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2. Trauma MCQs

Practice Set 414 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 8261

Topic: 2. Trauma
A surgeon is struggling with poor screw purchase in osteopenic bone during an open reduction and internal fixation of a distal humerus fracture. To maximize the pullout strength of a cortical screw, which of the following screw design modifications would be most effective?
. Increasing the inner (root) diameter
. Increasing the outer (thread) diameter
. Increasing the screw pitch
. Decreasing the thread length
. Decreasing the core diameter

Correct Answer & Explanation

. Increasing the outer (thread) diameter

Explanation

The pullout strength of a bone screw is directly proportional to the outer (thread) diameter, the length of thread engagement, and the shear strength of the bone. It is inversely proportional to the pitch. The formula for pullout strength is F = S * L * π * D, where S is the shear strength of the bone, L is the length of engagement, and D is the outer diameter. Increasing the outer diameter has the most profound effect on increasing pullout strength. Increasing the inner (root or core) diameter improves the bending strength of the screw but decreases the thread depth, which reduces pullout strength.

Question 8262

Topic: 2. Trauma

A surgeon is planning to use a solid intramedullary nail to treat a tibial shaft fracture. If the diameter of the nail is increased by a factor of 2, how does the torsional rigidity of the nail change?

. Increases by a factor of 2
. Increases by a factor of 4
. Increases by a factor of 8
. Increases by a factor of 16
. Increases by a factor of 32

Correct Answer & Explanation

. Increases by a factor of 16

Explanation

Torsional rigidity of a solid cylindrical implant is directly proportional to its polar moment of inertia, which is proportional to the radius (or diameter) to the fourth power (r^4). Therefore, increasing the diameter by a factor of 2 increases the torsional rigidity by a factor of 2^4, which equals 16.

Question 8263

Topic: 2. Trauma
A 35-year-old male is brought to the trauma bay after a high-speed motorcycle collision. His blood pressure is 80/50 mm Hg and heart rate is 125 beats/min. A FAST exam is negative for intra-abdominal fluid. An AP pelvic radiograph reveals an AP compression type III (APC-III) injury with severe symphyseal diastasis and disruption of both sacroiliac joints. A pelvic binder is appropriately applied. Following the administration of 2 liters of crystalloid and 2 units of uncrossmatched packed red blood cells, his blood pressure remains 85/55 mm Hg. What is the most appropriate next step in management?
. Application of a pelvic external fixator
. Retroperitoneal/preperitoneal pelvic packing and/or angioembolization
. Exploratory laparotomy
. Placement of an REBOA in Zone 1
. Emergent percutaneous iliosacral screw fixation

Correct Answer & Explanation

. Retroperitoneal/preperitoneal pelvic packing and/or angioembolization

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST (no major intra-abdominal bleeding source), the first step in mechanical stabilization is a pelvic binder. If the patient remains hemodynamically unstable despite resuscitation and mechanical stabilization, the shock is presumed to be from venous or arterial pelvic bleeding. The most appropriate next step is preperitoneal pelvic packing and/or pelvic angiography with embolization. External fixation provides mechanical stability similar to a binder but delays the necessary hemorrhage control. Exploratory laparotomy is not indicated with a negative FAST and releases the tamponade effect in the retroperitoneum.

Question 8264

Topic: 2. Trauma
A 28-year-old male sustains a completely displaced transcervical femoral neck fracture following a fall from height. Radiographs demonstrate a vertical fracture line measuring 65 degrees relative to the horizontal (Pauwels type III). He undergoes closed reduction and internal fixation. Compared to a Pauwels type I fracture, what biomechanical environment predominates at the fracture site in this patient's injury?
. Increased compressive forces leading to rapid osteosynthesis
. Increased shear forces leading to higher rates of varus collapse and nonunion
. Decreased bending moments, making percutaneous cannulated screws the gold standard implant
. Increased rotational stability due to the vertical orientation of the fracture line
. Decreased capsular pressure leading to a lower risk of avascular necrosis

Correct Answer & Explanation

. Increased shear forces leading to higher rates of varus collapse and nonunion

Explanation

The Pauwels classification of femoral neck fractures is based on the angle of the fracture line relative to the horizontal plane. Pauwels type III fractures have an angle greater than 50 degrees (highly vertical). This vertical orientation subjects the fracture to immense shear forces and significant bending moments rather than the stable compressive forces seen in horizontal (Pauwels I) fractures. Because of these shear forces, Pauwels III fractures have a notoriously high rate of loss of fixation, varus collapse, and nonunion, especially when treated with parallel cannulated screws alone. Fixed-angle constructs (e.g., sliding hip screws) are frequently favored biomechanically.

