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Wrist & Carpus MCQs

Practice Set 11 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 201

Topic: Wrist & Carpus

A 60-year-old female presents with acute pain and deformity in her wrist after a fall onto an outstretched hand. Radiographs show a Galeazzi fracture-dislocation (fracture of the distal radius with dislocation of the distal radioulnar joint). What is the preferred treatment for this injury in an adult?

. Closed reduction and long arm cast immobilization.
. External fixation.
. Open reduction and internal fixation (ORIF) of the radius and stabilization of the DRUJ.
. Percutaneous pinning of the radius.
. Distal radioulnar joint (DRUJ) fusion.

Correct Answer & Explanation

. Open reduction and internal fixation (ORIF) of the radius and stabilization of the DRUJ.

Explanation

A Galeazzi fracture-dislocation in an adult is an inherently unstable injury and typically requires open reduction and internal fixation (ORIF) of the radial shaft fracture to restore its length and rotation. Once the radius is anatomically reduced and fixed, the distal radioulnar joint (DRUJ) usually reduces spontaneously. The DRUJ must then be assessed for stability, and if unstable, it may require temporary K-wire fixation across the DRUJ and/or repair of the TFCC. Closed reduction and casting are rarely successful in adults due to the instability of the DRUJ. External fixation is generally reserved for severe open injuries or as a temporary measure. Percutaneous pinning is inadequate for this fracture pattern. DRUJ fusion is a salvage procedure, not a primary treatment.

Question 202

Topic: Wrist & Carpus

An examiner questions you on diagnostic tests. A new clinical test for diagnosing scaphoid fractures has a high positive predictive value (PPV). Which of the following epidemiological factors will most directly cause the PPV of this test to increase?

. An increase in the sensitivity of the test
. An increase in the prevalence of scaphoid fractures in the population
. A decrease in the specificity of the test
. An increase in the number of false-positive results
. A decrease in the prevalence of scaphoid fractures in the population

Correct Answer & Explanation

. An increase in the prevalence of scaphoid fractures in the population

Explanation

Positive predictive value is highly dependent on the prevalence of the disease in the tested population. As disease prevalence increases, the likelihood that a positive test truly represents the disease (PPV) also increases, assuming sensitivity and specificity remain constant.

Question 203

Topic: Wrist & Carpus

A 65-year-old female sustains a nondisplaced distal radius fracture and is treated non-operatively in a short arm cast. Six weeks later, she presents with an inability to actively extend her thumb interphalangeal joint. What is the most widely accepted mechanism for this specific complication following a nondisplaced distal radius fracture?

. Sharp mechanical attrition of the tendon against a displaced dorsal cortical fragment
. Ischemic necrosis of the tendon secondary to hematoma and increased pressure within the intact third extensor compartment
. Direct injury to the posterior interosseous nerve during the initial trauma
. Iatrogenic tethering of the tendon by a poorly molded cast
. Avulsion of the extensor pollicis longus muscle belly at the musculotendinous junction

Correct Answer & Explanation

. Ischemic necrosis of the tendon secondary to hematoma and increased pressure within the intact third extensor compartment

Explanation

The patient has experienced an Extensor Pollicis Longus (EPL) tendon rupture. In the setting of a non-displaced or minimally displaced distal radius fracture treated non-operatively, the prevailing theory for EPL rupture is vascular watershed ischemia. The intact extensor retinaculum confines the third dorsal compartment. Bleeding and edema from the fracture increase compartment pressure, compressing the precarious vascular supply to the EPL as it wraps around Lister's tubercle, leading to focal ischemic necrosis and delayed rupture (often around 4-8 weeks). Mechanical attrition is the usual cause after volar plating with prominent dorsal screws.

