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2. Trauma MCQs

Practice Set 113 of 640

This practice set contains high-yield board review questions covering key concepts in 2. Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2241

Topic: 2. Trauma

A 40-year-old patient with a non-union of a femoral shaft fracture is undergoing revision surgery. The previous screws showed signs of loosening. To improve the pull-out strength of the new screws, the surgeon decides to use a screw design that maximizes the number of turns of the spiral thread engaged in the bone cortex for a given depth. Which screw characteristic is the surgeon primarily optimizing?

. A. Lead
. B. Shank diameter
. C. Thread depth
. D. Pitch
. E. Countersink

Correct Answer & Explanation

. D. Pitch

Explanation

Correct Answer: DExplanation:The teaching case explicitly states, "The 'finer' the pitch, the more turns of the spiral thread engage in a given depth of cortex, creating greater resistance to pull-out." Therefore, to maximize the number of turns of the spiral thread engaged in the bone cortex for a given depth, the surgeon is primarily optimizing thepitchof the screw. A finer pitch (smaller distance between adjacent threads) means more threads will be engaged within the same length of bone, increasing the contact surface area and thus pull-out strength.Why other options are incorrect:A. Lead:Lead is the linear distance traveled by a screw for one complete turn. While related to pitch (for single-start screws, lead equals pitch), optimizing lead itself isn't the direct way to increase thenumber of turns engagedin a given depth. It's the fineness of the pitch that dictates how many threads are packed into that depth.B. Shank diameter:The shank is the unthreaded portion. While core diameter (the diameter of the screw without the threads) is relevant to thread depth, optimizing the shank diameter itself does not directly increase the number of engaged threads.C. Thread depth:Thread depth determines the amount of contact with bone for resistance to pull-out, and increasing it is beneficial. However, the question specifically asks about maximizing thenumber of turnsengaged in a given depth, which is a function of pitch.E. Countersink:The countersink is the undersurface of the head. Its primary role is to allow the screw head to seat flush or slightly below the surface of the plate or bone. It has no direct role in the number of threads engaged or pull-out strength.

Question 2242

Topic: 2. Trauma

A 50-year-old patient with a comminuted distal femur fracture is undergoing internal fixation. The surgeon is considering using screws with a specific thread geometry to enhance pull-out strength. Based on the case description, which characteristic of thread geometry is generally preferred for maximizing resistance to pull-out?

. A. Symmetrical thread geometry with minimal surface area.
. B. Asymmetrical thread geometry providing a wide surface for pulling.
. C. Threads designed for high frictional resistance on the underside.
. D. Threads with a very large pitch to minimize bone engagement.
. E. Threads that are smooth and rounded to reduce bone stress.

Correct Answer & Explanation

. B. Asymmetrical thread geometry providing a wide surface for pulling.

Explanation

Correct Answer: BExplanation:The teaching case explicitly states that "Thread geometry is usually asymmetrical and provides a wide surface for pulling and little frictional resistance on the underside." This asymmetrical design, with a wide surface on the side that resists pull-out, maximizes the contact area and mechanical interlock with the bone when an axial force attempts to extract the screw. This design is optimized for resisting pull-out forces.Why other options are incorrect:A. Symmetrical thread geometry with minimal surface area:Symmetrical threads might not be optimized for directional pull-out resistance, and minimal surface area would directly reduce pull-out strength.C. Threads designed for high frictional resistance on the underside:The case states that thread geometry provides "little frictional resistance on the underside." High friction on the underside would make insertion more difficult and could potentially damage bone during insertion, without necessarily enhancing pull-out strength in the desired direction.D. Threads with a very large pitch to minimize bone engagement:A very large (coarse) pitch minimizes the number of threads engaged in the bone for a given depth, thereby reducing pull-out strength. A finer pitch is preferred for maximizing engagement.E. Threads that are smooth and rounded to reduce bone stress:Smooth and rounded threads would significantly reduce the mechanical interlock with the bone, leading to very poor pull-out strength. Sharp, well-defined threads are necessary for effective purchase.

Question 2243

Topic: 2. Trauma

A 68-year-old patient with osteoporotic bone is undergoing fixation of a periprosthetic fracture. The surgeon is carefully selecting screws to maximize pull-out strength. Considering the biomechanical principles discussed, which combination of screw design parameters would offer the BEST resistance to pull-out in this challenging bone quality?

