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7. Hand and Wrist MCQs

Practice Set 157 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 3121

Topic: Nerve & Tendon

A 20-year-old collegiate baseball pitcher is undergoing an ulnar collateral ligament (UCL) reconstruction using a palmaris longus autograft and a muscle-splitting approach (modified Jobe technique). During the surgical approach to the medial elbow, which nerve is most commonly at risk and must be meticulously identified and protected?

. Ulnar nerve
. Medial antebrachial cutaneous nerve
. Median nerve
. Lateral antebrachial cutaneous nerve
. Anterior interosseous nerve

Correct Answer & Explanation

. Medial antebrachial cutaneous nerve

Explanation

During the medial approach for UCL reconstruction, the medial antebrachial cutaneous nerve (MABC) and its branches cross the operative field and are highly at risk of injury (reportedly injured in up to 10-20% of cases if not careful). Neuroma formation or numbness over the medial forearm can cause significant postoperative morbidity. While the ulnar nerve is also protected, MABC neuropraxia/injury is the most common iatrogenic nerve complication during the approach.

Question 3122

Topic: Nerve & Tendon

A 20-year-old collegiate baseball pitcher complains of medial elbow pain that is most severe during the late cocking and early acceleration phases of throwing. On physical examination, what is the most sensitive test for diagnosing ulnar collateral ligament (UCL) insufficiency?

. Milking maneuver
. Moving valgus stress test
. Valgus stress test at 0 degrees of flexion
. Tinel's sign at the cubital tunnel
. Posterolateral rotatory pivot-shift test

Correct Answer & Explanation

. Moving valgus stress test

Explanation

The moving valgus stress test is considered the most sensitive physical examination maneuver for evaluating UCL insufficiency in throwing athletes. It is performed by applying a constant valgus stress to the elbow while flexing and extending it. A positive test is the reproduction of medial elbow pain between 70 and 120 degrees of flexion (the 'shear zone'). Valgus stress at 0 degrees primarily tests the bony articulation and joint capsule, whereas the anterior bundle of the UCL is the primary restraint to valgus stress between 30 and 120 degrees of flexion.

Question 3123

Topic: Nerve & Tendon

A 20-year-old collegiate baseball pitcher presents with medial elbow pain occurring during the late cocking and early acceleration phases of throwing, accompanied by a decline in pitching velocity. Examination reveals tenderness just distal to the medial epicondyle and a positive moving valgus stress test. An MRI arthrogram confirms a high-grade partial tear of the anterior bundle of the ulnar collateral ligament (UCL). After 3 months of failed conservative management, he opts for surgical reconstruction using a palmaris longus autograft. During the surgical approach for the UCL reconstruction, which neural structure is at greatest risk of iatrogenic injury?

. Median nerve
. Ulnar nerve
. Radial nerve
. Posterior interosseous nerve
. Medial antebrachial cutaneous nerve

Correct Answer & Explanation

. Medial antebrachial cutaneous nerve

Explanation

The medial antebrachial cutaneous nerve (MABC) is at the highest risk of iatrogenic injury during ulnar collateral ligament (UCL) reconstruction due to its course traversing the medial epicondyle and its highly variable branching pattern. Neuroma formation or numbness in the MABC distribution is a well-documented complication of the medial approach to the elbow.

Question 3124

Topic: Nerve & Tendon

A 19-year-old collegiate baseball pitcher experiences an acute 'pop' and medial elbow pain while throwing. Physical examination reveals tenderness just distal to the medial epicondyle and a positive moving valgus stress test. After failing non-operative management, he is scheduled for an ulnar collateral ligament (UCL) reconstruction. During the surgical approach, which of the following cutaneous nerves is at greatest risk of iatrogenic injury, particularly if an ulnar nerve transposition is performed?

. Medial antebrachial cutaneous nerve
. Lateral antebrachial cutaneous nerve
. Posterior antebrachial cutaneous nerve
. Superficial branch of the radial nerve
. Palmar cutaneous branch of the median nerve

Correct Answer & Explanation

. Medial antebrachial cutaneous nerve

Explanation

The medial antebrachial cutaneous (MABC) nerve provides sensation to the medial forearm. Its posterior branch consistently crosses the surgical field during medial elbow approaches, including UCL reconstruction and ulnar nerve transpositions. Iatrogenic injury to this nerve can lead to painful neuromas or troublesome numbness for the throwing athlete.

