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2. Trauma MCQs

Practice Set 535 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 10681

Topic: 2. Trauma

During the ongoing resuscitation of a polytrauma patient in hemorrhagic shock, which of the following markers is considered the most reliable indicator of adequate global tissue perfusion and successful resuscitation?

. Normalization of blood pressure and heart rate
. Urine output consistently > 0.5 mL/kg/hr
. Clearance of serum lactate and normalization of base deficit
. Central venous pressure reading of 8-12 mmHg
. Hematocrit stabilization at > 30%

Correct Answer & Explanation

. Normalization of blood pressure and heart rate

Explanation

While vital signs and urine output are helpful, they can normalize while the patient remains in a state of 'occult hypoperfusion.' The clearance of serum lactate and the normalization of the base deficit are the most reliable and widely accepted biochemical markers of restored global tissue perfusion and the endpoint of shock resuscitation.

Question 10682

Topic: 2. Trauma

When constructing a unilateral external fixator for a tibial shaft fracture, which of the following modifications will most significantly increase the bending stiffness of the construct?

. Increasing the half-pin diameter from 4 mm to 5 mm
. Increasing the distance between the bone and the connecting longitudinal bar
. Placing all pins in a single bone fragment very close together
. Using pins made of titanium instead of stainless steel
. Increasing the distance from the fracture site to the innermost pins

Correct Answer & Explanation

. Increasing the half-pin diameter from 4 mm to 5 mm

Explanation

The bending stiffness of an external fixator pin is proportional to the radius of the pin to the fourth power (r^4). Therefore, increasing the pin diameter has an exponential effect and is the single most effective way to increase the stiffness of the construct. Other ways to increase stiffness include placing the bar closer to the bone, spreading pins further apart within a given fragment, and placing inner pins closer to the fracture.

Question 10683

Topic: 2. Trauma
A trauma patient presents with a heart rate of 130 bpm, blood pressure of 90/60 mmHg, respiratory rate of 35 breaths/min, and confused mental status. Estimated blood loss is approximately 35% of total blood volume. According to the ATLS classification, this patient is in which class of hemorrhagic shock?
. Class I
. Class II
. Class III
. Class IV
. Class V

Correct Answer & Explanation

. Class III

Explanation

According to the American College of Surgeons ATLS classification, Class III hemorrhagic shock corresponds to an estimated blood loss of 31-40%. It is clinically characterized by a drop in measurable blood pressure, tachycardia (heart rate > 120), tachypnea (RR 30-40), and altered mental status (confusion). Class IV shock involves >40% blood loss, heart rate >140, and profound lethargy.

Question 10684

Topic: 2. Trauma
A 26-year-old male is involved in a motorcycle collision and sustains a 'floating knee' injury comprising an ipsilateral femur fracture and tibia fracture. Imaging reveals intra-articular extension into the knee joint from both the distal femur and the proximal tibia. According to the Fraser classification, this is categorized as:
. Type I
. Type IIA
. Type IIB
. Type IIC
. Type III

Correct Answer & Explanation

. Type IIC

Explanation

The Fraser classification for floating knee injuries is as follows: Type I consists of pure diaphyseal fractures of both the femur and tibia. Type II involves articular fractures: Type IIA involves the femur articular surface, Type IIB involves the tibia articular surface, and Type IIC involves intra-articular extension in both the femur and the tibia.

Question 10685

Topic: 2. Trauma
In the contemporary paradigm of damage control resuscitation for a severely bleeding polytrauma patient, what is the optimal ratio of packed red blood cells (pRBCs) to fresh frozen plasma (FFP) to platelets recommended during massive transfusion?
. 3:1:1
. 1:1:1
. 4:2:1
. 1:2:2
. 6:1:1

Correct Answer & Explanation

. 1:1:1

Explanation

Modern damage control resuscitation guidelines strongly recommend a balanced 1:1:1 ratio of packed red blood cells, fresh frozen plasma, and platelets. This strategy, validated by the PROPPR trial, addresses the acute coagulopathy of trauma more effectively than historical crystalloid-heavy or pure RBC resuscitation strategies.

