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2. Trauma MCQs

Practice Set 577 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 11521

Topic: 2. Trauma

In a conscious patient with suspected acute compartment syndrome of the leg, which 'delta pressure' threshold is generally accepted as an objective indication for an urgent surgical fasciotomy?

. Absolute compartment pressure > 15 mmHg
. Absolute compartment pressure > 20 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Systolic blood pressure minus compartment pressure < 45 mmHg
. Mean arterial pressure minus compartment pressure < 50 mmHg

Correct Answer & Explanation

. Absolute compartment pressure > 15 mmHg

Explanation

The delta pressure, calculated as the patient's diastolic blood pressure minus the measured compartment pressure, is considered the most reliable threshold. A delta pressure of less than 30 mmHg (some sources say <20-30 mmHg) indicates inadequate tissue perfusion and is a strong indication for fasciotomy, regardless of the absolute pressure.

Question 11522

Topic: 2. Trauma
A 35-year-old male is struck by a motor vehicle and sustains a closed displaced acetabular fracture. Examination reveals a large, fluctuant soft-tissue swelling over the greater trochanter. Aspiration yields serosanguinous fluid. What is the most likely composition of the boundary of this fluid collection?
. True synovial lining
. Necrotic muscle tissue
. Granulation tissue and fibrin
. Pseudocapsule of compressed fibrous tissue
. Epithelial lining

Correct Answer & Explanation

. Pseudocapsule of compressed fibrous tissue

Explanation

The patient has a Morel-Lavallée lesion, which is a closed degloving injury where the skin and subcutaneous tissue are separated from the underlying fascia. The resulting potential space fills with blood, lymph, and necrotic fat, eventually forming a pseudocapsule made of compressed fibrous tissue, which often prevents spontaneous resolution and may require surgical excision or sclerodesis.

Question 11523

Topic: 2. Trauma

A 30-year-old male sustains a closed tibial shaft fracture. Two hours later, he complains of severe leg pain out of proportion to the injury. Compartment pressures are measured. Which of the following criteria is the most reliable threshold for diagnosing acute compartment syndrome and indicating emergent fasciotomy?

. Absolute compartment pressure > 20 mmHg
. Diastolic blood pressure minus compartment pressure (Delta P) < 30 mmHg
. Systolic blood pressure minus compartment pressure (Delta P) < 40 mmHg
. Mean arterial pressure minus compartment pressure > 30 mmHg
. Absolute compartment pressure > 25 mmHg

Correct Answer & Explanation

. Absolute compartment pressure > 20 mmHg

Explanation

The Delta P (diastolic blood pressure minus the measured compartment pressure) is the most reliable indicator for acute compartment syndrome. A Delta P of less than 30 mmHg signifies that local tissue perfusion pressure is inadequate, establishing the need for emergent fasciotomies.

Question 11524

Topic: 2. Trauma
According to the Gustilo-Anderson classification, a 4 cm laceration over a tibial shaft fracture with moderate soft tissue damage, but adequate periosteal coverage and no massive contamination, is classified as which of the following?
. Type I
. Type II
. Type IIIA
. Type IIIB
. Type IIIC

Correct Answer & Explanation

. Type II

Explanation

A Gustilo-Anderson Type II open fracture is defined as having an open wound > 1 cm and < 10 cm without extensive soft tissue damage, flaps, or avulsions. There is adequate soft tissue coverage of the bone and no massive contamination.

Question 11525

Topic: 2. Trauma
A 38-year-old male is brought to the trauma bay in hemorrhagic shock after a motorcycle crash. Pelvic radiographs show an APC-III pelvic ring injury. A pelvic binder is applied to reduce pelvic volume. Over which anatomic landmark should the binder be centered for maximal effectiveness?
. Iliac crests
. Anterior superior iliac spines
. Greater trochanters
. Symphysis pubis
. Sacral promontory

Correct Answer & Explanation

. Greater trochanters

Explanation

To effectively reduce pelvic volume in anteroposterior compression (open book) injuries, a pelvic binder or sheet must be centered directly over the greater trochanters. Placement higher over the iliac crests is less effective and can paradoxically open the pelvis further in certain fracture patterns.

