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2. Trauma MCQs

Practice Set 614 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 12261

Topic: 2. Trauma
A 25-year-old male sustains a high-energy Pauwels type III femoral neck fracture. He undergoes fixation with a dynamic hip screw and a derotational screw. Which of the following biomechanical characteristics most strongly predisposes this specific fracture pattern to failure?
. High shear forces leading to varus collapse
. High compressive forces leading to femoral shortening
. Tension failure of the lateral femoral cortex
. Dynamic hip screw sliding leading to valgus impaction
. Rotational instability causing posterior displacement

Correct Answer & Explanation

. High shear forces leading to varus collapse

Explanation

Pauwels type III femoral neck fractures have a vertical fracture line (angle > 50 degrees). This orientation subjects the fracture site to massive shear forces rather than compression, greatly predisposing it to varus collapse and nonunion.

Question 12262

Topic: 2. Trauma

A 35-year-old male is evaluated for compartment syndrome after a tibial plateau fracture. His diastolic blood pressure is 80 mmHg, and his mean arterial pressure is 95 mmHg. Which of the following compartment pressure measurements is the generally accepted threshold to indicate the need for 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 Delta P (diastolic blood pressure minus compartment pressure) is considered a more reliable indicator for compartment syndrome than absolute compartment pressures. A Delta P of less than 30 mmHg is an indication for emergent fasciotomy, as capillary perfusion pressure is inadequate.

Question 12263

Topic: 2. Trauma
A 40-year-old male is brought to the trauma bay in hemorrhagic shock following a motorcycle accident. Radiographs reveal an APC-III pelvic ring injury. A pelvic binder is ordered. To maximize reduction and stability, where should the binder be centered?
. Over the iliac crests
. Over the greater trochanters
. Midway between the umbilicus and the pubic symphysis
. Just proximal to the anterior superior iliac spine (ASIS)
. Around the proximal third of the femurs

Correct Answer & Explanation

. Over the greater trochanters

Explanation

A pelvic binder should be applied at the level of the greater trochanters to effectively close the pelvic volume by providing compressive force across the symphysis pubis and SI joints. Placement over the iliac crests can paradoxically open the true pelvis in certain fracture patterns.

Question 12264

Topic: 2. Trauma
In the Pauwels classification of femoral neck fractures, which of the following characterizes a Pauwels type III fracture, and what is its primary mechanical challenge?
. Fracture line < 30 degrees from the horizontal; high varus stress
. Fracture line > 50 degrees from the horizontal; high shear stress
. Fracture line < 30 degrees from the horizontal; high shear stress
. Fracture line > 50 degrees from the horizontal; high compressive forces
. Fracture line between 30 and 50 degrees; primarily rotational instability

Correct Answer & Explanation

. Fracture line > 50 degrees from the horizontal; high shear stress

Explanation

The Pauwels classification is based on the angle of the fracture line relative to the horizontal. Type I is <30 degrees, Type II is 30-50 degrees, and Type III is >50 degrees. A more vertical fracture line (Type III) is subjected to high shear stress, making it highly unstable and prone to nonunion and varus collapse.

Question 12265

Topic: 2. Trauma

Which of the following types of fracture fixation predominantly promotes primary bone healing via intramembranous ossification without the formation of an intermediate cartilaginous callus?

. Intramedullary nailing
. Bridge plating
. Absolute stability with lag screw and neutralization plate
. External fixation
. Cast immobilization

Correct Answer & Explanation

. Absolute stability with lag screw and neutralization plate

Explanation

Absolute stability (achieved via lag screws and compression plating) eliminates interfragmentary strain (<2%). This environment dictates primary bone healing (cutting cones) without an intermediate cartilaginous callus phase. Relative stability (IM nails, bridge plates, external fixators) results in higher strain (2-10%) and promotes secondary bone healing through enchondral ossification.

Question 12266

Topic: 2. Trauma

A surgeon utilizes a locked plate for a comminuted distal femur fracture in osteoporotic bone. Which of the following best describes the mechanical construct provided by a completely locked plate system?

