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2. Trauma MCQs

Practice Set 612 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 12221

Topic: 2. Trauma

A 32-year-old male sustains a closed tibial shaft fracture and develops compartment syndrome. The deep posterior compartment is most frequently missed during fasciotomy. What muscle's function must be evaluated to assess for deep posterior compartment ischemia?

. Tibialis anterior
. Extensor hallucis longus
. Flexor hallucis longus
. Peroneus brevis
. Gastrocnemius

Correct Answer & Explanation

. Flexor hallucis longus

Explanation

The deep posterior compartment of the leg contains the tibialis posterior, flexor digitorum longus, and flexor hallucis longus (FHL). Pain with passive extension of the great toe (stretching the FHL) is a key clinical indicator of deep posterior compartment ischemia.

Question 12222

Topic: 2. Trauma
According to the Gustilo-Anderson classification, a highly contaminated open tibial shaft fracture from a farm injury with a 12 cm laceration and extensive soft tissue stripping, but with adequate periosteal coverage and no arterial injury, is classified as:
. Type II
. Type IIIA
. Type IIIB
. Type IIIC
. Type IV

Correct Answer & Explanation

. Type IIIA

Explanation

A Gustilo-Anderson Type IIIA fracture is a high-energy open fracture with extensive soft tissue laceration (>10 cm), high contamination (e.g., farm injury), or crushing, but importantly it maintains adequate soft tissue bone coverage. If a local or free flap were required for coverage, it would be IIIB. Arterial injury requiring repair makes it IIIC.

Question 12223

Topic: 2. Trauma
A 25-year-old male is brought to the ER after a motor vehicle collision. His pelvis is fractured, BP is 85/50 mmHg, HR is 130 bpm, and respiratory rate is 28 breaths/min. His urine output is 10 mL/hr, and he appears anxious and confused. According to the ATLS classification, what class of hemorrhagic shock is this patient in?
. Class I
. Class II
. Class III
. Class IV
. Class V

Correct Answer & Explanation

. Class III

Explanation

The patient is in Class III hemorrhagic shock. Class III shock is characterized by a heart rate >120 bpm, decreased blood pressure, respiratory rate 30-40, decreased urine output (5-15 mL/hr), and confusion/anxiety. This corresponds to an estimated blood volume loss of 31-40%. Class IV involves HR >140, unmeasurable diastolic BP, and lethargy, representing >40% loss.

Question 12224

Topic: 2. Trauma

To maximize the biomechanical stiffness of an external fixator construct for a highly comminuted tibia fracture, which of the following modifications is most effective?

. Decreasing the pin diameter
. Increasing the distance between the fracture site and the closest pins
. Decreasing the distance between the bone and the longitudinal rod
. Using half-pins instead of transfixing pins
. Removing a second longitudinal rod

Correct Answer & Explanation

. Decreasing the distance between the bone and the longitudinal rod

Explanation

The stiffness of an external fixator is significantly increased by decreasing the bone-to-rod distance. Additionally, increasing pin diameter exponentially increases stiffness, as it is proportional to the radius to the fourth power.

Question 12225

Topic: 2. Trauma

The ischemic cascade in acute compartment syndrome rapidly causes irreversible muscle necrosis. What is the currently accepted clinical threshold for the "delta pressure" below which a fasciotomy is strongly recommended?

. 10 mmHg
. 20 mmHg
. 30 mmHg
. 45 mmHg
. 60 mmHg

Correct Answer & Explanation

. 30 mmHg

Explanation

A delta pressure (diastolic blood pressure minus the measured compartment pressure) of less than 30 mmHg indicates critically impaired capillary perfusion. This objective measurement is the widely accepted absolute indication for an urgent decompressive fasciotomy.

Question 12226

Topic: 2. Trauma

In the evaluation of acute compartment syndrome, the delta pressure is considered the most reliable indicator for fasciotomy. How is the delta pressure calculated?

. Mean arterial pressure minus compartment pressure
. Systolic blood pressure minus compartment pressure
. Diastolic blood pressure minus compartment pressure
. Systolic blood pressure minus mean arterial pressure
. Capillary wedge pressure minus compartment pressure

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure

Explanation

The delta pressure is calculated by subtracting the measured compartment pressure from the diastolic blood pressure. A delta pressure of less than 30 mmHg is the generally accepted threshold indicating the need for emergent fasciotomy.

Question 12227

Topic: 2. Trauma

A 25-year-old male sustains bilateral femoral shaft fractures. 48 hours later, he becomes confused, tachypneic, and hypoxemic. According to Gurd's criteria for Fat Embolism Syndrome, which of the following represents a major diagnostic criterion?

. Unexplained tachycardia
. Fever greater than 38.5 degrees Celsius
. Sudden drop in hematocrit
. Petechial rash over the axillae and thorax
. Oliguria

Correct Answer & Explanation

. Petechial rash over the axillae and thorax

Explanation

Gurd's major criteria for Fat Embolism Syndrome include a petechial rash, respiratory insufficiency, and cerebral involvement (confusion/coma). Tachycardia, fever, and drop in hematocrit are considered minor criteria.

