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7. Hand and Wrist MCQs

Practice Set 187 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 3721

Topic: 7. Hand and Wrist

What is the primary concern when considering non-union of the radius vs. the ulna in a both bones forearm fracture?

. Non-union of the ulna is more debilitating.
. Non-union of the radius carries a higher risk of associated wrist pathology.
. Non-union of the radius occurs more frequently due to smaller diameter.
. Non-union of the radius profoundly affects forearm rotation and load transmission.
. Non-union of the ulna has a higher rate of infection.

Correct Answer & Explanation

. Non-union of the radius profoundly affects forearm rotation and load transmission.

Explanation

Non-union of the radius profoundly affects forearm rotation and load transmission (Option D). The radius is the primary load-bearing bone of the forearm and is crucial for pronation and supination. A non-union here leads to instability, pain, and severe functional loss, often requiring revision surgery with bone grafting. While ulnar non-union (A) can be problematic, radial non-union is generally considered more functionally devastating due to its critical role in wrist articulation and forearm kinematics. Radial non-union can lead to positive ulnar variance and associated wrist pathology (B) but this is a consequence of the functional impairment.

Question 3722

Topic: 7. Hand and Wrist

A 35-year-old male presents to the emergency department after a fall onto an outstretched hand (FOOSH) with the wrist hyperextended and ulnarly deviated. Radiographs demonstrate the lunate remaining in articulation with the distal radius, but the capitate is dorsally dislocated, and all other carpal bones are displaced dorsally relative to the lunate. The lunate appears to have lost its articulation with the capitate. Which of the following best describes this injury pattern?

. Perilunate dislocation
. Lunate dislocation
. Scapholunate dissociation
. Trans-scaphoid perilunate dislocation
. Radial styloid avulsion fracture

Correct Answer & Explanation

. Perilunate dislocation

Explanation

The description of the lunate remaining articulated with the radius while the capitate and other carpal bones are displaced dorsally relative to the lunate is the classic definition of a perilunate dislocation. In a true lunate dislocation, the lunate itself dislocates volarly, losing articulation with both the radius and the capitate, often appearing like a 'spilled teacup' on lateral radiographs. Scapholunate dissociation is a ligamentous injury without gross carpal dislocation. Trans-scaphoid perilunate dislocation is a specific type of perilunate dislocation involving a scaphoid fracture, which is not mentioned here. Radial styloid avulsion is a fracture, not a carpal dislocation pattern.

Question 3723

Topic: 7. Hand and Wrist
Which carpal bone is most commonly affected by avascular necrosis following a lunate dislocation?
. Scaphoid
. Capitate
. Hamate
. Lunate
. Triquetrum

Correct Answer & Explanation

. Lunate

Explanation

The lunate is most susceptible to avascular necrosis (Kienböck's disease) after a lunate dislocation or perilunate dislocation due to its precarious blood supply. The lunate receives its blood supply primarily from two dorsal and two volar vessels, forming an intraosseous network. Dislocation can disrupt these vessels, leading to ischemia and subsequent avascular necrosis. While other carpal bones can suffer from vascular compromise, the lunate's anatomy makes it particularly vulnerable in this context.

Question 3724

Topic: 7. Hand and Wrist

On a true lateral radiograph of the wrist, a lunate dislocation is characterized by:

. The capitate articulating with the dorsal aspect of the lunate
. The lunate appearing triangular or 'piece of pie' shaped
. Loss of articulation between the lunate and the radius, with the lunate displaced volarly
. The lunate maintaining its normal articulation with the scaphoid
. Widening of the scapholunate interval

Correct Answer & Explanation

. Loss of articulation between the lunate and the radius, with the lunate displaced volarly

Explanation

A lunate dislocation on a true lateral radiograph is classically described as the lunate losing its normal articulation with the distal radius and rotating volarly, often appearing like a 'spilled teacup'. Option A describes a perilunate dislocation. Option B describes the lunate's appearance on an AP view in a perilunate dislocation or due to rotation. Option D is incorrect as lunate dislocation involves significant disruption of carpal alignment. Option E is characteristic of scapholunate dissociation, which can be part of a perilunate injury but not the defining feature of a lunate dislocation itself.

Question 3725

Topic: 7. Hand and Wrist

A patient presents with acute wrist pain, swelling, and paresthesias in the thumb, index, middle, and radial half of the ring finger after a high-energy fall. Examination reveals a tense median nerve compression. What is the most appropriate initial management step for a suspected lunate dislocation in this scenario?

