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Wrist & Carpus MCQs

Practice Set 25 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 481

Topic: Wrist & Carpus

What is the primary anatomical purpose of the pronator quadratus muscle in relation to volar plating of the distal radius?

. It stabilizes the distal radioulnar joint (DRUJ).
. It is a key landmark for identifying the radial artery.
. It protects the flexor tendons from hardware irritation.
. It contributes to wrist extension.
. It prevents dorsal displacement of the distal fragment.

Correct Answer & Explanation

. It protects the flexor tendons from hardware irritation.

Explanation

The pronator quadratus muscle is typically reflected from lateral to medial during a volar approach for distal radius plating. After plate application, it is usually repaired over the plate. Its primary purpose in this context is to provide a soft tissue coverage for the volar locking plate and screws, thus protecting the overlying flexor tendons (especially FPL and FDP) from direct contact and irritation by the hardware. While it contributes to pronation and DRUJ stability, its role in protecting tendons from hardware is crucial in volar plating.

Question 482

Topic: Wrist & Carpus
Which type of fracture would be classified as a Frykman Type II?
. Extra-articular distal radius fracture without ulnar styloid fracture
. Extra-articular distal radius fracture with ulnar styloid fracture
. Intra-articular distal radius fracture involving the radiocarpal joint only
. Intra-articular distal radius fracture involving both radiocarpal and DRUJ with ulnar styloid fracture
. Intra-articular distal radius fracture involving both radiocarpal and DRUJ without ulnar styloid fracture

Correct Answer & Explanation

. Extra-articular distal radius fracture with ulnar styloid fracture

Explanation

The Frykman classification system categorizes distal radius fractures based on articular involvement and the presence of an ulnar styloid fracture: Type I: Extra-articular, no ulnar styloid. Type II: Extra-articular, with ulnar styloid. Type III: Intra-articular (radiocarpal), no ulnar styloid. Type IV: Intra-articular (radiocarpal), with ulnar styloid. Type V: Intra-articular (radiocarpal + DRUJ), no ulnar styloid. Type VI: Intra-articular (radiocarpal + DRUJ), with ulnar styloid. Type VII: Intra-articular (DRUJ only), no ulnar styloid. Type VIII: Intra-articular (DRUJ only), with ulnar styloid. Therefore, Frykman Type II is an extra-articular distal radius fracture with an associated ulnar styloid fracture.

Question 483

Topic: Wrist & Carpus

What is the acceptable range for post-reduction volar tilt in a Colles fracture?

. 0 to 5 degrees dorsal tilt
. 10 to 20 degrees volar tilt
. Any degree of dorsal tilt is acceptable if radial length is restored
. -5 to 10 degrees (dorsal to slight volar)
. Strictly 11 degrees volar tilt

Correct Answer & Explanation

. -5 to 10 degrees (dorsal to slight volar)

Explanation

Acceptable post-reduction parameters for volar tilt generally range from neutral (0 degrees) to slight volar angulation (up to 10-15 degrees volar tilt). Some sources might accept a small degree of dorsal tilt (e.g., up to 5 degrees dorsal, or -5 degrees volar) in older, lower-demand patients, but beyond that, it signifies instability or malreduction with increased risk of functional impairment. The typical volar tilt of a normal distal radius is around 11-12 degrees. Therefore, -5 to 10 degrees is the most reasonable acceptable range, encompassing neutral or mild dorsal as potentially acceptable in certain contexts, and avoiding excessive dorsal tilt.

Question 484

Topic: Wrist & Carpus

The 'watershed line' on the volar aspect of the distal radius is an important surgical consideration to prevent which complication?

. Radial artery injury
. Median nerve compression
. Flexor tendon irritation/rupture
. DRUJ instability
. Nonunion of the distal radius

Correct Answer & Explanation

. Flexor tendon irritation/rupture

Explanation

The 'watershed line' on the volar aspect of the distal radius represents the distal limit for volar plate placement. Placing the plate or screws distal to this line risks impingement on and subsequent irritation or rupture of the flexor tendons, particularly the flexor pollicis longus (FPL). This line marks the insertion of the volar capsule and ligaments. Avoiding distal plate placement past this line is critical for preventing tendon complications.

Question 485

Topic: Wrist & Carpus

When assessing a Colles fracture on lateral radiographs, what measurement quantifies the normal volar angulation of the distal radial articular surface relative to the shaft?

. Radial inclination
. Ulnar variance
. Radial length
. Volar tilt (or Palmar tilt)
. Carpo-radial distance

Correct Answer & Explanation

. Volar tilt (or Palmar tilt)

Explanation

Volar tilt (also known as palmar tilt) quantifies the normal volar angulation of the distal radial articular surface relative to the longitudinal axis of the radial shaft on a lateral radiograph. Normal volar tilt is typically around 11-12 degrees. In a Colles fracture, this tilt is lost or reversed, resulting in dorsal tilt.