Question 3125

Topic: Nerve & Tendon

A 20-year-old collegiate baseball pitcher presents with medial elbow pain, decreased pitching velocity, and ulnar nerve paresthesias. MRI confirms a full-thickness tear of the anterior bundle of the ulnar collateral ligament (UCL). During UCL reconstruction, the ulnar bone tunnel is typically created at the sublime tubercle. Which nerve is at greatest risk of iatrogenic injury during the exposure and drilling of this ulnar tunnel?

. Anterior interosseous nerve
. Posterior interosseous nerve
. Median nerve
. Medial antebrachial cutaneous nerve
. Ulnar nerve

Correct Answer & Explanation

. Ulnar nerve

Explanation

The anterior bundle of the UCL inserts distally on the sublime tubercle of the ulna. The ulnar nerve runs immediately posterior to the medial epicondyle and the sublime tubercle in the cubital tunnel. During the dissection and drilling of the ulnar bone tunnels for UCL reconstruction, the ulnar nerve is at high risk of iatrogenic injury. While the medial antebrachial cutaneous nerve (MACN) is at risk during the superficial skin incision, the ulnar nerve is most at risk during the deep tunnel preparation.

Question 3126

Topic: Nerve & Tendon

A 20-year-old collegiate baseball pitcher presents with medial elbow pain during the late cocking and early acceleration phases of throwing. An MRI arthrogram reveals a high-grade partial tear of the ulnar collateral ligament (UCL). After failing 3 months of conservative management, surgical reconstruction is planned. Which of the following surgical approaches and techniques best minimizes the risk of postoperative ulnar neuropathy by allowing the ulnar nerve to remain in its native anatomic position?

. Classical Jobe figure-of-eight technique
. Muscle-splitting approach with the docking technique
. Medial epicondyle osteotomy
. Submuscular ulnar nerve transposition
. Flexor-pronator mass detachment approach

Correct Answer & Explanation

. Muscle-splitting approach with the docking technique

Explanation

The muscle-splitting approach, often used in conjunction with the docking technique for UCL reconstruction, involves longitudinally splitting the flexor carpi ulnaris (FCU) muscle belly to access the sublime tubercle without detaching the flexor-pronator mass. This approach avoids obligatory handling or transposition of the ulnar nerve, allowing it to safely remain in its native cubital tunnel. In contrast, the classic Jobe technique involved detachment of the flexor-pronator mass and routine ulnar nerve transposition, which was historically associated with a higher rate of postoperative ulnar neuropathy.

Question 3127

Topic: Nerve & Tendon

A 6-year-old girl falls from monkey bars and sustains a completely displaced, extension-type supracondylar fracture of the distal humerus.

During the preoperative evaluation, the hand is pink with palpable pulses, but she is unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which nerve is most likely injured, and what is the typical prognosis?

. Median nerve; requires immediate microsurgical exploration
. Anterior interosseous nerve; resolves spontaneously in 2 to 3 months
. Ulnar nerve; requires immediate nerve transposition
. Radial nerve; resolves spontaneously in 2 to 3 months
. Posterior interosseous nerve; requires exploration if no recovery by 3 weeks

Correct Answer & Explanation

. Anterior interosseous nerve; resolves spontaneously in 2 to 3 months

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures (often with posterolateral displacement). It is a purely motor branch of the median nerve, innervating the flexor pollicis longus and the flexor digitorum profundus to the index and long fingers. The injury is typically a neuropraxia, and spontaneous recovery usually occurs within 2 to 3 months. Acute exploration is not indicated.

Question 3128

Topic: Nerve & Tendon

A 6-year-old girl sustains an extension-type completely displaced supracondylar humerus fracture. Examination reveals she is unable to flex the interphalangeal joint of her thumb and the distal interphalangeal joint of her index finger. Which nerve is most likely injured?

. Ulnar nerve
. Radial nerve
. Anterior interosseous nerve
. Poster interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous 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 results in the inability to flex the interphalangeal joint of the thumb (flexor pollicis longus) and the distal interphalangeal joint of the index finger (flexor digitorum profundus).

