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Wrist & Carpus MCQs

Practice Set 21 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 401

Topic: Wrist & Carpus

Three months following volar plate fixation of a distal radius fracture, a patient experiences a spontaneous rupture of the flexor pollicis longus (FPL) tendon. What is the most likely technical error leading to this complication?

. Prominent dorsal screw tips
. Plate positioned distal to the watershed line
. Plate positioned proximal to the watershed line
. Inadequate reduction of the dorsal cortex
. Retained intra-articular hardware

Correct Answer & Explanation

. Plate positioned distal to the watershed line

Explanation

Volar plates placed too distally, beyond the watershed line of the distal radius, can impinge on the flexor tendons. This friction leads to tenosynovitis and subsequent rupture, most commonly affecting the FPL.

Question 402

Topic: Wrist & Carpus

During open reduction and internal fixation of a complex intra-articular distal radius fracture using a volar extended flexor carpi radialis (FCR) approach, the surgeon identifies a displaced radial styloid fragment. Releasing the insertion of which of the following muscles is most critical to neutralize the primary deforming force on this specific fragment?

. Pronator quadratus
. Flexor pollicis longus
. Brachioradialis
. Abductor pollicis longus
. Extensor carpi radialis brevis

Correct Answer & Explanation

. Brachioradialis

Explanation

The brachioradialis inserts directly onto the base of the radial styloid. Its persistent pull is the primary deforming force causing proximal and radial displacement of the radial styloid fragment, necessitating its release (or fractional lengthening) during surgical reduction.

Question 403

Topic: Wrist & Carpus

A 22-year-old gymnast presents with chronic ulnar-sided wrist pain. MRI shows a tear of the triangular fibrocartilage complex (TFCC). Healing potential is highly dependent on the vascularity of the TFCC. Which portion of the TFCC receives the most robust blood supply?

. Central articular disc
. Radial attachment
. Volar capsular margin
. Peripheral ulnar 10% to 20%
. Distal radioulnar ligament insertions

Correct Answer & Explanation

. Peripheral ulnar 10% to 20%

Explanation

The peripheral 10% to 20% of the TFCC is highly vascularized, receiving supply from branches of the ulnar artery and interosseous arteries. Central and radial tears are largely avascular and typically require debridement, whereas peripheral tears can be repaired.

Question 404

Topic: Wrist & Carpus

The triangular fibrocartilage complex (TFCC) is crucial for distal radioulnar joint (DRUJ) stability. The primary bony attachment of the deep radioulnar ligaments (ligamentum subcruentum) is located at which structure?

. Ulnar styloid tip
. Fovea of the ulnar head
. Triquetrum
. Lunate
. Sigmoid notch of the radius

Correct Answer & Explanation

. Fovea of the ulnar head

Explanation

The deep radioulnar ligaments (ligamentum subcruentum) of the TFCC attach to the fovea at the base of the ulnar styloid. This deep foveal attachment is the primary stabilizer of the DRUJ.

Question 405

Topic: Wrist & Carpus

A resident is evaluating a 7-year-old male with suspected Dysplasia Epiphysealis Hemimelica (DEH). Which of the following anatomical locations is considered extremely rare for this pathology?

. Distal femur
. Distal tibia
. Talus
. Distal radius

Correct Answer & Explanation

. Distal radius

Explanation

Correct Answer: Distal radiusDEH usually occurs in the lower limb, with the distal femur, distal tibia, and talus being the most commonly affected sites. Upper limb involvement (such as the distal radius) is extremely rare.

Question 406

Topic: Wrist & Carpus

When using a volar locking plate for a distal radius fracture, the screws are typically inserted in which orientation relative to the articular surface?

. Perpendicular to the plate, avoiding the articular surface.
. Parallel to the joint surface, supporting subchondral bone.
. Oblique to the joint, aiming for bicortical fixation.
. From dorsal to volar, engaging only the volar cortex.
. With a variable angle, directed away from the fracture line.

Correct Answer & Explanation

. Parallel to the joint surface, supporting subchondral bone.

Explanation

Volar locking plates for distal radius fractures are designed with screw holes that allow the distal screws to be inserted at fixed or variable anglesparallelto the joint surface. This creates a 'subchondral raft' of screws that buttress and support the articular fragments, preventing their collapse and maintaining the reduction of the joint surface. While bicortical engagement is often desired, the primary orientation is subchondral support. Perpendicular (A) would violate the joint. Oblique (C) might be true for some variable angles, but thegoalis parallel to the joint. Dorsal to volar (D) is incorrect for a volar plate. Directed away from fracture (E) is too vague.