Question 204

Topic: Wrist & Carpus
A 45-year-old manual laborer presents with chronic wrist pain and a known scaphoid nonunion. Radiographs demonstrate arthritis at the radioscaphoid and capitolunate joints, with preservation of the radiolunate joint. What is the SNAC stage and most appropriate definitive surgical treatment?
. SNAC I; Radial styloidectomy
. SNAC II; Proximal row carpectomy (PRC)
. SNAC III; Four-corner fusion with scaphoid excision
. SNAC III; Proximal row carpectomy (PRC)
. SNAC IV; Total wrist arthrodesis

Correct Answer & Explanation

. SNAC III; Four-corner fusion with scaphoid excision

Explanation

Scaphoid Nonunion Advanced Collapse (SNAC) is staged by the progression of arthritis. Stage I involves the radial styloid; Stage II involves the entire radioscaphoid joint; Stage III involves the capitolunate joint; Stage IV involves the entire carpus (including radiolunate). This patient is SNAC III. Proximal row carpectomy (PRC) is contraindicated in SNAC III because the capitate head is arthritic and would articulate with the lunate fossa. Therefore, four-corner fusion with scaphoid excision is the treatment of choice.

Question 205

Topic: Wrist & Carpus
A 35-year-old male laborer presents with chronic right wrist pain. Radiographs demonstrate a scaphoid nonunion with marked sclerosis, joint space narrowing at the radioscaphoid joint, and arthritic changes at the capitolunate joint. The radiolunate joint space is completely preserved. According to the Scaphoid Nonunion Advanced Collapse (SNAC) staging system, what is the correct stage of this patient's wrist?
. SNAC Stage I
. SNAC Stage II
. SNAC Stage III
. SLAC Stage II
. SLAC Stage III

Correct Answer & Explanation

. SNAC Stage III

Explanation

SNAC staging is progressive: Stage I involves arthrosis isolated to the radial styloid-scaphoid articulation. Stage II extends to involve the scaphocapitate joint. Stage III involves the capitolunate joint, leading to periscaphoid arthrosis. The radiolunate joint is characteristically spared in SNAC (and SLAC) wrists because the radiolunate ligament provides a concentric matching surface that resists shear forces.

Question 206

Topic: Wrist & Carpus

A 42-year-old male presents with chronic wrist pain and a history of a scaphoid fracture 10 years ago. Radiographs reveal a scaphoid nonunion advanced collapse (SNAC) pattern with severe arthritis involving the radioscaphoid joint and the capitolunate joint. The radiolunate joint is perfectly preserved. What stage of SNAC wrist is this, and which procedure is most appropriate?

. Stage 1; Radial styloidectomy
. Stage 2; Scaphoid excision and four-corner fusion
. Stage 3; Scaphoid excision and four-corner fusion
. Stage 3; Proximal row carpectomy
. Stage 4; Total wrist arthrodesis

Correct Answer & Explanation

. Stage 3; Scaphoid excision and four-corner fusion

Explanation

SNAC staging: Stage 1 = Arthritis between the radial styloid and distal scaphoid. Stage 2 = Scaphocapitate arthritis. Stage 3 = Capitolunate arthritis. Stage 4 = Pancarpal arthritis (including radiolunate). This patient has capitolunate involvement (Stage 3). Scaphoid excision and four-corner fusion is the treatment of choice. Proximal row carpectomy (PRC) is contraindicated in Stage 3 SNAC/SLAC because PRC relies on a healthy proximal capitate articulating with the lunate fossa, which is destroyed in Stage 3.

Question 207

Topic: Wrist & Carpus

A 65-year-old female undergoes volar locked plating for a displaced distal radius fracture. Three months postoperatively, she presents with an inability to extend her thumb at the interphalangeal joint. What is the most likely iatrogenic cause of this complication in the setting of volar plating?

. Vascular compromise to the tendon at Lister's tubercle
. Prominent distal screws penetrating the dorsal cortex
. Excessive retraction during the volar surgical approach
. Direct injury from the drill bit on the volar side
. Attrition of the tendon over a prominent volar plate

Correct Answer & Explanation

. Prominent distal screws penetrating the dorsal cortex

Explanation

Rupture of the extensor pollicis longus (EPL) tendon following volar plating of the distal radius is most commonly caused by prominent distal screws penetrating the dorsal cortex. The EPL runs in the third dorsal compartment, directly over the distal radius. Volar plate prominence or improper positioning on the watershed line typically causes flexor tendon ruptures (e.g., FPL), whereas dorsal screw prominence causes extensor tendon ruptures.