. A. Increased core diameter, decreased outer diameter, coarser pitch.
. B. Decreased core diameter, increased outer diameter, finer pitch.
. C. Equal core and outer diameters, moderate pitch.
. D. Increased core diameter, increased outer diameter, finer pitch.
. E. Decreased core diameter, decreased outer diameter, coarser pitch.

Correct Answer & Explanation

. B. Decreased core diameter, increased outer diameter, finer pitch.

Explanation

Correct Answer: BExplanation:To maximize pull-out strength, the goal is to increase the contact surface area between the screw threads and the bone. This is achieved by:Decreasing the core diameter:A smaller core diameter, for a given outer diameter, allows for deeper threads, increasing the thread-bone contact area.Increasing the outer diameter:A larger outer diameter means the threads engage a larger volume of bone, increasing the overall contact surface area.Finer pitch:A finer pitch means more threads are engaged per unit length of bone, further increasing the contact surface area and resistance to pull-out.Option B combines all three of these optimal characteristics for maximizing pull-out strength, particularly critical in osteoporotic bone where bone purchase is inherently compromised.Why other options are incorrect:A. Increased core diameter, decreased outer diameter, coarser pitch:All three of these parameters would significantlyreducepull-out strength. Increased core diameter means shallower threads, decreased outer diameter means less bone engagement, and coarser pitch means fewer engaged threads.C. Equal core and outer diameters, moderate pitch:Equal core and outer diameters would mean no threads, which is not a functional screw. Moderate pitch is not optimized for maximum pull-out strength.D. Increased core diameter, increased outer diameter, finer pitch:While increased outer diameter and finer pitch are beneficial, an increased core diameter would reduce thread depth, partially counteracting the benefits. The optimal is adecreasedcore diameter relative to the outer diameter.E. Decreased core diameter, decreased outer diameter, coarser pitch:Decreased core diameter is good, but decreased outer diameter and coarser pitch would significantly reduce pull-out strength, making this combination suboptimal.

Question 2244

Topic: 2. Trauma

A 58-year-old patient with a distal tibia fracture is undergoing internal fixation. The surgeon is using a non-locking cortical screw. To achieve optimal pull-out strength, the surgeon ensures that the screw engages both the near and far cortices. What is the primary biomechanical reason for engaging multiple cortices with a non-locking screw?

. A. To increase the screw's bending stiffness.
. B. To reduce stress shielding of the bone.
. C. To maximize the number of threads engaged in the bone cortex.
. D. To allow for dynamic compression at the fracture site.
. E. To prevent screw head stripping.

Correct Answer & Explanation

. C. To maximize the number of threads engaged in the bone cortex.

Explanation

Correct Answer: CExplanation:The teaching case highlights that pull-out strength can be increased by "increasing the number of threads engaged in the bone cortex." When a non-locking cortical screw engages both the near and far cortices, it significantly increases the total length of the screw's threaded portion that is in contact with bone. This direct increase in the number of engaged threads maximizes the contact surface area between the screw and the bone, thereby providing substantially greater resistance to axial pull-out forces compared to engaging only one cortex.Why other options are incorrect:A. To increase the screw's bending stiffness:While a longer screw might have different bending characteristics, the primary reason for bicortical engagement for pull-out strength is not to increase the screw's inherent bending stiffness, but to increase its purchase in the bone.B. To reduce stress shielding of the bone:Engaging multiple cortices with a rigid screw construct can sometimes contribute to stress shielding rather than reducing it, as the implant carries more load. This is not the primary reason for bicortical engagement for pull-out strength.D. To allow for dynamic compression at the fracture site:While cortical screws can be used in conjunction with dynamic compression plates (DCPs) to achieve interfragmentary compression, engaging both cortices is a prerequisite for effective compression, but the primary reason for bicortical engagementitselfin terms of pull-out strength is the increased thread engagement.E. To prevent screw head stripping:Screw head stripping is related to the torque applied during insertion and the integrity of the screwdriver-head interface. Engaging multiple cortices does not directly prevent screw head stripping.

