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7. Hand and Wrist MCQs

Practice Set 255 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 5081

Topic: 7. Hand and Wrist

A newborn is noted to have a claw hand deformity with weakness in intrinsic hand muscles and an absent grasp reflex. Biceps and deltoid functions are normal. This clinical picture is most consistent with an injury to which part of the brachial plexus?

. Upper trunk (C5, C6)
. Middle trunk (C7)
. Lower trunk (C8, T1)
. Posterior cord
. Lateral cord

Correct Answer & Explanation

. Lower trunk (C8, T1)

Explanation

The patient has Klumpke's palsy, which results from an injury to the lower trunk of the brachial plexus (C8, T1). This affects the intrinsic muscles of the hand and the flexors of the wrist and fingers, leading to a claw hand and absent grasp reflex. Erb's palsy involves the upper trunk (C5, C6).

Question 5082

Topic: 7. Hand and Wrist

During primary tendon repair in Zone II of the hand, maintaining the integrity of the vincular system is critical because the vincula:

. Provide the primary source of extrinsic healing fibroblasts
. Carry the segmental blood supply to the flexor tendons
. Prevent adhesion formation between the FDS and FDP
. Act as a pulley to prevent bowstringing
. Produce synovial fluid for intrinsic tendon nutrition

Correct Answer & Explanation

. Carry the segmental blood supply to the flexor tendons

Explanation

The vincula (vincula brevia and vincula longa) carry the segmental vascular supply to the flexor tendons within the digital sheath. Preserving them is crucial to maintain tendon perfusion, which aids in healing and helps prevent tendon necrosis or rupture.

Question 5083

Topic: Nerve & Tendon
Following a closed crush injury to the forearm, a patient suffers a median nerve palsy. If an exploratory nerve surgery were performed, it would reveal that the axons and their endoneurial tubes are completely disrupted, but the perineurium and epineurium remain perfectly intact. According to the Sunderland classification, this injury is a:
. Grade I
. Grade II
. Grade III
. Grade IV
. Grade V

Correct Answer & Explanation

. Grade III

Explanation

Sunderland Grade III nerve injuries involve disruption of the axon and the endoneurium, while the perineurium and epineurium remain intact. Grade I is neurapraxia (focal demyelination). Grade II is axonotmesis with intact endoneurium. Grade IV involves disruption of the perineurium (only epineurium intact). Grade V is a complete nerve transection.

Question 5084

Topic: 7. Hand and Wrist

A new clinical screening test for carpal tunnel syndrome is evaluated in a large trial. The study notes a surprisingly high rate of false positive results. Which of the following statistical metrics is most directly diminished by this finding?

. Sensitivity
. Negative predictive value
. Positive predictive value
. Reliability
. Power

Correct Answer & Explanation

. Positive predictive value

Explanation

Positive Predictive Value (PPV) is the probability that subjects with a positive screening test actually have the disease. An increase in false positives inflates the denominator of the PPV equation, thereby lowering the PPV.

Question 5085

Topic: 7. Hand and Wrist
A 25-year-old rugby player grabs an opponent's jersey and feels a sudden pop in his right ring finger. He presents unable to actively flex the distal interphalangeal (DIP) joint. MRI demonstrates a complete flexor digitorum profundus (FDP) avulsion. Which of the following Leddy-Packer classifications corresponds to the highest risk of tendon ischemia and requires the most urgent surgical intervention (within 7-10 days)?
. Avulsion with a small bony fragment retracted to the PIP joint
. Tendon retracted completely into the palm
. Avulsion with a large bony fragment trapped at the A4 pulley
. Avulsion with an intra-articular fracture of the distal phalanx
. Intact vincula with tendon retracted to the DIP joint

Correct Answer & Explanation

. Tendon retracted completely into the palm

Explanation

The patient has a 'Jersey finger'. The Leddy-Packer classification describes FDP avulsion injuries based on the level of tendon retraction. Type I is retraction into the palm. Because the vincula (blood supply) are completely ruptured, the tendon is ischemic. Type I requires urgent surgical repair (typically within 7-10 days) before the tendon undergoes severe contracture and necrosis. Type II retracts to the PIP joint (vincula intact, delayed repair possible). Type III is a large bony avulsion caught at the A4 pulley.

