Summary

De Quervain's Tenosynovitis is a painful stenosing inflammation of the 1st Dorsal Compartment of the wrist, containing the Abductor Pollicis Longus (APL) and Extensor Pollicis Brevis (EPB) tendons. It is a classic "overuse" injury, notoriously common in new mothers ("Baby Wrist") due to repetitive lifting. Diagnosis is confirmed by Finkelstein's Test. Treatment is highly effective: Splinting (Thumb Spica) and Steroid Injection resolve 80% of cases. Surgical release is reserved for refractory cases, but surgeons must beware of the Superficial Radial Nerve (SBRN) and the high incidence of a separate EPB sub-compartment (Septation). [1,2,3]

Key Facts

• Anatomy: The 1st Compartment is a fibrous tunnel on the radial styloid.
• Tendons: APL (Abductor - larger, often multiple slips) and EPB (Extensor - smaller).
• Septation: in 30-40% of people, the EPB has its own separate tunnel. This is the #1 cause of injection/surgery failure (missing the EPB).
• The Nerve: The Superficial Radial Nerve (SBRN) runs directly over the roof of the compartment. Injury causes a painful neuroma (worse than the original disease).

Clinical Pearls

"Finkelstein vs Eichhoff":

• Eichhoff's: Patient makes a fist with thumb inside -> Ulnar deviate. (Active). High False Positive rate.
• Finkelstein's: Examiner grasps the patient's thumb -> Rapidly ulnar deviates. (Passive). The true test.

"Intersection Syndrome": If the pain is 4cm proximal to the wrist (distal forearm) and "squeaks" (crepitus), it is Intersection Syndrome (2nd compartment crossing over 1st), NOT De Quervain's.

"Post-Partum Spike": New mothers present 4-6 weeks after birth. The cause is lifting the baby with thumbs abducted (ulnar deviation torque). It often resolves spontaneously when lifting stops (approx 12 months).

              DE QUERVAIN'S TENOSYNOVITIS
                          ↓
              SYMPTOMS MILD OR SEVERE?
              ┌───────────┴─────────────┐
             MILD                    SEVERE
         (Intermittent)          (Constant Pain)
              ↓                         ↓
         CONSERVATIVE               INJECTION
      (Splint + NSAIDs)            (Steroid)
              ↓                         ↓
           FAILS?                    FAILS?
              ↓                         ↓
          INJECTION              REPEAT INJECTION
                               (Ensure EPB targeted)
                                        ↓
                                     SURGERY
                                    (Release)

1. Splinting

• Type: Forearm-based Thumb Spica Splint.
• Rule: Must include the thumb IP joint? No, just the MCP. But must immobilise the wrist.
• Regimen: 6 weeks.
• Success: 50% alone. Higher with injection.

2. Steroid Injection (Steps to Success)

• Efficacy: 80-90% cure rate.
• Technique:
  • Target the 1st compartment.
  • Crucial: If a septum is suspected (based on ultrasound or feel), you must inject both sub-compartments (APL and EPB) separately. Failure to inject the EPB is the #1 cause of failure.
• Risk: Fat depigmentation (white spot).

1st Compartment Release

• Indications: Failure of 2 injections.
• Technique:
  1. Transverse incision over Radial Styloid.
  2. Identify and Protect the Superficial Radial Nerve (SBRN).
  3. Release the Dorsal roof of the compartment.
  4. Explore for Septation: Look for the EPB (it is often hidden in its own deep tunnel). If found, release that septum too.
  5. Check excursion.
• Outcome: >95% cure.

Peters-Veluthamaningal et al. (Cochrane 2009)

• Review of Corticosteroid Injections.
• Result: Injection is superior to splinting and NSAIDs.
• NNT: Number Needed to Treat is very low (highly effective).

Variation in Anatomy (Leslie et al.)

• Cadaveric study.
• Finding: A separate EPB compartment exists in 34% of wrists. APL has multiple slips in 85% of wrists. SBRN branches are highly variable.
• Lesson: Expect unusual anatomy.

What is it?

The tendons that pull your thumb up run through a tight tunnel on the side of your wrist. It's like a rope passing through a metal ring. If you use it too much (lifting the baby), the rope swells up and gets stuck. It rubs raw every time you move it.

Why "Mother's Thumb"?

When you lift a baby under the armpits, you stretch your thumbs wide and twist your wrists. This is the exact movement that grinds these tendons. The hormones from pregnancy/breastfeeding also make you retain fluid, making the tunnel tighter.

Will the injection hurt?

It stings for a few seconds. We numb the skin first. It works incredibly well - 8 or 9 out of 10 people are cured with one shot.

What if I need surgery?

It's a "day case" operation. We cut the roof of the tunnel to let the tendons breathe. The main risk is a small sensing nerve nearby that can be sensitive, but otherwise it fixes the problem permanently.

Q1: What are the contents of the 1st Dorsal Compartment? A: Abductor Pollicis Longus (APL) and Extensor Pollicis Brevis (EPB). (Mnemonic: 22-12-11. 1st comp has 2 tendons. 2nd has 2. 3rd has 1...)

Q2: What is the most common anatomical cause for surgical failure? A: Failure to recognize and release a separate sub-compartment for the EPB tendon (present in ~40% of patients).

Q3: Describe Finkelstein's Test. A: The examiner grasps the patient's thumb and sharply deviates the wrist into ulnar deviation. Pain at the radial styloid is positive. (Distinguish from Eichhoff's: Patient makes a fist).

Q4: What nerve is at risk during the approach? A: The Superficial Branch of the Radial Nerve (SBRN). It runs in the subcutaneous fat directly overlying the 1st compartment.

(End of Topic)