Question 2245

Topic: 2. Trauma

A 35-year-old male sustains a comminuted mid-shaft femoral fracture. During reamed IM nailing, his oxygen saturation drops, and he becomes hypotensive. What is the most likely acute intraoperative complication?

. Anaphylactic reaction to antibiotics.
. Myocardial infarction.
. Tension pneumothorax.
. Fat embolism syndrome.
. Hypovolemic shock from blood loss.

Correct Answer & Explanation

. Fat embolism syndrome.

Explanation

Correct Answer: DThe scenario described (oxygen desaturation, hypotension during reamed IM nailing of a long bone) is highly suggestive of acute intraoperative fat embolism syndrome (FES). Reaming and nail insertion increase intramedullary pressure, pushing marrow fat globules into the systemic circulation. These can cause pulmonary compromise and systemic effects. While other complications are possible, FES is a well-known risk of IM nailing, particularly reamed femoral nailing. Anaphylaxis would have other signs (rash, bronchospasm). MI is less common as an acute intraoperative event with this constellation. Tension pneumothorax would show specific chest exam/radiographic findings. Hypovolemic shock is always a concern but the rapid desaturation is more specific to FES.

Question 2246

Topic: 2. Trauma

What is the primary purpose of aiming for a snug fit (isthmic fill) of the intramedullary nail in the diaphyseal region?

. To minimize the risk of intraoperative thermal necrosis.
. To reduce stress shielding of the bone.
. To maximize bending and torsional stiffness of the construct.
. To facilitate easier nail removal in the future.
. To prevent excessive reaming and potential cortical thinning.

Correct Answer & Explanation

. To maximize bending and torsional stiffness of the construct.

Explanation

Correct Answer: CA snug fit, or 'isthmic fill,' of the intramedullary nail in the diaphyseal region is crucial for maximizing the biomechanical stability of the construct. By filling the canal effectively, the nail's moment of inertia is maximized, providing optimal bending and torsional stiffness. This enhanced stability is directly correlated with higher union rates and reduced risk of implant failure. While it helps distribute stress, its primary purpose isn't stress shielding. Easier nail removal is generally not a consideration in the design principle of isthmic fill. Proper reaming technique aims to prevent cortical thinning while achieving the desired fit.

Question 2247

Topic: 2. Trauma

A 68-year-old female sustains a shoulder fracture as shown in the provided imaging:

Based on Hertel's criteria, which of the following radiographic findings is the most reliable predictor of subsequent avascular necrosis of the humeral head?

. Metaphyseal-diaphyseal translation > 5 mm
. Medial metaphyseal head extension < 8 mm
. Head-shaft angle of 120 degrees
. Greater tuberosity displacement of 3 mm
. An intact medial hinge

Correct Answer & Explanation

. Medial metaphyseal head extension < 8 mm

Explanation

Hertel's criteria for predicting ischemia of the humeral head include a medial metaphyseal calcar segment (head extension) of less than 8 mm, disruption of the medial hinge, and an anatomical neck fracture pattern. These factors indicate compromised blood supply from the anterior circumflex humeral artery.

Question 2248

Topic: 2. Trauma

A 35-year-old male sustains a closed midshaft clavicle fracture. Which of the following combinations of factors represents the highest risk for nonunion if this fracture is treated nonoperatively?

. Distal third location and male gender
. Shortening of 1.5 cm and lack of comminution
. 100% displacement with > 2 cm of shortening and smoking
. Medial third location and advanced age
. Oblique fracture pattern and a non-smoker

Correct Answer & Explanation

. 100% displacement with > 2 cm of shortening and smoking

Explanation

Risk factors for nonunion of diaphyseal clavicle fractures include 100% displacement, shortening greater than 2 cm, comminution, advanced age, female gender, and smoking. The combination of severe displacement, shortening, and smoking drastically increases the nonunion rate with conservative management.

