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7. Hand and Wrist MCQs

Practice Set 179 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 3561

Topic: Nerve & Tendon

Which of the following is considered a potential consequence of an untreated cubitus valgus deformity following a malunited distal humerus fracture?

. Radial nerve palsy
. Median nerve entrapment
. Ulnar nerve neuropathy (tardy ulnar palsy)
. Compartment syndrome of the forearm
. Increased risk of shoulder dislocation

Correct Answer & Explanation

. Ulnar nerve neuropathy (tardy ulnar palsy)

Explanation

Cubitus valgus (increased valgus angle) deformity following a malunited distal humerus fracture can stretch and compress the ulnar nerve as it passes through the cubital tunnel posterior to the medial epicondyle. This chronic irritation can lead to a delayed or 'tardy' ulnar nerve palsy, characterized by paresthesia, weakness, and atrophy in the ulnar nerve distribution. Radial nerve palsy is associated with cubitus varus. Median nerve entrapment is not directly related to cubitus valgus. Compartment syndrome is acute. Shoulder dislocation is unrelated.

Question 3562

Topic: 7. Hand and Wrist

A 35-year-old male presents after a fall onto an outstretched hand (FOOSH) with the wrist in hyperextension and ulnar deviation. Radiographs reveal a complete dorsal dislocation of the capitate and other carpals relative to the lunate, which remains articulated with the radius. What is the most common direction of carpal displacement in a typical perilunate dislocation?

. Palmar
. Dorsal
. Radial
. Ulnar
. Proximal

Correct Answer & Explanation

. Dorsal

Explanation

Perilunate dislocations are typically classified by the displacement of the carpus relative to the lunate. In the vast majority of cases, the carpus dislocates dorsally while the lunate maintains its articulation with the radius. A true lunate dislocation, often referred to as a 'spilled teacup' sign on a lateral radiograph, involves the lunate displacing volarly, but this is asequelto a perilunate injury, not the initial perilunate displacement itself.

Question 3563

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 3564

Topic: 7. Hand and Wrist

A 40-year-old construction worker presents with acute wrist pain and marked swelling after falling from a ladder. Clinical examination reveals numbness and paresthesias in the thumb, index, and middle fingers, along with weakness of thumb abduction. Which of the following is the most likely cause of these neurological symptoms in the context of an acute perilunate dislocation?

. Radial nerve compression
. Ulnar nerve entrapment at Guyon's canal
. Median nerve compression within the carpal tunnel
. Brachial plexus injury
. Anterior interosseous nerve palsy

Correct Answer & Explanation

. Median nerve compression within the carpal tunnel

Explanation

Median nerve compression is a common and critical complication of acute perilunate dislocations, occurring in up to 30-50% of cases. The dislocated carpus, particularly the capitate, and often the associated soft tissue swelling, directly compress the median nerve within the confined space of the carpal tunnel. The symptoms described (numbness/paresthesias in thumb, index, middle fingers, and weakness of thumb abduction via abductor pollicis brevis) are classic for median nerve compression. Early recognition and reduction are crucial to prevent permanent nerve damage. Radial and ulnar nerve involvement are far less common with this specific injury pattern, and brachial plexus or anterior interosseous nerve injuries are unlikely to present solely with these wrist-level symptoms.

Question 3565

Topic: 7. Hand and Wrist

What is the most frequently associated carpal bone fracture seen in conjunction with a perilunate dislocation?

. Trapezium fracture
. Hamate fracture
. Scaphoid fracture
. Triquetrum fracture
. Pisiform fracture

Correct Answer & Explanation

. Scaphoid fracture

Explanation

The scaphoid is the most commonly fractured carpal bone in association with perilunate dislocations, occurring in approximately 50-70% of cases. This combination is often referred to as a trans-scaphoid perilunate dislocation. The mechanism involves the carpus 'peeling off' the lunate, and as the forces increase, the scaphoid is loaded in such a way that it fractures, typically through its waist. Other carpal fractures can occur but are less common than a scaphoid fracture in this setting.

Question 3566

Topic: 7. Hand and Wrist

Following an acute perilunate dislocation, what is the initial management priority after patient stabilization and pain control?