Question 11526

Topic: 2. Trauma

A patient complains of perineal numbness and erectile dysfunction after a prolonged femur fracture repair on a fracture table. This neuropraxia is due to compression of the pudendal nerve against the perineal post. What is the normal pelvic course of the pudendal nerve?

. Exits the pelvis through the lesser sciatic foramen and re-enters through the obturator foramen
. Exits the pelvis through the greater sciatic foramen and re-enters through the lesser sciatic foramen
. Passes strictly through the greater sciatic foramen without entering the lesser sciatic foramen
. Passes through the obturator canal directly into the perineum
. Courses anterior to the pubic symphysis into the perineum

Correct Answer & Explanation

. Exits the pelvis through the lesser sciatic foramen and re-enters through the obturator foramen

Explanation

The pudendal nerve (S2-S4) exits the pelvis through the greater sciatic foramen (inferior to the piriformis), crosses the sacrospinous ligament, and re-enters the pelvis through the lesser sciatic foramen to travel in Alcock's canal. It can be compressed by the perineal post on a fracture table.

Question 11527

Topic: 2. Trauma

Delayed union is common in fractures of the distal third of the tibial shaft. This is largely due to the watershed vascularity in this region. The primary nutrient artery of the tibia, which supplies the inner two-thirds of the cortex, originates from which vessel?

. Anterior tibial artery
. Posterior tibial artery
. Peroneal artery
. Popliteal artery directly
. Sural artery

Correct Answer & Explanation

. Anterior tibial artery

Explanation

The primary nutrient artery of the tibia originates from the posterior tibial artery. It enters the posterolateral cortex of the tibia just distal to the soleal line and supplies the medullary canal and the inner two-thirds of the cortex.

Question 11528

Topic: 2. Trauma

The diaphyseal cortex of an adult long bone receives its blood supply from both the medullary and periosteal systems. In a normal, intact adult long bone, what accurately describes the relative contribution and direction of blood flow in the cortical bone?

. Inner 2/3 supplied by the nutrient artery, with a predominantly centrifugal flow pattern
. Outer 2/3 supplied by the periosteal vessels, with a predominantly centripetal flow pattern
. Inner 1/3 supplied by the nutrient artery, with a predominantly centrifugal flow pattern
. Outer 1/3 supplied by the nutrient artery, with a predominantly centripetal flow pattern
. Entire cortex supplied by the periosteal vessels, with a predominantly centripetal flow pattern

Correct Answer & Explanation

. Inner 2/3 supplied by the nutrient artery, with a predominantly centrifugal flow pattern

Explanation

In mature long bones, the high-pressure medullary system (nutrient artery) supplies the inner 2/3 (up to 3/4) of the diaphysis, and the low-pressure periosteal system supplies the outer 1/3. Normal cortical capillary flow is predominantly from the high-pressure endosteum outwards to the periosteum (centrifugal flow). If the medullary supply is destroyed (e.g., by reaming), the flow temporarily reverses (centripetal) to rely on periosteal supply.

Question 11529

Topic: 2. Trauma

A 3-year-old child weighing 16 kg sustains an isolated, closed, diaphyseal femur fracture with 1 cm of shortening after a low-energy fall. What is the most appropriate initial management?

. Immediate early spica casting
. Flexible intramedullary nailing
. Submuscular bridge plating
. External fixation
. Rigid antegrade locked intramedullary nail

Correct Answer & Explanation

. Immediate early spica casting

Explanation

For children aged 6 months to 5 years (and usually under 20 kg) with isolated diaphyseal femur fractures and less than 2 cm of shortening, early spica casting is the standard of care. Flexible nailing is generally reserved for older children (typically 5-11 years) or those over 50 lbs (22 kg).

Question 11530

Topic: 2. Trauma

An 8-year-old boy weighing 35 kg sustains a closed, length-stable midshaft femur fracture after falling off a bicycle. What is the most widely accepted standard of care for definitive fixation?

. Immediate hip spica casting
. Flexible intramedullary nailing (titanium elastic nails)
. Rigid trochanteric-entry locked intramedullary nailing
. Open reduction internal fixation with a compression plate
. Application of a Pavlik harness

Correct Answer & Explanation

. Immediate hip spica casting

Explanation

Flexible intramedullary nails are the standard of care for length-stable femoral shaft fractures in children aged 5 to 11 years weighing less than 50 kg (110 lbs). Rigid antegrade nailing is contraindicated in this age group due to the risk of avascular necrosis from piriformis fossa entry.

