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2. Trauma MCQs

Practice Set 622 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 12421

Topic: 2. Trauma
According to the Advanced Trauma Life Support (ATLS) classification of hypovolemic shock, at what class of hemorrhage does an otherwise healthy adult patient typically first exhibit a drop in systolic blood pressure?
. Class I
. Class II
. Class III
. Class IV
. Blood pressure drop is not part of the ATLS shock classification

Correct Answer & Explanation

. Class III

Explanation

According to ATLS, Class III hemorrhage is defined by 31-40% blood volume loss and is the stage at which systolic blood pressure first drops significantly (hypotension). Class I (up to 15%) and Class II (15-30%) are characterized by normal systolic blood pressure, though Class II will show tachycardia and narrowed pulse pressure.

Question 12422

Topic: 2. Trauma

Age-related sarcopenia significantly increases the risk of falls and fragility fractures in the elderly population. This condition is characterized at the cellular level predominantly by which of the following morphologic changes?

. Atrophy of Type I (slow-twitch) muscle fibers
. Atrophy of Type II (fast-twitch) muscle fibers
. Hyperplasia of Type I (slow-twitch) muscle fibers
. Hypertrophy of Type II (fast-twitch) muscle fibers
. Equal, generalized atrophy of all muscle fiber types

Correct Answer & Explanation

. Atrophy of Type II (fast-twitch) muscle fibers

Explanation

Sarcopenia, the age-related loss of muscle mass and function, is characterized primarily by a disproportionate atrophy and loss of Type II (fast-twitch) muscle fibers. Type I (slow-twitch) fibers are relatively preserved with aging. This loss of fast-twitch fibers reduces muscle power and rapid response mechanisms necessary to prevent falls.

Question 12423

Topic: Pelvic & Acetabular Trauma
According to the Young-Burgess classification, an anterior posterior compression type II (APC-II) pelvic ring injury is classically characterized by the rupture of the anterior sacroiliac ligaments along with which other major ligamentous complexes?
. Posterior sacroiliac ligaments only
. Sacrotuberous and sacrospinous ligaments
. Iliolumbar ligaments
. Sacrospinous and posterior sacroiliac ligaments
. Symphyseal ligaments only with intact posterior structures

Correct Answer & Explanation

. Sacrotuberous and sacrospinous ligaments

Explanation

APC-I involves pubic symphysis diastasis (<2.5 cm) with intact posterior ligaments. APC-II involves a symphysis diastasis (>2.5 cm) with rupture of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments, but the strong posterior sacroiliac ligaments remain intact, causing rotational instability but vertical stability. APC-III involves complete disruption including the posterior SI ligaments.

Question 12424

Topic: 2. Trauma

A 28-year-old male sustains a closed tibial shaft fracture. He complains of excruciating leg pain out of proportion to the injury. Which of the following pressure criteria is considered the most reliable threshold for diagnosing acute compartment syndrome and indicating fasciotomy?

. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 30 mmHg
. Delta P (Mean Arterial Pressure minus Compartment Pressure) < 20 mmHg
. Delta P (Diastolic Blood Pressure minus Compartment Pressure) < 30 mmHg
. Delta P (Systolic Blood Pressure minus Compartment Pressure) < 40 mmHg

Correct Answer & Explanation

. Delta P (Diastolic Blood Pressure minus Compartment Pressure) < 30 mmHg

Explanation

The Delta P concept (Diastolic Blood Pressure minus the intracompartmental pressure) is the most reliable parameter for diagnosing compartment syndrome. A Delta P of less than 30 mmHg indicates that tissue perfusion is critically impaired, mandating emergent fasciotomy. Absolute pressures can be misleading in hypotensive or hypertensive patients.

Question 12425

Topic: 2. Trauma

When designing or selecting a cortical screw for fracture fixation, which of the following screw parameters has the greatest mathematical influence on its theoretical pullout strength?