Question 5086

Topic: 7. Hand and Wrist

A 35-year-old carpenter presents with the inability to form an 'OK' sign with his right hand. He maintains normal sensation over his entire hand and forearm. He is diagnosed with Anterior Interosseous Nerve (AIN) syndrome. Which of the following muscles will have normal function on physical examination?

. Flexor pollicis longus
. Flexor digitorum profundus to the index finger
. Flexor digitorum profundus to the long finger
. Flexor carpi radialis
. Pronator quadratus

Correct Answer & Explanation

. Flexor digitorum profundus to the long finger

Explanation

The Anterior Interosseous Nerve (AIN) is a purely motor branch of the median nerve. It innervates three muscles: the flexor pollicis longus (FPL), the radial half of the flexor digitorum profundus (FDP to the index and long fingers), and the pronator quadratus. Inability to pinch the thumb and index finger (loss of IP thumb flexion and DIP index flexion) yields a positive 'OK' sign test. The Flexor carpi radialis (FCR) is innervated by the main branch of the median nerve before the AIN branches off, so its function is preserved.

Question 5087

Topic: 7. Hand and Wrist

During flexor tendon repair in the hand, preservation of the annular pulley system is critical to maintain the biomechanics of digital flexion. Which two pulleys are mechanically the most important to preserve in order to prevent bowstringing of the flexor tendons?

. A1 and A3
. A1 and A5
. A2 and A4
. A3 and A5
. Palmar aponeurosis pulley and A1

Correct Answer & Explanation

. A2 and A4

Explanation

The A2 (located over the proximal phalanx) and A4 (located over the middle phalanx) pulleys are mechanically the most crucial for maintaining the tendon closely apposed to the bone. Disruption of these pulleys leads to significant flexor tendon bowstringing and loss of mechanical advantage.

Question 5088

Topic: 7. Hand and Wrist

A 22-year-old male sustains a proximal pole scaphoid fracture. Which of the following anatomical characteristics most directly explains the high rate of avascular necrosis associated with this specific injury?

. The proximal pole has no cartilaginous coverage
. Blood supply enters distally and flows in a retrograde fashion
. Vascular supply originates purely from the volar carpal branch of the radial artery
. The strong interosseous ligaments mechanically disrupt the blood supply
. The proximal pole relies solely on diffusion from synovial fluid

Correct Answer & Explanation

. Blood supply enters distally and flows in a retrograde fashion

Explanation

The primary blood supply to the scaphoid enters the dorsal ridge distally and supplies the proximal pole in a retrograde intraosseous fashion. Fractures of the proximal pole frequently disrupt this supply, leading to a high rate of avascular necrosis.

Question 5089

Topic: 7. Hand and Wrist

A rock climber experiences a sudden 'pop' in his ring finger while crimping. He exhibits bowstringing of the flexor tendons. Which pulley system is most critical to reconstruct to restore biomechanical function and prevent significant bowstringing?

. A1 and A3 pulleys
. A2 and A4 pulleys
. A3 and A5 pulleys
. C1 and C2 pulleys
. A1 and A5 pulleys

Correct Answer & Explanation

. A2 and A4 pulleys

Explanation

The A2 (located on the proximal phalanx) and A4 (on the middle phalanx) pulleys are the most mechanically critical annular pulleys. Their incompetence leads to severe bowstringing and a profound loss of mechanical advantage during digit flexion.

Question 5090

Topic: 7. Hand and Wrist

In the management of flexor tendon lacerations in the hand, Zone II represents a distinct surgical challenge. What anatomic boundaries define Zone II?

