Summary

The Distal Radioulnar Joint (DRUJ) is the critical pivot point for forearm rotation. Stability is provided by the Triangular Fibrocartilage Complex (TFCC), particularly its deep fibers (Ligamentum Subcruentum) which attach to the Fovea of the ulna. Injuries range from traumatic tears (Palmer 1) to degenerative wear (Palmer 2). "Ulnar Sided Wrist Pain" is the "Low Back Pain" of the wrist—complex and often chronic. A key concept is Ulnar Variance: patients with "Ulnar Positive Variance" (Ulna longer than Radius) are prone to Ulnar Impaction Syndrome where the ulnar head grinds into the lunate. Management involves Arthroscopy (Gold Standard) and surgical shortening of the ulna if impacted. [1,2,3]

Key Facts

• The "Black Box": The ulnar side of the wrist is anatomically complex.
• Mechanism: Fall on Outstretched Hand (FOOSH) with Hyper-pronation or distraction force (Power drill kickback).
• Blood Supply:
  • Peripheral 10-20%: Vascular. HEALS well.
  • Central 80%: Avascular (Cartilage). DOES NOT HEAL. Requires debridement.

Clinical Pearls

"The Fovea Sign": Press deep into the soft spot between the ulnar styloid and the FCU tendon. Tenderness here is 95% sensitive for a foveal attachment tear of the TFCC (the bad one).

"Piano Key vs Ballottement":

• Piano Key: Large instability (Galeazzi). The whole head moves.
• Ballottement: Subtle instability. Hold the radius firm, shunt the ulna back and forth. Compare to the other side. "Mushy" end point = Tear.

"Positive Variance Kills the Lunate": If the ulna is long (Positive Variance), it bears too much load. This wears out the TFCC and punches a hole in the Lunate cartilage (Ulnar Impaction).

                 ULNAR SIDED WRIST PAIN
                        ↓
            HISTORY: TRAUMA OR DEGENERATIVE?
             ┌──────────┴──────────┐
          TRAUMA                DEGENERATIVE
        (Acute Fall)         (Chronic/Loading)
             ↓                     ↓
       CHECK STABILITY       CHECK VARIANCE
       (Ballottement)         (X-Ray PA)
       ┌─────┴─────┐         ┌─────┴─────┐
    STABLE      UNSTABLE  NEUTRAL       POSITIVE
      ↓            ↓         ↓             ↓
    SPLINT/     MRI/MRA    SPLINT      ULNAR IMPACTION
    PHYSIO         ↓       STEROID     SYNDROME
   (4-6w)      REPAIRABLE?             ↓
                   ↓                DEBRIDEMENT
             ┌─────┴─────┐          SHORTENING
          YES (1B)    NO (1A)
             ↓           ↓
          REPAIR     DEBRIDE

1. Conservative

• Indication: Stable tears. Degenerative tears (Palmer 2).
• Technique:
  • Wrist Splint: Neutral splint.
  • Sugar Tong / Muenster Splint: Prevents rotation (for unstable injuries).
  • Steroid Injection: Into DRUJ or local to fovea. Diagnostic utility.
  • Proprioceptive Rehab: Isometric ECU strengthening (ECU stabilizes the ulnar head).

2. Surgical: TFCC Repair (Class 1B)

• Indication: Unstable foveal tear (1B). Failed conservative care.
• Technique:
  • Arthroscopic: Suture anchors or trans-osseous sutures reattach the ligament to the Fovea.
  • Open: For massive avulsions.
• Rehab: Immobilize 6 weeks in Muenster splint (no rotation).

3. Surgical: Ulnar Shortening Osteotomy

• Indication: Ulnar Impaction Syndrome (Positive Variance + Degenerative Tear).
• Technique: Remove a 2-4mm slice of the ulna shaft. Plate it.
• Effect: Retracts the ulnar head away from the carpus, unloading the TFCC and Lunate. Tightens the ulnocarpal ligaments.

4. Salvage: Darrach / Sauvé-Kapandji

• Indication: DRUJ Arthritis (Palmer 2E).
• Darrach: Excision of distal ulna.
• SK: Fusion of DRUJ + creation of a pseudarthrosis in ulna neck.

Palmer Classification utility

• Remains the gold standard for decision making.
• Central tears (1A) = Debride (Avscular).
• Peripheral tears (1B) = Repair (Vascularity allows healing).

Adams Procedure

• For chronic instability. Reconstruction of the Volar and Dorsal Radioulnar Ligaments using a Palmaris Longus tendon graft.

What is the TFCC?

It is a small cushion of cartilage and ligaments on the little-finger side of your wrist. It acts like the "meniscus" in your knee—a shock absorber and a stabilizer.

Why does it hurt?

You have torn the attachment of this cushion to the bone. Every time you turn your wrist (like opening a jar), the bone wobbles and pinches the torn cartilage.

The "Too Long" Bone (Impaction)

(If applicable) Your ulna bone is naturally a few millimeters longer than the other bone. This means it is constantly crushing the cartilage cushion against your hand bones. We might need to shorten the bone surgically to take the pressure off.

Q1: Describe the blood supply of the TFCC and its surgical implication. A: The peripheral 10-20% is vascularized by branches of the ulnar artery (amenable to repair/healing). The central 80% is avascular (cartilaginous) and receives nutrition via diffusion. Tears here will not heal and thus are treated by debridement (trimming), not repair.

Q2: What is the "Fovea Sign"? A: Tenderness located deep in the interval between the ulnar styloid process and the FCU tendon. It is highly specific for foveal disruption of the TFCC (the deep fibers responsible for stability).

Q3: Explain "Ulnar Variance" and how it is measured. A: It is the relative length of the distal articular surface of the ulna compared to the radius. It MUST be measured on a PA X-ray with the shoulder abducted 90° and elbow flexed 90° (neutral rotation). Pronation increases variance (makes ulna longer relative to radius); Supination decreases it.

(End of Topic)