Question 407

Topic: Wrist & Carpus

A trauma series radiograph of the wrist is performed for a patient suspected of a perilunate injury. On the lateral view, what is the key radiographic finding that indicates a perilunate dislocation (as opposed to a lunate dislocation)?

. Lunate appearing triangular and volar-displaced
. Loss of the normal collinear relationship between the radius, lunate, and capitate
. Widened scapholunate interval (Terry Thomas sign)
. Fracture of the waist of the scaphoid
. Disruption of Gilula's lines on the PA view

Correct Answer & Explanation

. Loss of the normal collinear relationship between the radius, lunate, and capitate

Explanation

On a true lateral radiograph, the hallmark of a perilunate dislocation is the loss of the normal collinear relationship between the radius, lunate, and capitate, specifically the capitate dislocating dorsally relative to the lunate. The lunate maintains its articulation with the radial facet. A lunate appearing triangular and volar-displaced (the 'spilled teacup' sign) is characteristic of a lunate dislocation, which often represents the final stage of a trans-scaphoperilunate injury where the lunate dislocates volarly. Widened scapholunate interval and disruption of Gilula's lines are primarily seen on the PA view, while a scaphoid fracture is an associated injury, not the defining radiographic feature of the dislocation itself.

Question 408

Topic: Wrist & Carpus
Which radiographic sign on the PA wrist view is most indicative of scapholunate dissociation, often seen accompanying perilunate dislocations?
. Positive ulnar variance
. Widened scapholunate interval (>3mm, 'Terry Thomas sign')
. Negative ulnar variance
. Lunate sclerosis
. Distal radioulnar joint (DRUJ) incongruity

Correct Answer & Explanation

. Widened scapholunate interval (>3mm, 'Terry Thomas sign')

Explanation

The 'Terry Thomas sign' refers to a widened scapholunate interval, typically >3mm (or >2mm when compared to the contralateral wrist), on the PA radiograph. This gap indicates dissociation between the scaphoid and lunate, a hallmark of scapholunate ligament injury.

Question 409

Topic: Wrist & Carpus

In the context of perilunate instability, what is the significance of the 'ring sign' on a PA wrist radiograph?

. It indicates avascular necrosis of the lunate.
. It signifies an associated scaphoid fracture.
. It suggests rotary subluxation of the scaphoid due to scapholunate dissociation.
. It demonstrates widening of the lunotriquetral interval.
. It represents a fracture of the triquetrum.

Correct Answer & Explanation

. It suggests rotary subluxation of the scaphoid due to scapholunate dissociation.

Explanation

The 'ring sign' (or 'signet ring sign') is seen on a PA radiograph when the scaphoid bone is rotated into flexion. This flexion creates a superimposition of its distal pole on its body, making the distal pole appear as a dense ring. This sign is indicative of rotary subluxation of the scaphoid, which occurs due to disruption of the scapholunate interosseous ligament, a key component of perilunate instability. It does not directly indicate AVN, scaphoid fracture (though often co-occurs), lunotriquetral widening, or triquetral fracture.

Question 410

Topic: Wrist & Carpus

What factor is most strongly associated with a higher likelihood of failure following surgical repair of perilunate dislocations?

. Patient age under 30
. Acute presentation (within 24 hours)
. Delay in surgical intervention beyond 6 weeks
. Absence of associated scaphoid fracture
. Use of K-wire stabilization

Correct Answer & Explanation

. Delay in surgical intervention beyond 6 weeks

Explanation

Delay in surgical intervention, particularly beyond 6 weeks (often considered chronic), is strongly associated with a higher likelihood of surgical failure, residual pain, stiffness, and the development of degenerative arthritis. With chronicity, soft tissues contract, articular cartilage may be damaged, and reduction becomes more challenging, often requiring salvage procedures rather than primary repair. Acute presentation and K-wire stabilization improve outcomes, and patient age or absence of scaphoid fracture are less dominant factors for failure compared to chronicity.

Question 411

Topic: Wrist & Carpus

Which of the following describes the anatomical defect in a 'trans-radial styloid perilunate dislocation'?

. A dislocation where the lunate is fractured.
. A perilunate dislocation associated with a fracture of the radial styloid process.
. A dislocation involving the distal radioulnar joint.
. A fracture of the capitate with perilunate instability.
. A dislocation where the scaphoid is excluded from the injury.