. It relies on friction between the plate and bone for stability.
. It acts as a load-sharing device, compressing the fracture ends.
. It functions as a single beam construct (fixed-angle device).
. It increases the pullout strength of individual screws by toggling.
. It requires exact contouring of the plate to the bone surface to achieve stability.

Correct Answer & Explanation

. It functions as a single beam construct (fixed-angle device).

Explanation

A locked plate functions as a fixed-angle construct. The screw heads thread directly into the plate, locking them at a fixed angle. Stability is achieved through the plate-screw interface rather than friction between the plate and bone. Thus, it acts as a single mechanical beam and is highly advantageous in osteoporotic bone.

Question 12267

Topic: 2. Trauma

A 22-year-old soccer player sustains a twisting injury to his knee. Radiographs reveal an avulsion fracture of the anterolateral tibial plateau. This pathognomonic 'Segond fracture' is most highly associated with an injury to which of the following structures?

. Posterior cruciate ligament
. Medial collateral ligament
. Anterior cruciate ligament
. Medial meniscus
. Patellar tendon

Correct Answer & Explanation

. Anterior cruciate ligament

Explanation

A Segond fracture is a cortical avulsion off the anterolateral tibial plateau, representing an avulsion of the anterolateral capsule/anterolateral ligament (ALL). It is highly pathognomonic (up to 75-100% predictive value) for an anterior cruciate ligament (ACL) tear.

Question 12268

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is involved in a high-speed motorcycle crash. Pelvic radiographs show a symphyseal diastasis of 3.5 cm and widening of the anterior sacroiliac joints bilaterally. The posterior sacroiliac complex appears intact. According to the Young-Burgess classification, which injury pattern does this represent?
. APC I
. APC II
. APC III
. LC I
. LC II

Correct Answer & Explanation

. APC II

Explanation

An anteroposterior compression (APC) II injury involves symphyseal diastasis >2.5 cm with tearing of the sacrotuberous, sacrospinous, and anterior sacroiliac ligaments. The posterior sacroiliac ligaments remain intact, leading to a rotationally unstable but vertically stable pelvis. APC III involves complete disruption of both anterior and posterior SI ligaments.

Question 12269

Topic: 2. Trauma

The scaphoid bone has a tenuous blood supply, making proximal pole fractures particularly susceptible to avascular necrosis. The primary blood supply to the scaphoid is derived from branches of which major artery?

. Ulnar artery
. Radial artery
. Anterior interosseous artery
. Posterior interosseous artery
. Deep palmar arch

Correct Answer & Explanation

. Radial artery

Explanation

The primary blood supply to the scaphoid is derived from the dorsal carpal branch of the radial artery. It enters the bone primarily at the distal pole and supplies the proximal pole via retrograde intraosseous flow, leading to a high rate of nonunion and avascular necrosis in proximal pole fractures.

Question 12270

Topic: 2. Trauma

Schatzker type II tibial plateau fractures involve a split and depression of the lateral articular surface. Which soft-tissue structure is most commonly injured in direct association with this specific fracture pattern?

. Medial meniscus
. Lateral meniscus
. Anterior cruciate ligament
. Posterior cruciate ligament
. Popliteal artery

Correct Answer & Explanation

. Lateral meniscus

Explanation

Lateral meniscal tears or entrapments occur in nearly 50% of Schatzker II (split-depression) tibial plateau fractures. The meniscus can become trapped within the depressed articular fragments, preventing anatomic reduction if not addressed during surgical fixation.

Question 12271

Topic: 2. Trauma

A 65-year-old male presents with severe right thigh pain. Radiographs reveal a large destructive lytic lesion in the subtrochanteric region of the femur with cortical thinning, but no frank fracture. Laboratory workup reveals hypercalcemia and an M-spike on serum protein electrophoresis. What is the most appropriate prophylactic surgical treatment?

