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 461
Topic: Wrist & Carpus
What is the recommended period of K-wire stabilization for an unstable DRUJ after Galeazzi fracture fixation?
Correct Answer & Explanation
. 4-6 weeks
Explanation
If K-wire stabilization of the DRUJ is performed, it is typically maintained for 4-6 weeks. This duration allows for sufficient capsuloligamentous healing of the DRUJ stabilizers (primarily the TFCC) while minimizing the risk of pin-site infection, pin loosening, and joint stiffness. After removal, a gradual progression of forearm range of motion exercises is initiated.
Question 462
Topic: Wrist & Carpus
Which of the following anatomical structures is crucial for maintaining stability of the DRUJ against proximal migration of the radius?
Correct Answer & Explanation
. The interosseous membrane
Explanation
The interosseous membrane (IOM) is a critical stabilizer of the forearm, particularly against proximal migration of the radius. Its fibers are obliquely oriented from the radius distally and medially to the ulna proximally. This allows it to transmit axial loads from the radius to the ulna and resist forces that would otherwise cause the radius to shorten relative to the ulna, thereby protecting the DRUJ.
Question 463
Topic: Wrist & Carpus
Which of the following statements regarding the stability of the DRUJ in a Galeazzi fracture is TRUE?
Correct Answer & Explanation
. The DRUJ is inherently unstable due to the loss of radial support and potential ligamentous injury.
Explanation
The DRUJ in a Galeazzi fracture is inherently unstable primarily due to the loss of stable bony support from the fractured radial shaft and often concomitant injury to the triangular fibrocartilage complex (TFCC) and its stabilizing ligaments. Restoring radial length and alignment is crucial but does not guarantee DRUJ stability, necessitating intraoperative assessment.
Question 464
Topic: Wrist & Carpus
A patient is undergoing revision surgery for a chronic, painful Galeazzi malunion with severe positive ulnar variance and irreducible DRUJ arthritis. Which salvage procedure would be most appropriate in this scenario?
Correct Answer & Explanation
. Sauve-Kapandji procedure
Explanation
For chronic, painful Galeazzi malunion with severe positive ulnar variance and irreducible DRUJ arthritis, the Sauve-Kapandji procedure (distal ulna pseudoarthrosis with DRUJ fusion) or a Darrach procedure (ulnar head excision) are considered salvage options. The Sauve-Kapandji preserves the distal ulna for stability while allowing forearm rotation through a created pseudoarthrosis proximal to the fused DRUJ. Radial shortening osteotomy would address the positive ulnar variance but not the irreducible arthritis. Wrist arthrodesis is a more extensive procedure for diffuse wrist arthritis.
Question 465
Topic: Wrist & Carpus
Which of the following is a critical intraoperative assessment to ensure successful fixation of a Galeazzi fracture?
Correct Answer & Explanation
. Testing forearm rotation with the DRUJ unpinned to confirm stability after radial fixation.
Explanation
A critical intraoperative step after achieving stable internal fixation of the radial shaft in a Galeazzi fracture is to dynamically assess the stability of the DRUJ by gently pronating and supinating the forearm. If the DRUJ remains unstable without K-wire stabilization, then further intervention, such as temporary K-wire fixation or TFCC repair, is required to prevent persistent instability and poor functional outcomes.
Question 466
Topic: Wrist & Carpus
What post-operative instruction is crucial for patients with Galeazzi fracture who have undergone K-wire stabilization of the DRUJ?
Correct Answer & Explanation
. Maintain strict immobilization of the forearm until K-wires are removed.
Explanation
Maintaining strict immobilization of the forearm (usually in a long arm cast or splint) is crucial when K-wires are in place for DRUJ stabilization. This protects the healing ligaments and prevents dislodgement of the wires, which could lead to loss of reduction or pin-site complications. Active forearm rotation is contraindicated until the pins are removed and DRUJ stability is confirmed.
Question 467
Topic: Wrist & Carpus
What is the primary role of the pronator quadratus muscle in the context of a Galeazzi fracture?
Correct Answer & Explanation
. It is a key pronator of the forearm and contributes to DRUJ stability.
Explanation
The pronator quadratus is the most distal of the pronator muscles and plays a critical role as a strong pronator of the forearm. It also acts as a primary dynamic stabilizer of the distal radioulnar joint (DRUJ), maintaining apposition of the radius and ulna. Its fibers run transversely, and its integrity is important for DRUJ function. It can be injured or interposed in Galeazzi fractures.
Question 468
Topic: Wrist & Carpus
What defines a 'bayonet apposition' on radiographs of a forearm fracture?
