posterior interosseous nerve provide articular sensation to the TFCC and DRUJ capsule

Clinical Significance

  • TFCC tear: Common in ulnar-sided wrist pain, often from twisting, traction, or axial loading

  • Degenerative changes: Seen in chronic ulnar impaction syndrome

  • Instability: DRUJ instability may occur with peripheral TFCC tears or ulnar styloid fractures

  • Classification:

    • Palmer type 1: Traumatic tears (1A–1D)

    • Palmer type 2: Degenerative lesions (2A–2E)

  • Symptoms: Ulnar wrist pain, clicking, decreased grip strength, and instability during rotation

  • Surgical relevance: Arthroscopic debridement or repair depends on tear location (central vs peripheral)

MRI Appearance

  • T1-weighted images:

    • TFCC: Low signal (dark), homogeneous structure between ulna and carpus

    • Ulnar head and carpal bones: Intermediate-to-bright marrow signal

    • Tears: Appear as linear or focal high-signal areas within the low-signal fibrocartilage

    • Ulnar styloid attachment: Best seen in coronal and axial planes

  • T2-weighted images:

    • Normal TFCC: Low signal intensity (dark triangular band)

    • Tears: Linear or focal hyperintense signal within the TFCC or extending to articular surfaces

    • Associated findings: Joint effusion or ulnar-sided fluid tracking into DRUJ or ulnocarpal space

  • STIR:

    • Normal TFCC: Intermediate-to-dark signal

    • Inflammation or tear: Bright hyperintense signal along TFCC margins or attachments

    • Ulnar impaction: Bone marrow edema in ulnar head or lunate seen as bright hyperintensity

  • Proton Density Fat-Saturated (PD FS):

    • Normal TFCC: Dark, well-defined triangular structure

    • Tear: Focal bright signal line or gap in low-signal structure

    • Chronic degeneration: Diffuse irregular brightening and thickening of TFCC

    • Best sequence for: Subtle tears, partial detachments, or mucoid degeneration

  • T1 Fat-Sat Post-Contrast:

    • Normal TFCC: Minimal enhancement

    • Inflammatory changes: Peripheral or linear enhancement along TFCC or DRUJ capsule

    • Post-surgical or chronic tear: Irregular enhancement in reparative fibrous tissue

MRI Arthrogram Appearance

  • Direct MR Arthrography:

    • Intra-articular contrast highlights the TFCC margins.

    • Tears: Contrast enters and fills the defect, producing bright signal through the disc.

    • Central perforation: Contrast passes between radiocarpal and DRUJ compartments.

    • Peripheral tear: Contrast outlines separation from ulnar attachment or capsule.

CT Appearance

Non-Contrast CT:

  • TFCC: Not distinctly visualized due to soft-tissue density

  • Bony landmarks: Ulnar head, lunate, triquetrum, and distal radius margins well defined

  • Pathology: Subchondral sclerosis, cysts, or ulnar variance indicating impaction

  • Fracture or avulsion: Ulnar styloid avulsion fragments may indicate TFCC detachment

Post-Contrast CT (standard):

  • Direct CT arthrography: Contrast outlines TFCC, appearing as a dark band surrounded by bright contrast in the DRUJ and ulnocarpal recesses

  • Tears: Contrast leakage through TFCC into DRUJ or ulnocarpal space indicates perforation or peripheral tear

  • Chronic injury: Thickened, irregular TFCC margins or associated osteoarthritic changes

MRI image

Triangular fibrocartilage complex (TFCC ) axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Triangular fibrocartilage complex (TFCC ) mri coronal image

MRI image

Triangular fibrocartilage complex (TFCC ) mri sagittal image