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Wrist & Carpus MCQs

Practice Set 31 of 33

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

Question 601

Topic: Wrist & Carpus
Which of the following radiographic parameters is most strongly associated with the biomechanical pathogenesis of Kienböck's disease?
. Positive ulnar variance
. Negative ulnar variance
. Increased radial inclination
. Decreased volar tilt of the distal radius
. Lunotriquetral coalition

Correct Answer & Explanation

. Negative ulnar variance

Explanation

Negative ulnar variance (ulna is shorter than the radius) was classically described by Hultén as being strongly associated with Kienböck's disease (avascular necrosis of the lunate). This anatomy increases shear forces and load transmission directly onto the lunate from the radius.

Question 602

Topic: Wrist & Carpus

During the surgical approach for a perilunate dislocation, the surgeon evaluates the volar wrist capsule and identifies the Space of Poirier. This anatomic weak point, which is frequently disrupted in perilunate injuries, is located between which two volar ligaments?

. Radioscaphocapitate and long radiolunate ligaments
. Long radiolunate and short radiolunate ligaments
. Palmar lunotriquetral and capitotriquetral ligaments
. Radioscaphocapitate and volar scapholunate ligaments
. Ulnolunate and ulnotriquetral ligaments

Correct Answer & Explanation

. Radioscaphocapitate and long radiolunate ligaments

Explanation

The Space of Poirier is a relative weakness in the palmar radiocarpal joint capsule located between the radioscaphocapitate (RSC) and long radiolunate (LRL) ligaments. It overlies the volar aspect of the midcarpal joint (capitolunate articulation) and is the site where the lunate typically escapes volarly during a perilunate/lunate dislocation.

Question 603

Topic: Wrist & Carpus

A 60-year-old woman is scheduled for a volar plating of a distal radius fracture. She has a high risk profile for developing Complex Regional Pain Syndrome (CRPS) Type I. Which of the following prophylactic medications, started at the time of injury or surgery, has been shown in some studies to decrease the risk of developing CRPS?

. Gabapentin 300 mg daily
. Vitamin C 500 mg daily
. Amitriptyline 25 mg daily
. Prednisone 10 mg daily
. Alendronate 70 mg weekly

Correct Answer & Explanation

. Vitamin C 500 mg daily

Explanation

Vitamin C (ascorbic acid), typically dosed at 500 mg daily for 50 days following a distal radius fracture, has been shown in some randomized controlled trials to significantly reduce the incidence of Complex Regional Pain Syndrome (CRPS) Type I. While gabapentin and amitriptyline are used to treat neuropathic pain, they are not established as standard prophylaxis for CRPS.

Question 604

Topic: Wrist & Carpus

An orthopedic researcher conducts a randomized controlled trial comparing two types of cast materials for distal radius fractures. The study fails to find a statistically significant difference, although a true clinical difference exists in reality. Which of the following would have most effectively decreased the probability of committing this Type II error?

. Decreasing the sample size of the trial
. Decreasing the statistical significance level (alpha) from 0.05 to 0.01
. Increasing the sample size to power the study adequately
. Utilizing a per-protocol analysis instead of an intention-to-treat analysis
. Increasing the random measurement error of the outcomes

Correct Answer & Explanation

. Increasing the sample size to power the study adequately

Explanation

A Type II error (beta) occurs when a study fails to reject a false null hypothesis (a false negative). The probability of avoiding a Type II error is known as statistical power (Power = 1 - beta). Increasing the sample size is the most direct and practical method to increase a study's statistical power, thereby decreasing the risk of a Type II error.

Question 605

Topic: Wrist & Carpus

A 65-year-old woman sustains a volar-angulated extra-articular distal radius fracture (Smith's fracture). Following closed reduction and volar locked plating, the patient develops an inability to flex the interphalangeal joint of her thumb. Which tendon is most likely ruptured?

. Flexor carpi radialis
. Flexor pollicis longus
. Extensor pollicis longus
. Abductor pollicis longus
. Flexor digitorum profundus to the index finger

Correct Answer & Explanation

. Flexor pollicis longus

Explanation

The Flexor Pollicis Longus (FPL) tendon is at high risk for irritation and rupture following volar plate fixation of distal radius fractures. This occurs especially if the plate is positioned too distally, projecting beyond the watershed line.