Correct Answer & Explanation
. Fragments are overlapping with no end-to-end contact
Explanation
Bayonet apposition describes a fracture pattern where the fracture fragments are overlapping but without end-to-end contact. This typically results in shortening of the bone, which in a Galeazzi fracture is detrimental as it leads to positive ulnar variance and DRUJ impingement/instability. It is a sign of significant displacement and instability.
Question 469
Topic: Wrist & Carpus
Which soft tissue structure provides the primary support against dorsal displacement of the ulna at the DRUJ in supination?
Correct Answer & Explanation
. Palmar radioulnar ligament of TFCC
Explanation
The palmar (volar) radioulnar ligament, a component of the TFCC, is the primary stabilizer against dorsal translation of the ulna relative to the radius, especially when the forearm is in supination. The dorsal radioulnar ligament serves a similar role but primarily against volar translation in pronation. Together, they are crucial for DRUJ stability.
Question 470
Topic: Wrist & Carpus
Which imaging modality can be particularly useful in evaluating the soft tissue structures of the DRUJ (e.g., TFCC) in the context of persistent instability after Galeazzi fixation?
Correct Answer & Explanation
. Magnetic Resonance Imaging (MRI) scan
Explanation
Magnetic Resonance Imaging (MRI) is the gold standard for evaluating soft tissue structures like the Triangular Fibrocartilage Complex (TFCC), ligaments, and capsule around the DRUJ. In cases of persistent instability after Galeazzi fixation, MRI can provide detailed information about the integrity of the TFCC and other soft tissues that may be contributing to the ongoing instability. CT is excellent for bony anatomy, and fluoroscopy for dynamic assessment, but MRI excels in soft tissue visualization.
Question 471
Topic: Wrist & Carpus
A 55-year-old active, healthy male sustains a high-energy fall onto an outstretched hand, resulting in a significantly comminuted, displaced intra-articular distal radius fracture (Frykman Type VIII). There is severe metaphyseal comminution and displacement of both radial styloid and dorsal ulnar corner fragments. What is the most appropriate definitive surgical approach to restore optimal function?
Correct Answer & Explanation
. Combined volar and dorsal plating.
Explanation
A Frykman Type VIII fracture indicates a comminuted intra-articular fracture involving both the radiocarpal and distal radioulnar joints. Given the high-energy mechanism, significant comminution, and displacement of both radial styloid and dorsal ulnar corner fragments, a highly stable fixation is required to restore anatomical alignment and allow early range of motion. While volar locking plates (Option 2) are the workhorse for most unstable distal radius fractures, a severely comminuted intra-articular fracture with significant dorsal comminution and dorsal ulnar corner involvement may not be adequately stabilized by a volar plate alone, especially if dorsal translation is an issue. Dorsal plating (Option 3) alone can be associated with extensor tendon irritation. In cases of severe comminution and instability with combined dorsal and volar displacement/damage, a combined volar and dorsal plating (Option 4) approach often provides superior stability and allows for more aggressive early rehabilitation, leading to better functional outcomes.
Question 472
Topic: Wrist & Carpus
A patient sustains a distal radius fracture and undergoes volar locked plating. Three months postoperatively, she develops an inability to actively extend the interphalangeal joint of her thumb. During exploration, a ruptured tendon is found within the third dorsal extensor compartment. Which of the following bony landmarks does this tendon natively use as a fulcrum?
Correct Answer & Explanation
. Lister's tubercle
Explanation
The tendon of the Extensor Pollicis Longus (EPL) resides solely within the 3rd dorsal extensor compartment. It uses Lister's tubercle (the dorsal tubercle of the radius) as a fulcrum to angle towards the thumb. EPL rupture is a known complication following both conservative and surgical management of distal radius fractures.
Question 473
Topic: Wrist & Carpus
A 40-year-old female presents with a highly comminuted, un-reconstructable radial head fracture and distal radioulnar joint (DRUJ) instability after a high-energy fall.
What is the primary reason why simple radial head excision is strictly contraindicated in this specific injury pattern?
Correct Answer & Explanation
. It will result in proximal migration of the radius and positive ulnar variance
Explanation
This patient has an Essex-Lopresti injury, characterized by a radial head fracture, rupture of the interosseous membrane (IOM), and disruption of the DRUJ. The interosseous membrane and the radial head act as the primary and secondary longitudinal stabilizers of the forearm. If the radial head is excised in the setting of an IOM tear, the radius will migrate proximally, resulting in ulnar-positive variance, chronic DRUJ pain, and functional impairment. Radial head arthroplasty is mandatory in this scenario.
