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2. Trauma MCQs

Practice Set 616 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 12301

Topic: 2. Trauma

A 40-year-old patient undergoes open reduction and internal fixation of a distal tibia fracture with a locking plate. Compared to conventional non-locking plating, which statement best describes the primary biomechanical advantage of a locking plate in promoting fracture healing, particularly in osteoporotic bone or comminuted fractures?

. Locking plates provide superior interfragmentary compression, accelerating primary bone healing
. Locking plates create a fixed-angle construct, acting as an internal fixator and promoting indirect (secondary) bone healing
. Locking plates are designed to be stiffer, completely eliminating micromotion at the fracture site
. Locking plates minimize stripping of the periosteum due to screw-bone interface at each hole
. Locking plates inherently increase blood supply to the fracture by preventing soft tissue dissection

Correct Answer & Explanation

. Locking plates create a fixed-angle construct, acting as an internal fixator and promoting indirect (secondary) bone healing

Explanation

Locking plates differ fundamentally from conventional plates. Conventional plates rely on friction between the plate and bone, generated by interfragmentary compression from screw tightening, to provide stability. Locking plates, however, have screws that thread into the plate, creating a fixed-angle construct. This essentially acts as an internal fixator, maintaining reduction and stability without requiring direct compression of the plate to the bone. This 'bridge plating' technique allows for controlled micromotion at the fracture site, which promotes indirect (secondary) bone healing through callus formation, rather than the primary healing mechanism often sought with absolute stability (e.g., lag screws). This is particularly advantageous in comminuted fractures where interfragmentary compression is difficult to achieve, or in osteoporotic bone where screw pullout strength is compromised with conventional plating. While locking plates also offer periosteal sparing by not requiring tight contact, their primary biomechanical advantage related to healing mechanism is the fixed-angle construct promoting indirect healing. They do not provide superior interfragmentary compression (often the opposite), do not completely eliminate micromotion (which is beneficial for secondary healing), and do not inherently increase blood supply beyond the benefit of less periosteal stripping.

Question 12302

Topic: 2. Trauma

A 32-year-old male sustains a closed Schatzker VI tibial plateau fracture. He has tense swelling and exquisite pain with passive stretch of the hallux. Compartment pressures measure 45 mmHg with a diastolic BP of 70 mmHg. What is the next best step?

. Ice, elevation, and re-evaluate in 2 hours
. Immediate four-compartment fasciotomy
. Spanning external fixation alone
. Immediate open reduction and internal fixation
. Non-invasive vascular studies

Correct Answer & Explanation

. Immediate four-compartment fasciotomy

Explanation

Delta pressure (Diastolic BP - compartment pressure) is 25 mmHg, which is less than 30 mmHg, indicating acute compartment syndrome. Immediate four-compartment fasciotomy is required to prevent irreversible ischemic muscle damage.

Question 12303

Topic: 2. Trauma

Which of the following fixation constructs relies primarily on primary (contact) bone healing without the formation of a visible fracture callus?

. Bridge plating of a comminuted femur fracture
. Intramedullary nailing of a tibial shaft fracture
. Absolute rigid compression plating of a transverse radius fracture
. External fixation of a distal radius fracture
. Casting of a non-displaced tibia fracture

Correct Answer & Explanation

. Absolute rigid compression plating of a transverse radius fracture

Explanation

Absolute stability achieved via compression plating eliminates interfragmentary strain, leading to direct (primary) bone healing via cutting cones. Constructs providing relative stability heal via secondary bone healing with callus formation.

Question 12304

Topic: 2. Trauma
A 30-year-old male sustains a vertically oriented, displaced basicervical femoral neck fracture (Pauwels III). What biomechanical complication is most highly associated with this fracture pattern compared to horizontal fracture patterns?
. Nonunion due to high shear forces
. Avascular necrosis due to medial circumflex artery transection
. Heterotopic ossification
. Implant infection
. Chondrolysis

Correct Answer & Explanation

. Nonunion due to high shear forces

Explanation

Pauwels III fractures have a fracture angle >50 degrees, resulting in tremendous shear forces across the fracture line. This significantly increases the risk of varus collapse, fixation failure, and nonunion compared to horizontal patterns.

