De Quervain's disease classically affects?

Explanation

## Correct Answer: B. Extensor pollicis brevis and abductor pollicis longus De Quervain's tenosynovitis is a stenosing tenosynovitis affecting the first dorsal compartment of the wrist. This compartment contains exactly two tendons: the **extensor pollicis brevis (EPB)** and the **abductor pollicis longus (APL)**. The inflammation and thickening of the synovial sheath surrounding these two tendons in the narrow fibro-osseous tunnel at the radial styloid causes pain, swelling, and restricted thumb movement. The condition is triggered by repetitive gripping, pinching, or radial deviation movements—common in Indian women performing household tasks (grinding, wringing clothes) and in occupational workers. The pathognomonic **Finkelstein test** (thumb flexion into palm with fingers flexed, then ulnar deviation of wrist) reproduces pain by compressing the inflamed tendons within the tight compartment. Both EPB and APL pass through the first dorsal compartment together; any other combination of muscles either involves different compartments or muscles that do not share the same synovial sheath, making them anatomically incorrect. ## Why the other options are wrong **A. Extensor pollicis brevis and abductor pollicis brevis** — This is wrong because **abductor pollicis brevis (APB)** is an intrinsic hand muscle located in the thenar eminence; it does NOT pass through the first dorsal compartment of the wrist. APB is innervated by the recurrent motor branch of the median nerve and lies superficial to the flexor pollicis longus. De Quervain's affects only the two extrinsic tendons (EPB and APL) that share the first dorsal compartment at the radial styloid. **C. Extensor pollicis longus and abductor pollicis longus** — This is wrong because **extensor pollicis longus (EPL)** passes through the third dorsal compartment at the dorsal wrist, NOT the first compartment. EPL runs in its own separate synovial sheath medial to Lister's tubercle. De Quervain's specifically involves the first dorsal compartment at the radial styloid, which contains only EPB and APL. Confusing EPL with EPB is a common anatomical trap. **D. Extensor pollicis longus and abductor pollicis brevis** — This is wrong because it combines two incorrect muscles: EPL (third compartment, not first) and APB (intrinsic hand muscle, not in any wrist compartment). Neither of these tendons is affected in De Quervain's disease. This option represents a double anatomical error and may trap students who confuse intrinsic and extrinsic thumb muscles. ## High-Yield Facts - **First dorsal compartment** at the radial styloid contains only EPB and APL—these are the two tendons affected in De Quervain's tenosynovitis. - **Finkelstein test** (thumb in palm, fingers flexed, ulnar deviation) is pathognomonic; positive test reproduces sharp pain at the radial styloid. - **EPB** is innervated by the posterior interosseous nerve (PIN); **APL** is also innervated by PIN—both are extrinsic thumb extensors/abductors. - **Risk factors** in Indian population: repetitive gripping (grinding spices, wringing clothes), pregnancy, rheumatoid arthritis, and occupational overuse. - **Treatment ladder**: NSAIDs + thumb spica immobilization (first-line), corticosteroid injection into the first dorsal compartment (second-line), surgical release of the compartment (third-line if conservative fails). ## Mnemonics **First Compartment = EPB + APL** **E**xtensor **P**ollicis **B**revis and **A**bductor **P**ollicis **L**ongus share the first dorsal compartment. Both are extrinsic thumb muscles innervated by PIN. Remember: 'EPB and APL are **E**xtensor and **A**bductor partners in the first compartment.' **Finkelstein = De Quervain's Diagnosis** **F**inkelstein test: **F**lexion (thumb into palm) + **F**ingers flexed + **F**orward ulnar deviation = **F**irst compartment pain. If positive, De Quervain's is confirmed. ## NBE Trap NBE may pair De Quervain's with EPL (extensor pollicis longus) to trap students who confuse the three thumb extensor muscles (EPB, EPL, and EIP) or who do not recall that EPL runs in the third dorsal compartment, not the first. The inclusion of APB (an intrinsic hand muscle) in option A exploits confusion between extrinsic wrist tendons and intrinsic hand muscles. ## Clinical Pearl In Indian clinical practice, De Quervain's is commonly seen in postpartum women (hormonal laxity + repetitive thumb use in childcare) and in workers performing repetitive pinching tasks. Early diagnosis via Finkelstein test and prompt corticosteroid injection into the first dorsal compartment can prevent the need for surgical release and preserve thumb function—critical for manual workers and farmers in rural India. _Reference: Bailey & Love Ch. 54 (Hand Surgery); Robbins Ch. 26 (Musculoskeletal Pathology)_