. Distal to the FDS insertion to the FDP insertion
. Proximal edge of the A1 pulley to the FDS insertion
. Distal edge of the carpal tunnel to the A1 pulley
. Musculotendinous junction to the carpal tunnel
. Distal to the A4 pulley to the FDP insertion

Correct Answer & Explanation

. Proximal edge of the A1 pulley to the FDS insertion

Explanation

Zone II, historically called "no man's land," extends from the proximal edge of the A1 pulley to the insertion of the flexor digitorum superficialis (FDS). It is notorious for poor healing and adhesions due to the tight fibro-osseous canal.

Question 5091

Topic: 7. Hand and Wrist

A 22-year-old male sustains a scaphoid waist fracture. The risk of avascular necrosis of the proximal pole is notoriously high due to retrograde blood supply. Which artery provides the predominant blood supply to the scaphoid?

. Volar carpal branch of the radial artery
. Dorsal carpal branch of the radial artery
. Ulnar artery via the deep palmar arch
. Anterior interosseous artery
. Posterior interosseous artery

Correct Answer & Explanation

. Dorsal carpal branch of the radial artery

Explanation

The dorsal carpal branch of the radial artery provides 70-80% of the blood supply to the scaphoid, entering distally and flowing retrograde to the proximal pole. Fractures at the waist disrupt this flow, leading to proximal pole AVN.

Question 5092

Topic: 7. Hand and Wrist
A 30-year-old male presents after falling onto an outstretched hand. Wrist radiographs demonstrate a perilunate dislocation. According to Mayfield's stages of perilunate instability, what structural failure corresponds with the final stage (Stage IV)?
. Scapholunate ligament rupture
. Capitohamate ligament rupture
. Lunotriquetral ligament rupture
. Lunate dislocation into the carpal tunnel
. Trans-scaphoid fracture

Correct Answer & Explanation

. Lunate dislocation into the carpal tunnel

Explanation

Mayfield's stages describe a progressive perilunate instability. Stage I is scapholunate failure, Stage II involves the space of Poirier (capitate dislocation), Stage III is lunotriquetral failure, and Stage IV occurs when the lunate dislocates volarly into the carpal tunnel.

Question 5093

Topic: Nerve & Tendon

A 32-year-old male presents with a severely displaced diaphyseal fracture of the radius and ulna. During his neurological examination, he demonstrates an inability to actively flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Sensation is intact. Which nerve is most likely injured?

. Median nerve main trunk
. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Superficial radial nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

The anterior interosseous nerve (AIN), a pure motor branch of the median nerve, 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 'OK sign' deficit.

Question 5094

Topic: Nerve & Tendon

A competitive cyclist complains of profound weakness in finger abduction and adduction, along with a positive Froment's sign. He reports completely normal sensation in his ring and small fingers. Which zone of Guyon's canal is the most likely site of ulnar nerve compression?

. Zone 1
. Zone 2
. Zone 3
. Zone 4
. Zone 5

Correct Answer & Explanation

. Zone 2

Explanation

Guyon's canal is divided into three zones. Zone 1 contains the main trunk of the ulnar nerve (compression causes both motor and sensory deficits). Zone 2 contains the deep motor branch (compression causes isolated motor deficits of the intrinsic muscles). Zone 3 contains the superficial sensory branch (compression causes isolated sensory deficits). The patient's isolated motor deficit localizes to Zone 2.

Question 5095

Topic: 7. Hand and Wrist

During an exploration of the flexor tendon sheath in the finger for a laceration, the surgeon must be careful to preserve the critical pulleys to prevent bowstringing of the tendon. Which two annular pulleys are considered the most biomechanically essential?

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

Correct Answer & Explanation

. A2 and A4

Explanation

The flexor tendon sheath contains five annular (A) pulleys and three cruciform (C) pulleys. The A2 pulley (over the proximal phalanx) and the A4 pulley (over the middle phalanx) are the major pulleys required to prevent bowstringing of the flexor tendons and must be preserved or reconstructed.