Question 12305

Topic: 2. Trauma

A 28-year-old male sustains a closed tibial shaft fracture. He develops severe pain out of proportion. His blood pressure is 110/70 mmHg. Compartment pressure measurement shows an anterior compartment pressure of 45 mmHg. What is the most appropriate management?

. Observation and elevate leg
. Ice and pain medication
. Four-compartment fasciotomy
. Bivalve cast and discharge
. Intravenous antibiotics

Correct Answer & Explanation

. Four-compartment fasciotomy

Explanation

Delta P is calculated as diastolic blood pressure minus compartment pressure (70 - 45 = 25 mmHg). A Delta P of less than 30 mmHg is an absolute indication for emergency four-compartment fasciotomy to prevent irreversible muscle necrosis.

Question 12306

Topic: 2. Trauma

A 25-year-old polytrauma patient sustains a closed tibial shaft fracture. He is intubated and sedated. Intracompartmental pressure testing is performed. Which of the following thresholds is most universally accepted as an indication for four-compartment fasciotomy?

. Absolute compartment pressure greater than 20 mmHg
. Absolute compartment pressure greater than 30 mmHg
. Differential pressure (Diastolic BP - Compartment Pressure) less than 30 mmHg
. Differential pressure (Mean Arterial BP - Compartment Pressure) less than 40 mmHg
. Differential pressure (Systolic BP - Compartment Pressure) less than 30 mmHg

Correct Answer & Explanation

. Differential pressure (Diastolic BP - Compartment Pressure) less than 30 mmHg

Explanation

A differential pressure (Delta P) of less than 30 mmHg (Diastolic blood pressure minus compartment pressure) is the most reliable indicator for compartment syndrome requiring fasciotomy. Absolute pressure thresholds are less reliable due to fluctuations in systemic perfusion.

Question 12307

Topic: 2. Trauma
A 6-year-old boy presents with a displaced Gartland Type III supracondylar humerus fracture. His hand is pink but pulseless. Capillary refill is less than 2 seconds. What is the most appropriate initial management?
. Immediate open exploration of the brachial artery
. CT angiography of the upper extremity
. Closed reduction and percutaneous pinning, followed by reassessment of the pulse
. Fasciotomy of the forearm to prevent compartment syndrome
. Observation with arm elevation and splinting

Correct Answer & Explanation

. Closed reduction and percutaneous pinning, followed by reassessment of the pulse

Explanation

In a "pink, pulseless" hand associated with a pediatric supracondylar humerus fracture, the initial step is urgent closed reduction and percutaneous pinning. The pulse often returns after fracture reduction relieves kinking or compression of the brachial artery.

Question 12308

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the trauma bay with a suspected pelvic ring injury after a motorcycle crash. An AP pelvis radiograph demonstrates a widened pubic symphysis (4 cm) and disruption of the anterior sacroiliac ligaments, but intact posterior sacroiliac ligaments. What is the Young-Burgess classification of this injury?
. Anterior-Posterior Compression (APC) I
. Anterior-Posterior Compression (APC) II
. Anterior-Posterior Compression (APC) III
. Lateral Compression (LC) I
. Vertical Shear (VS)

Correct Answer & Explanation

. Anterior-Posterior Compression (APC) II

Explanation

An APC II injury is characterized by symphyseal diastasis >2.5 cm and disruption of the anterior sacroiliac ligaments, sacrospinous, and sacrotuberous ligaments, while the posterior SI ligaments remain intact. This causes rotational instability but maintains vertical stability.

Question 12309

Topic: 2. Trauma

A 32-year-old male presents with a closed tibial shaft fracture following a high-energy trauma. Which of the following continuous compartment pressure measurements is most specific for diagnosing acute compartment syndrome?

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

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mm Hg

Explanation

The delta P (Diastolic BP minus compartment pressure) of less than 30 mm Hg is the most reliable and specific indicator for acute compartment syndrome. Absolute pressure readings alone have higher false-positive rates and can lead to unnecessary fasciotomies.

Question 12310

Topic: 2. Trauma

In the acute management of a hemodynamically unstable patient with an anterior-posterior compression (APC) pelvic ring injury, a pelvic binder should be positioned over which anatomical landmark for optimal volume reduction?

