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Wrist & Carpus MCQs

Practice Set 19 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 361

Topic: Wrist & Carpus

During a regional block for a complex distal radius fracture, a patient inadvertently receives an intravascular injection of bupivacaine. She rapidly develops perioral numbness, metallic taste, tinnitus, and subsequent tonic-clonic seizures. What is the fundamental cellular mechanism of action of this medication that leads to both its anesthetic effect and toxicity?

. Irreversible blockade of presynaptic calcium channels
. Prolongation of the refractory period of voltage-gated potassium channels
. Reversible blockade of voltage-gated sodium channels
. Irreversible binding to GABA-A receptors
. Competitive inhibition of acetylcholinesterase

Correct Answer & Explanation

. Reversible blockade of voltage-gated sodium channels

Explanation

Local anesthetics like bupivacaine work by reversibly binding to the intracellular portion of voltage-gated sodium channels, preventing the influx of sodium necessary for action potential generation and propagation. Systemic toxicity (LAST - Local Anesthetic Systemic Toxicity) occurs when high blood concentrations result in excessive blockade of these sodium channels in the central nervous system and cardiovascular system, leading to seizures, arrhythmias, and cardiovascular collapse.

Question 362

Topic: Wrist & Carpus

A 62-year-old woman is evaluated 6 months after undergoing volar locked plating of a distal radius fracture. She reports the sudden inability to actively flex the interphalangeal joint of her thumb. She denies any new trauma. Lateral radiographs show that the distal edge of the volar plate is positioned prominent and distal to the watershed line. Which of the following is the most likely cause of her presentation?

. Extensor pollicis longus (EPL) rupture
. Flexor pollicis longus (FPL) rupture
. Anterior interosseous nerve (AIN) palsy
. Flexor digitorum profundus (FDP) rupture
. Stenosing tenosynovitis (Trigger thumb)

Correct Answer & Explanation

. Flexor pollicis longus (FPL) rupture

Explanation

The patient presents with an inability to actively flex the thumb interphalangeal joint, indicating a failure of the flexor pollicis longus (FPL) tendon. Volar plates placed distal to the watershed line of the distal radius can irritate and eventually cause attritional rupture of the flexor tendons. The FPL tendon is most commonly affected due to its close anatomical proximity to the volar surface of the distal radius. EPL ruptures present as an inability to extend the thumb and are associated with nondisplaced fractures or prominent dorsal screws.

Question 363

Topic: Wrist & Carpus

A 45-year-old man falls onto an outstretched hand and sustains a distal radius fracture. CT imaging demonstrates a displaced volar marginal articular shear fracture (volar Barton's fracture) with associated volar subluxation of the carpus. What is the most appropriate surgical approach and fixation strategy?

. Dorsal approach with application of a dorsal spanning plate
. Volar approach with application of a volar buttress plate
. Closed reduction and percutaneous pinning with K-wires
. Application of a bridging external fixator alone
. Excision of the volar fragment and primary radiocarpal arthrodesis

Correct Answer & Explanation

. Volar approach with application of a volar buttress plate

Explanation

Volar shear fractures (volar Barton's fractures) are inherently unstable because the carpus follows the displaced volar articular fragment. To mechanically neutralize the volar shear forces, the gold standard treatment is a volar surgical approach and the application of a volar plate acting in a buttress mode. Dorsal plating, external fixation, or percutaneous pinning are biomechanically inadequate to resist the continuous volar translation forces and frequently lead to secondary displacement.

Question 364

Topic: Wrist & Carpus

During a standard volar (Henry) approach for open reduction and internal fixation of a distal radius fracture, the surgeon must carefully position the volar locking plate to minimize postoperative complications. Which of the following technical errors in plate placement is most strongly associated with late iatrogenic rupture of the flexor pollicis longus (FPL) tendon?

. Placement of the plate proximal to the watershed line
. Placement of the plate distal to the watershed line
. Using locking screws that protrude past the dorsal cortex
. Failure to anatomically repair the pronator quadratus
. Inadequate mobilization of the brachioradialis tendon

Correct Answer & Explanation

. Placement of the plate distal to the watershed line

Explanation

The watershed line is the distal margin of the pronator fossa on the volar radius. Placing a volar plate distal to the watershed line causes the implant to protrude anteriorly, placing it in direct mechanical contact with the overlying flexor tendons. This prominence causes mechanical attrition, most commonly leading to late rupture of the flexor pollicis longus (FPL) tendon.