Question 3129

Topic: Nerve & Tendon

A 6-year-old boy falls from the monkey bars and sustains a painful, swollen elbow. Radiographs demonstrate an extension-type supracondylar humerus fracture with posteromedial displacement of the distal fragment.

Based on the direction of displacement, which of the following nerve injuries is most likely to be present?

. Anterior interosseous nerve
. Radial nerve
. Ulnar nerve
. Median nerve (main trunk)
. Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve

Explanation

In extension-type supracondylar humerus fractures, the direction of displacement dictates the structures at risk. With posteromedial displacement of the distal fragment, the proximal fracture spike is driven anterolaterally. This places the radial nerve at the highest risk of injury. Conversely, if the distal fragment is displaced posterolaterally, the proximal spike is driven anteromedially, jeopardizing the median nerve and its anterior interosseous nerve (AIN) branch. The AIN is the most commonly injured nerve overall, but the radial nerve is specifically associated with posteromedial displacement.

Question 3130

Topic: 7. Hand and Wrist
A 6-year-old boy falls from a playground structure and sustains a widely displaced extension-type supracondylar humerus fracture. On initial presentation, his hand is pink with brisk capillary refill (< 2 seconds), but the radial pulse is absent. He is taken emergently to the operating room. Following a successful closed reduction and percutaneous pinning, the hand remains pink and warm, but the radial pulse remains unpalpable and absent on Doppler ultrasound. What is the most appropriate next step in management?
. Immediate exploration of the brachial artery by a vascular surgeon
. Removal of the pins and transition to an open reduction
. Perform a carpal tunnel release and forearm fasciotomies
. Application of a long-arm cast in 110 degrees of elbow flexion
. Application of a splint with the elbow in 45-60 degrees of flexion and close observation

Correct Answer & Explanation

. Application of a splint with the elbow in 45-60 degrees of flexion and close observation

Explanation

The management of a 'pulseless, pink' hand following adequate reduction and pinning of a pediatric supracondylar humerus fracture is observation. Because the hand is well-perfused (pink, warm, brisk capillary refill), the collateral circulation is sufficient. Vascular exploration is indicated only if the hand becomes poorly perfused (white, cool, pulseless) after reduction. A splint should be applied in mild flexion (45-60 degrees) rather than hyperflexion to avoid vascular compromise and compartment syndrome. The pulse often returns over the next several days as vasospasm resolves.

Question 3131

Topic: Nerve & Tendon

A 6-year-old boy sustains a completely displaced extension-type supracondylar fracture of the humerus. On physical examination in the emergency department, the patient is unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which of the following nerves is most likely injured?

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

Correct Answer & Explanation

. Anterior interosseous 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. It provides motor innervation to the flexor pollicis longus, the radial half of the flexor digitorum profundus, and the pronator quadratus. Injury results in the inability to form an 'A-OK' sign (loss of IP flexion of the thumb and DIP flexion of the index finger).

Question 3132

Topic: 7. Hand and Wrist

A 14-year-old boy presents with progressive hand clumsiness and clawing of the ring and small fingers. He reports sustaining an elbow fracture at age 4 that was treated in a cast. Radiographs reveal a nonunion of the lateral humeral condyle and cubitus valgus. Which nerve is most likely compromised?

. Median nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Ulnar nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Ulnar nerve

Explanation

Nonunion of a pediatric lateral condyle fracture frequently leads to progressive cubitus valgus. This deformity stretches the ulnar nerve over time, resulting in tardy ulnar nerve palsy characterized by intrinsic hand weakness and clawing.

Question 3133

Topic: Wrist & Carpus

During a regional block for a complex distal radius fracture, a patient inadvertently receives an intravascular injection of bupivacaine. She rapidly develops perioral numbness, metallic taste, tinnitus, and subsequent tonic-clonic seizures. What is the fundamental cellular mechanism of action of this medication that leads to both its anesthetic effect and toxicity?

. Irreversible blockade of presynaptic calcium channels
. Prolongation of the refractory period of voltage-gated potassium channels
. Reversible blockade of voltage-gated sodium channels
. Irreversible binding to GABA-A receptors
. Competitive inhibition of acetylcholinesterase

Correct Answer & Explanation

. Reversible blockade of voltage-gated sodium channels

Explanation

Local anesthetics like bupivacaine work by reversibly binding to the intracellular portion of voltage-gated sodium channels, preventing the influx of sodium necessary for action potential generation and propagation. Systemic toxicity (LAST - Local Anesthetic Systemic Toxicity) occurs when high blood concentrations result in excessive blockade of these sodium channels in the central nervous system and cardiovascular system, leading to seizures, arrhythmias, and cardiovascular collapse.