. Inner core diameter
. Outer thread diameter
. Thread pitch
. Length of engagement
. Head diameter

Correct Answer & Explanation

. Outer thread diameter

Explanation

The outer (thread) diameter has the most significant mathematical influence on screw pullout strength. Pullout strength is directly proportional to the outer diameter, the length of thread engagement, and the shear strength of the bone.

Question 12426

Topic: 2. Trauma

A 30-year-old multitrauma patient sustains a comminuted tibia fracture. The limb is tense and swollen. In diagnosing acute compartment syndrome, which of the following hemodynamic parameters represents the most reliable threshold for emergent fasciotomy?

. Absolute compartment pressure > 20 mm Hg
. Absolute compartment pressure > 30 mm Hg
. Absolute compartment pressure > 40 mm Hg
. Diastolic blood pressure minus compartment pressure < 30 mm Hg
. Mean arterial pressure minus compartment pressure < 20 mm Hg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mm Hg

Explanation

The Delta P (diastolic blood pressure minus compartment pressure) is the most reliable clinical indicator for acute compartment syndrome. A Delta P of less than 30 mm Hg is an absolute indication to perform emergent four-compartment fasciotomies.

Question 12427

Topic: 2. Trauma

A 28-year-old male sustains a closed tibial shaft fracture. Two hours post-injury, he develops severe leg pain out of proportion to the injury. Which of the following parameters is the most reliable threshold for diagnosing acute compartment syndrome and indicating a 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 < 30 mmHg
. Systolic blood pressure minus compartment pressure < 40 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The differential pressure (Delta P) between diastolic blood pressure and compartment pressure is the most reliable objective indicator for acute compartment syndrome. A Delta P of less than 30 mmHg correlates with significant muscle ischemia and is the standard threshold indicating the need for emergent fasciotomy.

Question 12428

Topic: 2. Trauma

A 24-year-old man falls on an outstretched hand and sustains a fracture of the scaphoid proximal pole. He is treated with cast immobilization. Why is this specific fracture pattern at a high risk for avascular necrosis and nonunion?

. The proximal pole has a robust capsular blood supply that is easily disrupted.
. Blood supply enters distally and flows retrograde to the proximal pole.
. The proximal pole is primarily supplied by the volar carpal branch of the radial artery.
. The nutrient artery enters the waist dorsally and flows antegrade.
. The proximal pole lacks articular cartilage, impeding synovial diffusion.

Correct Answer & Explanation

. Blood supply enters distally and flows retrograde to the proximal pole.

Explanation

The scaphoid receives its primary blood supply from the dorsal carpal branch of the radial artery. The vessels enter the bone distally (at the dorsal ridge near the waist) and flow in a retrograde fashion to supply the proximal pole. Fractures at the proximal pole effectively sever this retrograde flow, leading to very high rates of avascular necrosis and nonunion.

Question 12429

Topic: 2. Trauma

Biomechanically, how does a locked plating system primarily provide stability to a fracture compared to a conventional compression plating system?

. Friction between the plate and the bone
. High axial compression across the fracture site
. Fixed-angle construct relying on the screw-plate interface
. Dynamic compression during weight-bearing
. Increased screw pull-out strength in the near cortex

Correct Answer & Explanation

. Fixed-angle construct relying on the screw-plate interface

Explanation

Locked plating systems function as single-beam, fixed-angle constructs. The screw heads thread directly into the plate, locking them together. This relies on the threaded screw-plate interface for stability rather than relying on friction generated by compressing the plate against the bone surface, which is the mechanism of conventional non-locked plates.

Question 12430

Topic: 2. Trauma
A 42-year-old male sustains a Gustilo-Anderson IIIB open fracture of the middle third of the tibia. After serial debridements and external fixation, a 6 cm soft tissue defect with exposed bone remains. Which of the following is the most appropriate local muscle flap for coverage of this specific defect?
. Medial gastrocnemius flap
. Lateral gastrocnemius flap
. Soleus flap
. Reverse sural artery flap
. Gracilis free flap

Correct Answer & Explanation

. Soleus flap

Explanation

The lower extremity is historically divided into thirds for flap coverage. Proximal third defects are covered by the gastrocnemius flaps. Middle third defects of the tibia are classically covered by a proximally based soleus muscle flap. Distal third defects lack adequate local muscle bulk and typically require a free tissue transfer or a reverse sural artery flap.