Question 606

Topic: Wrist & Carpus

A 30-year-old male sustains a Galeazzi fracture-dislocation. Following rigid internal fixation of the radial shaft, the distal radioulnar joint (DRUJ) remains unstable in neutral rotation. In which position is the DRUJ typically most stable and thus recommended for postoperative immobilization?

. Pronation
. Supination
. Neutral rotation
. Palmar flexion
. Dorsiflexion

Correct Answer & Explanation

. Supination

Explanation

A Galeazzi fracture involves the distal third of the radius with disruption of the DRUJ. Following internal fixation of the radius, the DRUJ is evaluated. It is typically most stable in supination because the palmar radioulnar ligament (the primary stabilizer in supination) and the intact interosseous membrane are tensioned, reducing the ulnar head into the sigmoid notch.

Question 607

Topic: Wrist & Carpus

A 45-year-old patient undergoing an open reduction internal fixation of a distal radius fracture under an axillary block suddenly develops perioral numbness, tinnitus, tonic-clonic seizures, and subsequent cardiovascular collapse. Intravenous 20% lipid emulsion therapy is rapidly initiated. What was the most likely regional anesthetic agent used?

. Lidocaine
. Bupivacaine
. Ropivacaine
. Mepivacaine
. Chloroprocaine

Correct Answer & Explanation

. Bupivacaine

Explanation

The presentation is classic for local anesthetic systemic toxicity (LAST). Bupivacaine is a highly lipophilic, long-acting amide local anesthetic with a strong affinity for cardiac voltage-gated sodium channels. This strong binding makes it profoundly cardiotoxic compared to other agents. Intravenous lipid emulsion acts as a 'lipid sink' to draw the lipophilic bupivacaine away from the myocardium and central nervous system.

Question 608

Topic: Wrist & Carpus

Which of the following pharmacological agents has been shown in prospective randomized trials to significantly decrease the incidence of Complex Regional Pain Syndrome (CRPS) following closed treatment of distal radius fractures?

. Gabapentin
. Pregabalin
. Vitamin C (Ascorbic acid)
. Ibuprofen
. Amitriptyline

Correct Answer & Explanation

. Vitamin C (Ascorbic acid)

Explanation

Vitamin C (ascorbic acid), typically given at a dose of 500 mg daily for 50 days following injury, has been shown in several randomized controlled trials to significantly reduce the risk of developing Complex Regional Pain Syndrome (CRPS) after distal radius fractures.

Question 609

Topic: Wrist & Carpus

A 55-year-old female undergoes open reduction and internal fixation of a dorsally comminuted distal radius fracture with a volar locking plate. Six months postoperatively, she presents with an inability to extend her thumb interphalangeal joint. The attritional rupture of this tendon is most likely due to prominent screws penetrating the:

. First extensor compartment
. Second extensor compartment
. Third extensor compartment
. Fourth extensor compartment
. Fifth extensor compartment

Correct Answer & Explanation

. Third extensor compartment

Explanation

Volar plate screws that penetrate too far dorsally can cause attritional rupture of the extensor tendons. The Extensor Pollicis Longus (EPL) tendon, located uniquely in the third extensor compartment crossing Lister's tubercle, is the most frequently injured.

Question 610

Topic: Wrist & Carpus
Scapholunate Advanced Collapse (SLAC) follows a predictable, progressive pattern of degenerative arthritis. Which joint is typically the last to be involved in the SLAC progression, characteristically remaining spared even in advanced stages?
. Radioscaphoid joint
. Capitolunate joint
. Radiolunate joint
. Scaphotrapezial joint
. Scaphocapitate joint

Correct Answer & Explanation

. Radiolunate joint

Explanation

SLAC wrist arthritis follows a specific pattern: Stage I (radial styloid-scaphoid), Stage II (entire radioscaphoid facet), and Stage III (capitolunate joint). The radiolunate joint is characteristically spared from degenerative changes due to its concentric shape and the intact short radiolunate ligament preserving congruity.