Question 486

Topic: Wrist & Carpus
Which type of Colles fracture, according to Frykman's classification, carries the worst prognosis for post-traumatic arthritis?
. Type I
. Type II
. Type III
. Type IV
. Type VIII

Correct Answer & Explanation

. Type III

Explanation

Frykman Type IV fracture (intra-articular involving the radiocarpal joint, with an ulnar styloid fracture) carries a worse prognosis for post-traumatic arthritis among the initial types because it involves the radiocarpal articular surface, which is crucial for pain-free motion. More generally, any fracture with significant intra-articular involvement (Types III, IV, V, VI, VII, VIII) has a higher risk of post-traumatic arthritis, but Type IV specifically combines radiocarpal articular involvement with ulnar styloid involvement, indicating a more severe injury with potential DRUJ impact. Type VIII (intra-articular DRUJ only, with ulnar styloid) also has a poor prognosis for DRUJ arthritis. However, Type IV typically signifies significant articular disruption of the main radiocarpal joint.

Question 487

Topic: Wrist & Carpus

Which complication is most characteristic of a malunited Colles fracture with excessive radial shortening and positive ulnar variance?

. Radial nerve palsy
. Scaphoid nonunion
. Ulnar impaction syndrome
. Flexor carpi ulnaris tendonitis
. Extensor indicis proprius rupture

Correct Answer & Explanation

. Ulnar impaction syndrome

Explanation

Excessive radial shortening and positive ulnar variance (where the ulna is relatively longer than the radius) following a Colles fracture can lead to ulnar impaction syndrome. This condition is characterized by chronic pain at the ulnar side of the wrist, particularly with pronation and ulnar deviation, due to increased load transmission through the TFCC and impaction of the ulnar head against the carpus (specifically the triquetrum and lunate). Radial nerve palsy, scaphoid nonunion, and tendon ruptures are not directly caused by ulnar impaction, though other tendon issues can occur.

Question 488

Topic: Wrist & Carpus

In the presence of an associated ulnar styloid fracture in a Colles fracture, when does it most significantly impact management decisions?

. Always, as it is an absolute indication for surgery.
. When it is large and leads to gross instability of the distal radioulnar joint (DRUJ).
. When it is smaller than 2mm, indicating minimal trauma.
. Only if associated with median nerve palsy.
. Never, as it heals spontaneously without intervention.

Correct Answer & Explanation

. When it is large and leads to gross instability of the distal radioulnar joint (DRUJ).

Explanation

An associated ulnar styloid fracture most significantly impacts management decisions when it is large, displaced, or, most critically, leads to gross instability of the distal radioulnar joint (DRUJ). The TFCC attaches to the ulnar styloid, so a displaced styloid fracture can destabilize the DRUJ. If the DRUJ is unstable after distal radius fixation, surgical management of the ulnar styloid (e.g., fixation or excision if comminuted) might be considered. Small, minimally displaced ulnar styloid fractures often heal well conservatively and don't typically affect the overall management of the distal radius fracture unless there's underlying DRUJ instability. It is not an absolute indication for surgery merely by its presence.

Question 489

Topic: Wrist & Carpus

A 30-year-old construction worker falls from scaffolding, landing on his extended, ulnar-deviated wrist. Lateral radiographs of the wrist demonstrate that the lunate maintains its normal articulation with the distal radius, but the capitate is dorsally displaced relative to the lunate. What is the most likely diagnosis?

. Lunate dislocation
. Perilunate dislocation
. Scapholunate dissociation
. Barton's fracture
. Midcarpal dislocation

Correct Answer & Explanation

. Perilunate dislocation

Explanation

This describes a perilunate dislocation. On a lateral radiograph, the lunate maintains its 'teacup' articulation with the distal radius, but the capitate is dislocated dorsally out of the teacup. In contrast, a lunate dislocation (the end stage of perilunate instability) occurs when the lunate is tipped off the radius (volarly), appearing like a 'spilled teacup,' while the capitate remains aligned with the radius.

Question 490

Topic: Wrist & Carpus

A 28-year-old female sustains a Galeazzi fracture-dislocation. After Open Reduction and Internal Fixation (ORIF) of the radial shaft, the distal radioulnar joint (DRUJ) is noted to be unstable dorsally when evaluated. In what forearm position should the arm be splinted postoperatively to maximize DRUJ stability, and what anatomical structure is primarily tensioned in this position?