Question 208

Topic: Wrist & Carpus

A 45-year-old manual laborer presents with progressive wrist pain. Radiographs reveal a scaphoid nonunion with localized arthritis at the radial styloid-scaphoid articulation. The radioscaphoid joint is narrowed, but the midcarpal joint and the radiolunate articulation are completely preserved (SNAC Stage 1). Which of the following is the most appropriate surgical intervention?

. Proximal row carpectomy
. Four-corner arthrodesis
. Radial styloidectomy with scaphoid nonunion takedown and bone grafting
. Total wrist arthrodesis
. Scaphoid excision and capitolunate arthrodesis

Correct Answer & Explanation

. Radial styloidectomy with scaphoid nonunion takedown and bone grafting

Explanation

Scaphoid nonunion advanced collapse (SNAC) Stage 1 is characterized by arthritis limited to the radial styloid. For Stage 1 SNAC, an organ-preserving procedure is indicated, specifically radial styloidectomy combined with open reduction, internal fixation, and bone grafting of the scaphoid. Salvage procedures like proximal row carpectomy (PRC) or four-corner fusion are indicated for SNAC Stage 2 (scaphocapitate arthritis) and Stage 3 (periscaphoid arthritis).

Question 209

Topic: Wrist & Carpus
A 45-year-old man presents with chronic wrist pain and a known scaphoid nonunion. Radiographs reveal narrowing of the radioscaphoid joint and capitolunate joint, but the radiolunate joint is spared. What is the SNAC stage and most appropriate surgical treatment?
. SNAC Stage I - Radial styloidectomy
. SNAC Stage II - Proximal row carpectomy
. SNAC Stage III - Four-corner arthrodesis
. SNAC Stage III - Scaphoid excision and capitolunate arthrodesis
. SNAC Stage IV - Total wrist arthrodesis

Correct Answer & Explanation

. SNAC Stage III - Four-corner arthrodesis

Explanation

SNAC Stage III involves arthritis of the radioscaphoid and midcarpal (capitolunate) joints, while the radiolunate joint is characteristically spared. Four-corner fusion (capitate, hamate, lunate, triquetrum) with scaphoid excision is the standard treatment when the capitate is involved, precluding a proximal row carpectomy.

Question 210

Topic: Wrist & Carpus
The natural history of an untreated scaphoid nonunion progresses predictably to Scaphoid Nonunion Advanced Collapse (SNAC). Which specific joint articulation is initially spared in the early stages (SNAC Stage I and II) but eventually becomes involved in SNAC Stage III?
. Radioscaphoid joint
. Capitolunate joint
. Scaphotrapezial joint
. Radioscaphocapitate joint
. Distal radioulnar joint

Correct Answer & Explanation

. Capitolunate joint

Explanation

SNAC wrist progresses in a predictable pattern. Stage I involves the radial styloid-scaphoid articulation. Stage II involves the entire radioscaphoid articulation. Stage III progresses to involve the midcarpal joint, specifically the capitolunate joint. The radiolunate joint is characteristically spared in both SLAC and SNAC wrists due to the spherical articulation and the protective short radiolunate ligament.

Question 211

Topic: Wrist & Carpus
A patient with long-standing scaphoid nonunion presents with progressive wrist pain. Radiographs demonstrate early arthritic changes characteristic of Scaphoid Nonunion Advanced Collapse (SNAC). Which joint is typically the first to develop degenerative changes in the SNAC progression?
. Radioscaphoid joint (specifically the radial styloid and distal scaphoid)
. Capitolunate joint
. Scaphotrapeziotrapezoid (STT) joint
. Lunotriquetral joint
. Distal radioulnar joint (DRUJ)

Correct Answer & Explanation

. Radioscaphoid joint (specifically the radial styloid and distal scaphoid)

Explanation

In SNAC wrist, arthritis progresses in a predictable sequence. Stage I involves the radial styloid and the distal pole of the scaphoid (radioscaphoid joint). Stage II progresses to the entire radioscaphoid joint. Stage III involves the capitolunate joint. The radiolunate joint is characteristically spared due to a congruent spherical relationship.

