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2. Trauma MCQs

Practice Set 611 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 12201

Topic: 2. Trauma

When placing a cortical screw for fracture fixation, which of the following modifications will most significantly increase the pullout strength of the screw?

. Decreasing the outer diameter of the thread
. Increasing the inner root diameter
. Increasing the length of thread engagement in cortical bone
. Decreasing the thread pitch
. Using a partially threaded rather than fully threaded screw design

Correct Answer & Explanation

. Increasing the length of thread engagement in cortical bone

Explanation

Pullout strength is primarily determined by the outer thread diameter, the quality of the bone, and the volume of bone engaged. Increasing the length of thread engagement (e.g., achieving bicortical fixation) significantly increases the engaged bone volume, maximizing pullout strength.

Question 12202

Topic: 2. Trauma
A 28-year-old farmer sustains a severe open tibia fracture (Gustilo-Anderson Type IIIA) heavily contaminated with soil. In addition to a first-generation cephalosporin and an aminoglycoside, which antimicrobial agent must be added to provide appropriate empiric coverage for the most concerning pathogens in this specific setting?
. Clindamycin
. Vancomycin
. Penicillin
. Azithromycin
. Linezolid

Correct Answer & Explanation

. Penicillin

Explanation

Open fractures occurring in agricultural settings or those heavily contaminated with soil carry a high risk for Clostridium perfringens infection. High-dose intravenous penicillin is added to the standard prophylactic regimen specifically to cover these highly lethal anaerobic, spore-forming organisms.

Question 12203

Topic: 2. Trauma
A 25-year-old male with bilateral femur fractures develops hypoxemia, a petechial rash, and confusion 48 hours post-injury. What is the major biochemical mediator driving the pulmonary dysfunction in fat embolism syndrome?
. Mechanical occlusion of the pulmonary artery by large marrow fragments
. Toxicity of free fatty acids on pneumocytes and endothelium
. Systemic depletion of antithrombin III
. Hyperactive platelet aggregation triggered by collagen
. Systemic inflammatory response to fracture hematoma

Correct Answer & Explanation

. Toxicity of free fatty acids on pneumocytes and endothelium

Explanation

In Fat Embolism Syndrome, free fatty acids are released from the breakdown of marrow fat emboli by pneumocyte lipases. These free fatty acids cause direct toxic damage to pneumocytes and capillary endothelium, leading to ARDS.

Question 12204

Topic: 2. Trauma

Which of the following physiologic parameters is the primary indication for initiating damage control orthopedics (DCO) rather than early total care (ETC) in a polytrauma patient with bilateral femur fractures?

. Base deficit of 2.0 mmol/L
. Serum lactate of 1.5 mmol/L
. Core body temperature of 36.5°C
. Arterial pH of 7.15
. Systolic blood pressure of 110 mmHg

Correct Answer & Explanation

. Arterial pH of 7.15

Explanation

Indications for Damage Control Orthopedics (DCO) over Early Total Care (ETC) in a polytrauma patient include evidence of the 'lethal triad' or profound shock. Specific parameters prompting DCO include acidosis (pH < 7.24), hypothermia (Temp < 35°C), coagulopathy, severe prolonged hypotension, requirement of multiple blood transfusions (>10 units), and elevated serum lactate (> 2.5 mmol/L) or base deficit (> 6.0 mmol/L).

Question 12205

Topic: 2. Trauma
A 32-year-old farmer sustains a highly contaminated open tibial shaft fracture (Gustilo-Anderson Type IIIA) after being pinned under a tractor. According to the most recent evidence-based guidelines, what is the most appropriate initial prophylactic antibiotic regimen?
. Cefazolin alone
. Cefazolin and gentamicin
. Cefazolin, gentamicin, and penicillin
. Vancomycin and piperacillin-tazobactam
. Ciprofloxacin and clindamycin

Correct Answer & Explanation

. Cefazolin, gentamicin, and penicillin

Explanation

For Gustilo-Anderson Type III open fractures, standard prophylaxis includes a first-generation cephalosporin (for Gram-positive coverage) and an aminoglycoside (for Gram-negative coverage). In farm-related injuries with gross soil contamination, high-dose penicillin is added to provide coverage against anaerobic organisms, specifically Clostridium perfringens, to prevent gas gangrene.

