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2. Trauma MCQs

Practice Set 619 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 12361

Topic: Pelvic & Acetabular Trauma
In the acute management of a hemodynamically unstable patient with an anteroposterior compression Type III (APC-III) pelvic ring injury, what is the anatomically correct placement of a pelvic binder?
. Over the iliac crests
. At the level of the greater trochanters
. Over the anterior superior iliac spines
. Just above the umbilicus
. Distal to the lesser trochanters

Correct Answer & Explanation

. At the level of the greater trochanters

Explanation

Pelvic binders should be placed at the level of the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests is less effective and may inadvertently cause paradoxical widening of the true pelvis.

Question 12362

Topic: 2. Trauma

When treating an intertrochanteric femur fracture with a sliding hip screw, the Tip-Apex Distance (TAD) is measured to predict the risk of lag screw cut-out. To minimize this risk, the combined TAD on AP and lateral radiographs should ideally be less than:

. 10 mm
. 15 mm
. 25 mm
. 35 mm
. 45 mm

Correct Answer & Explanation

. 25 mm

Explanation

Baumgaertner described the Tip-Apex Distance (TAD) as a key predictor of lag screw cut-out in intertrochanteric fractures. A combined TAD of less than 25 mm on AP and lateral radiographs is associated with a significantly reduced risk of failure.

Question 12363

Topic: 2. Trauma
A 35-year-old male is brought to the trauma bay in hemorrhagic shock following a high-speed motorcycle collision. Pelvic radiographs reveal an anteroposterior compression (APC) Type III pelvic ring injury. What is the most common anatomical source of massive hemorrhage in this setting?
. Superior gluteal artery
. Internal pudendal artery
. Presacral venous plexus
. Obturator artery
. External iliac vein

Correct Answer & Explanation

. Presacral venous plexus

Explanation

The most common source of significant hemorrhage in pelvic ring disruptions is venous bleeding, primarily from the presacral venous plexus and fractured cancellous bone surfaces (accounting for 80-90% of bleeding). Arterial bleeding (e.g., from the superior gluteal or internal pudendal arteries) occurs less frequently (10-20%) but can be rapidly fatal if not embolized.

Question 12364

Topic: 2. Trauma
A 30-year-old male presents with a closed tibia fracture and severe leg pain out of proportion to injury. His blood pressure is 120/70 mmHg. The anterior compartment pressure is measured at 45 mmHg. Based on the concept of Delta P (∆P), what is his calculated ∆P, and is an emergency fasciotomy indicated?
. ∆P is 75 mmHg; fasciotomy is not indicated
. ∆P is 25 mmHg; fasciotomy is indicated
. ∆P is 25 mmHg; fasciotomy is not indicated
. ∆P is 45 mmHg; fasciotomy is indicated
. ∆P is 35 mmHg; fasciotomy is not indicated

Correct Answer & Explanation

. ∆P is 25 mmHg; fasciotomy is indicated

Explanation

Delta P (∆P) is defined as the diastolic blood pressure minus the absolute compartment pressure. In this patient, 70 mmHg (diastolic BP) - 45 mmHg = 25 mmHg. A ∆P of less than 30 mmHg signifies inadequate tissue perfusion and is an absolute indication for emergency fasciotomy.

Question 12365

Topic: 2. Trauma
The Pauwels classification of femoral neck fractures categorizes fractures based on the angle of the fracture line relative to the horizontal plane. Why do Pauwels Type III fractures (angle > 50 degrees) classically have a higher rate of nonunion compared to Type I fractures?
. They predominantly experience compressive forces across the fracture site
. They inherently disrupt the primary blood supply from the foveal artery
. They experience increased vertical shear forces at the fracture interface
. They have a higher degree of intra-articular hematoma leading to tamponade
. They occur exclusively in severely osteoporotic bone

Correct Answer & Explanation

. They experience increased vertical shear forces at the fracture interface

Explanation

Pauwels classification reflects the mechanical forces acting on the fracture. Type I fractures (< 30 degrees) experience mostly compressive forces, which promote healing. Type III fractures (> 50 degrees) are highly vertically oriented, meaning weight-bearing translates primarily into vertical shear forces across the fracture site, causing instability and significantly increasing the risk of nonunion and hardware failure.

Question 12366

Topic: 2. Trauma

Which of the following recombinant human bone morphogenetic proteins (rhBMPs) is an FDA-approved osteoinductive adjunct for the treatment of acute open tibial shaft fractures?

. rhBMP-2
. rhBMP-3
. rhBMP-4
. rhBMP-7
. rhBMP-9

Correct Answer & Explanation

. rhBMP-2

Explanation

rhBMP-2 is FDA approved for use in acute open tibial shaft fractures treated with an intramedullary nail. rhBMP-7 was previously approved under a humanitarian device exemption for recalcitrant nonunions but is no longer commercially available.

