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2. Trauma MCQs

Practice Set 623 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 12441

Topic: 2. Trauma

A 28-year-old male sustains a high-energy Schatzker VI tibial plateau fracture. Which of the following parameters is an absolute indication for emergency four-compartment leg fasciotomy?

. Absolute compartment pressure of 25 mmHg
. Delta pressure (Diastolic BP - Compartment Pressure) of 20 mmHg
. Delta pressure (Mean Arterial BP - Compartment Pressure) of 45 mmHg
. Loss of distal pulses
. Severe pain on passive stretch

Correct Answer & Explanation

. Delta pressure (Diastolic BP - Compartment Pressure) of 20 mmHg

Explanation

A Delta pressure (Diastolic blood pressure minus compartment pressure) of less than 30 mmHg is an absolute indication for fasciotomy. Loss of pulses is a late and unreliable sign of compartment syndrome.

Question 12442

Topic: 2. Trauma

A 25-year-old male sustains a closed Holstein-Lewis humerus fracture and presents with a secondary radial nerve palsy after closed reduction. If the nerve is undergoing Wallerian degeneration and subsequent regeneration, which muscle will be the first to show clinical signs of reinnervation?

. Extensor carpi radialis longus
. Extensor digitorum communis
. Extensor indicis proprius
. Brachioradialis
. Supinator

Correct Answer & Explanation

. Brachioradialis

Explanation

The brachioradialis is the first muscle innervated by the radial nerve distal to the spiral groove. Therefore, it is the first muscle to exhibit signs of clinical recovery during nerve regeneration.

Question 12443

Topic: Pelvic & Acetabular Trauma
In a hemodynamically unstable patient with an anterior-posterior compression (APC) type III pelvic ring injury, what is the most appropriate anatomical landmark for the correct placement of a circumferential pelvic binder?
. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Pubic symphysis
. L5-S1 junction

Correct Answer & Explanation

. Greater trochanters

Explanation

A pelvic binder should be centered over the greater trochanters to effectively close the pelvic volume and reduce pubic symphysis diastasis. Placement higher over the iliac crests is less effective and can paradoxically open the pelvis in some fracture patterns.

Question 12444

Topic: 2. Trauma

A 22-year-old male sustains a proximal pole scaphoid fracture. Which vascular anatomical feature explains the high rate of nonunion and avascular necrosis associated with this specific fracture pattern?

. The primary blood supply enters distally and flows in a retrograde fashion
. The proximal pole is supplied exclusively by the palmar carpal arch
. The deep branch of the ulnar artery provides the sole supply
. The blood supply enters proximally and flows distally
. The proximal pole lacks intraosseous vascularity entirely

Correct Answer & Explanation

. The primary blood supply enters distally and flows in a retrograde fashion

Explanation

The scaphoid receives its primary blood supply from branches of the radial artery that enter at the distal pole and dorsal ridge, flowing in a retrograde direction. Proximal pole fractures disrupt this supply, leading to high rates of AVN and nonunion.

Question 12445

Topic: 2. Trauma

A 28-year-old male sustains a severe closed tibial shaft fracture. Which of the following pressure measurements most accurately indicates the need for an emergent four-compartment fasciotomy?

. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 30 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Mean arterial pressure minus compartment pressure < 40 mmHg
. Systolic blood pressure minus compartment pressure < 30 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The Delta P (Diastolic blood pressure - compartment pressure) of less than 30 mmHg is the most reliable objective threshold for diagnosing acute compartment syndrome. Absolute pressure alone can be misleading, as tissue perfusion depends on the arteriovenous pressure gradient, which is better approximated by the difference between diastolic pressure and compartment pressure.

Question 12446

Topic: 2. Trauma

When applying a bridging plate to stabilize a highly comminuted diaphyseal femur fracture, increasing the working length of the plate has what specific biomechanical effect on the construct?

. Increases the axial stiffness of the construct
. Decreases the interfragmentary strain at the fracture site
. Decreases the overall flexibility of the construct
. Decreases the pullout strength of the locking screws
. Decreases the torsional rigidity of the construct

Correct Answer & Explanation

. Decreases the interfragmentary strain at the fracture site

Explanation

The working length of a plate is the unsupported distance between the two innermost screws spanning the fracture zone. Increasing this working length increases the flexibility of the construct, which functionally decreases the strain experienced at the fracture site by distributing the deformation over a wider area.

Question 12447

Topic: 2. Trauma

A 25-year-old man presents with a severely comminuted tibia fracture. His blood pressure is 120/80 mmHg. What compartment pressure measurement most reliably confirms the indication for an emergent fasciotomy?