Question 10686

Topic: 2. Trauma

A 28-year-old male is brought to the ED after a motor vehicle collision. He has a closed left femoral shaft fracture, right pulmonary contusion, and grade 2 splenic laceration. On arrival, BP 100/60, HR 110. Base deficit is 7 mmol/L and lactate is 3.5 mmol/L.

Which of the following is considered an absolute indication for damage control orthopedics (DCO) with external fixation of the femur rather than early total care (ETC)?

. Femoral fracture combined with a pulmonary contusion
. Base deficit > 8 mmol/L or worsening lactate
. Injury Severity Score (ISS) > 15
. Glasgow Coma Scale (GCS) < 12
. Age > 25 years

Correct Answer & Explanation

. Femoral fracture combined with a pulmonary contusion

Explanation

The principles of Damage Control Orthopedics (DCO) dictate that patients who are physiologically unstable should undergo temporizing fixation. Absolute indications for DCO include hemodynamic instability, core temperature < 32°C, pH < 7.24, base deficit > 8 mmol/L, and clinical coagulopathy. A femoral fracture with a pulmonary contusion or ISS > 15 represents a 'borderline' patient who may tolerate ETC if adequately resuscitated.

Question 10687

Topic: 2. Trauma

Which of the following is NOT a component of the Mangled Extremity Severity Score (MESS) used in evaluating severe limb trauma?

. Patient age
. Limb ischemia
. Presence of shock
. Degree of skeletal and soft tissue injury
. Neurological status of the limb

Correct Answer & Explanation

. Patient age

Explanation

The Mangled Extremity Severity Score (MESS) is calculated based on four variables: Skeletal and soft-tissue injury (1-4 points), Limb ischemia (1-3 points), Shock (0-2 points), and Age (0-2 points). Although severe neurological deficit (e.g., absent plantar sensation) is an important clinical factor, it is NOT a formal component of the MESS calculation.

Question 10688

Topic: 2. Trauma

In the management of a polytrauma patient, which of the following markers is considered the most reliable indicator of adequate tissue perfusion and successful systemic resuscitation?

. Normalization of blood pressure
. Normalization of heart rate
. Urine output > 0.5 mL/kg/hr
. Clearance of serum lactate
. Return of Glasgow Coma Scale to 15

Correct Answer & Explanation

. Normalization of blood pressure

Explanation

Serum lactate clearance and normalization of base deficit are the most reliable metabolic endpoints of resuscitation. Normalization of vital signs such as heart rate and blood pressure often occur before cellular hypoxia is completely resolved ('occult hypoperfusion').

Question 10689

Topic: 2. Trauma

Patients with severe traumatic brain injury (TBI) often demonstrate accelerated fracture healing and an increased risk of heterotopic ossification due to circulating humoral factors. What is the primary effect of concomitant traumatic brain injury on fracture healing?

. Delayed union due to hypermetabolism
. Decreased callus volume with increased biomechanical strength
. Increased callus volume and accelerated union times
. High rate of nonunion due to increased corticosteroid release
. Inhibition of endochondral ossification

Correct Answer & Explanation

. Delayed union due to hypermetabolism

Explanation

Clinical and basic science studies have demonstrated that patients with severe TBI undergo accelerated fracture healing characterized by an increased volume of fracture callus and faster clinical union times. This is mediated by circulating osteogenic factors (such as SDF-1, substance P, and other humoral factors) released following central nervous system injury.

Question 10690

Topic: 2. Trauma

The Reamer-Irrigator-Aspirator (RIA) system is commonly used today for large-volume autogenous bone graft harvest. However, it was originally developed to decrease the incidence of which of the following complications during intramedullary nailing?

. Thermal necrosis of the diaphysis
. Fat embolism syndrome
. Iatrogenic cortical fracture
. Intramedullary infection
. Hypertrophic nonunion

Correct Answer & Explanation

. Thermal necrosis of the diaphysis

Explanation

The RIA system was originally engineered to decrease intramedullary pressure during the reaming of long bones, thereby reducing the intravasation of marrow contents and the subsequent embolic load, which is a key factor in the development of Fat Embolism Syndrome (FES). It was later discovered to yield highly osteogenic graft material.