. Immediate open reduction and internal fixation
. MRI to assess ligamentous injury
. Closed reduction, typically under conscious sedation or general anesthesia
. Application of a sugar tong splint without reduction
. Referral for physiotherapy and hand therapy

Correct Answer & Explanation

. Closed reduction, typically under conscious sedation or general anesthesia

Explanation

The immediate priority for an acute perilunate dislocation, after addressing life-threatening injuries and achieving patient stability and adequate analgesia, is prompt closed reduction. This should ideally be performed as soon as possible, often under conscious sedation or general anesthesia, to decompress the median nerve, restore carpal alignment, and reduce the risk of avascular necrosis of the lunate. While often not definitive treatment, it is a critical temporizing measure. MRI is useful for surgical planning but not an acute priority over reduction. Open reduction and internal fixation is often indicated but usually follows a failed closed reduction or is part of a planned definitive surgical approach, not the absolute first step. A sugar tong splint without reduction is inadequate and harmful. Physiotherapy begins after stabilization.

Question 3567

Topic: 7. Hand and Wrist

Which ligament is considered the 'key' to carpal stability and is most commonly injured in the initial stages of a perilunate dislocation, according to Mayfield's progressive perilunar instability classification?

. Radioscaphocapitate ligament
. Lunotriquetral ligament
. Scapholunate interosseous ligament
. Dorsal radiocarpal ligament
. Transverse carpal ligament

Correct Answer & Explanation

. Scapholunate interosseous ligament

Explanation

According to Mayfield's progressive perilunar instability classification, the scapholunate interosseous ligament (SLIL) is the 'key' ligament involved in the initial stages (Stage I) of perilunate instability. Injury to the SLIL allows for dissociation between the scaphoid and lunate, which is the precursor to further carpal displacement. Subsequent stages involve disruption of the radiolunate, capitolunate, and finally the lunotriquetral ligaments or a complete lunate dislocation.

Question 3568

Topic: 7. Hand and Wrist

A patient undergoes closed reduction of an acute perilunate dislocation. Post-reduction radiographs demonstrate reasonable carpal alignment, but the scapholunate interval remains widened. What is the most appropriate next step in management?

. Discharge with a short arm cast
. Observation with repeat radiographs in 2 weeks
. Proceed with open reduction and internal fixation (ORIF) for ligament repair/reconstruction
. MRI to confirm carpal alignment
. Physiotherapy for range of motion exercises

Correct Answer & Explanation

. Proceed with open reduction and internal fixation (ORIF) for ligament repair/reconstruction

Explanation

Persistent widening of the scapholunate interval post-reduction, even with apparent general carpal alignment, indicates a persistent scapholunate dissociation and significant ligamentous injury. This instability necessitates surgical intervention, typically open reduction and internal fixation (ORIF) with ligament repair or reconstruction (e.g., K-wire stabilization of the scapholunate joint and repair of the dorsal capsular ligaments) to achieve stable anatomical reduction and prevent long-term instability and arthritis. Discharge, observation, or immediate physiotherapy are inappropriate and would lead to poor outcomes. MRI might be done pre-operatively, but the clinical decision is clear.

Question 3569

Topic: 7. Hand and Wrist

What is the primary role of an urgent CT scan of the wrist in the initial assessment of a suspected perilunate dislocation, especially after initial plain radiographs?

. To quantify the degree of median nerve compression
. To rule out chronic carpal instability
. To identify associated fractures (e.g., scaphoid, capitate) and confirm carpal alignment
. To assess the vascularity of the lunate
. To evaluate the integrity of the intrinsic carpal ligaments

Correct Answer & Explanation

. To identify associated fractures (e.g., scaphoid, capitate) and confirm carpal alignment

Explanation

While plain radiographs provide the initial diagnosis, a CT scan is invaluable in the acute setting of a perilunate dislocation, particularly if surgical intervention is planned. Its primary role is to precisely identify and characterize any associated fractures (e.g., scaphoid, capitate, triquetrum, radial styloid) that may not be clearly visible on plain films, and to confirm the exact alignment of the carpal bones. This information is crucial for surgical planning. MRI is better for ligamentous integrity and vascularity, and median nerve compression is a clinical diagnosis confirmed by nerve studies if necessary.

Question 3570

Topic: 7. Hand and Wrist

A 28-year-old female presents with a chronic, unreduced perilunate dislocation sustained 6 months prior. She complains of persistent pain, stiffness, and weakness. What is the most appropriate definitive management strategy for a chronic perilunate dislocation?

