Menu

2. Trauma MCQs

Practice Set 356 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 7101

Topic: 2. Trauma
A surgeon is applying a unilateral uniplanar external fixator for a tibial shaft fracture. Which of the following modifications will most effectively increase the bending stiffness of the construct?
. Decreasing the diameter of the half-pins
. Increasing the distance between the longitudinal rod and the bone
. Increasing the distance between the innermost pins and the fracture site
. Increasing the distance between the two pins within a single bone fragment
. Using pins made of titanium instead of stainless steel

Correct Answer & Explanation

. Increasing the distance between the two pins within a single bone fragment

Explanation

Increasing the distance (spread) between pins within the same fragment dramatically increases the working length of the pins within the bone, thereby increasing overall construct stiffness. Placing the rod closer to bone also increases stiffness.

Question 7102

Topic: 2. Trauma

Which Bone Morphogenetic Protein (BMP) is currently FDA-approved as an adjunct for the treatment of acute open tibial shaft fractures treated with an intramedullary nail?

. rhBMP-2
. rhBMP-3
. rhBMP-4
. rhBMP-7
. rhBMP-9

Correct Answer & Explanation

. rhBMP-2

Explanation

Recombinant human BMP-2 (rhBMP-2) is FDA-approved for use in acute open tibial shaft fractures treated with an IM nail, as well as for anterior lumbar interbody fusion (ALIF). rhBMP-7 was historically used for recalcitrant tibial nonunions.

Question 7103

Topic: 2. Trauma

What is the primary biomechanical advantage of using a locked plate construct over a conventional non-locked compression plate in osteoporotic bone?

. It relies heavily on friction between the plate and the bone surface.
. It acts as a single fixed-angle construct, resisting sequential screw pullout.
. It provides superior dynamic compression across the fracture site.
. It increases the working length of the fracture by bending.
. It allows the screws to toggle independently to distribute load.

Correct Answer & Explanation

. It relies heavily on friction between the plate and the bone surface.

Explanation

Locked plates function as fixed-angle constructs and do not rely on friction between the plate and the bone. This distributes forces evenly across all locked screws, preventing the sequential screw failure common in osteoporotic bone.

Question 7104

Topic: 2. Trauma

A 50-year-old smoker presents with a 9-month-old humeral shaft nonunion. Radiographs reveal a widened fracture gap with rounded, sclerotic bone ends and absent callus formation. What is the most appropriate management principle?

. Rigid fixation alone to address mechanical instability
. Bone grafting alone to address biological inactivity
. Rigid fixation combined with biological augmentation (e.g., bone graft)
. Dynamic external fixation to stimulate callus
. Electrical bone stimulation without surgery

Correct Answer & Explanation

. Rigid fixation alone to address mechanical instability

Explanation

The radiographic appearance (sclerotic ends, no callus) is characteristic of an atrophic nonunion, which lacks biological healing potential. Successful treatment requires both mechanical stabilization (rigid fixation) and biological augmentation (bone grafting).

Question 7105

Topic: 2. Trauma

A 35-year-old man sustains a diaphyseal tibia fracture treated with an unreamed intramedullary nail. Which of the following biomechanical adjustments will most effectively decrease the torsional stiffness of this construct?

. Increasing the nail diameter
. Decreasing the working length
. Increasing the working length
. Using a solid rather than a hollow nail
. Placing locking screws closer to the fracture site

Correct Answer & Explanation

. Increasing the nail diameter

Explanation

The working length of an intramedullary nail is the unsupported distance between the points of fixation on either side of the fracture. Increasing the working length significantly decreases both the torsional and bending stiffness of the construct.

Question 7106

Topic: 2. Trauma

A surgeon applies a unilateral external fixator for a severe open tibial shaft fracture. To maximize the bending stiffness of the construct, which of the following single modifications is most effective?

. Decrease the diameter of the Schanz pins
. Increase the distance between the bone and the longitudinal bar
. Decrease the distance between the pins within the same fragment
. Increase the diameter of the Schanz pins
. Use titanium rather than stainless steel pins

Correct Answer & Explanation

. Decrease the diameter of the Schanz pins

Explanation

Pin diameter is the most critical factor for external fixator stiffness, as bending stiffness is proportional to the pin's radius to the fourth power (r^4). Decreasing the bone-to-bar distance and increasing pin spread also increase stiffness but to a lesser mathematical extent.

Question 7107

Topic: 2. Trauma

A locking compression plate (LCP) functions primarily by which biomechanical principle when utilized to bridge a highly comminuted diaphyseal fracture?

