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2. Trauma MCQs

Practice Set 391 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 7801

Topic: 2. Trauma

In a bridge plating construct for a comminuted diaphyseal fracture, increasing the working length of the plate has which of the following biomechanical effects?

. Increases the torsional stiffness of the construct
. Decreases the axial stiffness, allowing more interfragmentary motion
. Concentrates stress directly at the fracture site, increasing breakage risk
. Decreases the strain tolerance of the fracture gap
. Increases the pullout strength of the applied screws

Correct Answer & Explanation

. Increases the torsional stiffness of the construct

Explanation

The working length is the distance between the closest screws on either side of the fracture. Increasing it decreases the overall axial stiffness of the construct, promoting secondary bone healing by allowing appropriate interfragmentary micromotion.

Question 7802

Topic: 2. Trauma

The pullout strength of a cortical screw used for fracture fixation is directly proportional to which of the following parameters?

. Inner core diameter
. Thread pitch
. Outer thread diameter
. Length of the screw head
. Screw insertion torque

Correct Answer & Explanation

. Inner core diameter

Explanation

Screw pullout strength is directly proportional to the outer thread diameter, length of thread engagement, and the shear strength of the bone. It is inversely proportional to the thread pitch, while the inner core diameter determines the screw tensile and torsional strength.

Question 7803

Topic: 2. Trauma

In bridge plating of a comminuted diaphyseal fracture, decreasing the working length of the plate will have what biomechanical effect on the construct?

. Decrease the torsional stiffness
. Increase the axial stiffness
. Increase the likelihood of primary bone healing
. Decrease the stress experienced by the plate
. Increase the strain at the fracture site

Correct Answer & Explanation

. Decrease the torsional stiffness

Explanation

The working length of a plate is the distance between the two closest screws on either side of the fracture. Decreasing the working length increases the stiffness of the construct but also concentrates stress over a shorter segment of the plate, increasing the risk of plate failure.

Question 7804

Topic: 2. Trauma

An orthopedic surgeon decides to ream a femoral shaft fracture to accommodate a larger diameter solid intramedullary nail. The torsional rigidity of the selected solid cylindrical nail is proportional to its radius raised to which power?

. Second power (r^2)
. Third power (r^3)
. Fourth power (r^4)
. Fifth power (r^5)
. Directly proportional (r)

Correct Answer & Explanation

. Second power (r^2)

Explanation

The torsional rigidity of a solid cylinder is proportional to its polar moment of inertia, which scales with the radius to the fourth power (r^4). For a hollow cylinder, it is proportional to the difference between the outer and inner radii to the fourth power.

Question 7805

Topic: 2. Trauma

Secondary fracture healing with callus formation is typically seen with cast immobilization or intramedullary nailing. Which of the following local factors strongly dictates the differentiation of mesenchymal stem cells into chondrocytes during the early stages of this process?

. High oxygen tension and absolute mechanical stability
. Low oxygen tension and moderate mechanical strain
. High pH and rigid internal fixation
. Complete absence of mechanical micromotion
. Elevated systemic levels of sclerostin

Correct Answer & Explanation

. High oxygen tension and absolute mechanical stability

Explanation

In secondary fracture healing, the initial hematoma and granulation tissue are hypoxic and subject to mechanical micromotion. This low oxygen tension and moderate strain environment specifically promotes chondrogenesis and endochondral ossification.

Question 7806

Topic: 2. Trauma

During fracture fixation, maximizing the pull-out strength of a cortical screw is highly dependent on screw geometry. Which of the following screw modifications will result in the greatest increase in pull-out strength?

. Decreasing the outer diameter
. Increasing the inner (core) diameter
. Decreasing the thread pitch
. Decreasing the thread depth
. Increasing the thread pitch

Correct Answer & Explanation

. Decreasing the outer diameter

Explanation

Pull-out strength is directly proportional to the outer diameter, thread engagement length, and the volume of bone between threads. Decreasing the thread pitch (distance between threads) increases the number of threads engaged in the bone, maximizing pull-out strength.