Question 2249

Topic: Upper Extremity Trauma
The concept of a 'floating shoulder' involves a double disruption of the Superior Shoulder Suspensory Complex (SSSC). Which of the following anatomic structures correctly defines the osseoligamentous ring of the SSSC?
. Glenoid, coracoid process, acromion, distal clavicle, acromioclavicular joint, and coracoclavicular ligaments
. Proximal humerus, glenoid, labrum, and inferior glenohumeral ligament
. Clavicle, sternum, sternoclavicular joint, and first rib
. Scapular body, spine, acromion, and trapezius insertion
. Coracoid process, conjoint tendon, pectoralis minor, and short head of biceps

Correct Answer & Explanation

. Glenoid, coracoid process, acromion, distal clavicle, acromioclavicular joint, and coracoclavicular ligaments

Explanation

The SSSC is an osseoligamentous ring consisting of the glenoid, coracoid process, coracoclavicular ligaments, distal clavicle, acromioclavicular joint, and acromion. A double disruption of this ring (e.g., ipsilateral clavicle and scapular neck fractures) creates a 'floating shoulder'.

Question 2250

Topic: 2. Trauma

A 45-year-old female presents with a distal third clavicle fracture following a fall. Radiographs demonstrate superior displacement of the medial fragment. Based on the Neer Type IIB classification, what is the status of the coracoclavicular ligaments?

. The conoid and trapezoid are both attached to the medial fragment.
. The conoid is torn, and the trapezoid is attached to the distal fragment.
. Both the conoid and trapezoid are torn from the distal fragment.
. The trapezoid is torn, and the conoid is attached to the distal fragment.
. Both ligaments are completely avulsed from the coracoid process.

Correct Answer & Explanation

. The conoid is torn, and the trapezoid is attached to the distal fragment.

Explanation

In a Neer Type IIB distal clavicle fracture, the fracture occurs between the conoid and trapezoid ligaments. The conoid ligament is typically torn from the medial fragment, allowing it to displace superiorly, while the trapezoid remains attached to the distal fragment.

Question 2251

Topic: 2. Trauma

When utilizing a locking plate for the treatment of a proximal humerus fracture, what is the primary biomechanical purpose of placing screws into the inferomedial quadrant of the humeral head (calcar screws)?

. To prevent anterior pullout of the plate
. To prevent varus collapse of the humeral head
. To prevent valgus overcorrection
. To improve primary healing of the greater tuberosity
. To increase subacromial clearance during elevation

Correct Answer & Explanation

. To prevent varus collapse of the humeral head

Explanation

Inferomedial calcar screws act as a buttress to the inferomedial humeral head. Their placement is critical in locking plate fixation of proximal humerus fractures to prevent postoperative varus collapse, a common complication.

Question 2252

Topic: 2. Trauma

A 42-year-old male sustains a displaced, extra-articular fracture of the scapular body and neck. Operative fixation is being considered based on angular deformity. Which of the following glenopolar angle (GPA) measurements is a recognized indication for surgical intervention?

. < 22 degrees
. 30-35 degrees
. 40-45 degrees
. 60-65 degrees
. > 90 degrees

Correct Answer & Explanation

. < 22 degrees

Explanation

The normal glenopolar angle (GPA) is between 30 and 45 degrees. A severely decreased GPA (< 22 degrees) indicates significant rotational malalignment of the glenoid and is a recognized indication for operative fixation of a scapular neck/body fracture to optimize functional outcomes.

Question 2253

Topic: Upper Extremity Trauma
A 28-year-old female accountant sustains a Type III acromioclavicular (AC) joint separation (100% displacement of the distal clavicle) after falling on her shoulder. What is the most appropriate initial management for this patient?
. Acute Hook plate fixation
. Acute coracoclavicular ligament reconstruction
. Nonoperative management with a brief period of sling immobilization and early range of motion
. Weaver-Dunn procedure
. Primary AC joint arthrodesis

Correct Answer & Explanation

. Nonoperative management with a brief period of sling immobilization and early range of motion

Explanation

Type III AC separations in most patients, especially non-laborers, are initially treated nonoperatively with a sling for comfort and early range of motion. Surgical reconstruction is typically reserved for those who fail conservative management or specific high-demand overhead laborers/athletes.

Question 2254

Topic: 2. Trauma

A 35-year-old male sustains a midshaft clavicle fracture. Which of the following radiographic or demographic factors is MOST strongly associated with the development of a nonunion with nonoperative management?