Question 10691

Topic: 2. Trauma

A 25-year-old male is trapped in a vehicle for 2 hours after a crash in winter. He arrives in the trauma bay intubated, with a pelvic ring injury and bilateral femur fractures. Which of the following accurately describes the 'lethal triad' of trauma that must be aggressively corrected?

. Hypocalcemia, hyperkalemia, acidosis
. Hypothermia, coagulopathy, acidosis
. Hypoxia, hypotension, coagulopathy
. Acidosis, hypothermia, hypoxia
. Coagulopathy, hyperkalemia, hypothermia

Correct Answer & Explanation

. Hypocalcemia, hyperkalemia, acidosis

Explanation

The 'lethal triad' in trauma consists of hypothermia, coagulopathy, and metabolic acidosis. These three conditions create a vicious cycle where hypothermia worsens coagulopathy, bleeding leads to reduced perfusion and worsening acidosis, which further depresses myocardial contractility and coagulation enzyme function.

Question 10692

Topic: 2. Trauma

A 22-year-old male with a closed femoral shaft fracture develops respiratory distress, confusion, and a petechial rash 48 hours after injury. According to Gurd and Wilson's criteria for Fat Embolism Syndrome, which of the following is considered a MAJOR criterion?

. Tachycardia > 120 bpm
. Temperature > 39.4°C
. Unexplained drop in hematocrit
. Petechial rash
. Retinal changes

Correct Answer & Explanation

. Tachycardia > 120 bpm

Explanation

Gurd and Wilson's major criteria for Fat Embolism Syndrome (FES) include: 1) Petechial rash (usually across the axilla and thorax), 2) Respiratory symptoms (hypoxia/radiographic changes), and 3) Neurological signs (confusion/coma). Tachycardia, fever, retinal changes, and drops in hematocrit/platelets are considered MINOR criteria.

Question 10693

Topic: 2. Trauma

You are instructing a junior resident on the application of a circumferential pelvic binder for a hemodynamically unstable patient with an open-book pelvic ring injury. To effectively reduce the pelvic volume and stabilize the fracture, over which specific anatomic landmark should the binder be centered?

. Anterior superior iliac spines (ASIS)
. Iliac crests
. Greater trochanters
. Symphysis pubis
. Umbilicus

Correct Answer & Explanation

. Anterior superior iliac spines (ASIS)

Explanation

A pelvic binder must be applied directly over the greater trochanters to effectively close an open-book pelvic injury. Placing the binder too high (over the iliac crests or ASIS) is a common error that fails to reduce the posterior pelvic ring and can paradoxically open the pelvis further in some fracture patterns.

Question 10694

Topic: 2. Trauma

A 45-year-old male presents with persistent mid-thigh pain 8 months after intramedullary nailing of a femoral shaft fracture. Radiographs reveal an 'elephant foot' appearance with abundant callus that does not bridge the fracture site.

What is the primary underlying cause of this specific type of nonunion?

. Inadequate biological environment
. Poor vascular supply to the fracture fragments
. Inadequate mechanical stability
. Undiagnosed deep infection
. Over-reaming of the medullary canal

Correct Answer & Explanation

. Inadequate biological environment

Explanation

A hypertrophic nonunion (characterized by 'elephant foot' or 'horse hoof' callus) has excellent biology and robust vascular supply but fails to unite primarily due to inadequate mechanical stability. Treatment generally involves increasing construct stiffness, often by exchanging to a larger intramedullary nail or adding a plate.

Question 10695

Topic: 2. Trauma

According to Perren's strain theory of fracture healing, primary (direct) bone healing without callus formation requires the interfragmentary strain to be kept below what specific threshold?

. 1%
. 2%
. 5%
. 10%
. 15%

Correct Answer & Explanation

. 1%

Explanation

Perren's strain theory states that the type of tissue that forms at a fracture site is determined by the interfragmentary strain. Primary (direct) bone healing via cutting cones requires absolute stability with strain levels below 2%. Strain between 2% and 10% promotes secondary bone healing (callus), while strain >10% leads to fibrous nonunion.