Question 12367

Topic: 2. Trauma

The fundamental pathophysiological mechanism precipitating acute compartment syndrome is related to:

. Decreased local arterial pressure compared to systemic pressure
. Increased local venous pressure exceeding arterial capillary pressure
. Decreased interstitial tissue pressure causing massive cellular edema
. Increased capillary permeability leading to rapid venous return
. Direct toxic effect of myoglobin on local vascular endothelium

Correct Answer & Explanation

. Increased local venous pressure exceeding arterial capillary pressure

Explanation

Compartment syndrome occurs when elevated tissue pressure exceeds the venous outflow pressure, leading to capillary collapse. This creates a local state where venous pressure exceeds arterial capillary pressure, resulting in anoxia, ischemia, and eventual tissue necrosis.

Question 12368

Topic: 2. Trauma

In a polytrauma patient, which of the following laboratory parameters is the most reliable indicator of adequate resuscitation and clearance for early total care fracture fixation?

. Serum base excess of -6 mEq/L
. Serum lactate less than 2.0 mmol/L
. Hemoglobin of 8.5 g/dL
. Urine output of 0.2 mL/kg/hr
. Platelet count of 75,000/mcL

Correct Answer & Explanation

. Serum lactate less than 2.0 mmol/L

Explanation

A serum lactate of less than 2.0 mmol/L and a normalizing base excess (between -2 and +2) are reliable markers of restored tissue perfusion. These physiological parameters help clear a polytrauma patient for definitive, prolonged orthopedic procedures instead of damage control orthopedics.

Question 12369

Topic: 2. Trauma
Based on the Gustilo-Anderson classification, an open tibial shaft fracture featuring a 6 cm clean laceration, adequate soft tissue coverage, and minimal periosteal stripping is best categorized as:
. Type I
. Type II
. Type IIIA
. Type IIIB
. Type IIIC

Correct Answer & Explanation

. Type II

Explanation

A Gustilo-Anderson Type II open fracture is characterized by a wound between 1 cm and 10 cm in length without extensive soft tissue damage, severe avulsion, or massive periosteal stripping. Type III fractures involve high-energy trauma, severe contamination, or wounds larger than 10 cm.

Question 12370

Topic: 2. Trauma

In a poly-trauma patient with a suspected compartment syndrome of the leg, what is the most widely accepted threshold for delta P (diastolic blood pressure minus intracompartmental pressure) to indicate the need for emergent fasciotomy?

. Delta P less than 10 mmHg
. Delta P less than 30 mmHg
. Delta P greater than 45 mmHg
. Absolute compartment pressure less than 15 mmHg
. Absolute compartment pressure greater than 20 mmHg

Correct Answer & Explanation

. Delta P less than 30 mmHg

Explanation

A delta P of less than 30 mmHg is the widely accepted threshold indicating inadequate tissue perfusion and the need for emergent fasciotomy. Using delta P is more accurate than an absolute pressure threshold, especially in hypotensive trauma patients.

Question 12371

Topic: 2. Trauma

The primary blood supply to the adult femoral head is crucial in evaluating the risk of avascular necrosis following a displaced femoral neck fracture. This critical vascularity is predominantly supplied by the:

. Artery of the ligamentum teres
. Inferior gluteal artery
. Deep branch of the medial femoral circumflex artery
. Descending branch of the lateral femoral circumflex artery
. First perforating branch of the profunda femoris

Correct Answer & Explanation

. Deep branch of the medial femoral circumflex artery

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) provides the primary blood supply to the adult femoral head. It ascends posterosuperiorly along the femoral neck to form the main retinacular vessels, making it highly vulnerable in displaced neck fractures.

Question 12372

Topic: 2. Trauma
A 35-year-old male presents with a pelvic ring injury after a high-speed motor vehicle collision. Radiographs reveal an APC-III (Anteroposterior Compression) injury. Which of the following neurologic structures is at the highest risk of injury in this specific fracture pattern?
. L5 nerve root
. S1 nerve root
. L4 nerve root
. Pudendal nerve
. Femoral nerve

Correct Answer & Explanation

. L5 nerve root

Explanation

APC (Anteroposterior compression) injuries, particularly APC-III with anterior and posterior sacroiliac joint disruption, most commonly injure the L5 nerve root as it passes over the sacral ala. Sacral fractures, which are more classically seen in lateral compression (LC) injuries, more commonly injure the S1 and S2 nerve roots.

Question 12373

Topic: 2. Trauma
A 28-year-old male sustains a closed tibia fracture. Which of the following pressure measurements is the most accurate diagnostic threshold for indicating an acute compartment syndrome requiring 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 < 40 mmHg
. Systolic blood pressure minus compartment pressure < 30 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

The delta pressure (ΔP) is defined as the diastolic blood pressure minus the absolute compartment pressure. A ΔP of less than 30 mmHg is considered the most reliable threshold for diagnosing acute compartment syndrome because it accounts for the patient's systemic perfusion pressure, mitigating false positives seen with absolute pressure measurements.

Question 12374

Topic: 2. Trauma

A 45-year-old female presents with a wrist injury after a fall. Radiographs demonstrate a displaced shear fracture of the volar articular margin of the distal radius with volar subluxation of the carpus. What is the correct eponym for this fracture pattern?