Question 8265

Topic: 2. Trauma

A 42-year-old skier sustains a high-energy Schatzker VI tibial plateau fracture. On presentation, the leg is tense and markedly swollen. Compartment pressures are measured, yielding a delta P (diastolic blood pressure minus compartment pressure) of 15 mm Hg. A decision is made to perform a two-incision, four-compartment fasciotomy. During the anterolateral incision to release the anterior and lateral compartments, which of the following nerves is at greatest risk of iatrogenic injury?

. Deep peroneal nerve
. Superficial peroneal nerve
. Saphenous nerve
. Sural nerve
. Tibial nerve

Correct Answer & Explanation

. Superficial peroneal nerve

Explanation

A delta P of less than 30 mm Hg is an absolute indication for emergency fasciotomy. In a standard two-incision technique for the leg, the anterolateral incision accesses the anterior and lateral compartments. The superficial peroneal nerve is at significant risk during this approach, particularly in the middle to distal third of the leg where it pierces the deep fascia to become subcutaneous. The surgeon must carefully identify and protect this nerve when incising the fascia of the lateral compartment. The saphenous nerve is medial, the sural nerve is posterior, and the deep peroneal nerve is protected deep within the anterior compartment along the interosseous membrane.

Question 8266

Topic: 2. Trauma

A 68-year-old woman presents with a 4-part proximal humerus fracture. In evaluating the initial plain radiographs and CT scan, the surgeon assesses the risk of subsequent humeral head ischemia. According to the Hertel criteria, which of the following combinations of features is the most reliable predictor of avascular necrosis (AVN) of the humeral head?

. Greater tuberosity displacement > 5 mm and varus angulation > 20 degrees
. Valgus impaction and an intact posteromedial hinge
. Anatomic neck fracture, disruption of the medial hinge, and a calcar segment < 8 mm
. Surgical neck fracture with metaphyseal comminution and intact lesser tuberosity
. Three-part fracture pattern with a metaphyseal head extension > 20 mm

Correct Answer & Explanation

. Anatomic neck fracture, disruption of the medial hinge, and a calcar segment < 8 mm

Explanation

Hertel et al. identified specific criteria that predict ischemia and subsequent AVN of the humeral head following proximal humerus fractures. The most highly predictive factors include: (1) an anatomic neck fracture (rather than surgical neck), (2) a short calcar segment attached to the articular fragment (metaphyseal extension < 8 mm), and (3) disruption of the medial hinge. When these criteria are present, the risk of AVN is exceedingly high due to the disruption of the anterior circumflex humeral artery and the intraosseous blood supply. Conversely, an intact medial hinge and a long calcar segment (> 8 mm) are protective against ischemia.

Question 8267

Topic: 2. Trauma
A 24-year-old farm worker caught his leg in a tractor mechanism, sustaining a severely contaminated open diaphyseal tibia fracture with a 12-cm soft tissue defect and exposed bone (Gustilo-Anderson IIIB). Soil and organic matter are heavily ground into the wound. He is brought to the trauma center within 1 hour. According to evidence-based guidelines for initial antibiotic prophylaxis in this specific scenario, what is the most appropriate empiric intravenous regimen?
. Cefazolin monotherapy
. Vancomycin and Ciprofloxacin
. Cefazolin, an aminoglycoside (e.g., Gentamicin), and Penicillin G
. Clindamycin and Ceftriaxone
. Cefoxitin monotherapy

Correct Answer & Explanation

. Cefazolin, an aminoglycoside (e.g., Gentamicin), and Penicillin G

Explanation

This is a highly contaminated Gustilo-Anderson IIIB open fracture occurring in an agricultural setting. Standard protocol for severe open fractures (Type III) includes a first-generation cephalosporin (Cefazolin) to cover Gram-positive organisms, plus an aminoglycoside (Gentamicin) or third-generation cephalosporin to cover Gram-negative organisms. Additionally, in the setting of farm/agricultural injuries or profound soil/fecal contamination, there is a distinct risk for Clostridium perfringens (gas gangrene) infection. High-dose Penicillin G is explicitly added to the regimen to provide coverage against these anaerobic, spore-forming organisms.