Question 7807

Topic: Lower Extremity Trauma

If the diameter of a solid intramedullary nail is increased from 10 mm to 12 mm, what is the approximate percentage increase in its bending stiffness?

. 20%
. 44%
. 73%
. 107%
. 150%

Correct Answer & Explanation

. 20%

Explanation

The bending stiffness of a solid cylinder is proportional to the radius to the fourth power (r^4). Increasing the diameter from 10 mm to 12 mm yields a ratio of 1.2^4, which equals 2.0736, representing an approximate 107% increase in bending stiffness.

Question 7808

Topic: 2. Trauma

Which of the following modifications will most effectively increase the mechanical stiffness of a standard uniplanar external fixator construct?

. Decreasing the distance between the bone and the connecting rod
. Decreasing the diameter of the Schanz pins
. Decreasing the distance between the pins within a single bone fragment
. Using a titanium connecting rod instead of stainless steel
. Increasing the distance between the fracture site and the innermost pins

Correct Answer & Explanation

. Decreasing the distance between the bone and the connecting rod

Explanation

To increase external fixator stiffness, the surgeon should increase pin diameter, decrease the bone-to-rod distance, increase the spread between pins in the same fragment, and place the innermost pins close to the fracture site.

Question 7809

Topic: 2. Trauma

In the context of an intramedullary nail utilized for a comminuted diaphyseal fracture, increasing the "working length" of the nail will result in which of the following mechanical changes?

. Increased bending stiffness
. Decreased torsional stiffness
. Decreased micromotion at the fracture site
. Decreased risk of implant fatigue failure
. Increased pullout strength of locking screws

Correct Answer & Explanation

. Increased bending stiffness

Explanation

The working length is the distance between the closest points of fixation on either side of the fracture. Increasing the working length makes the construct more flexible, leading to decreased torsional and bending stiffness.

Question 7810

Topic: 2. Trauma

What is the primary biomechanical advantage of a locking plate construct over a conventional non-locking compression plate in the treatment of osteoporotic metaphyseal fractures?

. It requires the plate to be perfectly contoured to the bone surface
. It relies heavily on friction between the plate and bone for stability
. It acts as a single fixed-angle beam construct, preventing screw toggle
. It converts shear stress into compressive stress at the fracture site
. It increases the area moment of inertia of the host bone

Correct Answer & Explanation

. It requires the plate to be perfectly contoured to the bone surface

Explanation

A locking plate functions as a fixed-angle construct where the screw heads lock into the plate. This prevents screw toggle and failure in osteoporotic bone without relying on plate-to-bone friction for stability.

Question 7811

Topic: 2. Trauma

In the application of a bridge plate for a comminuted diaphyseal fracture, decreasing the working length of the plate will have which of the following biomechanical effects?

. Increase the bending stiffness of the construct
. Decrease the bending stiffness of the construct
. Increase interfragmentary strain at the fracture site
. Decrease the torsional rigidity of the construct
. Accelerate secondary callus formation

Correct Answer & Explanation

. Increase the bending stiffness of the construct

Explanation

The working length of a plate is the distance between the two closest screws on either side of the fracture. Decreasing the working length increases the bending and torsional stiffness of the construct, thereby decreasing interfragmentary strain.

Question 7812

Topic: Lower Extremity Trauma



An orthopedic surgeon decides to over-ream a tibial diaphysis to insert a larger diameter intramedullary nail. By increasing the solid nail's radius by a factor of 2, the torsional rigidity of the nail increases by what factor?

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 2

Explanation

The torsional rigidity of a solid cylindrical intramedullary nail is proportional to the polar moment of inertia, which scales with the radius to the fourth power (r^4). Therefore, doubling the radius increases the torsional rigidity by a factor of 16 (2^4).

Question 7813

Topic: 2. Trauma

The successful application of a tension band construct for a transverse olecranon fracture relies on converting which type of force into a compressive force at the articular surface?

. Shear force
. Axial force
. Tensile force
. Torsional force
. Bending force

Correct Answer & Explanation

. Shear force

Explanation

The tension band principle involves placing a rigid fixation device on the tension side of a bone. This converts the distracting tensile forces generated by eccentric muscle pull (e.g., triceps) into dynamic compressive forces across the fracture site.