Question 5096

Topic: 7. Hand and Wrist

During a flexor tendon repair in Zone II of the hand, preserving the vincula is critical for intrinsic tendon healing. Which vascular structures primarily supply the vincula brevia and vincula longa?

. Superficial palmar arch
. Deep palmar arch
. Proper digital arteries
. Common digital arteries
. Princeps pollicis artery

Correct Answer & Explanation

. Proper digital arteries

Explanation

The vincula system provides the segmental blood supply to the flexor tendons within the fibro-osseous sheath. These vincula arise directly from the transverse communicating branches of the proper digital arteries.

Question 5097

Topic: Nerve & Tendon

A patient with a severe ulnar nerve injury at the elbow demonstrates noticeably less severe clawing of the ring and small fingers compared to a patient with an ulnar nerve injury at the wrist. What anatomical mechanism explains this presentation (the Ulnar Paradox)?

. Intact extensor digiti minimi function
. Paralysis of the flexor digitorum superficialis
. Paralysis of the ulnar half of the flexor digitorum profundus
. Intact function of the lumbricals
. Compensatory median nerve hypertrophy via the Martin-Gruber anastomosis

Correct Answer & Explanation

. Paralysis of the ulnar half of the flexor digitorum profundus

Explanation

The Ulnar Paradox refers to the phenomenon where a high ulnar nerve injury produces less severe clawing because it denervates the ulnar half of the flexor digitorum profundus (FDP). Without active FDP contraction, the distal interphalangeal joints do not actively flex, reducing the visible claw deformity.

Question 5098

Topic: 7. Hand and Wrist

During a classic open carpal tunnel release, the surgeon must identify and protect the recurrent motor branch of the median nerve. According to anatomical studies, what is the most common anatomical course of this motor branch in relation to the transverse carpal ligament?

. Transligamentous
. Subligamentous
. Extraligamentous with a recurrent course
. Ulnar to the main trunk of the median nerve
. Piercing the flexor retinaculum directly anteriorly

Correct Answer & Explanation

. Extraligamentous with a recurrent course

Explanation

The most common anatomical course of the recurrent motor branch of the median nerve (approximately 46-90% of cases) is extraligamentous. It branches off the median nerve distal to the transverse carpal ligament and takes a recurrent course to innervate the thenar musculature.

Question 5099

Topic: 7. Hand and Wrist

A laceration of both the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) in Zone II of the hand is classically known as 'no man\'s land'. The primary blood supply to these tendons within the digital sheath is provided by the:

. Paratenon vessels
. Vincula tendinum
. Digital arteries via direct branches
. Nutrient artery of the phalanx
. Lumbrical muscle vessels

Correct Answer & Explanation

. Vincula tendinum

Explanation

Within the digital flexor sheath (Zone II), the tendons are largely avascular but receive their segmental blood supply dorsally through the vincula tendinum (longa and brevia), which are delicate folds of mesotenon carrying vessels from the proper digital arteries.

Question 5100

Topic: 7. Hand and Wrist

A patient undergoing an open carpal tunnel release is at risk of iatrogenic injury to the recurrent motor branch of the median nerve. According to the Kaplan cardinal line, this branch typically arises from the median nerve at which of the following anatomical locations?

. Proximal to the transverse carpal ligament
. Deep to the transverse carpal ligament
. Just distal to the transverse carpal ligament
. Between the superficial and deep palmar arches
. Ulnar to the hook of the hamate

Correct Answer & Explanation

. Just distal to the transverse carpal ligament

Explanation

The recurrent motor branch of the median nerve (the 'million dollar nerve') most commonly exhibits an extraligamentous, recurrent course, arising just distal to the transverse carpal ligament and curving back to innervate the thenar musculature.

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