. Cephalomedullary nail
. Proximal femoral replacement (endoprosthesis)
. Open reduction internal fixation with a dynamic hip screw
. External fixation
. Conservative management with radiation therapy alone

Correct Answer & Explanation

. Cephalomedullary nail

Explanation

The patient has multiple myeloma with an impending subtrochanteric pathologic fracture. The standard of care for prophylactic fixation of impending subtrochanteric lesions is a long cephalomedullary nail, which spans the entire length of the bone and protects both the femoral neck and diaphysis.

Question 12272

Topic: Pelvic & Acetabular Trauma
According to the Young-Burgess classification, which pelvic ring injury pattern is most consistently associated with complete disruption of the posterior sacroiliac ligamentous complex, the highest volume of retroperitoneal hemorrhage, and the greatest requirement for massive transfusion?
. Anterior-posterior compression type I (APC-I)
. Anterior-posterior compression type II (APC-II)
. Anterior-posterior compression type III (APC-III)
. Lateral compression type II (LC-II)
. Vertical shear (VS)

Correct Answer & Explanation

. Anterior-posterior compression type III (APC-III)

Explanation

APC-III injuries involve complete disruption of the anterior and posterior sacroiliac ligaments, leading to a completely unstable hemipelvis. This mechanism typically results in the highest volume of retroperitoneal hemorrhage and has the highest mortality and transfusion requirement among pelvic ring injuries.

Question 12273

Topic: 2. Trauma

Which of the following is the most primary pathophysiological mechanism in the development of acute compartment syndrome?

. Increase in local arterial blood pressure causing hematoma expansion
. Decrease in local tissue venous pressure
. Decrease in the local arteriovenous pressure gradient
. Obstruction of the lymphatic drainage system
. Direct toxic effect of myoglobin on local capillary endothelium

Correct Answer & Explanation

. Decrease in the local arteriovenous pressure gradient

Explanation

Compartment syndrome occurs when increased tissue pressure reduces the arteriovenous pressure gradient. As interstitial pressure rises above venous pressure, venous outflow is obstructed. This further increases capillary pressure, eventually causing the arteriovenous gradient to fall below what is required for tissue perfusion, leading to ischemia.

Question 12274

Topic: 2. Trauma

A 32-year-old male sustains a closed tibial shaft fracture. Which of the following pressure measurements is most accurate for diagnosing acute compartment syndrome?

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

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mm Hg

Explanation

The delta pressure (Diastolic BP minus compartment pressure) of less than 30 mm Hg is the most reliable threshold for diagnosing acute compartment syndrome. Relying on absolute pressures can be falsely reassuring in hypotensive patients.

Question 12275

Topic: 2. Trauma
A 25-year-old male sustains a vertically oriented, displaced femoral neck fracture (Pauwels Type III). What is the primary biomechanical rationale for using a sliding hip screw with a derotation screw rather than three parallel cancellous screws?
. It provides superior resistance to varus collapse and shear forces
. It decreases the risk of avascular necrosis
. It avoids crossing the fracture site with multiple threads
. It stimulates endochondral ossification
. It allows for immediate full weight-bearing

Correct Answer & Explanation

. It provides superior resistance to varus collapse and shear forces

Explanation

Pauwels Type III fractures experience very high vertical shear forces. A sliding hip screw provides a fixed-angle construct that offers superior biomechanical resistance to vertical shear and varus collapse compared to parallel cancellous screws.

Question 12276

Topic: 2. Trauma

A 35-year-old male smoker presents 6 months after a closed tibial shaft fracture treated initially with a cast. Radiographs demonstrate a hypertrophic nonunion with an 'elephant foot' appearance. What is the primary underlying cause of this specific type of nonunion and the ideal treatment strategy?

. Biological failure; requires bone grafting
. Mechanical instability; requires rigid internal fixation
. Subclinical infection; requires debridement and culture-specific antibiotics
. Metabolic abnormality; requires vitamin D supplementation and smoking cessation
. Impaired angiogenesis; requires hyperbaric oxygen therapy

Correct Answer & Explanation

. Mechanical instability; requires rigid internal fixation

Explanation

Hypertrophic nonunions ('elephant foot' or 'horse hoof') are primarily caused by mechanical instability in the presence of adequate biological healing potential (good blood supply and callus formation). The definitive treatment is to provide rigid mechanical stability, usually through intramedullary nailing or compression plating, which allows the abundant callus to consolidate. Bone grafting is typically unnecessary because the biological potential is already robust.