Question 474
Topic: Wrist & Carpus
A 55-year-old female sustains a complex intra-articular fracture of the distal radius. Preoperative CT reveals a small, displaced volar ulnar corner (lunate facet) fragment. Why is fragment-specific fixation of this specific piece considered critical?
Correct Answer & Explanation
. The fragment acts as an essential buttress; failure to fix it leads to volar subluxation of the radiocarpal joint (carpus)
Explanation
The volar ulnar corner of the distal radius (volar lunate facet) contains the attachments of the stout volar radiocarpal ligaments (short radiolunate ligament). This fragment is often small and can easily 'escape' standard volar locking plates. If it is not anatomically reduced and stably fixed (e.g., with a fragment-specific hook plate or wire), the carpus will subluxate volarly with the fragment, leading to catastrophic joint failure and arthritis.
Question 475
Topic: Wrist & Carpus
A 45-year-old female sustains a volar Barton's fracture of the distal radius. During the injury, the carpus subluxates volarly in conjunction with the distal radius fracture fragment. Which of the following volar extrinsic radiocarpal ligaments is primarily responsible for pulling the carpus volarly with the fractured fragment?
Correct Answer & Explanation
. Radioscaphocapitate and short radiolunate ligaments
Explanation
A volar Barton's fracture is a fracture-dislocation where the volar rim of the distal radius shears off, and the carpus translates volarly with it. The carpus follows the volar rim fragment because the stout volar extrinsic ligaments—specifically the radioscaphocapitate (RSC) and the short radiolunate (SRL) ligaments—remain firmly attached to this volar bony fragment.
Question 476
Topic: Wrist & Carpus
Which of the following prophylactic regimens is supported by prospective randomized controlled trials to reduce the risk of Complex Regional Pain Syndrome (Algodystrophy) following a distal radius fracture?
Correct Answer & Explanation
. Vitamin C 500 mg daily for 50 days
Explanation
Vitamin C (ascorbic acid) at a dose of 500 mg daily for 50 days has been shown in randomized studies (e.g., Zollinger et al.) to significantly reduce the incidence of CRPS following distal radius fractures.
Question 477
Topic: Wrist & Carpus
A 45-year-old female presents 6 weeks after non-operative management of a distal radius fracture. She describes severe burning pain out of proportion to the injury, alongside stiffness and shiny skin changes.
Which of the following prophylactic medications, if given at the time of injury, has been shown to reduce the incidence of this condition?
Correct Answer & Explanation
. Vitamin C 500mg daily
Explanation
The patient has Complex Regional Pain Syndrome (CRPS/Algodystrophy). Vitamin C 500 mg daily for 50 days following a distal radius fracture has been shown in some studies to significantly decrease the risk of developing CRPS.
Question 478
Topic: Wrist & Carpus
A clinical trial comparing two internal fixation methods for distal radius fractures concludes there is no statistically significant difference in functional outcomes (p = 0.15). However, a true clinical difference does exist in the population. What type of statistical error has occurred, and what parameter is directly responsible for it?
Correct Answer & Explanation
. Type II error, influenced by inadequate sample size (low power)
Explanation
Failing to reject the null hypothesis when it is false (i.e., missing a true difference) is a Type II (beta) error. The probability of making a Type II error is denoted by beta. The power of a study is 1 - beta. The most common cause of a Type II error is inadequate statistical power due to a sample size that is too small to detect the existing difference.
Question 479
Topic: Wrist & Carpus
A randomized controlled trial comparing two surgical techniques for distal radius fractures finds no statistically significant difference in grip strength at 1 year (p = 0.15). However, a true difference actually exists in the population. Which of the following concepts describes this study's failure to detect the true difference?
Correct Answer & Explanation
. Type II error
Explanation
A Type II error (beta error) occurs when a study fails to reject a false null hypothesis—in this case, failing to detect a true difference that exists in reality. This is often due to an inadequate sample size, leading to low statistical power (Power = 1 - beta). A Type I error (alpha error) is the false positive conclusion that a difference exists when it actually does not.
Question 480
Topic: Wrist & Carpus
A patient with suspected avascular necrosis of the lunate (Kienböck's disease) presents. Which classification system is commonly used to stage this condition?
Correct Answer & Explanation
. Lichtman classification
Explanation
The Lichtman classification is the most commonly used staging system for Kienböck's disease (avascular necrosis of the lunate). It categorizes the disease into four stages based on radiographic findings, including sclerosis, collapse, fragmentation, and secondary degenerative changes, guiding treatment decisions. Watson classification is for scapholunate dissociation. Mayo classification is for elbow instability. Herbert classification is for scaphoid fractures. Garcia-Elias is not a widely recognized orthopedic classification.
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