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7. Hand and Wrist MCQs

Practice Set 138 of 266

This practice set contains high-yield board review questions covering key concepts in 7. Hand and Wrist. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2741

Topic: 7. Hand and Wrist

A 6-year-old boy sustains a widely displaced, extension-type supracondylar humerus fracture. Upon presentation, his hand is pink and well-perfused, but he is unable to actively flex the interphalangeal joint of his thumb. Which nerve is most likely injured?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve (AIN)
. Posterior interosseous nerve (PIN)
. Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus and the flexor digitorum profundus to the index finger.

Question 2742

Topic: Nerve & Tendon

A 6-year-old boy sustains a completely displaced, extension-type supracondylar fracture of the humerus. During the neurologic examination, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?

. Median nerve main trunk
. Anterior interosseous nerve
. Posterior interosseous nerve
. Ulnar nerve
. Radial nerve

Correct Answer & Explanation

. Median nerve main trunk

Explanation

The anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. Injury results in the inability to flex the IP joint of the thumb and the DIP joint of the index finger (the 'OK' sign). Radial nerve injuries are more common in posteromedial displacement, while ulnar nerve injuries are more common in flexion-type fractures or as an iatrogenic injury during medial pinning.

Question 2743

Topic: Nerve & Tendon
A 4-year-old boy sustains a minimally displaced (<2 mm) lateral condyle fracture of the humerus that is treated in a long-arm cast. He is lost to follow-up and returns 15 years later. Radiographs demonstrate an established nonunion of the lateral condyle. Which of the following clinical findings is most likely to be present on physical examination?
. Cubitus varus and median nerve palsy
. Cubitus valgus and tardy ulnar nerve palsy
. Flexion contracture and radial nerve palsy
. Cubitus rectus and anterior interosseous nerve palsy
. Gunstock deformity and posterior interosseous nerve palsy

Correct Answer & Explanation

. Cubitus valgus and tardy ulnar nerve palsy

Explanation

Lateral condyle fractures of the humerus have a high propensity for nonunion if not perfectly immobilized or surgically fixed when displaced, because fracture fluid bathes the site and muscle pull from the extensor origin prevents apposition. An established nonunion of the lateral condyle typically leads to progressive cubitus valgus due to the continued growth of the intact medial physis while the lateral side is deficient. This progressive valgus deformity stretches the ulnar nerve behind the medial epicondyle, classically resulting in a tardy ulnar nerve palsy years or decades after the initial injury.

Question 2744

Topic: 7. Hand and Wrist

A 6-year-old girl sustains a severely displaced extension-type supracondylar fracture of the humerus. On examination, the hand is pink but the radial pulse is absent. Neurologic examination reveals an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which nerve is most likely injured?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve

Explanation

The anterior interosseous nerve (AIN) is a branch of the median nerve and is the most commonly injured nerve in extension-type supracondylar humerus fractures, particularly those with posterolateral displacement. AIN palsy presents with weakness of the flexor pollicis longus and flexor digitorum profundus to the index and middle fingers, manifesting as an inability to make an 'OK' sign.

Question 2745

Topic: 7. Hand and Wrist

A 6-year-old boy falls onto an outstretched hand and sustains a widely displaced, extension-type supracondylar fracture of the humerus. On physical examination in the emergency department, his hand is pink and well-perfused with a palpable radial pulse. However, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve (AIN)
. Posterior interosseous nerve (PIN)
. Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. Injury to the AIN manifests clinically as an inability to flex the interphalangeal joint of the thumb (flexor pollicis longus) and the distal interphalangeal joint of the index finger (flexor digitorum profundus), resulting in the loss of the 'OK' sign. These neurapraxias typically resolve spontaneously over several months with conservative management.

Question 2746

Topic: 7. Hand and Wrist

A 6-year-old boy falls from the monkey bars and sustains a displaced extension-type supracondylar humerus fracture. Radiographs demonstrate posterolateral displacement of the distal fragment.

Based on the direction of displacement, which nerve is most at risk for injury, and what is its characteristic motor deficit?

. Anterior interosseous nerve; inability to flex the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger
. Radial nerve; inability to extend the wrist and metacarpophalangeal joints
. Ulnar nerve; inability to cross the fingers and weakness of intrinsic hand muscles
. Median nerve proper; isolated numbness over the thenar eminence
. Musculocutaneous nerve; inability to flex the elbow

Correct Answer & Explanation

. Anterior interosseous nerve; inability to flex the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger

Explanation

In extension-type supracondylar humerus fractures, the direction of distal fragment displacement predicts the nerve at risk due to the sharp spike of the proximal fragment. Posterolateral displacement of the distal fragment causes the proximal fragment to displace anteromedially, placing the median nerve and particularly the anterior interosseous nerve (AIN) at greatest risk. The classic clinical sign of an AIN palsy is the inability to form an 'OK' sign, due to weakness of the flexor pollicis longus and the flexor digitorum profundus to the index finger.