Correct Answer & Explanation

. A perilunate dislocation associated with a fracture of the radial styloid process.

Explanation

A 'trans-radial styloid perilunate dislocation' refers to a perilunate dislocation that is associated with a fracture of the radial styloid process. The force vector typically involves a radial component, causing the radial styloid to avulse or fracture as the carpus displaces. This is a common associated bony injury and falls under the 'greater arc' injury pattern when combined with the ligamentous disruption.

Question 412

Topic: Wrist & Carpus

Which of the following describes a key finding of a chronic perilunate instability on a lateral radiograph, even if not fully dislocated?

. Volar tilt of the distal radius
. Increased carpal height index
. Dorsal intercalated segmental instability (DISI) deformity
. Absence of a radiocarpal angle
. Flattening of the scaphoid

Correct Answer & Explanation

. Dorsal intercalated segmental instability (DISI) deformity

Explanation

Chronic perilunate instability often manifests as a Dorsal Intercalated Segmental Instability (DISI) deformity. On a lateral radiograph, this is characterized by the lunate being extended dorsally (tilted backward) and the scaphoid being flexed volarly, creating an increased capitolunate and radiolunate angle. This abnormal alignment results from the disruption of the scapholunate ligament, which normally couples the scaphoid and lunate movements. Other options are either incorrect or not specific to perilunate instability.

Question 413

Topic: Wrist & Carpus

What is the typical time frame considered for a perilunate dislocation to be classified as 'chronic' versus 'acute'?

. Within 24 hours vs. >24 hours
. Within 1 week vs. >1 week
. Within 3 weeks vs. >3 weeks
. Within 6-8 weeks vs. >6-8 weeks
. Within 6 months vs. >6 months

Correct Answer & Explanation

. Within 6-8 weeks vs. >6-8 weeks

Explanation

Perilunate dislocations are generally considered 'acute' if treated within 6 to 8 weeks of injury. Beyond this timeframe, they are typically classified as 'chronic'. The distinction is critical because chronic dislocations often involve significant soft tissue contracture, articular cartilage damage, and established degenerative changes, making anatomical reduction much more challenging, and often necessitating salvage procedures rather than primary ligament repair.

Question 414

Topic: Wrist & Carpus

When assessing a lateral radiograph for perilunate stability, what is the normal radiolunate angle?

. 0 to -10 degrees (lunate volar tilt)
. 15 to 30 degrees (lunate dorsal tilt)
. 45 to 60 degrees
. Greater than 90 degrees
. Always 0 degrees

Correct Answer & Explanation

. 0 to -10 degrees (lunate volar tilt)

Explanation

On a true lateral radiograph, the normal lunate has a slight volar tilt, meaning the long axis of the lunate should be collinear with the long axis of the radius, with a radiolunate angle typically between 0 and -10 degrees (representing slight volar tilt of the lunate relative to the radius). A dorsal tilt of the lunate (positive angle) is indicative of a DISI deformity, often seen in scapholunate dissociation. A volar tilt >30 degrees is seen in VISI deformity.

Question 415

Topic: Wrist & Carpus

If a chronic perilunate dislocation is left untreated, what is the most likely long-term degenerative pattern that will develop?

. Distal radioulnar joint arthritis
. Midcarpal arthritis only
. Scaphoid Nonunion Advanced Collapse (SNAC) wrist or Scapholunate Advanced Collapse (SLAC) wrist
. Isolated radiolunate arthritis
. Pisotriquetral arthritis

Correct Answer & Explanation

. Scaphoid Nonunion Advanced Collapse (SNAC) wrist or Scapholunate Advanced Collapse (SLAC) wrist

Explanation

Untreated chronic perilunate dislocations lead to progressive carpal collapse and arthritis, most commonly in the pattern of Scapholunate Advanced Collapse (SLAC) wrist. If a scaphoid fracture is also present and untreated (trans-scaphoid perilunate), it can progress to Scaphoid Nonunion Advanced Collapse (SNAC) wrist. Both SLAC and SNAC patterns involve progressive osteoarthritis of the radiocarpal and midcarpal joints due to the altered biomechanics and instability caused by the initial injury and subsequent collapse. These are the most common and severe degenerative sequelae.

Question 416

Topic: Wrist & Carpus

A 30-year-old patient undergoes ORIF for a trans-scaphoid perilunate dislocation. Post-operatively, K-wires are placed across the scapholunate and capitolunate joints. What is the approximate period of time the K-wires are typically left in place before removal?