Question 8268

Topic: 2. Trauma

A 32-year-old male is 8 weeks post-operative from an open reduction and internal fixation of a displaced talar neck fracture (Hawkins type II). Routine follow-up radiographs demonstrate a subchondral radiolucent band in the dome of the talus on the AP view. What is the clinical significance of this radiographic finding?

. It is an early radiographic sign of impending avascular necrosis (AVN)
. It indicates subchondral collapse and the rapid progression of post-traumatic arthritis
. It signifies intact vascularity to the talar body
. It represents a deep infection or osteomyelitis of the talar dome
. It is indicative of a talar neck nonunion

Correct Answer & Explanation

. It signifies intact vascularity to the talar body

Explanation

The finding described is the 'Hawkins sign'. It is a subchondral radiolucent band in the dome of the talus that typically appears 6 to 8 weeks after a talus fracture. This radiolucency represents subchondral osteopenia (bone resorption) secondary to disuse and active hyperemia. For active hyperemia and bone resorption to occur, the talar body must have an intact blood supply. Therefore, the presence of a Hawkins sign is a highly reliable indicator of intact vascularity and implies that avascular necrosis (AVN) of the talar body will not occur.

Question 8269

Topic: 2. Trauma

A 30-year-old male presents to the emergency department after a direct blow to the leg during a rugby match. Radiographs show a closed, comminuted midshaft tibia fracture. He is complaining of agonizing pain despite receiving intravenous opioids. The nurse notes that his foot is swollen. Which of the following physical examination findings is the most sensitive early clinical indicator of acute compartment syndrome?

. Absence of the dorsalis pedis and posterior tibial pulses
. Marked pallor and poikilothermia of the toes
. Pain with passive stretch of the toes and ankle
. Inability to actively dorsiflex the great toe
. Decreased capillary refill time > 4 seconds

Correct Answer & Explanation

. Pain with passive stretch of the toes and ankle

Explanation

Pain out of proportion to the injury and pain with passive stretch of the muscles traversing the affected compartment are the earliest, most sensitive clinical signs of acute compartment syndrome. While the '5 Ps' (Pain, Pallor, Pulselessness, Paresthesias, Paralysis) are classically taught, pallor, pulselessness, and paralysis are late findings that indicate severe, often irreversible, tissue ischemia. Waiting for the absence of pulses to diagnose compartment syndrome will result in catastrophic muscle necrosis and nerve damage.

Question 8270

Topic: Pelvic & Acetabular Trauma
A 35-year-old male is brought to the emergency department after a high-speed motorcycle collision. His blood pressure is 70/40 mm Hg and heart rate is 135 bpm. A FAST exam is negative. An anteroposterior pelvic radiograph shows a widened pubic symphysis of 4 cm and widened bilateral sacroiliac joints. A pelvic binder is placed, and he receives 2 units of uncrossmatched packed red blood cells. His blood pressure improves transiently to 85/50 mm Hg. What is the next most appropriate step in management?
. Transfer to the CT scanner to evaluate for retroperitoneal hemorrhage
. Immediate application of an anterior external fixator
. Preperitoneal pelvic packing or pelvic angioembolization
. Exploratory laparotomy
. Retrograde urethrogram

Correct Answer & Explanation

. Preperitoneal pelvic packing or pelvic angioembolization

Explanation

This patient has a hemodynamically unstable pelvic ring injury (APC-III equivalent). The initial step is stabilization with a pelvic binder and resuscitation. With a negative FAST exam, the abdomen is less likely to be the source of major hemorrhage, pointing toward retroperitoneal bleeding from the pelvis. If the patient remains unstable or transiently responds, definitive hemorrhage control via preperitoneal pelvic packing or angiography with embolization is the standard of care. CT scanning is contraindicated in a hemodynamically unstable patient. Exploratory laparotomy is not indicated for isolated retroperitoneal pelvic bleeding and releases the tamponade effect.