Question 12228

Topic: 2. Trauma

When inserting a cortical screw for fracture fixation, which of the following geometric parameters of the screw is the most critical determinant of its pullout strength?

. Inner (core) diameter
. Thread pitch
. Outer (major) diameter
. Screw head diameter
. Core taper angle

Correct Answer & Explanation

. Outer (major) diameter

Explanation

The pullout strength of a screw is primarily determined by the outer (major) diameter of its thread. Other factors include thread pitch, length of engagement, and bone density, but increasing the major diameter provides the most significant increase in pullout resistance.

Question 12229

Topic: 2. Trauma

A 25-year-old male with a comminuted tibia fracture complains of pain out of proportion. His diastolic blood pressure is 80 mmHg. What intracompartmental pressure reading strongly supports the diagnosis of acute compartment syndrome?

. Absolute pressure > 20 mmHg
. Absolute pressure > 25 mmHg
. Delta P < 30 mmHg
. Delta P > 45 mmHg
. Mean arterial pressure minus compartment pressure < 20 mmHg

Correct Answer & Explanation

. Delta P < 30 mmHg

Explanation

Acute compartment syndrome is definitively diagnosed when the Delta P (Diastolic Blood Pressure minus Intracompartmental Pressure) drops below 30 mmHg. Relying purely on absolute pressure measurements can lead to overdiagnosis.

Question 12230

Topic: Pelvic & Acetabular Trauma

In a hemodynamically unstable trauma patient with an anteroposterior compression (APC) pelvic ring injury, at what anatomical landmark should a pelvic binder be centered to effectively reduce pelvic volume?

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

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders must be centered directly over the greater trochanters to generate the appropriate force vector to close the pubic diastasis. Placement over the iliac crests is ineffective and can paradoxically open the pelvis further.

Question 12231

Topic: Lower Extremity Trauma

In performing a transfemoral amputation, myodesis is crucial to prevent adductor roll and optimize prosthetic fitting. To which structure should the adductor magnus be secured?

. Iliotibial band
. Linea aspera
. Lateral femur
. Distal posterior femur
. Anterior cortex of the distal femur

Correct Answer & Explanation

. Lateral femur

Explanation

In a transfemoral amputation, the adductor magnus is typically secured to the lateral aspect of the distal femur (adductor myodesis). This preserves the biomechanical advantage of the adductors and prevents an abduction contracture.

Question 12232

Topic: 2. Trauma

A 45-year-old female develops severe burning pain, allodynia, and skin color changes in her hand after a distal radius fracture without any identifiable major nerve injury. What is the most likely diagnosis?

. Complex Regional Pain Syndrome Type 2
. Complex Regional Pain Syndrome Type 1
. Compartment Syndrome
. Neuroma-in-continuity
. Glomus tumor

Correct Answer & Explanation

. Complex Regional Pain Syndrome Type 1

Explanation

Complex Regional Pain Syndrome (CRPS) Type 1 occurs without a definable major nerve injury (formerly called reflex sympathetic dystrophy). CRPS Type 2 (formerly causalgia) is associated with a distinct, identifiable major peripheral nerve injury.

Question 12233

Topic: Pelvic & Acetabular Trauma
A 30-year-old male presents after a motorcycle collision with a hemodynamically unstable anteroposterior compression (APC) type III pelvic ring injury. After a pelvic binder is placed, he remains hypotensive despite aggressive fluid resuscitation. FAST exam is negative. What is the most appropriate next step in acute management?
. Immediate open reduction and internal fixation of the symphysis pubis
. Exploratory laparotomy
. Preperitoneal pelvic packing
. Application of a pelvic C-clamp
. Retrograde urethrogram

Correct Answer & Explanation

. Preperitoneal pelvic packing

Explanation

In a hemodynamically unstable patient with a pelvic ring injury despite binder application and adequate resuscitation (and a negative FAST exam), preperitoneal pelvic packing or pelvic angiography with embolization is indicated. Packing directly addresses the most common source of bleeding (venous plexus). A C-clamp is contraindicated in APC injuries.

Question 12234

Topic: 2. Trauma

A 24-year-old professional soccer player sustains an acute fracture at the metaphyseal-diaphyseal junction of the fifth metatarsal. He wishes to return to play as soon as possible. What is the most appropriate management?

. Non-weight bearing in a short leg cast for 6 weeks
. Weight bearing as tolerated in a hard-soled shoe
. Intramedullary screw fixation
. Tension band wiring
. Plate and screw fixation

Correct Answer & Explanation

. Intramedullary screw fixation

Explanation

A fracture at the metaphyseal-diaphyseal junction of the fifth metatarsal is a Jones fracture, which occurs in a vascular watershed area prone to nonunion. In elite athletes, early intramedullary screw fixation is the standard of care to reduce the risk of nonunion and allow a predictable, rapid return to play.