Question 11531

Topic: Lower Extremity Trauma

A 2-year-old girl is evaluated for bilateral genu varum. Which radiographic finding is most predictive of progression to infantile Blount disease rather than physiologic bowing?

. Metaphyseal-diaphyseal angle of Drennan greater than 16 degrees
. Tibiofemoral angle of 10 degrees
. Medial cortical thickening of the tibia
. Presence of a proximal tibial metaphyseal beak
. Physeal widening at the distal femur

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle of Drennan greater than 16 degrees

Explanation

A metaphyseal-diaphyseal angle (MDA) of Drennan greater than 16 degrees has a high positive predictive value for progression to infantile Blount disease. Angles less than 10 degrees typically resolve spontaneously as physiologic bowing.

Question 11532

Topic: 2. Trauma
In evaluating an obtunded, intubated polytrauma patient with a comminuted tibia fracture for acute compartment syndrome, which of the following objective measurement parameters is the most specific threshold to mandate emergency fasciotomy?
. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 30 mmHg
. Mean arterial pressure minus compartment pressure < 30 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Systolic blood pressure minus compartment pressure < 30 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

Delta pressure (ΔP) is the most reliable objective indicator for acute compartment syndrome, particularly in hypotensive or obtunded patients. It is calculated as Diastolic Blood Pressure minus Compartment Pressure. A ΔP of less than 30 mmHg is the widely accepted threshold indicating inadequate tissue perfusion and the need for fasciotomy.

Question 11533

Topic: 2. Trauma

In the setting of Damage Control Orthopedics (DCO) for a hemodynamically unstable polytrauma patient with bilateral femur fractures, serial monitoring of metabolic parameters is critical. Which of the following profiles most reliably indicates that the patient has been adequately resuscitated and may safely undergo conversion from external fixation to definitive intramedullary nailing?

. Serum lactate > 4.0 mmol/L and increasing base deficit
. Urine output consistently < 0.5 mL/kg/hr
. Serum lactate < 2.5 mmol/L and a clearing base deficit
. Systemic inflammatory response syndrome (SIRS) score of 4
. Platelet count rapidly dropping below 50,000/mm^3

Correct Answer & Explanation

. Serum lactate > 4.0 mmol/L and increasing base deficit

Explanation

Successful resuscitation in polytrauma dictates the transition from damage control to definitive fixation. Serum lactate and base deficit are excellent markers of global tissue perfusion. A serum lactate of less than 2.5 mmol/L and an improving (clearing) base deficit reflect resolved physiologic debt, identifying the optimal 'window of opportunity' for secondary definitive surgery.

Question 11534

Topic: 2. Trauma

When evaluating a patient for suspected acute compartment syndrome of the lower extremity, which of the following pressure measurements or gradients is the most widely accepted threshold for performing an emergency fasciotomy?

. Absolute compartment pressure > 20 mm Hg
. Absolute compartment pressure > 25 mm Hg
. Delta P (Diastolic blood pressure minus compartment pressure) < 30 mm Hg
. Delta P (Mean arterial pressure minus compartment pressure) < 40 mm Hg
. Delta P (Systolic blood pressure minus compartment pressure) < 50 mm Hg

Correct Answer & Explanation

. Absolute compartment pressure > 20 mm Hg

Explanation

A delta P (diastolic blood pressure minus the measured compartment pressure) of less than 30 mm Hg is the most universally accepted threshold indicating inadequate tissue perfusion, necessitating emergent four-compartment fasciotomy.

Question 11535

Topic: Lower Extremity Trauma

A 45-year-old male sustains a high-energy knee injury. Radiographs and CT demonstrate a fracture of the medial tibial plateau with significant depression, as well as a separate fracture line extending into the lateral plateau. What is the correct Schatzker classification?

. Schatzker II
. Schatzker IV
. Schatzker V
. Schatzker VI
. Schatzker VII

Correct Answer & Explanation

. Schatzker II

Explanation

Schatzker V designates a bicondylar tibial plateau fracture. The presence of both medial and lateral plateau involvement makes it a Type V. Type VI would involve complete metaphyseal-diaphyseal dissociation. Type IV is an isolated medial plateau fracture.