Question 8271

Topic: 2. Trauma
A 28-year-old man sustains a completely displaced, vertically oriented (Pauwels type III) femoral neck fracture after falling from a roof. He is taken to the operating room for closed reduction and internal fixation. Which of the following biomechanical constructs provides the most stable fixation for this specific fracture pattern?
. Three parallel cannulated screws in an inverted triangle configuration
. Two parallel cannulated screws
. Fixed-angle sliding hip screw with a derotational screw
. Dynamic condylar screw
. Standard cephalomedullary nail

Correct Answer & Explanation

. Fixed-angle sliding hip screw with a derotational screw

Explanation

Pauwels type III femoral neck fractures have a highly vertical orientation (angle > 50 degrees), which creates large shear forces across the fracture site. This makes them highly unstable and prone to varus collapse and nonunion. Biomechanical studies have demonstrated that a fixed-angle device, such as a sliding hip screw (often supplemented with a derotational screw to prevent rotation of the femoral head), provides superior biomechanical stability and resistance to vertical shear compared to multiple parallel cannulated screws.

Question 8272

Topic: 2. Trauma

A 42-year-old woman sustains a high-energy distal femur fracture. A CT scan of the knee reveals a displaced coronal plane fracture of the lateral femoral condyle. What is the most appropriate fixation strategy for this specific articular fragment?

. Anterior-to-posterior oriented lag screws
. Posterior-to-anterior oriented lag screws
. Medial-to-lateral oriented lag screws
. Lateral-to-medial oriented lag screws
. Distal-to-proximal oriented lag screws

Correct Answer & Explanation

. Anterior-to-posterior oriented lag screws

Explanation

A coronal plane fracture of the femoral condyle is known as a Hoffa fracture, most commonly involving the lateral condyle. Because the fragment is located posteriorly, the standard surgical technique for fixation involves placing lag screws in an anterior-to-posterior direction to compress the fracture fragment against the intact anterior condyle. Screws are often countersunk within the articular cartilage if placed through the weight-bearing zone, or placed outside the articular margin when possible.

Question 8273

Topic: 2. Trauma
A 33-year-old man sustains a Gustilo-Anderson Type IIIB open tibia fracture involving the distal third of the tibial diaphysis with a large 10x12 cm anterior soft tissue defect. After aggressive serial debridements and skeletal stabilization, he requires soft tissue coverage. Which of the following options is the most reliable soft tissue flap for this specific defect?
. Gastrocnemius rotational flap
. Soleus rotational flap
. Free tissue transfer (e.g., anterolateral thigh flap)
. V-Y advancement flap
. Sural nerve flap

Correct Answer & Explanation

. Free tissue transfer (e.g., anterolateral thigh flap)

Explanation

The lower extremity is traditionally divided into thirds when planning soft tissue coverage for open tibia fractures. The proximal third is typically covered by a gastrocnemius rotational flap, while the middle third is usually covered by a soleus rotational flap. The distal third of the tibia lacks adequate local muscle bulk for reliable rotational coverage of large defects; therefore, a free tissue transfer (e.g., anterolateral thigh flap, latissimus dorsi, or rectus abdominis) is the gold standard for robust coverage.

Question 8274

Topic: 2. Trauma

A 45-year-old male undergoes open reduction and internal fixation of a Schatzker VI tibial plateau fracture. Postoperatively, he requires rapidly increasing amounts of intravenous opioids. On examination, his leg is tense, and he experiences excruciating pain with passive stretch of his great toe. His dorsalis pedis pulse is palpable. Intracompartmental pressure testing shows an absolute pressure of 45 mm Hg in the anterior compartment, and his diastolic blood pressure is 65 mm Hg. What is the most appropriate next step?