. Male gender
. Initial shortening of greater than 2 cm
. Inferior displacement of the medial fragment
. Oblique fracture pattern
. Age less than 40 years

Correct Answer & Explanation

. Initial shortening of greater than 2 cm

Explanation

Risk factors for nonunion of midshaft clavicle fractures include completely displaced fractures, shortening greater than 2 cm, severe comminution, advanced age, and female gender.

Question 2255

Topic: 2. Trauma

Which of the following arteries provides the primary blood supply to the humeral head and is most at risk in a 4-part proximal humerus fracture?

. Anterior humeral circumflex artery
. Posterior humeral circumflex artery
. Thoracoacromial artery
. Suprascapular artery
. Profunda brachii artery

Correct Answer & Explanation

. Posterior humeral circumflex artery

Explanation

Recent anatomical studies demonstrate that the posterior humeral circumflex artery provides the predominant blood supply to the humeral head, rather than the anterolateral branch of the anterior humeral circumflex artery.

Question 2256

Topic: 2. Trauma

A 42-year-old male falls from a height and sustains a closed scapula fracture. Which of the following is an absolute indication for open reduction and internal fixation?

. Coracoid base fracture
. Scapular body fracture with 50% displacement
. Intra-articular glenoid fracture with 5 mm of step-off
. Medial border fracture
. Scapular neck fracture with 10 degrees of angulation

Correct Answer & Explanation

. Intra-articular glenoid fracture with 5 mm of step-off

Explanation

Absolute indications for operative fixation of a scapula fracture include intra-articular glenoid displacement or step-off of 4 mm or greater, to prevent post-traumatic arthrosis.

Question 2257

Topic: 2. Trauma

A 28-year-old skier sustains an isolated, closed greater tuberosity fracture of the proximal humerus. At what degree of superior displacement is operative intervention generally recommended to prevent subacromial impingement?

. 2 mm
. 5 mm
. 10 mm
. 15 mm
. 20 mm

Correct Answer & Explanation

. 5 mm

Explanation

In active individuals, superior displacement of an isolated greater tuberosity fracture by 5 mm or more is an indication for surgical fixation to prevent significant subacromial impingement and loss of abduction.

Question 2258

Topic: 2. Trauma

When utilizing a locking anatomic plate for the fixation of a proximal humerus fracture, what is the biomechanical purpose of placing inferomedial (calcar) screws?

. To compress the greater tuberosity fragment
. To prevent varus collapse of the humeral head
. To avoid penetration into the glenohumeral joint
. To increase torsional rigidity of the diaphyseal fixation
. To capture the lesser tuberosity

Correct Answer & Explanation

. To prevent varus collapse of the humeral head

Explanation

Inferomedial (calcar) locking screws provide structural support to the medial cortex of the proximal humerus. This is crucial for preventing postoperative varus collapse of the humeral head.

Question 2259

Topic: 2. Trauma

A 34-year-old male sustains a spiral fracture of the distal third of the humeral shaft. He has an absent brachioradialis reflex and inability to extend his wrist. Which of the following eponymous terms describes this fracture pattern and associated neurologic deficit?

. Galeazzi fracture
. Monteggia fracture
. Holstein-Lewis fracture
. Barton fracture
. Nightstick fracture

Correct Answer & Explanation

. Holstein-Lewis fracture

Explanation

A Holstein-Lewis fracture is a spiral fracture of the distal one-third of the humeral shaft. It is classically associated with a radial nerve palsy due to entrapment or tethering of the nerve as it passes through the lateral intermuscular septum.

Question 2260

Topic: Upper Extremity Trauma

A 45-year-old mountain biker falls directly onto his shoulder and sustains an acromioclavicular (AC) joint injury. Radiographs show 150% superior displacement of the clavicle relative to the acromion. Which of the following represents the optimal management?

. Broad arm sling for 6 weeks
. Figure-of-eight brace
. Surgical reconstruction of the coracoclavicular ligaments
. Mumford procedure (distal clavicle excision)
. Primary arthrodesis of the AC joint

Correct Answer & Explanation

. Surgical reconstruction of the coracoclavicular ligaments

Explanation

A Type V AC joint injury involves greater than 100% superior displacement of the distal clavicle and disruption of the deltotrapezial fascia. Operative reconstruction of the coracoclavicular (CC) ligaments is indicated.

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