. Friction between the plate and the underlying bone cortex
. Interfragmentary compression via eccentric screw placement
. Tension band principles acting on the convex cortex
. A fixed-angle construct independent of plate-to-bone friction
. Dynamic compression driven by weight-bearing

Correct Answer & Explanation

. Friction between the plate and the underlying bone cortex

Explanation

A locking plate functions effectively as an internal external-fixator, relying on the threaded interface between the screw head and the plate to create a rigid fixed-angle construct. Because it does not require friction against the bone to maintain stability, it preserves periosteal blood supply.

Question 7108

Topic: 2. Trauma

When a surgeon applies a rigid plate to the lateral aspect of the femur to stabilize a subtrochanteric fracture, the plate functions primarily via which biomechanical principle?

. Neutralization
. Bridge plating
. Tension band plating
. Buttress plating
. Dynamic compression

Correct Answer & Explanation

. Neutralization

Explanation

The lateral cortex of the femur naturally experiences tension during physiologic weight-bearing. A plate applied to the tension side of an eccentrically loaded bone acts as a tension band, converting disruptive tensile forces into stabilizing compressive forces at the opposite (medial) cortex.

Question 7109

Topic: Lower Extremity Trauma

Which of the following modifications to an intramedullary nail design will most significantly increase its torsional rigidity?

. Increasing the working length
. Adding a full-length longitudinal slot
. Increasing the outer diameter of the nail
. Decreasing the inner diameter by 1 mm
. Changing the material from titanium to standard stainless steel

Correct Answer & Explanation

. Increasing the working length

Explanation

The torsional rigidity of a solid or hollow cylinder is proportional to the radius raised to the fourth power. Therefore, increasing the outer diameter is the most effective way to exponentially increase both torsional and bending rigidity.

Question 7110

Topic: 2. Trauma

According to beam theory, the bending stiffness of a solid rectangular fracture plate is a function of its width (b) and thickness (h). Assuming the material remains constant, how does doubling the plate's thickness affect its area moment of inertia?

. Increases it by a factor of 2
. Increases it by a factor of 4
. Increases it by a factor of 8
. Increases it by a factor of 16
. Decreases it by a factor of 2

Correct Answer & Explanation

. Increases it by a factor of 2

Explanation

The area moment of inertia for a rectangular structure subjected to bending is calculated as (b * h^3) / 12. Therefore, doubling the thickness (h) increases the bending stiffness exponentially by a factor of eight (2^3 = 8).

Question 7111

Topic: Lower Extremity Trauma

When considering the structural rigidity of a diaphyseal bone or an intramedullary nail, bending stiffness is proportional to the area moment of inertia. For a hollow cylinder, if the outer radius is increased, how does the area moment of inertia change?

. It increases proportionally to the radius squared
. It increases proportionally to the radius cubed
. It increases proportionally to the radius to the fourth power
. It remains unchanged
. It decreases proportionally to the radius

Correct Answer & Explanation

. It increases proportionally to the radius squared

Explanation

The area moment of inertia for a hollow cylinder is proportional to the difference between the fourth powers of the outer and inner radii. Therefore, slightly increasing the outer radius exponentially increases the bending stiffness.

Question 7112

Topic: 2. Trauma

In plate osteosynthesis of a comminuted diaphyseal fracture using a bridge plating technique, increasing the "working length" of the plate will have what biomechanical effect?

. Increase the torsional stiffness of the construct
. Decrease the axial stiffness, allowing more interfragmentary motion
. Increase the bending stiffness of the construct
. Decrease the risk of screw pullout
. Eliminate secondary bone healing

Correct Answer & Explanation

. Increase the torsional stiffness of the construct

Explanation

The working length of a plate is the distance between the innermost screws on either side of the fracture. Increasing this distance decreases the axial stiffness of the construct, allowing for more controlled interfragmentary motion to promote robust secondary bone healing.

Question 7113

Topic: Lower Extremity Trauma

When calculating the bending stiffness of an intramedullary nail modeled as a solid cylinder, the stiffness is directly proportional to which specific parameter of its radius (r)?

. r
. r squared
. r cubed
. r to the fourth power
. Inversely proportional to r squared

Correct Answer & Explanation

. r

Explanation

The bending stiffness of a solid cylinder is directly proportional to its area moment of inertia. For a solid cylinder, the area moment of inertia is proportional to the radius to the fourth power.

Question 7114

Topic: 2. Trauma

During internal fixation of a diaphyseal femur fracture, a surgeon wishes to maximize the pullout strength of a cortical screw. Which of the following screw design modifications provides the greatest increase in pullout strength?