Question 12206

Topic: 2. Trauma

In the pathogenesis of acute compartment syndrome following a tibia fracture, which of the following represents the initial physiologic derangement?

. Arterial occlusion
. Arteriolar spasm
. Myocyte necrosis
. Venous outflow obstruction
. Peripheral nerve demyelination

Correct Answer & Explanation

. Venous outflow obstruction

Explanation

Acute compartment syndrome begins when increasing intracompartmental tissue pressure eventually surpasses venous pressure, causing venous outflow obstruction. This leads to further fluid engorgement, escalating pressure that subsequently compromises the arteriolar-venous gradient, ultimately terminating capillary perfusion and causing tissue ischemia.

Question 12207

Topic: Pelvic & Acetabular Trauma
According to the Young-Burgess classification for pelvic ring injuries, what specific anatomical disruption differentiates an Anteroposterior Compression Type III (APC III) injury from an APC II injury?
. Symphyseal diastasis greater than 2.5 cm
. Disruption of the anterior sacroiliac ligaments
. Disruption of the posterior sacroiliac ligaments
. Disruption of the sacrotuberous ligaments
. Disruption of the sacrospinous ligaments

Correct Answer & Explanation

. Disruption of the posterior sacroiliac ligaments

Explanation

In the Young-Burgess classification, APC II injuries involve symphyseal diastasis with disruption of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments, but the strong posterior sacroiliac ligaments remain intact (opening book). APC III injuries involve complete disruption of the anterior AND posterior sacroiliac ligaments, leading to complete hemipelvic instability.

Question 12208

Topic: 2. Trauma
In diagnosing acute compartment syndrome of the lower extremity, measuring intra-compartmental pressure is the gold standard when clinical signs are ambiguous. Which of the following pressure parameters is considered the most reliable threshold indicative of compartment syndrome necessitating fasciotomy?
. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 25 mmHg
. Delta pressure (Diastolic BP - Compartment Pressure) < 30 mmHg
. Delta pressure (Systolic BP - Compartment Pressure) < 45 mmHg
. Mean Arterial Pressure (MAP) - Compartment Pressure < 20 mmHg

Correct Answer & Explanation

. Delta pressure (Diastolic BP - Compartment Pressure) < 30 mmHg

Explanation

The delta pressure (ΔP) is the difference between the patient's diastolic blood pressure and the measured compartment pressure. A delta pressure of less than or equal to 30 mmHg is considered the most reliable indicator of tissue ischemia and acute compartment syndrome, warranting emergent fasciotomy.

Question 12209

Topic: Pelvic & Acetabular Trauma
A 25-year-old male is brought to the ED after a motorcycle collision. Pelvic radiographs show a symphysis pubis diastasis of 3.5 cm and widening of the anterior sacroiliac joints bilaterally. The posterior sacroiliac ligaments are intact. According to the Young-Burgess classification, what is this injury?
. Anterior-Posterior Compression (APC) I
. Anterior-Posterior Compression (APC) II
. Anterior-Posterior Compression (APC) III
. Lateral Compression (LC) I
. Lateral Compression (LC) II

Correct Answer & Explanation

. Anterior-Posterior Compression (APC) II

Explanation

APC II injuries are characterized by symphysis diastasis > 2.5 cm and widening of the anterior SI joints, indicating disruption of the anterior SI ligaments, as well as the sacrotuberous and sacrospinous ligaments. The posterior SI ligaments remain intact, maintaining vertical stability. APC III involves disruption of both anterior and posterior SI ligaments, causing complete spinopelvic instability.

Question 12210

Topic: 2. Trauma

Which of the following clinical scenarios presents the highest statistical risk for developing acute compartment syndrome of the lower extremity?

. Open midshaft tibia fracture treated with immediate intramedullary nailing
. Closed spiral fracture of the distal tibia with a butterfly fragment
. High-energy proximal third tibia fracture with a crush mechanism
. Isolated fracture of the fibular shaft
. Anterior cruciate ligament reconstruction using a bone-patellar tendon-bone autograft

Correct Answer & Explanation

. High-energy proximal third tibia fracture with a crush mechanism

Explanation

Acute compartment syndrome is most commonly associated with fractures of the tibia. The highest risk profile includes young male patients with high-energy, closed proximal-third tibia fractures, particularly those with a crush mechanism. While open fractures allow some pressure release, they do not eliminate the risk, but the proximal closed crush injury represents the classic highest-risk presentation.