. Immediate operative exploration and reduction
. Application of a sugar tong splint and pain control
. Closed reduction under conscious sedation or regional anesthesia
. Referral for urgent MRI to assess ligamentous damage
. Neurophysiologic studies to confirm median neuropathy

Correct Answer & Explanation

. Closed reduction under conscious sedation or regional anesthesia

Explanation

Acute median nerve compression in the setting of a lunate dislocation is a surgical emergency. The initial management should be prompt closed reduction under conscious sedation or regional anesthesia to decompress the median nerve and attempt to restore carpal alignment. This is often the first step before considering open reduction. While operative exploration may be necessary if closed reduction fails or if instability persists, it's not the absolute initial step unless reduction is impossible. A splint alone won't address the nerve compression. MRI and neurophysiologic studies, while useful for planning definitive care, are not initial emergency interventions for acute nerve compression.

Question 3726

Topic: Wrist & Carpus
What is the Mayfield classification system primarily used to describe in the context of carpal injuries?
. Severity of Kienböck's disease
. Stages of lunate and perilunate instability
. Types of distal radius fractures
. Grading of triangular fibrocartilage complex (TFCC) tears
. Assessment of ulnar impaction syndrome

Correct Answer & Explanation

. Stages of lunate and perilunate instability

Explanation

The Mayfield classification system describes the progressive stages of perilunate instability and dislocation. It outlines a sequential pattern of ligamentous disruption around the lunate, starting from scapholunate dissociation (Stage I), progressing to capitolunate dislocation (Stage II), triquetrolunate disruption (Stage III), and ultimately lunate dislocation (Stage IV), where the lunate itself displaces volarly. It is not used for Kienböck's disease, distal radius fractures, TFCC tears, or ulnar impaction.

Question 3727

Topic: Wrist & Carpus

Which ligament is typically the first to fail in the Mayfield Stage I pattern of perilunate instability?

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

Correct Answer & Explanation

. Scapholunate interosseous ligament

Explanation

Mayfield Stage I involves disruption of the scapholunate interosseous ligament (SLIL), leading to scapholunate dissociation. This is the initial step in the progressive arc of perilunate instability. Subsequent stages involve further ligamentous disruptions around the carpus. The other ligaments mentioned become involved in later stages or are not the primary initial failure point in this specific classification system.

Question 3728

Topic: 7. Hand and Wrist

Following successful closed reduction of a lunate dislocation, which imaging modality is typically recommended to assess for associated occult carpal fractures or persistent instability?

. Standard wrist radiographs only
. Ultrasound
. CT scan
. Bone scintigraphy
. Electromyography (EMG)

Correct Answer & Explanation

. CT scan

Explanation

A CT scan is highly recommended after closed reduction of a lunate or perilunate dislocation. It provides excellent bony detail to identify occult carpal fractures (e.g., scaphoid, triquetrum, radial styloid) that may not be evident on plain radiographs, assess the accuracy of reduction, and identify any remaining carpal malalignment. Ultrasound is not ideal for deep carpal bone assessment. Bone scintigraphy is for metabolic activity, not acute injury detail. EMG is for nerve function. While radiographs are essential, they often miss subtle but critical bony injuries in this complex region.

Question 3729

Topic: 7. Hand and Wrist
What is the primary goal of surgical management for chronic, irreducible lunate dislocations?
. Restoration of full wrist range of motion
. Decompression of the ulnar nerve
. Pain relief and maintenance of a stable, functional wrist
. Prevention of Kienböck's disease in the unaffected wrist
. Immediate return to high-impact activities

Correct Answer & Explanation

. Pain relief and maintenance of a stable, functional wrist

Explanation

For chronic, irreducible lunate dislocations, the primary goal of surgical management shifts from complete anatomical restoration (which is often impossible) to pain relief and the creation of a stable, functional wrist. This may involve salvage procedures like proximal row carpectomy or wrist arthrodesis. Full range of motion is rarely achievable in chronic cases. Ulnar nerve decompression is not typically the primary issue with lunate dislocation (median nerve is more common). Preventing Kienböck's in the unaffected wrist is irrelevant. Immediate return to high-impact activities is unrealistic and often contraindicated.

Question 3730

Topic: 7. Hand and Wrist

A patient presents 3 weeks after a FOOSH injury with persistent wrist pain, stiffness, and weakness. Initial radiographs at an outside facility were reported as normal. Current radiographs show a 'spilled teacup' sign on the lateral view and a 'piece of pie' sign on the AP view. What is the most likely diagnosis?

. Scaphoid fracture with nonunion
. Triquetral avulsion fracture
. Lunate dislocation
. Distal radius fracture
. Carpal bossing

Correct Answer & Explanation

. Lunate dislocation

Explanation

The 'spilled teacup' sign on a lateral view (volar displacement and rotation of the lunate) and the 'piece of pie' sign on the AP view (lunate appears triangular due to rotation) are pathognomonic for a lunate dislocation. The scenario suggests a missed diagnosis, which is common if initial radiographs are suboptimal or misread. The other options do not present with these specific radiographic findings.