Question 611

Topic: Wrist & Carpus

In a prospective randomized clinical trial comparing two fixation methods for distal radius fractures, the researchers conclude there is no significant difference between the two treatments. However, a true difference actually exists in the population. Which of the following statistical errors has occurred, and what parameter quantifies its probability?

. Type I error; quantified by Alpha
. Type I error; quantified by Beta
. Type II error; quantified by Alpha
. Type II error; quantified by Beta
. Type II error; quantified by 1 - Beta (Power)

Correct Answer & Explanation

. Type II error; quantified by Beta

Explanation

A Type II error occurs when researchers fail to reject a false null hypothesis (i.e., failing to find a difference that actually exists). The probability of committing a Type II error is denoted by beta. Power (1 - beta) is the probability of correctly rejecting the null hypothesis when a true difference exists. A Type I error (alpha) is finding a difference when none exists.

Question 612

Topic: Wrist & Carpus

A 40-year-old female presents after a fall on an outstretched hand. Radiographs reveal a fracture of the volar lip of the distal radius with volar subluxation of the carpus. Which of the following is the most appropriate definitive management?

. Closed reduction and long-arm cast in flexion
. Closed reduction and short-arm cast in extension
. Volar buttress plating
. Dorsal spanning plate
. External fixation with distraction

Correct Answer & Explanation

. Volar buttress plating

Explanation

A Volar Barton fracture is an intra-articular shear fracture of the distal radius with associated volar radiocarpal subluxation. It is inherently unstable and is best managed with open reduction and internal fixation using a volar buttress plate to counteract the volar shear forces.

Question 613

Topic: Wrist & Carpus

In Scaphoid Nonunion Advanced Collapse (SNAC), the pattern of degenerative arthritis predictably progresses through specific stages. Unlike Scapholunate Advanced Collapse (SLAC), the radiolunate joint is typically spared in SNAC wrists. What biomechanical mechanism accounts for the preservation of the radiolunate joint in a SNAC wrist?

. The lunate remains tethered to the triquetrum causing volar intercalated segment instability (VISI)
. The distal scaphoid fragment maintains its ligamentous attachment to the lunate
. The intact scapholunate ligament maintains normal lunate extension and concentric radiolunate articulation
. The capitate migrates proximally, unloading the radiolunate joint
. The radioscaphocapitate ligament hypertrophies, shielding the radiolunate facet

Correct Answer & Explanation

. The distal scaphoid fragment maintains its ligamentous attachment to the lunate

Explanation

In a SNAC wrist, the proximal pole of the scaphoid remains firmly attached to the lunate via the intact scapholunate (SL) ligament. This maintains the lunate in a relatively extended but congruous position within the spherical lunate fossa of the radius, thereby preserving the radiolunate joint. The distal scaphoid fragment flexes, leading to progressive arthritis at the radioscaphoid and midcarpal joints.

Question 614

Topic: Wrist & Carpus

A randomized controlled trial comparing two surgical techniques for distal radius fractures finds no statistically significant difference in DASH scores at 1 year (p = 0.08). However, a true clinical difference actually exists in the population. This scenario represents which of the following statistical concepts?

. Type I error
. Type II error
. Selection bias
. Confounding
. Observer bias

Correct Answer & Explanation

. Type II error

Explanation

A Type II error (beta error) occurs when a study fails to reject a false null hypothesis—in simpler terms, concluding there is no difference when one truly exists. This is typically due to an inadequate sample size (low statistical power). A Type I error (alpha error) would be finding a difference when none exists (a false positive).

Question 615

Topic: Wrist & Carpus

During a fluoroscopically assisted closed reduction of a distal radius fracture, the surgeon consciously steps back from the C-arm to reduce scatter radiation exposure. According to the inverse square law of radiation physics, doubling the distance from the primary radiation source reduces the exposure dose to what fraction of the original?

. One-half
. One-third
. One-quarter
. One-eighth
. One-sixteenth

Correct Answer & Explanation

. One-quarter

Explanation

The inverse square law states that the intensity of radiation is inversely proportional to the square of the distance from the source. Therefore, if the distance from the source is doubled (multiplied by 2), the radiation exposure is reduced to 1/(2^2), or one-quarter of the original dose. This is a fundamental principle of radiation safety in the operating room.