. Pronation, to tension the dorsal radioulnar ligament
. Supination, to tension the palmar radioulnar ligament
. Pronation, to tension the interosseous membrane
. Supination, to tension the dorsal radioulnar ligament
. Neutral position, to relax both radioulnar ligaments

Correct Answer & Explanation

. Supination, to tension the palmar radioulnar ligament

Explanation

In a Galeazzi fracture, most DRUJ dislocations are volar (ulnar head is volar to the radius) and are most stable in supination. Supination confers stability by moving the radius relative to the ulna to reduce the joint, tensioning the intact palmar radioulnar ligament, and relaxing the deforming force of the pronator quadratus. Note: If the ulnar head dislocates dorsally, stability is usually achieved in pronation. However, standard teaching states that DRUJ volar dislocations (classic Galeazzi) require immobilization in supination to tighten the palmar radioulnar ligament.

Question 491

Topic: Wrist & Carpus

A 27-year-old construction worker sustains a Galeazzi fracture (fracture of the distal third of the radial shaft with associated distal radioulnar joint (DRUJ) disruption). Following anatomic open reduction and internal fixation of the radius with a volar plate, the surgeon must assess the DRUJ. Which fracture characteristic is most predictive of persistent DRUJ instability requiring intraoperative stabilization?

. Fracture location > 7.5 cm proximal to the radiocarpal joint
. Fracture location < 7.5 cm proximal to the radiocarpal joint
. Associated fracture of the base of the ulnar styloid
. Volar displacement of the initial radial shaft fracture
. Associated minimally displaced scaphoid waist fracture

Correct Answer & Explanation

. Fracture location < 7.5 cm proximal to the radiocarpal joint

Explanation

Galeazzi fractures located within 7.5 cm of the radiocarpal joint have a significantly higher rate of persistent DRUJ instability following anatomic fixation of the radius compared to those located > 7.5 cm proximal. This proximity to the joint is strongly associated with severe disruption of the triangular fibrocartilage complex (TFCC) and supporting radioulnar ligaments, often necessitating DRUJ pinning or direct TFCC repair.

Question 492

Topic: Wrist & Carpus

A 25-year-old male falls from a height onto a hyperextended wrist. Lateral radiographs show the capitate rests dorsally to the lunate, while the lunate maintains its normal articulation with the distal radius. According to Mayfield's stages of perilunate instability, which ligamentous structure is disrupted first?

. Scapholunate interosseous ligament
. Lunotriquetral ligament
. Radioscaphocapitate ligament
. Dorsal radiocarpal ligament
. Ulnocarpal ligament

Correct Answer & Explanation

. Scapholunate interosseous ligament

Explanation

Mayfield described a progressive, four-stage perilunate instability pattern starting radially and progressing ulnarly. Stage I involves disruption of the scapholunate interosseous ligament.

Question 493

Topic: Wrist & Carpus

A 42-year-old female presents with a highly comminuted radial head fracture and distal radioulnar joint (DRUJ) instability after a fall from a height. She undergoes radial head replacement. Intraoperatively, the DRUJ remains grossly unstable. What is the most appropriate next step in management for this Essex-Lopresti injury?

. Radial head excision
. Ulnar shortening osteotomy
. Pinning of the DRUJ in supination
. Pinning of the DRUJ in pronation
. Casting in neutral rotation

Correct Answer & Explanation

. Pinning of the DRUJ in supination

Explanation

Essex-Lopresti injuries involve a radial head fracture, interosseous membrane disruption, and DRUJ dislocation. Following radial head replacement, if the DRUJ remains unstable, it should be pinned in supination to maximize stability and allow ligamentous healing.

Question 494

Topic: Wrist & Carpus

A 25-year-old manual laborer presents with dorsal wrist pain, decreased grip strength, and limited range of motion. Radiographs demonstrate sclerosis and fragmentation of the lunate. Which of the following anatomic variants is most strongly associated with the development of this condition?

. Positive ulnar variance
. Negative ulnar variance
. Madelung deformity
. Scapholunate diastasis
. Ulnar impaction syndrome

Correct Answer & Explanation

. Negative ulnar variance

Explanation

Kienbock's disease (avascular necrosis of the lunate) is strongly associated with negative ulnar variance. A relatively short ulna increases the radiolunate contact stress, predisposing the lunate to microtrauma and ischemia.

Question 495

Topic: Wrist & Carpus

A 24-year-old male sustains a displaced proximal pole scaphoid fracture. The primary blood supply at highest risk of disruption enters the scaphoid at which anatomic location?

. Volar tubercle
. Dorsal ridge
. Proximal pole
. Distal pole articular surface
. Scapholunate ligament insertion

Correct Answer & Explanation

. Dorsal ridge

Explanation

The primary blood supply to the scaphoid is retrograde, entering via branches of the radial artery at the dorsal ridge. Proximal pole fractures therefore carry a high risk of avascular necrosis.