. Absolute compartment pressure of 25 mmHg
. Absolute compartment pressure of 30 mmHg
. Diastolic pressure minus compartment pressure is less than 30 mmHg
. Mean arterial pressure minus compartment pressure is greater than 40 mmHg
. Systolic pressure minus compartment pressure is less than 30 mmHg

Correct Answer & Explanation

. Diastolic pressure minus compartment pressure is less than 30 mmHg

Explanation

The delta P, defined as the diastolic blood pressure minus the compartment pressure, is the most reliable threshold for diagnosing acute compartment syndrome. A delta P of less than 30 mmHg indicates inadequate capillary perfusion and necessitates emergent fasciotomy.

Question 12448

Topic: 2. Trauma

A surgeon uses a bridge plating technique for a comminuted femoral shaft fracture. How does increasing the working length of the plate affect the biomechanical construct?

. Increases torsional stiffness
. Decreases bending stiffness
. Increases the risk of early plate failure by fatigue
. Increases axial stiffness
. Eliminates all interfragmentary motion

Correct Answer & Explanation

. Decreases bending stiffness

Explanation

The working length of a plate is the distance between the two innermost screws spanning the fracture gap. Increasing this distance decreases the bending and torsional stiffness of the construct, allowing for more flexible fixation which promotes callus formation.

Question 12449

Topic: 2. Trauma

In a patient with a tibia fracture and suspected acute compartment syndrome, which pressure measurement parameter is the most reliable threshold for indicating the need for emergent fasciotomy?

. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 30 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Mean arterial pressure minus compartment pressure < 40 mmHg
. Systolic blood pressure minus compartment pressure < 20 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The Delta P (diastolic blood pressure minus compartment pressure) is the most reliable indicator of compartment syndrome. A Delta P of less than 30 mmHg indicates critically compromised tissue perfusion and is a strong indication for fasciotomy.

Question 12450

Topic: 2. Trauma

A 32-year-old male presents with a closed tibial shaft fracture. He develops severe pain out of proportion to his injury. Which of the following pressure measurements is the most reliable threshold for diagnosing acute compartment syndrome and indicating fasciotomy?

. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 30 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Mean arterial pressure minus compartment pressure < 40 mmHg
. Systolic blood pressure minus compartment pressure < 20 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The Delta P (Diastolic blood pressure - compartment pressure) of less than 30 mmHg is the most reliable indicator for acute compartment syndrome, as it accounts for the perfusion pressure threshold of the microcirculation, minimizing unnecessary fasciotomies compared to absolute pressure.

Question 12451

Topic: Pelvic & Acetabular Trauma

To maximize mechanical advantage and effectively reduce pelvic volume in a hemodynamically unstable anterior-posterior compression (APC) pelvic ring injury, a pelvic binder should be centered precisely over which anatomical landmark?

. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Pubic symphysis
. Sacroiliac joints

Correct Answer & Explanation

. Greater trochanters

Explanation

For optimal biomechanical reduction of a pelvic ring injury and to appropriately decrease intrapelvic volume to tamponade bleeding, a pelvic binder or sheet must be placed at the level of the greater trochanters. Placement higher over the iliac crests is less effective and may cause abdominal compression.

Question 12452

Topic: 2. Trauma
A 25-year-old farm worker sustains a severe open tibia fracture with extensive soft tissue damage and heavy soil contamination (Gustilo-Anderson Grade IIIb). In addition to aggressive surgical debridement and standard cephalosporin/aminoglycoside coverage, which of the following antibiotics should ideally be added?
. Clindamycin
. Vancomycin
. High-dose Penicillin
. Ciprofloxacin
. Metronidazole

Correct Answer & Explanation

. High-dose Penicillin

Explanation

In severe open fractures heavily contaminated with soil, feces, or organic matter (such as farm injuries), there is a significant risk of clostridial infection (gas gangrene). High-dose Penicillin is traditionally added to specifically cover for Clostridium species.

Question 12453

Topic: 2. Trauma

In a hemodynamically unstable polytrauma patient, damage control orthopedics (DCO) is indicated. Which systemic inflammatory marker is most commonly used to assess the resolution of the "second hit" phenomenon before definitive fracture fixation?

. Interleukin-1 (IL-1)
. Interleukin-6 (IL-6)
. Tumor Necrosis Factor-alpha (TNF-alpha)
. C-reactive protein (CRP)
. Erythrocyte sedimentation rate (ESR)

Correct Answer & Explanation

. Interleukin-6 (IL-6)

Explanation

IL-6 is a reliable marker of the systemic inflammatory response in polytrauma patients. Its level peaks early, and a return to baseline helps indicate a safe physiological window for definitive surgery.