Question 2747

Topic: Nerve & Tendon

A 22-year-old man undergoes a Latarjet procedure for recurrent anterior instability with 25% glenoid bone loss. Postoperatively, he exhibits weakness in elbow flexion and numbness over the lateral aspect of the forearm. Which nerve was most likely injured during the procedure?

. Median nerve
. Radial nerve
. Musculocutaneous nerve
. Ulnar nerve
. Suprascapular nerve

Correct Answer & Explanation

. Median nerve

Explanation

The musculocutaneous nerve is at high risk during the Latarjet procedure, particularly during aggressive medial retraction of the conjoint tendon. Injury results in weakness of the biceps and brachialis, as well as sensory deficits in the distribution of the lateral antebrachial cutaneous nerve.

Question 2748

Topic: 7. Hand and Wrist

When advising a patient with unilateral hip osteoarthritis to use a cane, in which hand should it be held and what is the primary biomechanical advantage?

. Ipsilateral hand; it reduces the joint reaction force by shifting the center of gravity.
. Ipsilateral hand; it decreases the moment arm of the body weight.
. Contralateral hand; it increases the abductor muscle force required.
. Contralateral hand; it decreases the abductor muscle force required to maintain a level pelvis.
. Contralateral hand; it increases the joint reaction force to stimulate bone healing.

Correct Answer & Explanation

. Ipsilateral hand; it reduces the joint reaction force by shifting the center of gravity.

Explanation

Holding a cane in the contralateral hand provides a counter-moment that reduces the required force of the hip abductors to maintain a level pelvis. Because abductor force is the largest contributor to joint reaction force, this significantly unloads the affected hip.

Question 2749

Topic: Nerve & Tendon

The ulnar nerve is compressed at the elbow in a 45-year-old patient. During surgical release of the cubital tunnel, the surgeon must divide the fascial roof of the tunnel. What structure forms this roof?

. Medial collateral ligament
. Osborne's ligament
. Struthers' arcade
. Lacertus fibrosus
. Deep fascia of the flexor carpi radialis

Correct Answer & Explanation

. Medial collateral ligament

Explanation

The roof of the cubital tunnel is formed by Osborne's ligament, a fascial band connecting the two heads of the flexor carpi ulnaris. The floor is formed by the medial collateral ligament and joint capsule.

Question 2750

Topic: 7. Hand and Wrist

A cyclist presents with numbness in the little finger and weakness in finger abduction. Entrapment is suspected in Guyon's canal. Which structures form the floor of Guyon's canal?

. Pisiform and hook of the hamate
. Volar carpal ligament and palmaris brevis
. Transverse carpal ligament and pisohamate ligament
. Flexor retinaculum only
. Triquetrum and lunate

Correct Answer & Explanation

. Pisiform and hook of the hamate

Explanation

The floor of Guyon's canal is formed by the transverse carpal ligament and the pisohamate ligament. The roof is formed by the volar carpal ligament and palmaris brevis.

Question 2751

Topic: Nerve & Tendon

A patient exhibits an inability to make an "OK" sign, demonstrating weakness in flexing the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which muscle is typically NOT innervated by the affected nerve?

. Flexor pollicis longus
. Pronator quadratus
. Flexor digitorum profundus to the index finger
. Flexor digitorum profundus to the middle finger
. Flexor digitorum superficialis

Correct Answer & Explanation

. Flexor pollicis longus

Explanation

The anterior interosseous nerve (AIN) innervates the flexor pollicis longus, pronator quadratus, and the radial half of the flexor digitorum profundus. The flexor digitorum superficialis is innervated by the main branch of the median nerve, not the AIN.

Question 2752

Topic: Wrist & Carpus

The triangular fibrocartilage complex (TFCC) is the primary stabilizer of the distal radioulnar joint. Which portion of the articular disc has the best potential for healing after repair due to its rich vascularity?

. Central articular disc
. Volar radial attachment
. Dorsal radial attachment
. Peripheral ulnar attachment
. Radial sigmoid notch attachment

Correct Answer & Explanation

. Central articular disc

Explanation

The peripheral 10-20% of the TFCC, specifically its ulnar attachment, is well-vascularized by branches of the ulnar artery and anterior interosseous artery. This periphery has an excellent capacity to heal after surgical repair, whereas the central portion is avascular.

Question 2753

Topic: Nerve & Tendon

A 28-year-old carpenter suffers a deep laceration to the base of his thenar eminence. He subsequently presents with an inability to perform palmar abduction of the thumb, but thumb interphalangeal joint flexion is preserved. Which of the following muscles is paralyzed due to this isolated nerve injury?

. Adductor pollicis
. Flexor pollicis longus
. Abductor pollicis longus
. First dorsal interosseous
. Abductor pollicis brevis

Correct Answer & Explanation

. Adductor pollicis

Explanation

The recurrent motor branch of the median nerve supplies the thenar muscles: abductor pollicis brevis, opponens pollicis, and the superficial head of the flexor pollicis brevis. Palmar abduction is the primary function of the abductor pollicis brevis.

