Correct Answer: D. Abductor poliicis longus and extensor pollicis brevis
The clinical presentation of lateral wrist pain with a positive test (implied to be Finkelstein's test) indicates de Quervain's tenosynovitis, an inflammation of the tendon sheath in the first dorsal compartment of the wrist. This compartment contains exactly two tendons: the Abductor Pollicis Longus (APL) and the Extensor Pollicis Brevis (EPB). These tendons run together through a single fibro-osseous tunnel on the radial (lateral) side of the wrist. When the patient makes a fist with the thumb tucked inside the fingers and deviates the wrist ulnarly (Finkelstein's test), the tendons are stretched within the inflamed sheath, reproducing sharp lateral wrist pain. This condition is common in Indian women engaged in repetitive gripping activities (grinding, wringing clothes, repetitive hand work). The anatomical compartmentalization is key: APL and EPB share the first dorsal compartment, distinct from other extensor compartments. Inflammation here causes localized swelling and tenderness over the radial styloid process, pathognomonic for this diagnosis.
Why the other options are wrong
A. Abductor pollicis brevis and extensor pollicis brevis — This is wrong because Abductor Pollicis Brevis (APB) is an intrinsic hand muscle located in the thenar eminence and runs through the carpal tunnel, NOT the first dorsal compartment. While EPB is correct, APB involvement would present with thenar eminence swelling and carpal tunnel symptoms, not isolated lateral wrist pain. The compartment anatomy is violated here. B. Abductor pollicis brevis and extensor pollicis longus — This is wrong because APB (thenar intrinsic, carpal tunnel) is anatomically incorrect for de Quervain's. Additionally, Extensor Pollicis Longus (EPL) runs through the third dorsal compartment (around Lister's tubercle), not the first. EPL tenosynovitis causes dorsal wrist pain and thumb IP joint extension loss, a different clinical entity entirely. C. Abductor pollicis longus and extensor pollicis longus — This is wrong because while APL is correct, EPL runs in the third dorsal compartment, not the first. This pairing violates the anatomical compartmentalization of the wrist. EPL involvement alone causes dorsal wrist swelling and thumb IP extension weakness, not the classic lateral wrist pain of de Quervain's syndrome.
High-Yield Facts
- First dorsal compartment of the wrist contains APL and EPB tendons exclusively—this is the anatomical basis of de Quervain's tenosynovitis.
- Finkelstein's test (thumb-in-fist with ulnar deviation) reproduces sharp lateral wrist pain in de Quervain's by stretching the inflamed APL and EPB sheaths.
- Radial styloid process is the site of maximum tenderness in de Quervain's; swelling here is pathognomonic.
- APL originates from radius/interosseous membrane and abducts the thumb at the CMC joint; EPB extends the thumb IP joint—both pass through the first compartment.
- EPL runs in the third dorsal compartment (around Lister's tubercle), a common exam trap to distinguish from EPB in the first compartment.
- Indian epidemiology: de Quervain's is common in women doing repetitive hand work (grinding, wringing, textile work) and in new mothers (repetitive lifting).
Mnemonics
First Compartment = APL + EPB ("APE") Abductor Pollicis Longus + Extensor Pollicis Brevis = first dorsal compartment. Remember: APL is the longer abductor, EPB is the shorter extensor—both share the first (most radial) compartment. Compartment Sequence (Radial to Ulnar) 1st: APL + EPB | 2nd: ECRB + ECRL | 3rd: EPL | 4th: EDC + EIP | 5th: EDM | 6th: ECU. Use this to rule out other compartments when a question mentions different tendons.
NBE Trap
NBE commonly pairs EPL with APL (option C) to trap students who know APL is correct but confuse the extensor compartments. The key discriminator is that EPL is in the third compartment (around Lister's tubercle), not the first, and causes dorsal wrist pain, not lateral pain.
Clinical Pearl
In Indian clinical practice, de Quervain's is often seen in new mothers and women doing repetitive hand work. Early diagnosis via Finkelstein's test and NSAIDs (ibuprofen 400 mg TDS) with thumb spica immobilization prevents progression to tendon rupture. Ultrasound shows tendon sheath effusion and thickening around the first compartment.
_Reference: Bailey & Love Ch. 59 (Wrist and Hand); Clinically Oriented Anatomy (Moore) Ch. 6 (Upper Limb)_