Question 616

Topic: Wrist & Carpus

A 60-year-old female presents 6 weeks after non-operative management of a minimally displaced distal radius fracture. She reports sudden inability to actively extend her thumb interphalangeal joint. The extensor pollicis longus (EPL) tendon is suspected to have ruptured. What is the most widely accepted mechanism for this complication in non-displaced or minimally displaced fractures?

. Attritional wear from a prominent volar plate
. Primary laceration by sharp bone fragments at the time of injury
. Synovial ischemia due to increased pressure within the intact third dorsal compartment
. Entrapment of the tendon within the fracture site
. Iatrogenic injury from casting

Correct Answer & Explanation

. Synovial ischemia due to increased pressure within the intact third dorsal compartment

Explanation

EPL ruptures are most commonly associated with non-displaced or minimally displaced distal radius fractures. Because the extensor retinaculum remains intact, bleeding and edema increase pressure within the tightly constrained third dorsal compartment, leading to microvascular ischemia and subsequent delayed rupture of the EPL tendon.

Question 617

Topic: Wrist & Carpus

A 28-year-old manual laborer presents with dorsal wrist pain. Radiographs reveal sclerosis and fragmentation of the lunate. Which of the following anatomic variants is most strongly associated with the pathogenesis of this condition?

. Positive ulnar variance
. Negative ulnar variance
. Type II lunate morphology
. Lunotriquetral coalition
. Madelung deformity

Correct Answer & Explanation

. Negative ulnar variance

Explanation

Kienbock disease is characterized by avascular necrosis of the lunate. Negative ulnar variance is strongly associated with this condition, as it leads to increased radiolunate contact stresses and potential vascular compromise.

Question 618

Topic: Wrist & Carpus

A patient undergoes a Bier block using intravenous lidocaine for a distal radius fracture reduction. She suddenly develops tinnitus, perioral numbness, and a metallic taste. What is the most appropriate initial medical antidote for this severe toxicity?

. Intravenous flumazenil
. Intravenous naloxone
. Intravenous 20% lipid emulsion
. Intravenous calcium gluconate
. Immediate hemodialysis

Correct Answer & Explanation

. Intravenous 20% lipid emulsion

Explanation

The patient is exhibiting signs of Local Anesthetic Systemic Toxicity (LAST). The primary specific treatment includes airway management and prompt administration of 20% intravenous lipid emulsion to sequester the lipophilic anesthetic molecules.

Question 619

Topic: Wrist & Carpus

An orthopedic study compares a new plate design to a standard plate for distal radius fractures. The study concludes there is no significant difference in union rates, but the actual true difference was missed due to an insufficient sample size. This is an example of which of the following statistical errors?

. Type I error
. Type II error
. Selection bias
. Recall bias
. Confounding

Correct Answer & Explanation

. Type II error

Explanation

A Type II error (beta error) occurs when a study fails to reject the null hypothesis when it is actually false (a false negative). This is most commonly due to low statistical power resulting from an inadequate sample size. A Type I error (alpha error) is a false positive.

Question 620

Topic: Wrist & Carpus
A 35-year-old manual laborer presents with chronic dorsal wrist pain. Radiographs reveal sclerosis and fragmentation of the lunate, with proximal migration of the capitate and a negative ulnar variance. This represents Lichtman Stage IIIb Kienböck's disease. Which of the following biomechanical factors is most strongly associated with the development of this condition?
. Positive ulnar variance
. Negative ulnar variance
. Scapholunate ligament dissociation
. Distal radioulnar joint instability
. Volar intercalated segment instability (VISI)

Correct Answer & Explanation

. Negative ulnar variance

Explanation

Kienböck's disease is avascular necrosis of the lunate. It is strongly associated with negative ulnar variance (where the ulna is shorter than the radius at the distal articular surface). This anatomic variant leads to increased shear and compressive forces transmitted from the radius directly to the lunate, predisposing it to microfracture, vascular compromise, and subsequent osteonecrosis. Joint leveling procedures (e.g., radial shortening osteotomy) are often utilized to offload the lunate in early stages.

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