Question 3731

Topic: 7. Hand and Wrist

Which of the following ligaments is crucial for maintaining the stability of the proximal carpal row and is often injured in perilunate dislocations?

. Ulnocarpal ligament complex
. Dorsal radiocarpal ligament
. Scapholunate interosseous ligament
. Radioscaphocapitate ligament
. Transverse carpal ligament

Correct Answer & Explanation

. Scapholunate interosseous ligament

Explanation

The scapholunate interosseous ligament (SLIL) is a critical stabilizer of the proximal carpal row, particularly between the scaphoid and lunate. Its rupture is the initiating event in Mayfield Stage I perilunate instability and is often involved in more severe perilunate and lunate dislocations. The dorsal radiocarpal and radioscaphocapitate ligaments are also important but the SLIL is key for proximal row integrity. The ulnocarpal complex is important for ulnar-sided stability. The transverse carpal ligament forms the roof of the carpal tunnel.

Question 3732

Topic: 7. Hand and Wrist

When performing an open reduction of a perilunate or lunate dislocation, a combined dorsal and volar approach is often favored. What is the primary advantage of the volar approach in this context?

. Better visualization of the dorsal radiocarpal ligaments
. Facilitates reduction of dorsally displaced carpal bones
. Allows for primary repair of the dorsal capsule
. Enables decompression of the median nerve and repair of volar ligaments
. Provides direct access to the pisiform-triquetrum joint

Correct Answer & Explanation

. Enables decompression of the median nerve and repair of volar ligaments

Explanation

The volar approach is crucial for decompressing the median nerve, which is frequently compressed by the volarly displaced lunate or edematous tissues in lunate dislocations. It also allows direct access for the repair of the crucial volar ligaments, such as the radioscaphocapitate and long radiolunate ligaments, which are often torn. The dorsal approach is better for visualizing and reducing dorsally displaced carpal bones and repairing dorsal ligaments. Thus, a combined approach addresses both aspects.

Question 3733

Topic: Wrist & Carpus

What is the typical timeframe within which closed reduction and percutaneous pinning are most likely to be successful for a lunate or perilunate dislocation?

. Within 24 hours of injury
. Within 1 week of injury
. Within 3 weeks of injury
. Within 6 weeks of injury
. Anytime within 6 months of injury

Correct Answer & Explanation

. Within 1 week of injury

Explanation

Closed reduction and percutaneous pinning are generally most successful if performed within 1 week of injury. Beyond this timeframe, soft tissue swelling, adhesions, and muscle spasm make closed reduction increasingly difficult, and the chances of successful anatomical reduction diminish significantly, often necessitating open reduction. While 24 hours is ideal, up to a week is generally considered the window for attempts at closed reduction before considering open options.

Question 3734

Topic: 7. Hand and Wrist

A patient undergoes open reduction and internal fixation (ORIF) for a perilunate dislocation. Post-operatively, serial radiographs are obtained. Which finding on follow-up imaging would raise the most concern for inadequate reduction or impending carpal collapse?

. Presence of K-wires in situ
. Mild residual swelling around the wrist joint
. Decreased capitolunate angle to 15 degrees
. An increase in the scapholunate angle to 70 degrees
. Mild joint space narrowing at the radiocarpal joint

Correct Answer & Explanation

. An increase in the scapholunate angle to 70 degrees

Explanation

A normal scapholunate angle is typically between 30-60 degrees. An increase to 70 degrees (or more) indicates persistent scapholunate dissociation and dorsal intercalated segmental instability (DISI), which is a significant concern for inadequate reduction, persistent instability, and future carpal collapse (SNAC wrist). K-wires are expected post-ORIF. Mild swelling is common. A capitolunate angle of 15 degrees is within the normal range (typically <30 degrees). Mild joint space narrowing may indicate pre-existing arthritis or post-traumatic changes, but an increased scapholunate angle is a more acute indicator of instability in this context.

Question 3735

Topic: Wrist & Carpus

Which of the following associated injuries is most frequently found in conjunction with a perilunate dislocation, particularly in high-energy trauma?

. Distal radius fracture
. Metacarpal fracture
. Scaphoid fracture
. Ulnar styloid fracture
. Phalangeal fracture

Correct Answer & Explanation

. Scaphoid fracture

Explanation

A scaphoid fracture is the most common associated bony injury with perilunate dislocations, leading to a 'trans-scaphoid perilunate dislocation'. This injury occurs when the force of the dislocation propagates through the scaphoid bone instead of rupturing the scapholunate ligament alone. It's important to specifically look for this given its high incidence and implications for treatment.