Question 3134

Topic: 7. Hand and Wrist
Following a traumatic complete transection of the ulnar nerve at the wrist, Wallerian degeneration occurs in the distal nerve stump. During this process, which of the following cell types is primarily responsible for clearing myelin debris, proliferating, and forming the bands of Büngner to guide the regenerating axon?
. Astrocytes
. Oligodendrocytes
. Schwann cells
. Fibroblasts
. Microglia

Correct Answer & Explanation

. Schwann cells

Explanation

In the peripheral nervous system, Schwann cells are the critical mediators of Wallerian degeneration and subsequent nerve regeneration. Following injury, Schwann cells dedifferentiate, proliferate, and work alongside recruited macrophages to clear myelin and axonal debris. They then align to form longitudinal columns called bands of Büngner, secreting neurotrophic factors (like NGF and BDNF) to guide the sprouting axons from the proximal stump. Astrocytes, oligodendrocytes, and microglia are support cells of the central nervous system.

Question 3135

Topic: 7. Hand and Wrist
A 32-year-old patient sustains a complete peripheral nerve transection (Sunderland Grade V) of the ulnar nerve at the wrist, which undergoes primary epineurial repair. During the subsequent regenerative phase following Wallerian degeneration, what is the primary role of the bands of Büngner?
. They are specialized macrophage clusters responsible for clearing distal myelin debris
. They are longitudinally oriented columns of proliferating Schwann cells that guide regenerating axonal sprouts
. They are dense collagen tubes formed by endoneurial fibroblasts to provide structural integrity
. They are newly formed nodes of Ranvier undergoing rapid remyelination
. They are specialized neurotrophic factors secreted by the target end-organ to promote chemotaxis

Correct Answer & Explanation

. They are longitudinally oriented columns of proliferating Schwann cells that guide regenerating axonal sprouts

Explanation

Following a nerve transection, the distal stump undergoes Wallerian degeneration where axons and myelin are cleared by macrophages. Subsequently, Schwann cells proliferate rapidly and align longitudinally within the preserved endoneurial basal lamina tubes. These organized columns of Schwann cells are known as the bands of Büngner. They act as the vital physical and chemical pathways, expressing neurotrophic factors and adhesion molecules, to attract and guide the regenerating axonal growth cones toward their distal target organs.

Question 3136

Topic: 7. Hand and Wrist

Articular cartilage has a specific zonal anatomy that determines its mechanical properties. Which of the following accurately describes the composition of the deep zone compared to the superficial zone?

. Highest water content and collagen fibers oriented parallel to the joint surface
. Highest concentration of proteoglycans and collagen fibers oriented perpendicular to the joint surface
. Lowest concentration of proteoglycans and collagen fibers oriented obliquely
. Highest concentration of chondrocytes and primarily Type I collagen
. Lowest water content and highest concentration of Type I collagen

Correct Answer & Explanation

. Highest concentration of proteoglycans and collagen fibers oriented perpendicular to the joint surface

Explanation

The deep (basal) zone of articular cartilage is characterized by the highest concentration of proteoglycans and the lowest water content. The collagen fibers in this zone (primarily Type II) are arranged perpendicularly to the joint surface and cross the tidemark into the calcified zone, anchoring the cartilage to the subchondral bone. The superficial (tangential) zone, on the other hand, possesses the highest water content, the lowest proteoglycan content, and collagen fibers oriented parallel to the joint surface to effectively resist shear forces.

Question 3137

Topic: 7. Hand and Wrist

A 65-year-old right-hand-dominant woman presents to the clinic 6 months after undergoing volar locking plate fixation for a displaced distal radius fracture. The fracture has healed well radiographically. She now reports a sudden inability to actively flex the interphalangeal (IP) joint of her thumb, though she has no pain. Which of the following technical errors during her index procedure is the most likely cause of this complication?