Question 12211

Topic: 2. Trauma
When evaluating a patient for suspected acute compartment syndrome, you decide to measure intra-compartmental pressures. Which pressure parameter is considered the most reliable indicator requiring emergent fasciotomy?
. Absolute compartment pressure greater than 20 mmHg
. Absolute compartment pressure greater than 25 mmHg
. Difference between diastolic blood pressure and compartment pressure less than 30 mmHg
. Difference between systolic blood pressure and compartment pressure less than 40 mmHg
. Difference between mean arterial pressure and compartment pressure less than 20 mmHg

Correct Answer & Explanation

. Difference between diastolic blood pressure and compartment pressure less than 30 mmHg

Explanation

The delta pressure (Diastolic Blood Pressure - Intra-compartmental Pressure) is the most reliable and widely accepted threshold for diagnosing acute compartment syndrome. A delta pressure (Δp) of less than 30 mmHg indicates inadequate capillary perfusion pressure to the tissue and is a strong, definitive indication for emergent fasciotomy.

Question 12212

Topic: Pelvic & Acetabular Trauma
In the management of pelvic ring injuries, the volume of the true pelvis plays a critical role in hemodynamics. Which of the following injury patterns is associated with the greatest increase in pelvic volume, thereby accommodating the largest amount of retroperitoneal hemorrhage?
. Lateral Compression Type I (LC-I)
. Anteroposterior Compression Type III (APC-III)
. Lateral Compression Type III (LC-III)
. Isolated pubic rami fractures
. Vertical Shear (VS) with superior migration

Correct Answer & Explanation

. Anteroposterior Compression Type III (APC-III)

Explanation

Anteroposterior Compression Type III (APC-III) injuries involve complete disruption of the symphysis pubis and both the anterior and posterior sacroiliac ligaments. This 'open book' deformity significantly increases the internal volume of the pelvis, negating the tamponade effect and allowing for massive, life-threatening retroperitoneal venous and arterial hemorrhage. Lateral compression injuries generally decrease pelvic volume.

Question 12213

Topic: 2. Trauma

A 30-year-old male sustains a Hawkins Type II talar neck fracture. At the 8-week postoperative follow-up, an AP radiograph of the ankle demonstrates a subchondral radiolucent band in the dome of the talus (Hawkins sign). What does this radiographic finding indicate?

. Impending avascular necrosis (AVN) of the talar body
. Nonunion at the talar neck fracture site
. Intact vascular supply to the talar body
. Post-traumatic subtalar arthritis
. Osteochondral defect of the talar dome

Correct Answer & Explanation

. Intact vascular supply to the talar body

Explanation

The Hawkins sign is a subchondral radiolucent band seen in the dome of the talus on an AP or mortise radiograph, typically appearing 6 to 8 weeks post-injury. It represents subchondral bone resorption due to disuse osteopenia. Because osteopenia requires an intact blood supply to allow osteoclastic activity, a positive Hawkins sign is an excellent prognostic indicator that the talar body is vascularized and avascular necrosis (AVN) is unlikely.

Question 12214

Topic: 2. Trauma

A 40-year-old construction worker falls from a height and sustains a Schatzker VI tibial plateau fracture. Which of the following best defines the anatomic hallmark of a Schatzker VI fracture?

. Pure cleavage fracture of the lateral plateau
. Depression fracture of the lateral plateau without a split
. Isolated medial plateau fracture
. Bicondylar fracture with metaphyseal-diaphyseal dissociation
. Lateral plateau split with central depression

Correct Answer & Explanation

. Bicondylar fracture with metaphyseal-diaphyseal dissociation

Explanation

The Schatzker classification is used for tibial plateau fractures. Schatzker VI represents the most severe form, characterized by a transverse or oblique fracture through the metaphysis that separates the articular surfaces (condyles) from the diaphysis. This is known as metaphyseal-diaphyseal dissociation. It typically involves high-energy trauma and has a high risk of compartment syndrome.