Question 212

Topic: Wrist & Carpus

When utilizing a volar locking plate for fixation of a distal radius fracture, placement of the plate at or distal to the watershed line significantly increases the risk of rupture of which tendon?

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

Correct Answer & Explanation

. Flexor pollicis longus

Explanation

The watershed line is a transverse anatomical ridge on the volar margin of the distal radius. Plate prominence at or distal to this line causes attritional wear on the flexor pollicis longus (FPL) tendon due to its immediate proximity as it courses over the distal radius, leading to a high risk of iatrogenic rupture.

Question 213

Topic: Wrist & Carpus

In the natural history of Scaphoid Nonunion Advanced Collapse (SNAC), degenerative arthritic changes progress through a predictable radiographic sequence. Which specific articulation is classically spared from this degenerative cascade due to its uniquely preserved concentric spherical kinematics?

. Radioscaphoid joint
. Capitolunate joint
. Scaphocapitate joint
. Radiolunate joint
. Triscaphe (STT) joint

Correct Answer & Explanation

. Radiolunate joint

Explanation

The radiolunate articulation is classically spared in both Scapholunate Advanced Collapse (SLAC) and Scaphoid Nonunion Advanced Collapse (SNAC) wrists. This is because the lunate maintains a congruent, concentric, spherical relationship with the lunate fossa of the radius, even when it assumes an extended (DISI) posture, thereby avoiding abnormal cartilage loading and shear stresses.

Question 214

Topic: Wrist & Carpus
A 55-year-old male presents with advanced Scapholunate Advanced Collapse (SLAC) wrist arthritis. Radiographs show arthritic changes involving the radioscaphoid and capitolunate joints, with preservation of the radiolunate joint. What is the most appropriate surgical treatment?
. Proximal row carpectomy (PRC)
. Scaphoid excision and four-corner fusion
. Scapholunate ligament reconstruction
. Radial styloidectomy
. Distal radius core decompression

Correct Answer & Explanation

. Scaphoid excision and four-corner fusion

Explanation

In Stage III SLAC wrist, arthritic changes involve the radioscaphoid and capitolunate joints. Because the capitate head is arthritic, a proximal row carpectomy (PRC) is contraindicated, as the arthritic capitate would articulate with the lunate fossa, leading to persistent pain and failure. Scaphoid excision and four-corner fusion is the treatment of choice. The radiolunate joint is characteristically spared in SLAC and SNAC arthritis, making radiolunate-preserving procedures like four-corner fusion ideal.

Question 215

Topic: Wrist & Carpus

A 55-year-old female undergoes volar locking plate fixation for a displaced distal radius fracture. Six months postoperatively, she presents with a sudden inability to actively flex the interphalangeal joint of her thumb. Which of the following plate placement errors most likely contributed to this specific complication?

. Placement of the plate proximal to the watershed line
. Placement of the plate distal to the watershed line
. Use of excessively long dorsal screws
. Failure to repair the pronator quadratus
. Inadequate reduction of the volar lunate facet

Correct Answer & Explanation

. Placement of the plate distal to the watershed line

Explanation

Flexor pollicis longus (FPL) tendon rupture is a known complication of volar plating of the distal radius. It is most commonly caused by placement of the plate too distally (distal to the 'watershed line'), leading to mechanical attrition of the tendon against the prominent distal edge of the plate during active thumb motion.

Question 216

Topic: Wrist & Carpus

A 50-year-old female presents with a sudden inability to actively flex the interphalangeal joint of her thumb. Three years prior, she underwent volar plate fixation of a distal radius fracture. The spontaneous rupture of the flexor pollicis longus (FPL) tendon in this setting is most commonly associated with which of the following intraoperative technical errors?

. Excessive dorsal screw prominence
. Volar plate placement distal to the watershed line
. Intra-articular screw penetration into the radiocarpal joint
. Inadequate restoration of radial inclination
. Failure to address ulnar positive variance

Correct Answer & Explanation

. Volar plate placement distal to the watershed line

Explanation

FPL attrition and spontaneous rupture is a well-recognized complication of volar locking plating for distal radius fractures. It most commonly occurs when the plate is placed too distally, crossing the "watershed line" of the distal radius, creating a mechanical prominence that directly abrades the FPL tendon (Soong Grade 2).