Question 7814

Topic: 2. Trauma

Which of the following fracture fixation constructs relies entirely on primary bone healing for fracture union?

. Intramedullary nail
. Bridge plate
. External fixator
. Lag screw and neutralization plate
. Cast immobilization

Correct Answer & Explanation

. Intramedullary nail

Explanation

Primary bone healing occurs under conditions of absolute stability, achieved with techniques like a lag screw and neutralization plate. This involves direct Haversian remodeling without the formation of a fracture callus.

Question 7815

Topic: Lower Extremity Trauma

A solid titanium intramedullary nail's resistance to bending (bending rigidity) is directly proportional to its radius raised to what power?

. First power
. Second power
. Third power
. Fourth power
. Fifth power

Correct Answer & Explanation

. First power

Explanation

The bending rigidity of a solid cylindrical implant is proportional to its area moment of inertia, which scales with the radius to the fourth power (r^4). Therefore, small increases in nail diameter drastically increase bending stiffness.

Question 7816

Topic: 2. Trauma

How does decreasing the "working length" of a bridge plate construct affect its mechanical properties?

. Increases torsional flexibility
. Decreases bending stiffness
. Increases construct stiffness
. Increases interfragmentary strain tolerance
. Eliminates the risk of plate failure

Correct Answer & Explanation

. Increases torsional flexibility

Explanation

The working length of a plate is the distance between the two closest screws on either side of the fracture. Decreasing the working length increases the overall construct stiffness, which concentrates stress over a shorter segment of the plate and may increase the risk of implant failure.

Question 7817

Topic: 2. Trauma

In plate osteosynthesis of a diaphyseal fracture, decreasing the "working length" of the plate has what effect on the construct?

. Decreases axial stiffness
. Increases torsional stiffness
. Increases interfragmentary strain
. Promotes secondary bone healing
. Decreases bending stiffness

Correct Answer & Explanation

. Decreases axial stiffness

Explanation

The working length of a plate is the distance between the two closest screws on either side of the fracture. Decreasing the working length increases the overall stiffness of the construct (both axial and torsional) and decreases interfragmentary strain.

Question 7818

Topic: 2. Trauma

Which of the following modifications will most significantly increase the overall stiffness of a unilateral external fixator construct?

. Decreasing the pin diameter
. Increasing the distance between the bone and the rod
. Decreasing the distance between the bone and the rod
. Using titanium pins instead of stainless steel
. Increasing the distance between the pins in each fracture fragment

Correct Answer & Explanation

. Decreasing the pin diameter

Explanation

Bringing the rod closer to the bone (decreasing the offset) significantly increases the stiffness of an external fixator construct. Increasing pin diameter also has a profound effect on stiffness, as it is proportional to the radius to the fourth power.

Question 7819

Topic: 2. Trauma

The bending stiffness of a fracture fixation plate is proportional to the plate’s thickness raised to what power?

. First power
. Second power
. Third power
. Fourth power
. Fifth power

Correct Answer & Explanation

. First power

Explanation

The bending stiffness (area moment of inertia) of a rectangular plate is proportional to its width times the thickness cubed (base × height³ / 12). Therefore, a small increase in plate thickness exponentially increases its bending stiffness.

Question 7820

Topic: Lower Extremity Trauma

An orthopedic surgeon decides to over-ream the femoral canal to insert a solid intramedullary nail with a 12-mm outer diameter rather than a 10-mm outer diameter. Assuming the material is identical, the bending rigidity of the nail increases by approximately what factor?

. 1.2
. 1.4
. 2.1
. 1.7
. 2.5

Correct Answer & Explanation

. 1.2

Explanation

The bending rigidity of a solid cylinder is proportional to its area moment of inertia, which is calculated based on the radius to the fourth power (r^4). Increasing the diameter from 10 mm to 12 mm (a 1.2-fold increase) increases the bending rigidity by a factor of 1.2^4, which is approximately 2.1.

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