. Anterior superior iliac spines
. Iliac crests
. Greater trochanters
. Pubic symphysis
. Femoral shafts

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders must be centered directly over the greater trochanters to effectively close the pelvic ring and reduce bleeding in open-book fractures. Placement over the iliac crests is mechanically disadvantaged and can paradoxically widen the pelvis.

Question 12311

Topic: 2. Trauma
According to ATLS protocols, which of the following vital sign changes is the most defining and sensitive indicator of transitioning into class III hemorrhagic shock?
. Tachycardia > 100 bpm
. Decreased systolic blood pressure
. Decreased pulse pressure
. Altered mental status
. Capillary refill > 2 seconds

Correct Answer & Explanation

. Decreased systolic blood pressure

Explanation

Class III hemorrhagic shock (indicating 30-40% blood volume loss) is defined by the onset of a drop in systolic blood pressure. Tachycardia and decreased pulse pressure manifest earlier in Class II shock.

Question 12312

Topic: 2. Trauma

A 75-year-old osteoporotic female sustains a highly unstable intertrochanteric femur fracture characterized by a detached lesser trochanter and a large posteromedial defect. Which type of implant provides the most biomechanically stable fixation?

. Multiple parallel cancellous screws
. Dynamic hip screw with a 2-hole side plate
. Cephalomedullary nail
. Proximal femoral locking plate
. Bipolar hemiarthroplasty

Correct Answer & Explanation

. Cephalomedullary nail

Explanation

Unstable intertrochanteric fractures, particularly those with a loss of posteromedial support or reverse obliquity patterns, are best treated with a cephalomedullary nail. Its intramedullary position reduces the bending moment and prevents excessive medialization of the femoral shaft.

Question 12313

Topic: 2. Trauma
A 32-year-old male sustains a closed, displaced talar neck fracture (Hawkins Type III) and undergoes urgent open reduction and internal fixation. At 8 weeks postoperatively, an AP mortise radiograph reveals a distinct subchondral radiolucent band in the talar dome. What does this radiographic finding indicate?
. Impending avascular necrosis and structural collapse of the talar body
. Progressive subchondral collapse indicating early post-traumatic arthritis
. Active revascularization and intact blood supply to the talar body
. Subacute deep infection and osteomyelitis of the talar dome
. Hypertrophic nonunion of the talar neck requiring revision surgery

Correct Answer & Explanation

. Active revascularization and intact blood supply to the talar body

Explanation

A subchondral radiolucent band in the talar dome seen 6 to 8 weeks post-injury is known as the Hawkins sign. It represents localized subchondral osteopenia secondary to hyperemia, indicating that the vascularity to the talar body is intact and effectively ruling out avascular necrosis.

Question 12314

Topic: 2. Trauma

A 40-year-old male sustains a closed comminuted tibia fracture treated with reamed intramedullary nailing. Overnight, he develops intractable leg pain exacerbated by passive stretch of his great toe. Compartment manometry reveals an anterior compartment pressure of 35 mmHg, while his concurrent diastolic blood pressure is 60 mmHg. What is the mandatory next step?

. Immediate open four-compartment fasciotomy of the leg
. Administration of intravenous mannitol and extreme elevation of the extremity
. Release of all restrictive dressings and continued hourly clinical examinations
. Placement of an epidural catheter for aggressive pain management
. Immediate removal of the intramedullary nail and conversion to external fixation

Correct Answer & Explanation

. Immediate open four-compartment fasciotomy of the leg

Explanation

The patient demonstrates classic clinical symptoms of acute compartment syndrome combined with a Delta pressure (diastolic pressure minus compartment pressure) of 25 mmHg. A Delta pressure of 30 mmHg or less, alongside clinical findings, is an absolute indication for emergent four-compartment fasciotomy to prevent irreversible ischemic necrosis.

Question 12315

Topic: 2. Trauma

In the context of locked plating for a comminuted diaphyseal fracture, increasing the working length of the plate has which of the following biomechanical effects?

. Increases construct stiffness
. Decreases the strain at the fracture site
. Increases the risk of screw pullout
. Promotes primary bone healing
. Decreases interfragmentary motion

Correct Answer & Explanation

. Decreases the strain at the fracture site

Explanation

Increasing the working length of a locking plate (the distance between the innermost screws on either side of the fracture) decreases the stiffness of the construct. This distributes strain over a larger area, thereby decreasing the strain at the fracture site and promoting secondary bone healing through callus formation.