Question 12454

Topic: Pelvic & Acetabular Trauma

A 30-year-old male presents with an acute lateral compression type II (LC-II) pelvic ring injury. Which of the following ligaments is considered the strongest posterior stabilizer of the pelvic ring?

. Sacrotuberous ligament
. Sacrospinous ligament
. Anterior sacroiliac ligament
. Interosseous sacroiliac ligament
. Iliolumbar ligament

Correct Answer & Explanation

. Interosseous sacroiliac ligament

Explanation

The interosseous sacroiliac ligament is the strongest ligament in the body and serves as the primary stabilizer of the posterior pelvic ring. It effectively resists anteroposterior translation and extreme rotational forces.

Question 12455

Topic: 2. Trauma

In a polytrauma patient, which of the following parameters is considered an absolute indication for Damage Control Orthopedics (DCO) rather than Early Total Care (ETC)?

. Platelet count of 120,000/microL
. Arterial pH of 7.20
. Serum lactate of 1.5 mmol/L
. Core body temperature of 36.5 C
. Isolated bilateral femoral shaft fractures

Correct Answer & Explanation

. Arterial pH of 7.20

Explanation

Damage control orthopedics is indicated in physiologically unstable patients. Established parameters for instability include an arterial pH < 7.24, temperature < 34 C, and serum lactate > 2.5 mmol/L.

Question 12456

Topic: 2. Trauma

When utilizing a fluoroscopic C-arm during fracture fixation, which configuration minimizes radiation exposure to the surgeon's eyes and thyroid?

. X-ray source below the table and image intensifier above
. X-ray source above the table and image intensifier below
. Increasing the distance between the patient and image intensifier
. Maximizing the magnification mode
. Placing the surgeon on the X-ray tube side of the C-arm

Correct Answer & Explanation

. X-ray source below the table and image intensifier above

Explanation

Placing the X-ray source below the operating table and the image intensifier close to the patient above the table minimizes scatter radiation. Scatter radiation is most intense on the side of the X-ray tube.

Question 12457

Topic: 2. Trauma
A 25-year-old male sustains a Gustilo-Anderson Type IIIB open tibia fracture. According to recent evidence-based guidelines, what is the most critical factor in reducing his risk of deep infection?
. Time to initial surgical debridement < 6 hours
. Administration of intravenous antibiotics within 1 hour of injury
. Use of high-pressure pulsatile lavage
. Primary closure of the wound
. Application of a negative pressure wound therapy device

Correct Answer & Explanation

. Administration of intravenous antibiotics within 1 hour of injury

Explanation

The most critical factor in preventing infection in open fractures is the early administration of systemic antibiotics, ideally within 60 minutes. The strict "6-hour rule" for surgical debridement is no longer supported as an independent predictor of infection.

Question 12458

Topic: 2. Trauma

The pathogenesis of acute compartment syndrome involves a cycle of rising tissue pressure leading to microvascular compromise. Tissue ischemia strictly begins when the local interstitial tissue pressure exceeds which of the following physiological parameters?

. Systolic blood pressure
. Mean arterial pressure
. Capillary perfusion pressure
. Venous outflow pressure
. Lymphatic drainage pressure

Correct Answer & Explanation

. Capillary perfusion pressure

Explanation

Compartment syndrome develops when increased pressure within a closed osteofascial compartment rises above the capillary perfusion pressure. This collapse of the capillary beds halts local microcirculation, leading to cellular hypoxia, muscle and nerve ischemia, and eventual necrosis, long before the pressure approaches mean arterial or systolic blood pressures.

Question 12459

Topic: 2. Trauma

When placing a cortical screw for fracture fixation, achieving adequate pullout strength is essential for construct stability. From a biomechanical and geometric standpoint, which parameter of the screw is the primary determinant of its pullout strength?

. Core diameter
. Pitch
. Outer thread diameter
. Thread depth
. Length of the unthreaded shaft

Correct Answer & Explanation

. Outer thread diameter

Explanation

The pullout strength of a bone screw is directly proportional to the outer thread diameter, the length of the thread engaged in the bone, and the shear strength of the surrounding bone. While the core diameter determines the screw's resistance to bending and torsional forces (fatigue strength), the outer thread diameter is the main geometric driver of pullout strength.

Question 12460

Topic: Lower Extremity Trauma

A solid cylindrical intramedullary nail is being redesigned to increase its bending rigidity. If the radius of the solid nail is increased by a factor of two, by what factor does its bending rigidity increase?

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 16

Explanation

Bending rigidity of a solid cylinder is proportional to the area moment of inertia, which scales with the radius to the fourth power (r^4). Therefore, doubling the radius increases the bending rigidity by a factor of 2^4, or 16.

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