Question 10696

Topic: 2. Trauma

Following severe polytrauma, a patient initially develops Systemic Inflammatory Response Syndrome (SIRS) followed by a Compensatory Anti-inflammatory Response Syndrome (CARS), rendering them highly susceptible to nosocomial infections. Which of the following markers is most characteristic of the CARS phase?

. Elevated Tumor Necrosis Factor-alpha (TNF-a)
. Decreased HLA-DR expression on monocytes
. Elevated Interleukin-1 (IL-1)
. Increased circulating neutrophil counts
. Increased systemic vascular resistance

Correct Answer & Explanation

. Elevated Tumor Necrosis Factor-alpha (TNF-a)

Explanation

The Compensatory Anti-inflammatory Response Syndrome (CARS) is a state of immune suppression following major trauma. A classic and reliable biomarker for this 'immune paralysis' is the significant down-regulation of HLA-DR expression on the surface of circulating monocytes, which impairs antigen presentation.

Question 10697

Topic: 2. Trauma

In the pathophysiology of acute compartment syndrome, what is the initial microvascular event that initiates the cascade of tissue ischemia?

. Arterial occlusion
. Venous outflow obstruction
. Arteriolar spasm
. Capillary endothelial damage
. Lymphatic blockage

Correct Answer & Explanation

. Arterial occlusion

Explanation

The pathophysiology of compartment syndrome begins when tissue pressure rises above the intraluminal pressure of the thin-walled post-capillary venules. This causes venous outflow obstruction, leading to further fluid engorgement, escalating compartment pressure, and eventually exceeding capillary perfusion pressure, causing muscle and nerve ischemia.

Question 10698

Topic: 2. Trauma

The severity of tissue destruction in ballistic trauma is most directly related to the kinetic energy transferred to the tissue. Which of the following parameters of the projectile has the greatest exponential influence on its kinetic energy?

. Mass of the bullet
. Velocity of the bullet
. Caliber of the weapon
. Density of the target tissue
. Yaw of the bullet upon impact

Correct Answer & Explanation

. Mass of the bullet

Explanation

The kinetic energy of a projectile is calculated by the formula KE = 1/2 * mass * velocity^2. Because velocity is squared in this equation, doubling the velocity quadruples the kinetic energy, making velocity the most critical determinant of the wounding potential of a gunshot.

Question 10699

Topic: 2. Trauma

A 35-year-old male sustains a high-energy distal femur fracture (OTA 33-C3). A Hoffa fragment is suspected. Which of the following statements regarding Hoffa fractures is most accurate?

. They are most commonly found on the medial femoral condyle.
. They are best visualized on a standard anteroposterior (AP) radiograph.
. They involve a fracture of the femoral condyle in the coronal plane.
. Nonoperative management is preferred for non-displaced fragments.
. They are typically associated with anterior cruciate ligament (ACL) tears.

Correct Answer & Explanation

. They are most commonly found on the medial femoral condyle.

Explanation

Hoffa fractures are coronal plane fractures of the femoral condyle (OTA 33-B3). They are more common on the lateral condyle. Because they are in the coronal plane, they are frequently missed on standard AP radiographs and are best visualized on lateral radiographs or CT scans. Operative fixation is indicated even if non-displaced due to the high risk of displacement under shear forces and the need to restore intra-articular congruity.

Question 10700

Topic: Pelvic & Acetabular Trauma
Which of the following pelvic ring injury patterns is most highly associated with a massive retroperitoneal hemorrhage requiring angiographic embolization?
. Lateral compression type I (LC-I)
. Lateral compression type III (LC-III)
. Anteroposterior compression type I (APC-I)
. Anteroposterior compression type III (APC-III)
. Isolated pubic rami fractures

Correct Answer & Explanation

. Anteroposterior compression type III (APC-III)

Explanation

APC-III (open book) pelvic fractures involve complete disruption of the symphysis pubis and both the anterior and posterior sacroiliac ligaments, leading to massive pelvic volume expansion. This pattern is highly associated with severe retroperitoneal venous and arterial hemorrhage. The internal pudendal and superior gluteal arteries are frequently injured. Angiography is often required if the patient remains hemodynamically unstable despite mechanical stabilization.

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