Advanced Extensor Digitorum Quiz

Q1. A lesion of the posterior interosseous nerve would most directly impair which action of extensor digitorum?

• Extension of digits 2 to 5 at the metacarpophalangeal joints
• Flexion of digits 2 to 5 at the distal interphalangeal joints
• Adduction of the thumb
• Thumb opposition

Q2. Why can a patient with posterior interosseous nerve palsy have marked finger drop without cutaneous sensory loss?

• The posterior interosseous nerve is predominantly motor
• The posterior interosseous nerve supplies only skin
• Extensor digitorum is supplied by the median nerve
• Finger extension does not require peripheral innervation

Q3. At each metacarpophalangeal joint, which structures help keep the extensor digitorum tendon centered over the metacarpal head?

• Sagittal bands
• Annular ligament of the radius
• Flexor retinaculum
• Transverse carpal ligament

Q4. What can occur after disruption of a sagittal band at a metacarpophalangeal joint?

• Dislocation of the radial head
• Compression of the median nerve in the carpal tunnel
• Subluxation of the extensor tendon
• Rupture of the biceps tendon

Q5. An injury that disrupts the central slip of the extensor expansion at a proximal interphalangeal joint can lead to which deformity?

• Dupuytren contracture
• Trigger thumb
• Boutonniere deformity
• Mallet finger

Q6. Disruption of the terminal extensor tendon at the distal interphalangeal joint most commonly produces which deformity?

• Mallet finger
• Boutonniere deformity
• Carpal tunnel syndrome
• Claw thumb

Q7. Why is isolated extension of the ring finger often more limited than extension of the index finger?

• The index finger lacks an extensor expansion
• Intertendinous connections restrict independent movement, and the index has an additional extensor
• The ring finger has no extensor tendon
• The ring finger is extended only by the ulnar nerve

Q8. If an extensor digitorum tendon is lacerated on the dorsum of the hand, why might some extension of the affected finger initially remain possible?

• The median nerve directly extends the finger
• Juncturae tendinum can transmit force from adjacent extensor tendons
• Flexor tendons automatically become extensors
• The palmar aponeurosis substitutes for the extensor tendon

Q9. Why can the intrinsic muscles of the hand extend the interphalangeal joints even though they flex the metacarpophalangeal joints?

• They act only through the wrist joint
• They reverse the direction of extensor digitorum contraction
• They insert directly into the flexor retinaculum
• They insert into the extensor expansions while passing anterior to the metacarpophalangeal joint axes

Q10. Which description best summarizes the anatomy of extensor digitorum?

• It is a superficial posterior forearm muscle supplied by the posterior interosseous nerve that sends tendons to the extensor expansions of digits 2 to 5
• It is a superficial anterior forearm muscle supplied by the median nerve that inserts on the metacarpal bases
• It is an intrinsic hand muscle supplied by the ulnar nerve that abducts digits 2 to 5
• It is a deep anterior forearm muscle supplied by the median nerve that flexes digits 2 to 5