Question 11536

Topic: 2. Trauma
A 35-year-old cyclist is struck by a motor vehicle and sustains a severe pelvic ring injury. Examination of his lateral thigh reveals a massive, fluctuant, soft-tissue swelling with overlying skin ecchymosis but no open wounds. What is the pathophysiologic mechanism of this specific soft-tissue lesion?
. Closed compartment syndrome of the vastus lateralis
. Accumulation of arterial blood secondary to superior gluteal artery rupture
. Traumatic closed degloving resulting from shearing of the subcutaneous tissue away from the underlying fascia
. Herniation of the gluteus medius muscle through an acute fascial defect
. Massive localized deep venous thrombosis of the femoral system

Correct Answer & Explanation

. Traumatic closed degloving resulting from shearing of the subcutaneous tissue away from the underlying fascia

Explanation

The patient has a Morel-Lavallée lesion. This is a closed degloving injury caused by high-energy shearing forces that separate the skin and subcutaneous tissue from the underlying dense fascia. This creates a potential space that rapidly fills with blood, lymph, and necrotic fat. They have a high rate of bacterial colonization and subsequent infection.

Question 11537

Topic: Pelvic & Acetabular Trauma
In the management of pelvic ring injuries, the primary structural distinction between an Anteroposterior Compression (APC) Type II and Type III injury according to the Young-Burgess classification is the complete disruption of which of the following?
. Symphysis pubis
. Anterior sacroiliac ligaments
. Sacrospinous ligaments
. Sacrotuberous ligaments
. Posterior sacroiliac ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligaments

Explanation

An APC II injury involves symphyseal diastasis and disruption of the anterior sacroiliac (SI), sacrospinous, and sacrotuberous ligaments, but the posterior SI ligaments remain intact (providing vertical stability despite rotational instability). An APC III injury involves disruption of both anterior and posterior SI ligaments, resulting in complete spinopelvic dissociation with both rotational and vertical instability.

Question 11538

Topic: 2. Trauma

In evaluating a patient with suspected acute compartment syndrome of the leg, understanding tissue ischemia limits is crucial to avoiding permanent disability. Muscle tissue typically begins to sustain irreversible ischemic damage after how many hours of total ischemia?

. 1 to 2 hours
. 3 to 4 hours
. 6 to 8 hours
. 10 to 12 hours
. 14 to 16 hours

Correct Answer & Explanation

. 1 to 2 hours

Explanation

Skeletal muscle tissue generally tolerates warm ischemia for up to 4 hours well. Irreversible changes, including muscle necrosis and fibrosis (leading to Volkmann's ischemic contracture), begin to occur after 6 to 8 hours of total ischemia. This physiological limit dictates the absolute necessity of performing emergent fasciotomies within a 6-hour window from the onset of symptoms.

Question 11539

Topic: 2. Trauma

A 32-year-old male sustains a closed tibia fracture. Clinical exam raises suspicion for compartment syndrome. His blood pressure is 110/70 mmHg. Intracompartmental pressures are measured at 45 mmHg in the anterior compartment and 35 mmHg in the deep posterior compartment. What is the most appropriate next step in management?

. Observation and recheck in 2 hours
. Four-compartment fasciotomy
. Single-incision fasciotomy
. Elevation of the leg above the heart level
. Bivalve the cast and observe

Correct Answer & Explanation

. Observation and recheck in 2 hours

Explanation

The delta P (diastolic BP minus compartment pressure) is 70 - 45 = 25 mmHg. A delta P less than 30 mmHg is an absolute indication for emergency four-compartment fasciotomy.

Question 11540

Topic: 2. Trauma
In a 25-year-old patient with a displaced femoral neck fracture (Pauwels Type III), what is the biomechanical rationale for using a sliding hip screw with a derotation screw rather than three parallel cancellous screws?
. Increased resistance to vertical shear forces
. Better preservation of the medial circumflex femoral artery
. Decreased risk of avascular necrosis
. Elimination of fracture site compression
. Improved rotational control in osteoporotic bone

Correct Answer & Explanation

. Increased resistance to vertical shear forces

Explanation

Pauwels Type III fractures have a high vertical shear angle (greater than 50 degrees). A sliding hip screw provides a fixed-angle construct that better resists vertical shear forces compared to parallel screws, reducing the risk of varus collapse.

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