Question 3736

Topic: 7. Hand and Wrist

A 40-year-old construction worker sustained a lunate dislocation 8 weeks ago. He now presents with persistent pain, stiffness, and signs of median nerve compression despite an attempted closed reduction at an outside facility. Radiographs confirm irreducible volar displacement of the lunate. What surgical approach would be most appropriate at this stage?

. Dorsal approach alone for reduction
. Volar approach alone for nerve decompression
. Combined dorsal and volar approach for open reduction, ligament repair, and nerve decompression
. Proximal row carpectomy as the primary definitive treatment
. Wrist arthrodesis

Correct Answer & Explanation

. Combined dorsal and volar approach for open reduction, ligament repair, and nerve decompression

Explanation

For a subacute (8 weeks) and irreducible lunate dislocation with persistent median nerve symptoms, a combined dorsal and volar approach is typically indicated. The volar approach allows for median nerve decompression and volar ligament repair/reconstruction. The dorsal approach is crucial for achieving anatomical reduction of the lunate, especially when it's volarly dislocated, and for addressing dorsal ligamentous injuries. Proximal row carpectomy or wrist arthrodesis are salvage procedures usually reserved for chronic cases with significant arthrosis or failed ligament repair, not necessarily as the primary approach for a subacute irreducible dislocation, unless salvage is the only option due to extensive damage.

Question 3737

Topic: 7. Hand and Wrist

Which of the following is NOT a typical radiographic sign of a lunate dislocation?

. Spilled teacup sign on lateral view
. Piece of pie sign on AP view
. Increased scapholunate interval (Terry Thomas sign)
. Loss of parallelism between the proximal and distal carpal rows on lateral view
. The lunate appearing to articulate with the distal radius on AP view

Correct Answer & Explanation

. The lunate appearing to articulate with the distal radius on AP view

Explanation

In a lunate dislocation, the lunate loses its normal articulation with the distal radius and displaces volarly. Therefore, the lunate will NOT appear to articulate normally with the distal radius on any view; it will be displaced. The other options are classic signs: 'spilled teacup' (volar displacement/rotation of lunate), 'piece of pie' (lunate appears triangular on AP due to rotation), increased scapholunate interval (often associated, as it's a progression from perilunate), and loss of carpal row parallelism, indicating disruption of normal alignment.

Question 3738

Topic: 7. Hand and Wrist

What is the primary mechanism by which median nerve neuropathy occurs in acute lunate dislocations?

. Direct transection of the nerve by bone fragments
. Compression of the nerve by the volarly displaced lunate and surrounding edema within the carpal tunnel
. Stretching of the nerve as it wraps around the distal radius
. Ischemic injury due to disruption of arterial supply to the nerve
. Compression by a fractured scaphoid

Correct Answer & Explanation

. Compression of the nerve by the volarly displaced lunate and surrounding edema within the carpal tunnel

Explanation

The most common mechanism of median nerve neuropathy in acute lunate dislocations is compression. The lunate dislocates volarly and rotates, falling directly into the carpal tunnel. This, combined with significant soft tissue edema and hemorrhage, dramatically increases pressure within the unyielding carpal tunnel, leading to acute compression of the median nerve. Direct transection is rare, stretching is less common, and ischemic injury is less likely the primary cause compared to direct compression.

Question 3739

Topic: 7. Hand and Wrist

After open reduction and internal fixation of a perilunate dislocation, what is the recommended minimum duration of immobilization in a cast?

. 1-2 weeks
. 2-4 weeks
. 4-6 weeks
. 6-8 weeks
. 10-12 weeks

Correct Answer & Explanation

. 6-8 weeks

Explanation

Following ORIF of a perilunate or lunate dislocation, immobilization in a cast (typically forearm-based or long-arm, depending on stability and surgeon preference) is recommended for 6-8 weeks. This allows sufficient time for initial ligamentous healing and fibrous stabilization around the reduced carpal bones. Premature mobilization can lead to loss of reduction and recurrent instability. After 6-8 weeks, K-wires are typically removed, and a controlled rehabilitation program begins.

Question 3740

Topic: 7. Hand and Wrist

Which of the following indicates a successful closed reduction of a lunate dislocation on a lateral radiograph?

. The lunate appearing volar to the capitate
. The lunate appearing dorsal to the capitate
. The lunate, capitate, and distal radius aligned in a single column
. The capitate appearing volar to the lunate
. A persistent 'piece of pie' sign

Correct Answer & Explanation

. The lunate, capitate, and distal radius aligned in a single column

Explanation

A successful reduction of a lunate dislocation is indicated when the lunate, capitate, and distal radius are aligned in a single column on a lateral radiograph. This demonstrates the restoration of normal carpal alignment and articulation. Options A, B, D describe various forms of malalignment. A persistent 'piece of pie' sign indicates residual rotation of the lunate, suggesting incomplete reduction or a perilunate variant.

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