Question 12431

Topic: Pelvic & Acetabular Trauma

In an anteroposterior compression type II (APC-II) pelvic ring injury, which of the following sets of ligaments are characteristically ruptured?

. Symphyseal ligaments and anterior sacroiliac ligaments only
. Symphyseal ligaments, anterior and posterior sacroiliac ligaments
. Anterior sacroiliac ligaments and sacrospinous ligaments only
. Symphyseal ligaments, sacrospinous, sacrotuberous, and anterior sacroiliac ligaments
. Iliolumbar ligaments and posterior sacroiliac ligaments

Correct Answer & Explanation

. Symphyseal ligaments, sacrospinous, sacrotuberous, and anterior sacroiliac ligaments

Explanation

An APC-II injury (an 'open book' pelvis) involves the rupture of the anterior symphyseal ligaments, the pelvic floor ligaments (sacrospinous and sacrotuberous), and the anterior sacroiliac ligaments. Crucially, the strong posterior sacroiliac ligaments remain intact, providing vertical stability but allowing significant rotational instability.

Question 12432

Topic: 2. Trauma

A patient sustains a closed midshaft humerus fracture and presents with an immediate wrist drop. Electromyography (EMG) performed at 4 weeks shows fibrillation potentials but no voluntary motor unit action potentials. What is the most likely peripheral nerve injury grade according to the Seddon classification?

. Neurapraxia
. Axonotmesis
. Neurotmesis
. Neuroma-in-continuity
. Wallerian degeneration

Correct Answer & Explanation

. Axonotmesis

Explanation

Axonotmesis involves disruption of the axon and myelin sheath but preservation of the connective tissue framework (epineurium, perineurium, and endoneurium). EMG at 4 weeks showing denervation changes (fibrillations) without voluntary potentials confirms axonal disruption. Recovery is expected at approximately 1mm/day. Neurapraxia would typically not show fibrillations.

Question 12433

Topic: 2. Trauma

A 24-year-old male is admitted with bilateral closed femur fractures. On hospital day 2, he develops confusion, a petechial rash on his axilla, and significant hypoxia. Which of the following is the most appropriate initial management for his condition?

. High-dose systemic corticosteroids
. Intravenous heparin infusion
. Supportive care with aggressive oxygenation and mechanical ventilation if needed
. Immediate placement of an inferior vena cava (IVC) filter
. Administration of low molecular weight dextran

Correct Answer & Explanation

. Supportive care with aggressive oxygenation and mechanical ventilation if needed

Explanation

The patient is presenting with the classic triad of Fat Embolism Syndrome (FES): hypoxemia, neurologic abnormalities, and a petechial rash. The mainstay of treatment is supportive care, ensuring adequate oxygenation and ventilation, and maintaining hemodynamics. Heparin, dextran, and corticosteroids are not indicated as primary treatment for established FES.

Question 12434

Topic: 2. Trauma

Which of the following fracture patterns in a 6-month-old child has the highest specificity for non-accidental trauma (child abuse)?

. Linear parietal skull fracture
. Midshaft clavicle fracture
. Posterior rib fractures
. Distal radius buckle fracture
. Spiral fracture of the tibia (Toddler's fracture)

Correct Answer & Explanation

. Posterior rib fractures

Explanation

Posterior rib fractures are highly specific for non-accidental trauma in infants, usually resulting from squeezing the child's chest. Metaphyseal corner fractures and scapular fractures are also highly specific. Clavicle and linear skull fractures are common in accidental trauma, and a spiral tibial fracture is common in walking toddlers (though suspicious in a 6-month-old, posterior rib fractures carry higher inherent specificity).