Question 365

Topic: Wrist & Carpus

A 65-year-old woman is treated nonoperatively in a short arm cast for a nondisplaced extra-articular fracture of the distal radius. Six weeks later, the cast is removed, and radiographs show a healed fracture. However, she suddenly notes an inability to actively extend her thumb interphalangeal joint. The tenodesis effect is absent for the thumb. What is the most appropriate surgical treatment for this complication?

. Primary end-to-end repair of the affected tendon
. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer
. Palmaris longus autograft interposition reconstruction
. Arthrodesis of the thumb interphalangeal joint
. Brachioradialis to extensor pollicis longus (EPL) tendon transfer

Correct Answer & Explanation

. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer

Explanation

The patient has sustained an extensor pollicis longus (EPL) tendon rupture, a known complication following distal radius fractures, even those that are nondisplaced. The rupture typically occurs at Lister's tubercle due to vascular ischemia in the tendon's watershed zone or mechanical attrition from fracture callus. Because the tendon ends are typically frayed, retracted, and degenerated, primary repair is usually impossible. The gold standard treatment is a tendon transfer utilizing the extensor indicis proprius (EIP) to the EPL.

Question 366

Topic: Wrist & Carpus

A 55-year-old woman returns to the clinic 6 weeks after a non-displaced distal radius fracture that was treated successfully in a short-arm cast. She reports a sudden inability to actively extend the interphalangeal joint of her right thumb. Examination confirms an isolated loss of active thumb extension. What is the most appropriate surgical treatment?

. Primary end-to-end repair of the extensor pollicis longus (EPL) tendon
. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer
. Extensor carpi radialis longus (ECRL) to extensor pollicis longus (EPL) tendon transfer
. Free palmaris longus interposition tendon graft
. Arthrodesis of the thumb interphalangeal joint

Correct Answer & Explanation

. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer

Explanation

This patient has suffered an extensor pollicis longus (EPL) tendon rupture, a known complication following non-displaced distal radius fractures. The rupture occurs at Lister's tubercle due to a combination of mechanical attrition and a zone of hypovascularity within the intact third dorsal compartment. Primary end-to-end repair is usually impossible due to tendon retraction and degeneration. The gold standard surgical treatment is a tendon transfer using the Extensor Indicis Proprius (EIP) to the EPL.

Question 367

Topic: Wrist & Carpus

A 65-year-old female undergoes volar locked plating for a displaced intra-articular distal radius fracture. Four months postoperatively, she returns to the clinic with a sudden inability to actively flex the interphalangeal joint of her thumb. Which of the following surgical technique errors is most likely responsible for this complication?

. Penetration of the dorsal cortex by the distal locking screws
. Placement of the plate distal to the watershed line
. Over-distraction of the fracture during reduction
. Dissection radial to the flexor carpi radialis (FCR) tendon
. Failure to repair the pronator quadratus muscle

Correct Answer & Explanation

. Placement of the plate distal to the watershed line

Explanation

The sudden inability to flex the thumb IP joint indicates a 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 spontaneous rupture if the volar plate is placed too distally, projecting anteriorly over the 'watershed line' of the distal radius. Penetration of the dorsal cortex by screws puts the extensor tendons (such as the EPL) at risk, not the flexors.

Question 368

Topic: Wrist & Carpus

A 55-year-old woman was treated non-operatively in a cast for 6 weeks for a minimally displaced, extra-articular distal radius fracture. Three weeks after cast removal, she reports a sudden inability to actively extend her thumb interphalangeal joint. She denies any new trauma. Radiographs show a healing distal radius fracture with maintained alignment. What is the most appropriate surgical management for this complication?

. Primary end-to-end repair of the ruptured tendon
. Transfer of the extensor carpi radialis longus (ECRL) to the ruptured tendon
. Transfer of the extensor indicis proprius (EIP) to the ruptured tendon
. Corticosteroid injection into the first dorsal compartment
. Transfer of the flexor carpi radialis (FCR) to the ruptured tendon

Correct Answer & Explanation

. Transfer of the extensor indicis proprius (EIP) to the ruptured tendon

Explanation

This patient has experienced an attrition rupture of the extensor pollicis longus (EPL) tendon, a classic complication following both non-operative and operative management of distal radius fractures. The tendon degenerates due to mechanical attrition at Lister's tubercle and focal ischemia. Because the tendon ends are typically frayed and retracted, primary end-to-end repair is rarely possible. The gold standard treatment is a tendon transfer using the extensor indicis proprius (EIP) to the EPL, which effectively restores thumb extension without causing significant functional deficit to the index finger.