. 2-3 weeks
. 4-6 weeks
. 8-12 weeks
. 4-6 months
. Indefinitely

Correct Answer & Explanation

. 8-12 weeks

Explanation

K-wires are typically left in place for approximately 8-12 weeks after surgical repair of perilunate dislocations. This duration allows for sufficient healing of the repaired ligaments and the scaphoid fracture (if present). Removing them too early risks redislocation or nonunion, while leaving them in too long increases the risk of infection, pin tract problems, and prolonged stiffness. After removal, a period of protected motion and strengthening follows.

Question 417

Topic: Wrist & Carpus
In the Frykman classification system for distal radius fractures, what does the term 'Type VII' specifically denote?
. Extra-articular
. Intra-articular involving the radiocarpal joint only
. Intra-articular involving the DRUJ only
. Intra-articular involving both radiocarpal and DRUJ joints
. Open fracture

Correct Answer & Explanation

. Intra-articular involving both radiocarpal and DRUJ joints

Explanation

The Frykman classification categorizes distal radius fractures based on intra-articular extension and associated ulnar fracture. Even numbers (II, IV, VI, VIII) indicate an associated ulnar fracture, while odd numbers (I, III, V, VII) indicate no associated ulnar fracture. The specific articular involvement follows: Type I/II (extra-articular), Type III/IV (radiocarpal intra-articular), Type V/VI (DRUJ intra-articular), and Type VII/VIII (both radiocarpal and DRUJ intra-articular). Therefore, Type VII signifies an intra-articular fracture involving both the radiocarpal joint and the distal radioulnar joint (DRUJ), without an associated ulnar fracture.

Question 418

Topic: Wrist & Carpus

Following stable open reduction and internal fixation of a distal radius fracture with a volar locking plate, what is typically the recommended rehabilitation protocol?

. Immobilization for 6-8 weeks, followed by gentle range of motion
. Immediate initiation of active and passive range of motion exercises
. Strict immobilization for 2 weeks, then active range of motion
. Active range of motion after 4 weeks, passive after 6 weeks
. Begin strengthening exercises immediately

Correct Answer & Explanation

. Immediate initiation of active and passive range of motion exercises

Explanation

The primary advantage of stable internal fixation with modern volar locking plates is the ability to initiate early active and passive range of motion (ROM) exercises. This helps prevent stiffness, tendon adhesions, and CRPS. Immobilization is typically minimal (e.g., a splint for comfort for a few days) or not required at all beyond the immediate post-operative period. Strengthening is generally delayed until adequate bone healing is evident (typically 6 weeks or more).

Question 419

Topic: Wrist & Carpus
A Frykman Type VIII distal radius fracture indicates involvement of:
. Extra-articular, no ulnar fracture
. Radiocarpal joint intra-articular, with ulnar fracture
. DRUJ intra-articular, no ulnar fracture
. Both radiocarpal and DRUJ intra-articular, no ulnar fracture
. Both radiocarpal and DRUJ intra-articular, with ulnar fracture

Correct Answer & Explanation

. Both radiocarpal and DRUJ intra-articular, with ulnar fracture

Explanation

Revisiting Frykman: Odd numbers = no ulnar fracture; Even numbers = with ulnar fracture. Types I/II: Extra-articular. Types III/IV: Radiocarpal intra-articular. Types V/VI: DRUJ intra-articular. Types VII/VIII: Both radiocarpal and DRUJ intra-articular. Therefore, Type VIII combines intra-articular involvement of both the radiocarpal and DRUJ joints with an associated ulnar fracture.

Question 420

Topic: Wrist & Carpus

According to the AO/OTA classification, what does a '23-C3' distal radius fracture signify?

. Extra-articular, simple
. Extra-articular, multifragmentary
. Intra-articular, partial articular, simple
. Intra-articular, complete articular, simple
. Intra-articular, complete articular, multifragmentary

Correct Answer & Explanation

. Intra-articular, complete articular, multifragmentary

Explanation

The AO/OTA classification for distal radius fractures (23) is hierarchical: Type A: Extra-articular. Type B: Partial articular (part of the joint surface involved). Type C: Complete articular (entire joint surface involved). The subdivisions further define complexity: C1 (complete articular, simple, 2-part), C2 (complete articular, multifragmentary metaphysis), C3 (complete articular, multifragmentary articular). Therefore, 23-C3 indicates a complete articular fracture that is multifragmentary (severely comminuted) at the articular level.

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