Question 12277

Topic: 2. Trauma
A 45-year-old male is brought into the trauma bay after a severe motorcycle crash. A pelvic binder is applied, and radiographs demonstrate an anteroposterior compression (APC) type III pelvic ring injury. He remains hemodynamically unstable despite receiving 2 units of packed red blood cells. The Focused Assessment with Sonography for Trauma (FAST) exam is negative. What is the most appropriate immediate orthopedic intervention to address his pelvic hemorrhage?
. Exploratory laparotomy with internal iliac artery ligation
. Placement of a resuscitative endovascular balloon occlusion of the aorta (REBOA)
. Open reduction and internal fixation of the pubic symphysis
. Preperitoneal pelvic packing or pelvic angiography with embolization
. Application of an external fixator to replace the binder

Correct Answer & Explanation

. Preperitoneal pelvic packing or pelvic angiography with embolization

Explanation

In a hemodynamically unstable patient with a mechanically unstable pelvic fracture (APC III) and a negative FAST (ruling out massive intra-abdominal hemorrhage), the source of bleeding is presumed to be the pelvis (venous plexus or arterial). Once pelvic volume is reduced (via binder), the next algorithmic step for persistent hemodynamic instability is either preperitoneal pelvic packing (PPP) or pelvic angiography with embolization, depending on institutional protocols and immediate availability.

Question 12278

Topic: 2. Trauma

A 42-year-old male sustains a high-energy trauma to his right knee. Radiographs demonstrate a bicondylar tibial plateau fracture with dissociation of the metaphysis from the diaphysis. What is the correct Schatzker classification for this fracture, and what is the most critical associated soft tissue emergency?

. Schatzker IV; peroneal nerve palsy
. Schatzker V; popliteal artery injury
. Schatzker VI; acute compartment syndrome
. Schatzker VI; complete medial collateral ligament rupture
. Schatzker V; acute compartment syndrome

Correct Answer & Explanation

. Schatzker V; acute compartment syndrome

Explanation

A bicondylar tibial plateau fracture with metaphyseal-diaphyseal dissociation is classified as a Schatzker VI fracture. Because of the high-energy nature of this injury, severe soft-tissue compromise is the rule rather than the exception. The most critical and immediate limb-threatening complication is acute compartment syndrome, which occurs in a significant percentage of Schatzker VI fractures and requires high clinical suspicion and potential four-compartment fasciotomy.

Question 12279

Topic: 2. Trauma

During a volar fasciotomy for acute forearm compartment syndrome, releasing all fascial compartments is imperative. Which of the following structures is contained within the 'mobile wad of Henry', representing a specific compartment that must be addressed?

. Flexor carpi radialis
. Extensor carpi ulnaris
. Brachioradialis
. Flexor digitorum profundus
. Pronator quadratus

Correct Answer & Explanation

. Brachioradialis

Explanation

The 'mobile wad of Henry' is an anatomic muscle group in the lateral aspect of the forearm consisting of three muscles: the brachioradialis, the extensor carpi radialis longus (ECRL), and the extensor carpi radialis brevis (ECRB). In the setting of forearm compartment syndrome, it is considered a separate functional compartment (along with the volar and dorsal compartments) that requires specific evaluation and potential fascial release.

Question 12280

Topic: 2. Trauma

Which recombinant human bone morphogenetic protein (rhBMP) is FDA-approved for use as an adjunct in acute open tibial shaft fractures treated with an intramedullary nail?

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

Correct Answer & Explanation

. rhBMP-2

Explanation

rhBMP-2 (Infuse) is FDA-approved for the treatment of acute open tibial shaft fractures stabilized with intramedullary nailing, as well as for anterior lumbar interbody fusion (ALIF). rhBMP-7 (OP-1) was previously approved under a humanitarian device exemption for recalcitrant tibial nonunions.

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