Question 12316

Topic: 2. Trauma

A 25-year-old male sustains a closed tibia fracture. Which of the following pressure measurements is most indicative of the need for an emergent fasciotomy?

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

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The delta pressure (Diastolic BP - Compartment Pressure) is the most reliable indicator of compartment syndrome. A delta pressure of less than 30 mmHg signifies inadequate tissue perfusion and is an absolute indication for emergent fasciotomy.

Question 12317

Topic: 2. Trauma

A 24-year-old male with bilateral femur fractures develops respiratory distress, confusion, and a petechial rash on his chest 36 hours post-injury. What is the major pathophysiologic mechanism leading to the pulmonary manifestations of this syndrome?

. Deep vein thrombosis leading to pulmonary embolism
. Free fatty acids causing endothelial damage and acute respiratory distress syndrome (ARDS)
. Cardiogenic shock secondary to hypovolemia
. Bacterial pneumonia secondary to prolonged recumbency
. Direct pulmonary contusion from the initial trauma

Correct Answer & Explanation

. Free fatty acids causing endothelial damage and acute respiratory distress syndrome (ARDS)

Explanation

The patient has Fat Embolism Syndrome (FES). The pathophysiology involves both mechanical obstruction by fat globules and a biochemical response where fat breaks down into toxic free fatty acids (FFAs). FFAs cause direct endothelial damage in the pulmonary circulation, leading to capillary leak and ARDS.

Question 12318

Topic: Lower Extremity Trauma

During a posteromedial approach to the proximal tibia for fixation of a complex Schatzker IV plateau fracture, the surgeon develops the primary deep interval to expose the posterior aspect of the medial tibial condyle. Which two structures define this standard internervous/anatomical interval?

. Tibialis anterior and extensor digitorum longus
. Medial head of the gastrocnemius and the pes anserinus (semimembranosus)
. Lateral head of the gastrocnemius and the popliteus
. Soleus and flexor hallucis longus
. Tibialis posterior and flexor digitorum longus

Correct Answer & Explanation

. Medial head of the gastrocnemius and the pes anserinus (semimembranosus)

Explanation

The classic posteromedial approach to the tibial plateau utilizes the interval between the medial head of the gastrocnemius (which is retracted posterolaterally to protect the neurovascular bundle) and the pes anserinus / semimembranosus (which is retracted anteromedially). This safely exposes the posteromedial cortex of the proximal tibia.

Question 12319

Topic: 2. Trauma

According to Perren's strain theory of fracture healing, what is the maximum interfragmentary strain that will still permit primary (osteonal/contact) bone healing?

. Less than 2%
. 2% to 10%
. 10% to 30%
. 30% to 50%
. Greater than 50%

Correct Answer & Explanation

. Less than 2%

Explanation

Perren's strain theory dictates that primary (direct or osteonal) bone healing occurs when absolute stability is achieved. This requires an interfragmentary strain of less than 2%. Strains between 2% and 10% tolerate the formation of cartilage (secondary bone healing via callus formation), while strains above 10% result in granulation tissue and eventual nonunion.

Question 12320

Topic: Pelvic & Acetabular Trauma
A 28-year-old male is brought to the ED after a severe crush injury. Radiographs show a widened pubic symphysis of 3.5 cm and widening of the right sacroiliac joint anteriorly and posteriorly. This corresponds to a Young-Burgess Anteroposterior Compression (APC) Type III injury. Which of the following ligamentous structures is disrupted in an APC III injury but typically remains intact in an APC II injury?
. Anterior sacroiliac ligament
. Sacrospinous ligament
. Sacrotuberous ligament
. Posterior sacroiliac ligament
. Symphyseal ligaments

Correct Answer & Explanation

. Posterior sacroiliac ligament

Explanation

In the Young-Burgess classification, an APC I injury involves only symphyseal widening (< 2.5 cm). APC II involves rupture of the symphysis, anterior sacroiliac ligaments, sacrotuberous, and sacrospinous ligaments, but the posterior sacroiliac ligaments remain intact (opening book). APC III implies a complete disruption, including the robust posterior sacroiliac ligaments, leading to full hemipelvis instability.

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