9 Triangular Fibrocartilage Complex and Distal Radioulnar Joint Pathology

Cory Lebowitz and Jonas L. Matzon

Abstract

The triangular fibrocartilage complex (TFCC) and distal radioulnar joint (DRUJ) are complex structures. This chapter provides details on the anatomy and function of these structures. Furthermore, it reviews the diagnosis and treatment of pathologies, such as TFCC tears, ulnar impaction syndrome, and DRUJ instability.

Triangular fibrocartilage complex (TFCC) – distal radioulnar joint (DRUJ) – ulnar impaction syndrome – TFCC tears – DRUJ instability – arthroscopy

9 Triangular Fibrocartilage Complex and Distal Radioulnar Joint Pathology

I. Introduction

A. Background

The distal radioulnar joint (DRUJ) is an inherently unstable joint.
The triangular fibrocartilage complex (TFCC) is a ligamentous structure that provides support to the DRUJas well as several ulnocarpal articulations.

B. Epidemiology

TFCC injury is a common cause of ulnar-sided wrist pain.
- Evidence of torn TFCC is seen in 78% ofdistal radius fractures. ¹
- As patients age, degenerative TFCC tears become nearly universal. ²
Traumatic TFCC injuries have the potential to cause DRUJ instability.

II. Anatomy and Function

A. Triangular Fibrocartilage Complex

Radioulnar ligaments (RUL): Originate from the palmar and dorsal margins of the sigmoid notch to insert superficially at the ulnar styloid and deep at the fovea (► Fig. 9.1).
- Function: Primary stabilizers of the DRUJ.
- The ligamentum subcruentum is the tissue between the superficial and deep insertions of the RUL.
Articular disk: Avascular, triangular-shaped fibrocartilage that attaches radially at the sigmoid notch of the radius and then blends peripherally to the RUL.
- Function: Transmits and absorbs compressive forces through the wrist.
Meniscal homologue (MH): Fibrous tissue that adds to the hammock-like shape of the distal portion of the TFCC between the ulnar capsule, disk, and triquetrum.
Ulnocarpal ligaments: Volar structures that include the ulnolunate, ulnotriquetral, and ulnocapitate ligaments.
Extensor carpi ulnar (ECU) sheath: Reinforces the dorsal capsule.

**Fig. 9.1** Illustration of the major components of the triangular fibrocartilage complex and distal radioulnar joint. The primary stabilizer of the distal radioulnar joint is the triangular fibrocartilage complex. Used with permission of Mespreuve et al. ³

B. Distal Radioulnar Joint

Osseous anatomy is responsible for 20% of joint stability. ⁴
- Sigmoid notch is concave with a large radius of curvature to support the convex ulnar head and to allow for controlled pronation and supination.
Soft-tissue anatomy is responsible for 80% of joint stability. ⁴
- Palmar and dorsal RUL (see above).
- The ECU and pronator quadratus (PQ) dynamically stabilize the distal ulna and DRUJ.
- The distal interosseous membrane (IOM) restricts movement of the radius during forearm rotation.
Function: Allows forearm rotation and transmits forces across the wrist.

III. Diagnosis

A. History

Ulnar-sided wrist pain
- Traumatic onset: Classic mechanism is falling on an outstretched, pronated arm.
- Atraumatic onset: Pain that worsens with pronation/supination and/or power grip.

B. Physical Examination

Inspection for any deformity, swelling, and/or asymmetry.
Active and passive wrist range of motion focusing on pronation and supination
Provocative maneuvers:
- Foveal sign: Tenderness to palpation at the fovea, which is the soft spot between the ECU and flexor carpi ulnaris (FCU), proximal to the pisiform and just distal to the ulnar styloid.
  - 95.2% sensitivity and 86.5% specificity for TFCC tear. ⁵
- Ulnocarpal stress test: Pain with ulnar deviation and forearm rotation.
  - Sensitive for ulnar impaction syndrome, but not specific.
- Shuck test: Performed by stabilizing the radius and translating the ulna in full supination, pronation, and neutral while comparing with contralateral extremity.
  - Used to assess DRUJ stability.
- Press test: Patient uses the arms of a chair to rise from a seated position, which in turn creates dynamic loading.
  - The sensitivity of detecting TFCC lesions is up to 100%. ⁶