Question 369

Topic: Wrist & Carpus

A 55-year-old woman undergoes volar locked plating for a displaced intra-articular distal radius fracture. Postoperative radiographs show the plate positioned distal to the watershed line of the distal radius. Six months later, she presents to the clinic with an inability to actively flex the interphalangeal joint of her thumb. Which of the following is the most likely cause?

. Anterior interosseous nerve neuropraxia
. Extensor pollicis longus rupture
. Flexor pollicis longus rupture
. Missed concomitant scaphoid fracture
. Volar compartment syndrome

Correct Answer & Explanation

. Flexor pollicis longus rupture

Explanation

Plate placement distal to the watershed line of the distal radius increases the risk of flexor tendon irritation and subsequent attrition rupture. The flexor pollicis longus (FPL) tendon is most commonly affected due to its anatomical proximity to the prominent distal edge of the volar plate.

Question 370

Topic: Wrist & Carpus
A 28-year-old tennis player complains of chronic ulnar-sided wrist pain. MRI confirms a central articular disc tear of the triangular fibrocartilage complex (TFCC) (Palmer Type 1A). Radiographs reveal a positive ulnar variance of 4 mm. Conservative management has failed. What is the most appropriate surgical management?
. Arthroscopic debridement of the TFCC only.
. Open TFCC repair to the fovea.
. Arthroscopic TFCC debridement combined with an ulnar shortening osteotomy.
. Darrach procedure (distal ulna resection).
. Sauvé-Kapandji procedure.

Correct Answer & Explanation

. Arthroscopic TFCC debridement combined with an ulnar shortening osteotomy.

Explanation

The patient has a Palmer Type 1A TFCC tear (central, avascular portion of the articular disc) associated with significant positive ulnar variance, indicative of ulnocarpal impaction syndrome. Central tears lack blood supply and are generally treated with arthroscopic debridement rather than repair. However, addressing the underlying ulnocarpal impaction with an ulnar shortening osteotomy (USO) is crucial to relieve the excessive mechanical load on the ulnar carpus. Debridement alone without joint leveling would lead to persistent symptoms.

Question 371

Topic: Wrist & Carpus

A 65-year-old woman is 6 months status-post open reduction and internal fixation of a distal radius fracture with a volar locking plate. She presents with a sudden inability to actively flex the interphalangeal joint of her thumb. Which of the following surgical errors is most commonly associated with this complication?

. Placement of the plate too proximal to the watershed line
. Prominence of screws penetrating the dorsal cortex
. Placement of the plate distal to the watershed line
. Failure to repair the pronator quadratus
. Use of locking screws instead of non-locking screws

Correct Answer & Explanation

. Placement of the plate distal to the watershed line

Explanation

Flexor pollicis longus (FPL) tendon rupture is a well-known complication of volar plating of distal radius fractures. It is most commonly caused by placement of the plate distal to the watershed line, resulting in prominence of the distal edge of the plate and subsequent attrition and rupture of the FPL tendon. Prominent dorsal screws typically cause extensor tendon irritation or rupture (e.g., extensor pollicis longus).

Question 372

Topic: Wrist & Carpus

A 28-year-old male sustains a diaphyseal fracture of the middle third of the radius with an associated disruption of the distal radioulnar joint (DRUJ) after a fall. Intraoperatively, after rigid open reduction and internal fixation of the radius, the DRUJ is found to reduce anatomically and is stable in supination, but it readily subluxates when the forearm is placed in pronation. What is the most appropriate management of the DRUJ?

. Pinning of the DRUJ with Kirschner wires in pronation for 6 weeks
. Immobilization in a long arm cast in supination for 4 to 6 weeks
. Open repair of the triangular fibrocartilage complex (TFCC)
. Darrach procedure
. Immobilization in a short arm cast in pronation for 4 weeks

Correct Answer & Explanation

. Immobilization in a long arm cast in supination for 4 to 6 weeks

Explanation

This describes a Galeazzi fracture-dislocation. Following rigid internal fixation of the radial shaft, the stability of the DRUJ must be assessed. If the DRUJ is reducible and stable in supination (the position that tightens the palmar radioulnar ligaments and stabilizes dorsal dislocations), the recommended management is immobilization in a long arm splint or cast in supination for 4 to 6 weeks. If the DRUJ remains unstable in all positions or cannot be reduced, open reduction and TFCC repair or percutaneous pinning of the DRUJ is indicated.

Question 373

Topic: Wrist & Carpus

A 55-year-old woman sustained a non-displaced distal radius fracture treated non-operatively in a short arm cast. Eight weeks post-injury, she reports a sudden, painless inability to extend her thumb interphalangeal joint. On examination, she is unable to lift her thumb off the table when the palm is laid flat. What is the most appropriate surgical management to restore thumb kinematics?