Question 12215

Topic: 2. Trauma

A 32-year-old man sustains a closed tibial shaft fracture. Twelve hours later, he complains of severe pain out of proportion to the injury, unrelieved by intravenous opioids. Which of the following intracompartmental pressure measurements is the most accepted threshold for performing a four-compartment fasciotomy?

. Absolute compartment pressure greater than 15 mm Hg
. Absolute compartment pressure greater than 20 mm Hg
. Difference between diastolic blood pressure and compartment pressure less than 30 mm Hg
. Difference between mean arterial pressure and compartment pressure less than 45 mm Hg
. Difference between systolic blood pressure and compartment pressure less than 30 mm Hg

Correct Answer & Explanation

. Difference between diastolic blood pressure and compartment pressure less than 30 mm Hg

Explanation

The delta p (diastolic blood pressure minus compartment pressure) is the most reliable indicator for acute compartment syndrome. A delta p of less than 30 mm Hg is an absolute indication for emergency fasciotomy, as perfusion to the muscle and nerve tissues is critically compromised.

Question 12216

Topic: 2. Trauma
According to the Advanced Trauma Life Support (ATLS) classification of hemorrhagic shock, which of the following clinical signs is first observed when a patient transitions into Class III shock (31-40% blood volume loss)?
. Tachycardia (>100 bpm)
. Normal blood pressure with widened pulse pressure
. Hypotension
. Lethargy and coma
. Normal urine output

Correct Answer & Explanation

. Hypotension

Explanation

Class III hemorrhagic shock (31-40% blood loss) is the point at which compensatory mechanisms fail, and the patient first develops measurable hypotension. Class II shock manifests with tachycardia and a narrow pulse pressure, but systolic blood pressure remains normal.

Question 12217

Topic: 2. Trauma
A 35-year-old male sustains a severe open tibial shaft fracture treated with intramedullary nailing. The surgeon considers an osteoinductive adjunct to promote bone healing. Which of the following recombinant human bone morphogenetic proteins (rhBMPs) is FDA-approved specifically for acute, open tibial shaft fractures treated with an intramedullary nail?
. rhBMP-2
. rhBMP-3
. rhBMP-4
. rhBMP-7
. Transforming Growth Factor Beta (TGF-β)

Correct Answer & Explanation

. rhBMP-2

Explanation

rhBMP-2 is an osteoinductive protein that acts by stimulating mesenchymal stem cells to differentiate into osteoblasts. It 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 (OP-1) was previously approved under a Humanitarian Device Exemption for recalcitrant long bone nonunions but is no longer widely commercially available. rhBMP-3 is actually osteoinhibitory.

Question 12218

Topic: 2. Trauma

When inserting a cortical screw for fracture fixation, which of the following alterations in screw design will maximize its pullout strength from the bone?

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

Correct Answer & Explanation

. Increasing the outer diameter

Explanation

Pullout strength of a screw is directly proportional to the volume of bone engaged by the threads. It is maximized by increasing the outer diameter, decreasing the inner (core) diameter (which increases thread depth), and decreasing the thread pitch.

Question 12219

Topic: 2. Trauma

When inserting a cortical screw for fracture fixation, which of the following geometric properties of the screw most significantly determines its pullout strength?

. Inner (root) diameter
. Outer (thread) diameter
. Thread pitch
. Screw length
. Core diameter

Correct Answer & Explanation

. Outer (thread) diameter

Explanation

The pullout strength of a bone screw is most highly correlated with its outer (thread) diameter. Other major contributing factors include the length of thread engagement in the bone and the shear strength of the surrounding bone.

Question 12220

Topic: 2. Trauma

A 32-year-old man sustains a closed high-energy tibial shaft fracture. Two hours post-injury, he complains of severe leg pain disproportionate to the injury. Which early clinical finding is the most sensitive for impending acute compartment syndrome?

. Loss of palpable distal pulses
. Pallor of the distal extremity
. Pain with passive stretch of the involved muscles
. Motor paralysis of the affected compartment
. Decreased capillary refill time

Correct Answer & Explanation

. Pain with passive stretch of the involved muscles

Explanation

Pain with passive stretch of the muscles in the affected compartment is typically the most sensitive and earliest clinical sign of acute compartment syndrome. Pulselessness, pallor, and paralysis are late and notoriously unreliable signs.

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