. Colles fracture
. Smith fracture
. Barton fracture (volar)
. Chauffeur fracture
. Die-punch fracture

Correct Answer & Explanation

. Barton fracture (volar)

Explanation

A volar Barton fracture is defined as an intra-articular shear fracture of the volar lip of the distal radius that is associated with volar subluxation or dislocation of the radiocarpal joint. A Smith fracture is classically an extra-articular distal radius fracture with volar angulation.

Question 12375

Topic: 2. Trauma

According to the Denis three-column classification of spinal fractures, which anatomical structure is considered the most posterior boundary of the middle column?

. The anterior longitudinal ligament
. The posterior half of the vertebral body
. The posterior longitudinal ligament
. The pedicles
. The ligamentum flavum

Correct Answer & Explanation

. The posterior longitudinal ligament

Explanation

In the Denis classification, the anterior column contains the ALL and anterior half of the vertebral body/annulus. The middle column comprises the posterior half of the body/annulus and the Posterior Longitudinal Ligament (PLL). The posterior column includes all structures posterior to the PLL (pedicles, facets, lamina, spinous processes, ligamentum flavum).

Question 12376

Topic: Lower Extremity Trauma
Based on the principles of biomechanics, if the outer radius of a solid cylindrical intramedullary nail is doubled while maintaining the same material, by what factor does its bending stiffness (area moment of inertia) increase?
. 2 times
. 4 times
. 8 times
. 16 times
. 32 times

Correct Answer & Explanation

. 16 times

Explanation

Bending stiffness of a solid cylinder is proportional to its area moment of inertia, which is calculated by the formula (π * r^4) / 4. Because the radius (r) is raised to the fourth power, doubling the radius (2^4) results in a 16-fold increase in the bending stiffness of the nail.

Question 12377

Topic: 2. Trauma

A 30-year-old male sustains a closed tibia fracture. The surgical team is concerned about acute compartment syndrome and measures the intracompartmental pressures. The 'delta P' is used to determine the need for fasciotomy. Delta P is defined as the difference between the compartment pressure and which of the following systemic values?

. Mean arterial pressure
. Systolic blood pressure
. Diastolic blood pressure
. Pulse pressure
. Central venous pressure

Correct Answer & Explanation

. Diastolic blood pressure

Explanation

Delta P is calculated as the Diastolic Blood Pressure minus the Intracompartmental Pressure. A Delta P of less than 30 mm Hg is an absolute indication for emergency fasciotomy. Using absolute compartment pressures alone can be misleading, especially in hypotensive trauma patients, whereas Delta P accounts for the driving perfusion pressure of the limb.

Question 12378

Topic: 2. Trauma

A 45-year-old heavy smoker is seen 9 months after a closed midshaft tibia fracture treated with an intramedullary nail. He complains of persistent pain. Radiographs demonstrate a visible fracture line with tapered, sclerotic bone ends and absent callus formation. What is the most appropriate surgical management for this complication?

. Dynamization of the current intramedullary nail
. Exchange nailing, debridement of the nonunion site, and autologous bone grafting
. Pulsed electromagnetic field therapy and cast immobilization
. Exchange nailing with a larger diameter nail without opening the nonunion
. Plate osteosynthesis without bone grafting

Correct Answer & Explanation

. Exchange nailing, debridement of the nonunion site, and autologous bone grafting

Explanation

The patient has an atrophic nonunion, characterized radiographically by sclerotic, tapered bone ends and a lack of callus, which implies a failure of biology (poor vascularity and osteogenic potential). Management of atrophic nonunions requires optimizing both biology and stability. This involves debridement of the sclerotic bone ends down to bleeding bone, addition of bone graft (to stimulate biology), and ensuring rigid stabilization (e.g., exchange nailing or plating). Dynamization or simply exchange nailing alone is insufficient because it does not address the lack of biological activity.

Question 12379

Topic: 2. Trauma

A 30-year-old trauma patient presents in hemorrhagic shock with an "open book" pelvic fracture. A pelvic binder is to be applied. What is the optimal anatomic landmark for centering the binder to effectively reduce pelvic volume?

. Iliac crests
. Anterior superior iliac spines
. Greater trochanters
. Pubic symphysis
. Subtrochanteric femur

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders should be centered directly over the greater trochanters to effectively compress the pelvic ring and reduce pelvic volume. Placement over the iliac crests is incorrect and can paradoxically open the pelvis in certain fracture patterns.

Question 12380

Topic: 2. Trauma

A 24-year-old male falls onto an outstretched hand and sustains a displaced fracture through the proximal pole of the scaphoid. Why is this specific fracture pattern at an exceptionally high risk for avascular necrosis (AVN)?

. The proximal pole entirely lacks a cartilaginous covering
. Blood supply enters at the distal pole and flows retrograde
. Robust intrinsic ligaments constantly distract the proximal fragment
. The proximal pole relies entirely on the anterior interosseous artery
. High concentrations of synovial fluid inhibit primary bone healing

Correct Answer & Explanation

. Blood supply enters at the distal pole and flows retrograde

Explanation

The primary blood supply to the scaphoid is derived from branches of the radial artery that enter distally and flow in a retrograde direction to perfuse the proximal pole. Fractures through the proximal pole disrupt this tenuous supply, leading to high rates of AVN.

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