. Repeat closed reduction attempts with percutaneous pinning
. Wrist arthroscopy for debridement
. Observation with pain management and activity modification
. Staged reconstruction or salvage procedure (e.g., proximal row carpectomy, wrist arthrodesis)
. Dynamic wrist splinting and extensive physiotherapy

Correct Answer & Explanation

. Staged reconstruction or salvage procedure (e.g., proximal row carpectomy, wrist arthrodesis)

Explanation

Chronic, unreduced perilunate dislocations (typically defined as older than 6-8 weeks) often lead to significant pain, stiffness, and degenerative changes, making anatomical reduction difficult and often impossible without significant bony or soft tissue releases. In these cases, the goal shifts from anatomical reduction and primary ligament repair to salvage procedures. Options include proximal row carpectomy (PRC) if the articular cartilage of the lunate fossa and capitate head is preserved, or wrist arthrodesis (fusion) for severe degenerative changes or when PRC is not feasible. Simple closed reduction, arthroscopy, observation, or splinting are inadequate for long-standing dislocations with established pathology.

Question 3571

Topic: 7. Hand and Wrist
What is a potential long-term complication of a perilunate dislocation, even after successful reduction and stabilization, particularly if scaphoid avascular necrosis occurs?
. Malunion of the distal radius
. Lunate AVN (Kienböck's disease)
. Carpal tunnel syndrome
. Scaphoid nonunion advanced collapse (SNAC) wrist
. Ulnar impaction syndrome

Correct Answer & Explanation

. Scaphoid nonunion advanced collapse (SNAC) wrist

Explanation

A direct consequence of an untreated or complicated trans-scaphoid perilunate dislocation is Scaphoid Nonunion Advanced Collapse (SNAC) wrist. If the scaphoid is fractured and fails to unite (nonunion), the altered mechanics of the wrist lead to progressive collapse and arthritis, starting in the radioscaphoid joint.

Question 3572

Topic: 7. Hand and Wrist

During open reduction and internal fixation of a perilunate dislocation, which surgical approach provides the best exposure for dorsal ligament repair and reduction of dorsal carpal displacement?

. Volar approach through the carpal tunnel
. Ulnar approach just dorsal to the extensor carpi ulnaris
. Dorsal approach between the third and fourth extensor compartments
. Radial approach along the first extensor compartment
. Combination of volar and radial approaches

Correct Answer & Explanation

. Dorsal approach between the third and fourth extensor compartments

Explanation

The dorsal approach to the wrist, typically between the third (extensor pollicis longus) and fourth (extensor digitorum communis and indicis proprius) extensor compartments, provides excellent exposure for visualization of the dorsal carpal ligaments, the scapholunate joint, and for reduction of dorsally dislocated carpal bones. It allows for repair of the dorsal scapholunate ligament and placement of K-wires to stabilize the scapholunate and capitolunate joints. A volar approach is primarily for addressing median nerve compression or for certain lunate dislocations, but less ideal for primary dorsal ligament repair. Other approaches are less suitable for the primary dorsal instability.

Question 3573

Topic: 7. Hand and Wrist

A patient with a perilunate dislocation presents with profound median nerve symptoms. After urgent closed reduction, the symptoms persist without improvement. What is the most appropriate next step?

. Wait 24-48 hours for nerve recovery
. Prescribe oral corticosteroids and nerve glide exercises
. Perform an urgent carpal tunnel release
. Repeat closed reduction attempt with more force
. Obtain an MRI of the cervical spine

Correct Answer & Explanation

. Perform an urgent carpal tunnel release

Explanation

Persistent profound median nerve symptoms after successful closed reduction of a perilunate dislocation necessitate urgent carpal tunnel release. While some transient symptoms may improve with reduction, persistent or worsening signs of nerve compression suggest ongoing impingement, potentially by soft tissue swelling, hematoma, or even incarcerated ligaments/bone fragments within the carpal tunnel. Delaying decompression risks permanent median nerve damage. Waiting or non-surgical treatments are inappropriate in this acute, symptomatic scenario. Repeating reduction could cause further harm if the nerve is already compressed. Cervical spine imaging is not indicated for acute wrist-level median nerve symptoms.

Question 3574

Topic: 7. Hand and Wrist
Which of the following describes a Stage III perilunate instability according to Mayfield's classification?
. Scapholunate dissociation only
. Scapholunate dissociation with capitohamate disruption
. Scapholunate and lunotriquetral dissociation
. Scapholunate dissociation, capitolunate dissociation, and triquetrolunate disruption
. Complete lunate dislocation into the carpal tunnel

Correct Answer & Explanation

. Scapholunate dissociation, capitolunate dissociation, and triquetrolunate disruption

Explanation

Mayfield's classification describes progressive carpal instability: Stage I involves rupture of the scapholunate interosseous ligament. Stage II progresses to disruption of the capitolunate relationship. Stage III involves additional disruption of the lunotriquetral interosseous ligament. Stage IV represents a complete dislocation of the lunate volarly into the carpal tunnel.