. Placement of the volar plate distal to the watershed line
. Use of locking screws that are excessively long dorsally
. Failure to anatomically repair the pronator quadratus over the plate
. Over-reduction of the volar tilt beyond 11 degrees
. Excessive traction on the median nerve during the modified Henry approach

Correct Answer & Explanation

. Placement of the volar plate distal to the watershed line

Explanation

The patient has sustained an iatrogenic rupture of the flexor pollicis longus (FPL) tendon. The FPL tendon is highly vulnerable to attrition over prominent hardware on the volar aspect of the distal radius. Placement of a volar plate distal to the 'watershed line' (the distinct ridge on the volar margin of the distal radius) positions the hardware prominently within the floor of the flexor tendon sheath, leading to FPL tendinopathy and eventual rupture. Screws that are too long dorsally cause extensor tendon irritation or rupture (commonly EPL). Repair of the pronator quadratus has not been consistently shown to prevent FPL rupture if the plate is malpositioned.

Question 3138

Topic: Wrist & Carpus

A 62-year-old woman is evaluated 6 months after undergoing volar locked plating of a distal radius fracture. She reports the sudden inability to actively flex the interphalangeal joint of her thumb. She denies any new trauma. Lateral radiographs show that the distal edge of the volar plate is positioned prominent and distal to the watershed line. Which of the following is the most likely cause of her presentation?

. Extensor pollicis longus (EPL) rupture
. Flexor pollicis longus (FPL) rupture
. Anterior interosseous nerve (AIN) palsy
. Flexor digitorum profundus (FDP) rupture
. Stenosing tenosynovitis (Trigger thumb)

Correct Answer & Explanation

. Flexor pollicis longus (FPL) rupture

Explanation

The patient presents with an inability to actively flex the thumb interphalangeal joint, indicating a failure of the flexor pollicis longus (FPL) tendon. Volar plates placed distal to the watershed line of the distal radius can irritate and eventually cause attritional rupture of the flexor tendons. The FPL tendon is most commonly affected due to its close anatomical proximity to the volar surface of the distal radius. EPL ruptures present as an inability to extend the thumb and are associated with nondisplaced fractures or prominent dorsal screws.

Question 3139

Topic: Wrist & Carpus

A 45-year-old man falls onto an outstretched hand and sustains a distal radius fracture. CT imaging demonstrates a displaced volar marginal articular shear fracture (volar Barton's fracture) with associated volar subluxation of the carpus. What is the most appropriate surgical approach and fixation strategy?

. Dorsal approach with application of a dorsal spanning plate
. Volar approach with application of a volar buttress plate
. Closed reduction and percutaneous pinning with K-wires
. Application of a bridging external fixator alone
. Excision of the volar fragment and primary radiocarpal arthrodesis

Correct Answer & Explanation

. Volar approach with application of a volar buttress plate

Explanation

Volar shear fractures (volar Barton's fractures) are inherently unstable because the carpus follows the displaced volar articular fragment. To mechanically neutralize the volar shear forces, the gold standard treatment is a volar surgical approach and the application of a volar plate acting in a buttress mode. Dorsal plating, external fixation, or percutaneous pinning are biomechanically inadequate to resist the continuous volar translation forces and frequently lead to secondary displacement.

Question 3140

Topic: 7. Hand and Wrist

A 28-year-old male presents with chronic radial-sided wrist pain 18 months after an untreated fall onto his outstretched hand. Imaging reveals a scaphoid waist nonunion with avascular necrosis of the proximal pole. He has an associated humpback deformity with a dorsal intercalated segment instability (DISI) pattern, but no radiocarpal arthritis. Which of the following surgical management strategies is most appropriate to restore carpal kinematics and achieve union?

. Non-vascularized corticocancellous distal radius bone graft and screw fixation
. 1,2-Intercompartmental supraretinacular artery (1,2-ICSRA) vascularized bone graft
. Free vascularized bone graft from the medial femoral condyle and screw fixation
. Proximal row carpectomy
. Scaphoid excision and four-corner carpal fusion

Correct Answer & Explanation

. Free vascularized bone graft from the medial femoral condyle and screw fixation

Explanation

In the setting of a scaphoid nonunion with avascular necrosis of the proximal pole AND a humpback deformity (structural collapse), the 1,2-ICSRA pedicled graft is insufficient because it lacks structural integrity. A free vascularized bone graft from the medial femoral condyle provides both robust vascularity for the AVN and structural corticocancellous support to correct the DISI/humpback deformity.

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