Question 12435

Topic: 2. Trauma
According to the Gustilo-Anderson classification, an open tibial shaft fracture with a 12 cm laceration, severe muscle crushing, periosteal stripping, but adequate soft-tissue coverage (bone can be covered without requiring a local or free flap) is classified as:
. Type II
. Type IIIA
. Type IIIB
. Type IIIC
. Type IV

Correct Answer & Explanation

. Type IIIA

Explanation

Gustilo-Anderson Type IIIA is a high-energy injury with extensive soft tissue laceration (>10 cm) or adequate soft tissue coverage of the fractured bone despite extensive periosteal stripping. Type IIIB requires a local or free flap for coverage. Type IIIC involves an arterial injury requiring repair.

Question 12436

Topic: 2. Trauma

A 45-year-old male presents 8 months after a midshaft humerus fracture treated with casting. Radiographs show a distinct "elephant shoe" appearance at the fracture site with no bridging callus. What is the most appropriate definitive management?

. Pulsed electromagnetic field therapy
. Rigid internal fixation without bone grafting
. Exchange nailing with reaming
. Bone grafting alone
. Platelet-rich plasma injection

Correct Answer & Explanation

. Rigid internal fixation without bone grafting

Explanation

The "elephant shoe" appearance indicates a hypertrophic nonunion, which has excellent biological healing potential but lacks adequate mechanical stability. The treatment of choice is rigid internal fixation to provide stability, typically without the need for bone grafting.

Question 12437

Topic: 2. Trauma

Which of the following biomechanical environments is an absolute requirement for primary (strain-free) bone healing to occur?

. High strain environment to stimulate callous formation
. Presence of a robust hematoma and intact periosteum
. Micro-motion at the fracture site to induce endochondral ossification
. Absolute stability with less than 2% strain at the fracture site
. Relative stability with up to 10% strain

Correct Answer & Explanation

. Absolute stability with less than 2% strain at the fracture site

Explanation

Primary bone healing requires absolute stability with less than 2% strain and direct apposition of fracture fragments. This allows cutting cones to directly cross the fracture site without the formation of an intermediate cartilaginous callus.

Question 12438

Topic: 2. Trauma

A 30-year-old male with a closed, highly comminuted tibial shaft fracture develops severe pain out of proportion to the injury. Which of the following Delta pressure measurements (diastolic blood pressure minus compartment pressure) is considered an absolute indication for emergent fasciotomy?

. Greater than 40 mmHg
. Greater than 30 mmHg
. Less than 30 mmHg
. Less than 45 mmHg
. Less than 10 mmHg absolute pressure

Correct Answer & Explanation

. Less than 30 mmHg

Explanation

A Delta pressure (diastolic blood pressure minus compartment pressure) of less than 30 mmHg indicates inadequate tissue perfusion and is the standard threshold indicating the need for an emergent fasciotomy to treat compartment syndrome.

Question 12439

Topic: Pelvic & Acetabular Trauma
An anteroposterior compression (APC) Type III pelvic ring injury involves complete disruption of the pubic symphysis and both the anterior and posterior sacroiliac ligaments. What is statistically the most common anatomical source of life-threatening hemorrhage in such injuries?
. Superior gluteal artery
. Presacral venous plexus
. External iliac artery
. Obturator artery
. Internal pudendal artery

Correct Answer & Explanation

. Presacral venous plexus

Explanation

While arterial bleeding (e.g., superior gluteal or internal pudendal) can be fatal and requires embolization, the majority (approximately 80%) of massive retroperitoneal bleeding in pelvic ring disruptions originates from the presacral venous plexus and bleeding cancellous bone surfaces.

Question 12440

Topic: 2. Trauma

A 35-year-old female falls from a height and sustains a sacral fracture. According to the Denis classification, which zone of injury carries the highest risk of neurological deficit?

. Zone 1 (Alar)
. Zone 2 (Foraminal)
. Zone 3 (Central canal)
. Zone 4 (Sacroiliac joint)
. Zone 5 (Coccygeal)

Correct Answer & Explanation

. Zone 3 (Central canal)

Explanation

Denis Zone 3 involves the central sacral canal and carries the highest risk of neurological injury (up to 57%), commonly affecting bowel, bladder, and sexual function.

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