Acute Triangular Fibrocartilage Complex Tears

Tamara John

Seth D. Dodds

INTRODUCTION

General considerations
- Triangular fibrocartilage complex (TFCC) injuries: major cause of ulnar-sided wrist pain
- Important stabilizer of distal radioulnar joint (DRUJ)
- Absorbs some wrist load from the ulnocarpal (UC) joints¹
- Stabilizes forearm rotation—strong connection between distal radius and ulna
- Supports ulnar carpus²
Blood supply/nerve supply
- Enters from the periphery (like meniscus in knee)
- Peripheral tears more amenable to healing.³
- Ulnar artery—Supplies ulnar TFCC through dorsal and palmar radiocarpal branches
- Dorsal and palmar branches of anterior interosseous artery: supply the radial periphery TFCC
- Central TFCC not amenable to repair; avascular
- Nerve supply: only to the peripheral aspect of the TFCC, from posterior interosseus nerve, ulnar nerve, and dorsal sensory branch of ulnar nerve.⁴,⁵
Components of TFCC (Table 24.1 and Figure 24.1)
- Articular disk (triangular fibrocartilage)
- Dorsal and volar distal radioulnar ligaments
- Ligamentous insertion to the fovea
- Meniscus homologue
- UC ligaments
- Ulnar collateral ligament (UCL)
- Subsheath of the extensor carpi ulnaris (ECU)
Articular disk (triangular fibrocartilage)
- Base of articular disk attached to sigmoid notch of radius
- Apex of articular disk attached to the dorsal and volar capsule of the UC joint
- Disk continues ulnarly and volarly to merge with the UCL
- Distal: combined ligaments become thickened (meniscus homologue)—inserts distally on triquetrum, hamate, and base of the fifth metacarpal bone²,⁶
- Definition of meniscus homologue: Fibrocartilaginous rim of dense connective tissue that joins with dorsal and volar distal radioulnar ligaments⁷
Superficial dorsal and volar distal radioulnar ligaments (Figure 24.2)
- Origin—dorsal and volar aspects of the radial sigmoid notch
- Insertion—dorsal ulnar head and volar ulnar head, respectively
- Deep fibers insert onto ulnar fovea
- Superficial fibers insert onto the ulnar styloid fossa⁸
Ligamentous foveal insertion of the TFCC (Figure 24.3)
- Independent structure—ligamentum subcruentum
- Triangular in shape, supported by loose fibrovascular connective tissue
- Comprises deep dorsal and volar distal radioulnar ligaments
- Shares common origin with superficial ligaments; inserts deep to superficial radioulnar ligaments onto fovea
- Intermediate to high signal intensity on fluid-sensitive Magnetic resonance imaging (MRI) sequences should raise suspicion for subcruentum injury⁹
UC ligaments
- Components—ulnolunate, ulnotriquetral, and ulnocapitate ligaments
- Origin—triangular fibrocartilage
- Insertion—respective carpal bone
ECU subsheath and UCL
- ECU subsheath more important stabilizer of ulnar wrist compared to UCL
- UCL weaker structure with more laxity¹⁰
- Major intrinsic stabilizer of DRUJ: TFCC
- Major extrinsic stabilizers of DRUJ: ECU subsheath, distal fibers of interosseous membrane, pronator quadratus
- Mechanism of injury/epidemiology
  - Biomechanics—ulnar side of wrist/TFCC sees 18% to 20% load across wrist
  - Ulnar deviation—increases load across TFCC
  - Increased ulnar variance = increased force across TFCC
  - Maximal grip and pronation increase ulnar variance, increased force across TFCC¹¹
  - Injury mechanism—axial load with wrist extended and pronated—for example, falling on outstretched hand
  - Twisting injury—torque to wrist and forearm during racquet sport
  - Idiopathic pain, clicking without known trauma¹²
  - 3% to 9% of all athletic injuries involve the hand/wrist
  - Common in athletes but no specific TFCC epidemiologic data
  - Result of acute trauma, fall, overuse, repetitive trauma

TABLE 24.1 Structures of the TFCC

TFCC Structure	Origin	Insertion
Articular disk (triangular fibrocartilage)	Radius: sigmoid notch Ulna: fovea/ulnar head	Merges with UCL; triquetrum, hamate, base of fifth MC
Dorsal radioulnar ligament	Sigmoid notch of the radius (dorsal aspect)	Head of ulna (dorsally)
Volar radioulnar ligament	Sigmoid notch of the radius (volar aspect)	Head of ulna (volarly)
Meniscus homologue	TFC	Ulnar styloid
Ulnocarpal ligaments Ulnolunate Ulnotriquetral Ulnocapitate	Triangular fibrocartilage	Respective carpal bones
UCL	Styloid process of the ulna	First fasciculus: medial triquetrum Second fasciculus: pisiform/flexor retinaculum
ECU subsheath	ECU tendon sheath	Ulnar head/TFC
Abbreviations: UCL, ulnar collateral ligament; ECU, extensor carpi ulnaris; MC, metacarpal; TFC, triangular fibrocartilage complex; tfnTFCC, triangular fibrocartilage complex.

FIGURE 24.1 This line drawing illustrates the triangular fibrocartilage complex and its principal components, the palmar and dorsal radioulnar ligaments, the articular disc, and the meniscal homologue. S, scaphoid; L, lunate; tq, triquetrum; P, pisiform; R, radius; U, ulna.

FIGURE 24.2 The illustration demonstrates soft tissue layers overlying the TFCC. There are tears of the palmar and dorsal radioulnar ligaments as well as the lunotriquetral ligaments. ECU, extensor carpi ulnaris; TFCC, triangular fibrocartilage complex; UCL, ulnar collateral ligament; R, radius; U, ulna; L, lunate; tq, triquetrum; EIP, extensor indicis proprius; EDM, extensor digiti minimi; USN, ulnar sensory nerve.

FIGURE 24.3 This T2-weighted MR arthrogram reveals an intact ligamentous, foveal insertion of the triangular fibrocartilage complex, noted by at the asterisk.

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