Question 217

Topic: Wrist & Carpus

A 60-year-old woman undergoes volar locking plate fixation for a displaced, comminuted distal radius fracture. Six months postoperatively, she presents with the sudden inability to actively flex the interphalangeal joint of her thumb. She denies any new trauma. This complication is most strongly associated with which of the following intraoperative technical errors?

. Screws penetrating the dorsal cortex of the distal radius
. Placement of the volar plate distal to the watershed line
. Failure to repair the pronator quadratus during closure
. Over-distraction of the radiocarpal joint during reduction
. Use of a non-locking screw in the most ulnar distal plate hole

Correct Answer & Explanation

. Placement of the volar plate distal to the watershed line

Explanation

The patient has experienced an attritional rupture of the flexor pollicis longus (FPL) tendon. In volar plating of the distal radius, the FPL tendon is at high risk of attrition and rupture if the plate is positioned too far distally, crossing the 'watershed line' (the bony ridge marking the volar margin of the distal radius articular surface). Prominent hardware at this level directly rubs against the flexor tendons. Dorsal screw penetration causes extensor tendon ruptures (most commonly EPL).

Question 218

Topic: Wrist & Carpus
A 40-year-old male presents with chronic wrist pain and an untreated scaphoid fracture sustained 10 years ago. Radiographs reveal osteoarthritis involving the radioscaphoid joint and the capitolunate joint, but the radiolunate joint is remarkably spared. What is the correct stage of Scaphoid Nonunion Advanced Collapse (SNAC)?
. Stage I
. Stage II
. Stage III
. Stage IV
. SLAC Stage III

Correct Answer & Explanation

. Stage II

Explanation

SNAC staging describes the predictable progression of wrist arthritis following a scaphoid nonunion. Stage I involves the radial styloid and distal scaphoid. Stage II involves the entire radioscaphoid joint. Stage III adds involvement of the capitolunate joint. Stage IV involves the entire carpus. The radiolunate joint is typically spared in both SNAC and SLAC due to the spherical congruency of that articulation.

Question 219

Topic: Wrist & Carpus

A 55-year-old female presents with an inability to actively flex the interphalangeal joint of her thumb 8 months after undergoing volar plate fixation of a distal radius fracture. Radiographs show a healed fracture but the distal edge of the volar plate is positioned anterior to the watershed line. Which tendon is most likely ruptured due to attritional wear against the plate?

. Flexor carpi radialis (FCR)
. Flexor digitorum superficialis (FDS) to the index finger
. Flexor digitorum profundus (FDP) to the index finger
. Flexor pollicis longus (FPL)
. Extensor pollicis longus (EPL)

Correct Answer & Explanation

. Flexor pollicis longus (FPL)

Explanation

Placement of a volar plate distal to the watershed line of the distal radius places the prominent hardware in direct contact with the flexor tendons. The Flexor Pollicis Longus (FPL) tendon runs intimately over this area and is at the highest risk for attritional rupture when the plate is positioned too distally or stands proud of the bone (Soong Grade 2).

Question 220

Topic: Wrist & Carpus

A 60-year-old female underwent volar locking plate fixation for a comminuted distal radius fracture. Eight months postoperatively, she returns complaining of a sudden inability to actively flex the interphalangeal joint of her thumb. Which of the following technical errors during the index surgery is the most likely culprit?

. Placement of the volar plate distal to the watershed line
. Prominent dorsal projection of distal locking screws
. Failure to repair the pronator quadratus muscle
. Over-reduction of the normal volar tilt
. Placement of the plate deep to the flexor carpi radialis tendon

Correct Answer & Explanation

. Placement of the volar plate distal to the watershed line

Explanation

Rupture of the flexor pollicis longus (FPL) tendon is a well-documented complication of volar plating of the distal radius. It occurs due to mechanical attrition and fraying of the tendon against the prominent distal edge of a plate that has been improperly positioned distal to the watershed line of the radius.

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