Question 2754

Topic: 7. Hand and Wrist

A professional rock climber presents with a 'bowstringing' deformity of his middle finger flexor tendons after feeling a loud pop during a difficult hold. To maintain proper flexor tendon biomechanics and prevent bowstringing, which two annular pulleys are considered the most critical to preserve or reconstruct?

. A1 and A3
. A2 and A4
. A3 and A5
. A1 and A5
. A2 and A3

Correct Answer & Explanation

. A1 and A3

Explanation

The A2 (proximal phalanx) and A4 (middle phalanx) pulleys are the most biomechanically important annular pulleys in the flexor tendon sheath. Their disruption leads to clinically significant bowstringing and loss of flexor excursion.

Question 2755

Topic: Nerve & Tendon

A 48-year-old mechanic undergoes an in situ decompression of the ulnar nerve for advanced cubital tunnel syndrome. During the release, the primary compressive fascial structure forming the roof of the cubital tunnel between the medial epicondyle and the olecranon must be divided. This structure is known as:

. Arcade of Struthers
. Ligament of Struthers
. Lacertus fibrosus
. Osborne's ligament
. Medial intermuscular septum

Correct Answer & Explanation

. Arcade of Struthers

Explanation

Osborne's ligament (or the cubital tunnel retinaculum) forms the roof of the cubital tunnel, bridging the two heads of the flexor carpi ulnaris from the medial epicondyle to the olecranon. Division of this ligament is the key step in in situ ulnar nerve decompression.

Question 2756

Topic: 7. Hand and Wrist

A 45-year-old cyclist complains of little finger numbness and hand weakness. Examination localizes compression to Guyon's canal. Which structure forms the floor of this anatomical space?

. Palmar carpal ligament
. Transverse carpal ligament (flexor retinaculum)
. Pisohamate ligament
. Volar radiocarpal ligament
. Deep transverse metacarpal ligament

Correct Answer & Explanation

. Palmar carpal ligament

Explanation

The floor of Guyon's canal is primarily formed by the transverse carpal ligament (flexor retinaculum) and the pisohamate ligament. The roof is formed by the volar carpal ligament (palmar carpal ligament).

Question 2757

Topic: 7. Hand and Wrist

A patient presents with numbness in the radial 3.5 digits and aching pain in the proximal forearm. Sensation over the thenar eminence is decreased. Electrodiagnostic studies suggest a proximal median nerve compression. Which of the following structures is the most likely site of entrapment?

. Transverse carpal ligament
. Ligament of Struthers
. Arcade of Frohse
. Two heads of the flexor carpi ulnaris
. Osborne's ligament

Correct Answer & Explanation

. Transverse carpal ligament

Explanation

Sensory loss over the thenar eminence indicates compression proximal to the carpal tunnel, as the palmar cutaneous branch arises proximal to the transverse carpal ligament. Entrapment sites for pronator syndrome include the Ligament of Struthers, lacertus fibrosus, and the two heads of the pronator teres.

Question 2758

Topic: 7. Hand and Wrist

When repairing a flexor tendon laceration in Zone II of the hand, preserving the intricate pulley system is critical. Which two pulleys are considered the most biomechanically essential to prevent bowstringing of the flexor tendons?

. A1 and A3
. A1 and A5
. A2 and A4
. A3 and A5
. C1 and C3

Correct Answer & Explanation

. A1 and A3

Explanation

The A2 and A4 pulleys are the most critical for maintaining the mechanical advantage of the flexor tendons and preventing bowstringing. The A2 pulley is located over the proximal phalanx, and the A4 pulley is located over the middle phalanx.

Question 2759

Topic: Wrist & Carpus

A 65-year-old female experiences isolated rupture of the flexor pollicis longus (FPL) tendon following a volar plate fixation for a distal radius fracture. Which anatomical landmark on the distal radius is most commonly associated with FPL tendon attrition in this setting?

. Lister's tubercle
. Radial styloid
. Volar lip of the lunate fossa
. Watershed line
. Sigmoid notch

Correct Answer & Explanation

. Lister's tubercle

Explanation

The "watershed line" is a critical volar bony landmark on the distal radius. Placement of a volar plate distal to this line significantly increases the risk of flexor tendon irritation and subsequent rupture, most commonly the FPL.

Question 2760

Topic: Wrist & Carpus

A 45-year-old woman develops a spontaneous rupture of the extensor pollicis longus (EPL) tendon following a nondisplaced distal radius fracture treated in a cast. Around which bony prominence does this tendon normally pivot, making it susceptible to attrition?

. Radial styloid
. Lister's tubercle
. Ulnar styloid
. Pisiform
. Hook of the hamate

Correct Answer & Explanation

. Radial styloid

Explanation

The EPL tendon travels in the 3rd dorsal extensor compartment and uses Lister's tubercle as a fulcrum to change direction toward the thumb. Callus formation or undisplaced fracture lines in this area can lead to attrition and rupture of the EPL.

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