Question 496

Topic: Wrist & Carpus

A 45-year-old female sustains a comminuted intra-articular distal radius fracture.

The presence of a separate volar marginal fragment of the lunate facet (volar Barton's variant) is highly important to identify because:

. It invariably requires excision and proximal row carpectomy.
. It is easily captured by standard dorsal spanning plates.
. It acts as a critical stabilizer to prevent volar subluxation of the carpus.
. It indicates an associated distal radioulnar joint (DRUJ) dislocation.
. It is non-articular and can be managed non-operatively.

Correct Answer & Explanation

. It acts as a critical stabilizer to prevent volar subluxation of the carpus.

Explanation

The volar marginal fragment of the lunate facet is critical for the stability of the radiocarpal joint. The short radiolunate ligament originates from this fragment, and if it remains displaced, the entire carpus may subluxate volarly. Standard volar locking plates may not adequately capture small, very distal volar ulnar corner fragments, sometimes necessitating fragment-specific fixation.

Question 497

Topic: Wrist & Carpus

A hand surgeon is evaluating a patient with a suspected triangular fibrocartilage complex (TFCC) tear. When considering potential for spontaneous healing or surgical repair of a TFCC tear, the surgeon must account for its vascular supply. Which portion of the TFCC is considered vascularized and capable of healing?

. The central articular disc
. The entire complex is completely avascular
. The peripheral 10% to 25%
. The central 50%
. The radial insertion site at the sigmoid notch

Correct Answer & Explanation

. The peripheral 10% to 25%

Explanation

The blood supply to the triangular fibrocartilage complex (TFCC) originates from branches of the ulnar artery and anterior interosseous artery, penetrating only the peripheral 10% to 25% (the capsular attachments). The central portion and the radial insertion (sigmoid notch) are avascular and receive nutrition via synovial fluid diffusion. Therefore, only peripheral tears (e.g., Palmer Class 1B) are amenable to direct surgical repair, whereas central tears (Palmer Class 1A) typically require debridement due to poor healing potential.

Question 498

Topic: Wrist & Carpus
In the progressive sequence of perilunate instability described by Mayfield, what specific anatomical disruption defines Stage II?
. Scapholunate interosseous ligament dissociation
. Lunotriquetral interosseous ligament dissociation
. Dorsal radiocarpal ligament rupture
. Volar radiolunate ligament failure
. Capitolunate articulation disruption

Correct Answer & Explanation

. Lunotriquetral interosseous ligament dissociation

Explanation

Mayfield's stages of perilunate instability follow a progressive pattern around the lunate: Stage I involves scapholunate dissociation. Stage II involves disruption of the capitolunate articulation as force propagates through the space of Poirier, leading to dorsal capitate dislocation. Stage III is lunotriquetral dissociation, and Stage IV is complete lunate dislocation.

Question 499

Topic: Wrist & Carpus

A 25-year-old elite gymnast presents with ulnar-sided wrist pain and instability of the distal radioulnar joint (DRUJ). An MRI reveals a traumatic avulsion of the triangular fibrocartilage complex (TFCC) from its bony insertion at the ulnar fovea. What is the correct Palmer classification for this specific injury?

. Class 1A
. Class 1B
. Class 1C
. Class 1D
. Class 2A

Correct Answer & Explanation

. Class 1B

Explanation

The Palmer classification divides TFCC tears into traumatic (Class 1) and degenerative (Class 2). Class 1A is a central slit/perforation. Class 1B is an ulnar-sided avulsion from the fovea or base of the ulnar styloid (often causing DRUJ instability). Class 1C is a distal avulsion from the carpus, and Class 1D is a radial-sided avulsion from the sigmoid notch.

Question 500

Topic: Wrist & Carpus

A 65-year-old patient with long-standing rheumatoid arthritis presents with a new inability to actively extend the small and ring fingers at the metacarpophalangeal (MCP) joints. Extension at the PIP joints is preserved, and passive MCP extension is full. This clinical picture (Vaughan-Jackson syndrome) is most often caused by attrition and rupture of the extensor tendons over which specific bony prominence?

. Lister's tubercle
. The distal pole of the scaphoid
. A prominent, dorsally subluxated distal ulna
. The volar rim of the distal radius
. The hook of the hamate

Correct Answer & Explanation

. A prominent, dorsally subluxated distal ulna

Explanation

Vaughan-Jackson syndrome is the sequential, ulnar-to-radial rupture of the extensor digitorum communis (EDC) tendons in rheumatoid arthritis. It is caused by mechanical attrition over a prominent, dorsally subluxated distal ulna head (Caput ulnae syndrome) secondary to destruction of the distal radioulnar joint (DRUJ).

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