. Primary end-to-end repair of the ruptured tendon
. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer
. Flexor carpi radialis (FCR) to EPL tendon transfer
. Tenolysis of the first dorsal compartment
. Palmaris longus to EPL tendon transfer

Correct Answer & Explanation

. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer

Explanation

The patient has experienced an extensor pollicis longus (EPL) tendon rupture, a known complication of distal radius fractures, particularly non-displaced fractures due to localized ischemia and attrition at Lister's tubercle. Because the ruptured tendon ends are typically severely frayed, degenerated, and retracted, primary repair is usually impossible. An EIP to EPL tendon transfer is the standard of care, providing appropriately matched excursion and vector pull without significant donor site morbidity.

Question 374

Topic: Wrist & Carpus

A 65-year-old woman sustained a non-displaced distal radius fracture treated in a short arm cast for 4 weeks. Six weeks post-injury, she reports a sudden, painless loss of the ability to extend her thumb at the interphalangeal joint. Tenodesis effect of the thumb is absent. What is the most likely diagnosis?

. Flexor pollicis longus rupture
. Extensor pollicis longus rupture
. Anterior interosseous nerve palsy
. Posterior interosseous nerve palsy
. Trigger thumb (stenosing tenosynovitis)

Correct Answer & Explanation

. Extensor pollicis longus rupture

Explanation

Extensor pollicis longus (EPL) tendon rupture is a known complication following non-displaced or minimally displaced distal radius fractures. It occurs secondary to mechanical attrition or relative ischemia within the intact third dorsal compartment as a fracture hematoma expands. A painless drop of the thumb IP joint and loss of thumb retropulsion are classic findings.

Question 375

Topic: Wrist & Carpus

A 62-year-old woman presents with the sudden inability to bend the tip of her thumb. Twelve months prior, she underwent open reduction and internal fixation of a distal radius fracture with a volar locking plate. Lateral radiographs show the plate is positioned prominent and distal to the watershed line. Given the likely diagnosis, what is the most appropriate surgical treatment?

. Hardware removal and direct end-to-end repair of the ruptured tendon
. Hardware removal and transfer of the ring finger flexor digitorum superficialis (FDS) to the ruptured tendon
. Thumb interphalangeal (IP) joint arthrodesis
. Hardware removal and transfer of the extensor indicis proprius (EIP) to the ruptured tendon
. Hardware removal and tenolysis of the flexor pollicis longus (FPL)

Correct Answer & Explanation

. Hardware removal and transfer of the ring finger flexor digitorum superficialis (FDS) to the ruptured tendon

Explanation

The patient has a flexor pollicis longus (FPL) tendon rupture, a known complication of prominent volar hardware placed distal to the watershed line of the distal radius. Chronic attrition leads to rupture with retracted and degenerated tendon ends, precluding direct repair. The standard treatment is hardware removal and tendon transfer, most commonly utilizing the flexor digitorum superficialis (FDS) of the ring finger.

Question 376

Topic: Wrist & Carpus

A 22-year-old male presents with a proximal pole scaphoid fracture after a fall. Operative fixation is planned. Which of the following is true regarding the surgical approach and relevant anatomy for this specific fracture pattern?

. A volar approach is preferred to preserve the dorsal vascular supply.
. The blood supply to the proximal pole is direct from the superficial palmar arch.
. A dorsal approach allows for a screw trajectory perpendicular to the fracture and along the central axis of the scaphoid.
. A volar approach provides the most direct visualization of the proximal pole.
. The dorsal approach requires complete division of the radioscapholunate ligament.

Correct Answer & Explanation

. A dorsal approach allows for a screw trajectory perpendicular to the fracture and along the central axis of the scaphoid.

Explanation

Proximal pole scaphoid fractures are best approached dorsally. The blood supply to the scaphoid enters the dorsal ridge at the waist and flows in a retrograde fashion to the proximal pole. A dorsal approach, when done carefully, does not compromise this blood supply. More importantly, it provides direct access to the proximal pole, allowing for a screw trajectory that is parallel to the central axis of the scaphoid and perpendicular to the fracture plane, which maximizes biomechanical compression.

Question 377

Topic: Wrist & Carpus

A 55-year-old woman presents with sudden inability to actively flex the interphalangeal joint of her right thumb. She underwent open reduction and internal fixation of a right distal radius fracture with a volar locking plate 4 years ago. Radiographs show the plate is positioned distally, overriding the watershed line. Which of the following is the most appropriate definitive management for her current condition?