. Increasing the outer thread diameter
. Increasing the inner core diameter
. Increasing the thread pitch
. Decreasing the length of engagement
. Increasing the screw head size

Correct Answer & Explanation

. Increasing the outer thread diameter

Explanation

Screw pullout strength is most highly dependent on the outer thread diameter. Other factors that improve pullout strength include decreased thread pitch, decreased inner core diameter, and an increased length of engagement within the bone.

Question 7115

Topic: 2. Trauma

According to Perren's strain theory, secondary fracture healing (callus formation via endochondral ossification) is optimally promoted when the interfragmentary strain is within which of the following ranges?

. Less than 2%
. Between 2% and 10%
. Between 10% and 30%
. Between 30% and 50%
. Greater than 50%

Correct Answer & Explanation

. Less than 2%

Explanation

According to Perren's strain theory, secondary bone healing occurs when interfragmentary strain is between 2% and 10%. Strain less than 2% promotes primary (direct) bone healing, whereas strain greater than 10% favors fibrous tissue formation and nonunion.

Question 7116

Topic: 2. Trauma

What structure does the radial nerve pierce as it passes from the posterior to the anterior compartment of the arm?

. Medial intermuscular septum
. Lateral intermuscular septum
. Coracobrachialis
. Brachialis
. Triceps aponeurosis

Correct Answer & Explanation

. Medial intermuscular septum

Explanation

The radial nerve pierces the lateral intermuscular septum approximately 10 cm proximal to the lateral epicondyle to enter the anterior compartment of the arm. This fixed anatomical point places the nerve at high risk during distal third humeral shaft fractures (Holstein-Lewis fractures).

Question 7117

Topic: 2. Trauma

When performing a lateral approach to the fibula for open reduction and internal fixation of an ankle fracture, identifying the superficial peroneal nerve is critical. Where does this nerve typically pierce the deep crural fascia to become subcutaneous?

. 5 cm proximal to the lateral malleolus
. 10-12 cm proximal to the lateral malleolus
. 15-20 cm proximal to the lateral malleolus
. 2-3 cm distal to the fibular head
. Just posterior to the lateral malleolus

Correct Answer & Explanation

. 5 cm proximal to the lateral malleolus

Explanation

The superficial peroneal nerve typically pierces the deep fascia of the lateral compartment approximately 10 to 12 cm proximal to the tip of the lateral malleolus. It becomes a subcutaneous structure at this level, making it vulnerable during lateral incisions.

Question 7118

Topic: 2. Trauma

A 34-year-old male develops a compartment syndrome of the anterior leg following a tibia fracture. If left untreated, which of the following sensory deficits is most likely to be present due to nerve ischemia in this specific compartment?

. Plantar aspect of the foot
. Dorsal first web space
. Lateral aspect of the foot
. Medial aspect of the leg
. Dorsum of the foot excluding the first web space

Correct Answer & Explanation

. Plantar aspect of the foot

Explanation

The deep peroneal nerve courses through the anterior compartment of the leg. Ischemia of this nerve secondary to anterior compartment syndrome results in sensory loss isolated to the dorsal first web space.

Question 7119

Topic: 2. Trauma

When performing a posterolateral approach to the ankle for a posterior malleolus fracture, the sural nerve is at risk. What vascular structure normally accompanies the sural nerve in this region?

. Great saphenous vein
. Small saphenous vein
. Posterior tibial artery
. Peroneal artery
. Dorsalis pedis artery

Correct Answer & Explanation

. Great saphenous vein

Explanation

The sural nerve courses distally in the posterolateral leg alongside the small saphenous vein. Both structures travel directly posterior to the lateral malleolus.

Question 7120

Topic: 2. Trauma

A patient sustains a midshaft fibula fracture and subsequently develops a compartment syndrome requiring fasciotomies. The surgeon must be mindful of the superficial peroneal nerve as it exits the deep fascia to become subcutaneous. At what approximate level does this transition normally occur?

. 2 to 3 cm proximal to the tip of the lateral malleolus
. 10 to 12 cm proximal to the tip of the lateral malleolus
. 20 to 22 cm proximal to the tip of the lateral malleolus
. Immediately distal to the fibular head
. At the inferior extensor retinaculum

Correct Answer & Explanation

. 2 to 3 cm proximal to the tip of the lateral malleolus

Explanation

The superficial peroneal nerve provides motor innervation to the lateral compartment before piercing the crural fascia to become subcutaneous, typically 10 to 12 cm proximal to the lateral malleolus.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page