Question 12235

Topic: 2. Trauma

A 25-year-old man sustains a severe closed tibial plateau fracture. He is complaining of out-of-proportion pain that is exacerbated by passive stretch of the hallux. His blood pressure is 110/70 mmHg. Compartment pressures are measured using a slit catheter. Which of the following thresholds is widely accepted as an absolute indication for an emergency four-compartment fasciotomy?

. Absolute anterior compartment pressure of 20 mmHg
. Absolute deep posterior compartment pressure of 25 mmHg
. Difference between diastolic blood pressure and compartment pressure of 30 mmHg or less
. Difference between systolic blood pressure and compartment pressure of 40 mmHg or less
. Difference between mean arterial pressure and compartment pressure of 50 mmHg or less

Correct Answer & Explanation

. Difference between diastolic blood pressure and compartment pressure of 30 mmHg or less

Explanation

Acute compartment syndrome is diagnosed when tissue pressure exceeds perfusion pressure. A Delta P (Diastolic Blood Pressure minus absolute Compartment Pressure) of 30 mmHg or less is the widely accepted standard indication for emergent fasciotomy, as it accounts for the patient's systemic perfusion pressure rather than relying strictly on an absolute pressure number.

Question 12236

Topic: 2. Trauma

A 32-year-old male sustains a closed tibial shaft fracture. Two hours later, he develops severe pain out of proportion to the injury. Which of the following is the earliest and most sensitive physical exam finding in acute compartment syndrome?

. Absent distal pulses
. Paresthesias in the first web space
. Pain with passive stretch of the toes
. Palpable firmness of the compartment
. Motor paralysis of the deep posterior compartment

Correct Answer & Explanation

. Pain with passive stretch of the toes

Explanation

Pain with passive stretch of the muscles in the involved compartment is classically the most sensitive and earliest clinical sign of acute compartment syndrome. Pulselessness and paralysis are late, often irreversible findings.

Question 12237

Topic: 2. Trauma

A 42-year-old female sustains a lateral compression type II (LC-2) pelvic ring injury. According to the Young-Burgess classification, which of the following specifically defines an LC-2 fracture pattern?

. Sacral compression fracture with ipsilateral rami fractures
. Anterior ring injury with an ipsilateral crescent fracture of the ilium
. Contralateral open book (APC) injury
. Bilateral pubic rami fractures with a floating symphysis
. Sacroiliac joint disruption with a completely unstable hemipelvis

Correct Answer & Explanation

. Anterior ring injury with an ipsilateral crescent fracture of the ilium

Explanation

A Lateral Compression type II (LC-2) fracture is characterized by an anterior ring injury combined with an ipsilateral crescent fracture of the posterior ilium. An LC-1 involves a sacral compression fracture instead of an iliac wing fracture.

Question 12238

Topic: 2. Trauma

A 24-year-old male has a displaced fracture of the proximal pole of the scaphoid. What anatomical characteristic is the primary reason this specific fracture pattern carries a high rate of nonunion and avascular necrosis?

. High ratio of cortical to cancellous bone
. Inability to achieve rigid immobilization
. Retrograde intraosseous blood supply
. Tethering by the radioscaphocapitate ligament
. Lack of periosteum around the scaphoid

Correct Answer & Explanation

. Retrograde intraosseous blood supply

Explanation

The major blood supply to the scaphoid enters distally and flows proximally, creating a retrograde intraosseous blood supply. Fractures of the proximal pole mechanically isolate this segment from its blood supply, predisposing it to ischemia.

Question 12239

Topic: 2. Trauma

A 25-year-old male sustains a closed tibial shaft fracture. Within 12 hours, he develops severe pain out of proportion to the injury. Intracompartmental pressure measurements reveal a pressure of 45 mmHg with a diastolic blood pressure of 60 mmHg. Which of the following is the most appropriate management?

. Elevate the leg above the heart and observe
. Bivalve the cast and reassess in 2 hours
. Perform a single-incision, four-compartment fasciotomy
. Perform a two-incision, four-compartment fasciotomy
. Administer IV mannitol and monitor

Correct Answer & Explanation

. Perform a two-incision, four-compartment fasciotomy

Explanation

The patient has acute compartment syndrome indicated by a delta pressure less than 30 mmHg (60 - 45 = 15 mmHg). A two-incision, four-compartment fasciotomy is the gold standard surgical treatment to adequately decompress the leg.

Question 12240

Topic: 2. Trauma

When inserting a cortical screw for fracture fixation, which of the following modifications will most significantly increase the pull-out strength of the screw?

. Increasing the core diameter while keeping outer diameter constant
. Decreasing the thread pitch
. Increasing the outer diameter of the screw
. Using a self-tapping screw instead of a non-tapping screw
. Decreasing the length of the screw engagement

Correct Answer & Explanation

. Increasing the outer diameter of the screw

Explanation

Pull-out strength of a screw is most significantly influenced by the major (outer) diameter of the screw. Decreasing thread pitch also increases pull-out strength, but increasing the outer diameter has a much larger exponential effect.

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