. Flexor pollicis longus primary repair
. Flexor digitorum superficialis to flexor pollicis longus tendon transfer
. Flexor digitorum profundus to flexor pollicis longus tendon transfer
. Extensor indicis proprius to flexor pollicis longus tendon transfer
. Thumb interphalangeal joint arthrodesis

Correct Answer & Explanation

. Flexor digitorum superficialis to flexor pollicis longus tendon transfer

Explanation

The patient has a rupture of the Flexor Pollicis Longus (FPL) tendon, a known complication of volar plating of the distal radius when the plate is placed distal to the watershed line, leading to attrition over the hardware. Because the rupture often presents late with tendon retraction and poor tissue quality, primary repair is usually impossible. The standard treatment is hardware removal and a tendon transfer, most commonly using the Flexor Digitorum Superficialis (FDS) of the ring or middle finger to restore FPL function.

Question 378

Topic: Wrist & Carpus

A 62-year-old female who was treated nonoperatively for a nondisplaced distal radius fracture presents 6 weeks post-injury with a sudden inability to actively extend her right thumb. Examination reveals a lack of active retropulsion of the thumb, but she is able to extend the interphalangeal joint when the thumb is held in adduction. Which of the following is the most appropriate surgical intervention?

. Primary end-to-end repair of the extensor pollicis longus (EPL)
. Extensor indicis proprius (EIP) to EPL tendon transfer
. Extensor carpi radialis longus (ECRL) to EPL tendon transfer
. Flexor digitorum superficialis (FDS) to EPL tendon transfer
. Tenolysis and corticosteroid injection

Correct Answer & Explanation

. Extensor indicis proprius (EIP) to EPL tendon transfer

Explanation

Extensor pollicis longus (EPL) rupture is a classic complication following distal radius fractures, particularly those treated nonoperatively. The rupture is typically due to attrition over the bony callus or ischemia within the third dorsal compartment. Because the tendon ends are usually retracted and degenerated, primary end-to-end repair is rarely feasible. The standard of care is a tendon transfer, with the extensor indicis proprius (EIP) to EPL transfer being the most common and reliable procedure.

Question 379

Topic: Wrist & Carpus

A 65-year-old woman presents with the sudden inability to extend her thumb. She reports that 5 weeks ago she sustained a nondisplaced distal radius fracture, which was treated nonoperatively in a short arm cast. Physical examination reveals an inability to retro-extend the thumb at the interphalangeal joint, but tenodesis effect is intact. What is the most appropriate surgical management?

. Observation and physical therapy
. Primary end-to-end repair of the ruptured tendon
. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer
. Flexor carpi radialis (FCR) to EPL tendon transfer
. Interposition tendon grafting using the palmaris longus

Correct Answer & Explanation

. Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) tendon transfer

Explanation

The patient has experienced an extensor pollicis longus (EPL) tendon rupture, a known complication of nondisplaced distal radius fractures. The rupture typically occurs at Lister's tubercle due to a combination of mechanical attrition and vascular ischemia within the intact third extensor compartment. Because of the delay in presentation and degeneration of the tendon ends, primary end-to-end repair is usually impossible. The gold standard treatment is a tendon transfer utilizing the extensor indicis proprius (EIP).

Question 380

Topic: Wrist & Carpus

A 65-year-old woman undergoes volar locked plating for a displaced intra-articular distal radius fracture. Postoperative lateral radiographs demonstrate that the plate is positioned distally, bridging the watershed line. Three months postoperatively, she presents with an inability to actively flex the interphalangeal joint of her thumb. Which of the following is the most likely cause of her current presentation?

. Rupture of the flexor pollicis longus (FPL) tendon due to plate prominence
. Iatrogenic anterior interosseous nerve injury during the surgical approach
. Adhesion of the FPL tendon to the pronator quadratus
. Extensor pollicis longus (EPL) rupture secondary to dorsal screw penetration
. Unrecognized concomitant FPL laceration at the time of the initial injury

Correct Answer & Explanation

. Rupture of the flexor pollicis longus (FPL) tendon due to plate prominence

Explanation

The watershed line is a critical anatomic landmark for volar plating of distal radius fractures. Plates placed distal to this line become prominent and impinge on the flexor tendons, particularly the flexor pollicis longus (FPL), leading to attrition and secondary rupture. Soong et al. classified volar plate position relative to the watershed line, with grade 2 (plate completely distal to the watershed line) having the highest risk of FPL rupture. Dorsal screw penetration is a well-known risk for EPL rupture, not FPL.

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