Question 3575

Topic: 7. Hand and Wrist

In a trans-scaphoid perilunate dislocation, after open reduction and K-wire stabilization of the scapholunate and capitolunate joints, what is the most critical aspect for surgical repair of the scaphoid fracture?

. Application of a circular external fixator
. Rigid internal fixation with a headless compression screw
. Bone grafting from the iliac crest
. Simple dorsal capsular repair
. Serial casting without internal fixation

Correct Answer & Explanation

. Rigid internal fixation with a headless compression screw

Explanation

For a trans-scaphoid perilunate dislocation, once carpal alignment is restored and stabilized (often with K-wires), the scaphoid fracture requires anatomical reduction and rigid internal fixation. The gold standard for scaphoid waist fractures is a headless compression screw, which provides stable fixation, allows for early rehabilitation (relative to cast alone), and minimizes the risk of nonunion and subsequent SNAC wrist. External fixation, bone grafting (unless there's significant bone loss), simple capsular repair, or serial casting alone are generally not sufficient for this complex injury pattern.

Question 3576

Topic: 7. Hand and Wrist

What is the primary goal of K-wire stabilization following open reduction of a perilunate dislocation?

. To prevent median nerve compression
. To provide rigid fixation to allow immediate weight-bearing
. To maintain anatomical reduction of the carpal bones and protect ligament repairs during healing
. To stimulate bone healing in associated fractures
. To enhance blood supply to the lunate

Correct Answer & Explanation

. To maintain anatomical reduction of the carpal bones and protect ligament repairs during healing

Explanation

K-wire stabilization, typically involving wires across the scapholunate and capitolunate joints, serves to temporarily maintain the anatomical reduction of the carpal bones and protect the repaired or reconstructed ligaments while they heal. It provides a stable environment for soft tissue healing, preventing redislocation. It does not provide rigid fixation for immediate weight-bearing, directly affect median nerve compression (though reduction helps), or primarily stimulate bone healing or enhance lunate blood supply. These wires are usually removed at 8-12 weeks.

Question 3577

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 3578

Topic: 7. Hand and Wrist

After surgical repair of a perilunate dislocation, what is the recommended typical duration for K-wire removal?

. 1-2 weeks
. 3-4 weeks
. 8-12 weeks
. 6 months
. K-wires are permanent

Correct Answer & Explanation

. 8-12 weeks

Explanation

K-wires used to stabilize carpal alignment following perilunate dislocation repair are typically removed at 8-12 weeks post-operatively. This timeframe allows sufficient healing of the repaired ligaments and dorsal capsule. Earlier removal risks redislocation due to inadequate healing, while leaving them in longer increases the risk of pin track infection and stiffness. The exact timing can vary slightly based on surgeon preference and the specific injury/repair.

Question 3579

Topic: 7. Hand and Wrist

What is the critical distinction between a perilunate dislocation and a lunate dislocation on a lateral wrist radiograph?

. The presence of a scaphoid fracture
. The position of the radius relative to the carpus
. The relationship of the capitate to the lunate
. The presence of a Terry Thomas sign
. The extent of ulnar styloid fracture

Correct Answer & Explanation

. The relationship of the capitate to the lunate

Explanation

On a lateral wrist radiograph, the defining difference is the relationship of the lunate to the radius. In a perilunate dislocation, the lunate maintains its articulation with the distal radius, while the capitate and the rest of the carpus dislocate dorsally. In a lunate dislocation, the lunate itself dislocates volarly into the carpal tunnel, losing its articulation with both the radius and the capitate (which then aligns with the radius). The 'spilled teacup' sign refers to the volar-tilted and dislocated lunate in a lunate dislocation.

Question 3580

Topic: 7. Hand and Wrist

Which intrinsic carpal ligament plays a crucial role in preventing dorsal intercalated segmental instability (DISI) deformities?

. Lunotriquetral interosseous ligament
. Scapholunate interosseous ligament (SLIL)
. Radioscaphocapitate ligament
. Volar carpal ligament
. Dorsal radiolunotriquetral ligament

Correct Answer & Explanation

. Scapholunate interosseous ligament (SLIL)

Explanation

The scapholunate interosseous ligament (SLIL) is critical for preventing dorsal intercalated segmental instability (DISI) deformities. When the SLIL is disrupted, the scaphoid flexes volarly, and the lunate extends dorsally (due to the pull of the triquetrum via the intact lunotriquetral ligament and extrinsic ligaments), leading to the characteristic DISI posture. Conversely, lunotriquetral ligament injury leads to volar intercalated segmental instability (VISI).

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