Advanced Extensor Pollicis Brevis Quiz

Q1. Inflammation involving extensor pollicis brevis and abductor pollicis longus within the first dorsal compartment is characteristic of which condition?

• Carpal tunnel syndrome
• De Quervain tenosynovitis
• Guyon canal syndrome
• Posterior interosseous syndrome

Q2. Which anatomical variation within the first dorsal compartment can contribute to persistent symptoms if not recognized during surgical treatment of de Quervain tenosynovitis?

• Insertion of extensor pollicis brevis on the pisiform
• Passage of the median nerve through the first compartment
• A separate subcompartment for extensor pollicis brevis
• Passage of flexor pollicis longus through the first compartment

Q3. A lesion of the posterior interosseous nerve would directly weaken which action of extensor pollicis brevis?

• Opposition of the thumb
• Extension of the thumb at the metacarpophalangeal joint
• Adduction of the thumb
• Flexion of the thumb at the interphalangeal joint

Q4. Why can posterior interosseous nerve palsy cause weakness of extensor pollicis brevis without producing cutaneous sensory loss in the hand?

• Thumb extension is controlled entirely by the median nerve
• The radial nerve contains no sensory fibers
• The posterior interosseous nerve is predominantly motor
• Extensor pollicis brevis has no nerve supply

Q5. Which anatomical relationship allows extensor pollicis brevis to serve as a palpable landmark for the anatomical snuffbox?

• It forms the floor with flexor pollicis longus
• It passes through the center of the snuffbox with the radial artery
• It forms the lateral boundary with abductor pollicis longus
• It forms the medial boundary with extensor pollicis longus

Q6. Which finding would most specifically indicate preserved extensor pollicis brevis function during examination?

• Resisted extension of the proximal phalanx of the thumb
• Resisted adduction of the thumb
• Resisted flexion of the distal phalanx of the thumb
• Resisted opposition of the thumb

Q7. Why does isolated extensor pollicis brevis paralysis not necessarily abolish all active thumb extension?

• Flexor pollicis longus becomes an extensor
• Adductor pollicis becomes the primary thumb extensor
• Extensor pollicis longus can still contribute to thumb extension
• Pronator quadratus directly extends the thumb

Q8. A patient can extend the thumb interphalangeal joint but has weakness extending the proximal phalanx at the metacarpophalangeal joint. Dysfunction of which muscle should be specifically considered?

• Extensor pollicis longus
• Adductor pollicis
• Extensor pollicis brevis
• Flexor pollicis longus

Q9. Why can a septum within the first dorsal compartment be clinically important in de Quervain tenosynovitis?

• It redirects the radial artery through the carpal tunnel
• It separates the median nerve from the flexor tendons
• It can create separate tendon channels that may require complete decompression
• It changes extensor pollicis brevis into a thumb flexor

Q10. Which description best summarizes the anatomy of extensor pollicis brevis?

• It is an intrinsic thenar muscle supplied by the ulnar nerve that primarily adducts the thumb
• It is a superficial anterior forearm muscle supplied by the median nerve that inserts on the distal phalanx of the thumb
• It is a superficial posterior forearm muscle arising from the lateral epicondyle and inserting on the fifth metacarpal
• It is a deep posterior forearm muscle supplied by the posterior interosseous nerve that inserts on the proximal phalanx of the thumb