. Elevate the leg above the level of the heart
. Administer intravenous mannitol
. Immediate four-compartment fasciotomy
. Remove the surgical dressings and re-evaluate in 2 hours
. Perform an urgent lower extremity CT angiogram

Correct Answer & Explanation

. Immediate four-compartment fasciotomy

Explanation

The patient exhibits classic clinical signs of acute compartment syndrome (pain out of proportion, pain with passive stretch, tense compartments) and has an objective Delta P (diastolic blood pressure minus absolute compartment pressure) of 20 mm Hg (65 - 45 = 20 mm Hg). A Delta P of less than 30 mm Hg is an absolute indication for emergency fasciotomy. The presence of a palpable pulse does not rule out compartment syndrome, as arterial pressure remains higher than compartment pressure until late in the disease process. Immediate four-compartment fasciotomy is required.

Question 8275

Topic: 2. Trauma

A 22-year-old man presents to the emergency department after sustaining a single gunshot wound to the right knee. Radiographs reveal a retained bullet lodged entirely within the intra-articular space of the knee joint. There is no associated fracture. After appropriate initial tetanus prophylaxis and administration of antibiotics, what is the most appropriate definitive management of the retained bullet?

. Leave the bullet in place and allow immediate weight-bearing
. Arthroscopic or open surgical removal of the bullet
. Administer a course of intravenous chelation therapy
. Local wound care and delayed primary closure only
. Immobilization in a knee immobilizer for 6 weeks

Correct Answer & Explanation

. Arthroscopic or open surgical removal of the bullet

Explanation

Bullets lodged within an intra-articular space (such as the knee joint) must be surgically removed, either arthroscopically or via arthrotomy. The synovial fluid within the joint acts as a solvent for lead, which can lead to systemic lead toxicity (plumbism). Additionally, a retained intra-articular bullet acts as a third body, causing rapid mechanical destruction of the articular cartilage. Extra-articular bullets embedded in muscle or soft tissue without neurovascular compromise can generally be left in place.

Question 8276

Topic: Pelvic & Acetabular Trauma
A 45-year-old man is brought to the emergency department after a high-speed motorcycle collision. He is hemodynamically unstable with a blood pressure of 80/40 mm Hg and a heart rate of 125 beats/min. A FAST examination is negative. The anteroposterior pelvic radiograph reveals an Anteroposterior Compression Type III (APC-III) pelvic ring injury. A pelvic binder is ordered to assist with hemodynamic stabilization. What is the most appropriate anatomical landmark for the optimal placement of the pelvic binder to effectively reduce the pelvic volume?
. Centered over the iliac crests
. Centered over the greater trochanters
. Centered over the anterior superior iliac spines
. Centered over the symphysis pubis and the sacrum
. Midway between the iliac crests and the greater trochanters

Correct Answer & Explanation

. Centered over the greater trochanters

Explanation

Pelvic binders are most effective in reducing pelvic volume and controlling venous hemorrhage when placed centered over the greater trochanters. Placement over the iliac crests is a common error and is less effective; in certain fracture patterns (such as some lateral compression injuries), high placement can paradoxically exacerbate the deformity or internal bleeding.

Question 8277

Topic: 2. Trauma

A 38-year-old man sustains a closed, high-energy injury to his right knee. A computed tomography (CT) scan reveals a bicondylar tibial plateau fracture with a large, displaced posteromedial shear fragment. What is the most appropriate surgical approach to achieve anatomical reduction and stable buttress fixation of this specific posteromedial fragment?

. Anterolateral approach with submeniscal arthrotomy
. Direct anterior approach with tibial tubercle osteotomy
. Posteromedial approach utilizing the interval between the medial head of the gastrocnemius and the pes anserinus
. Posterolateral approach with fibular osteotomy
. Standard medial parapatellar approach

Correct Answer & Explanation

. Posteromedial approach utilizing the interval between the medial head of the gastrocnemius and the pes anserinus

Explanation

The posteromedial shear fragment in tibial plateau fractures (often part of Schatzker IV or VI patterns) is difficult or impossible to effectively reduce and buttress from an anterior or anterolateral approach. The optimal approach is a posteromedial approach. This typically utilizes the interval between the medial head of the gastrocnemius (which is retracted laterally) and the pes anserinus tendons (which are retracted medially or anteriorly) to place a posterior buttress plate directly opposing the deforming forces.

Question 8278

Topic: 2. Trauma
A 25-year-old man sustains a vertical, displaced femoral neck fracture (Pauwels type III) after a fall from a height. He is taken to the operating room for closed reduction and internal fixation. Which of the following fixation constructs provides the greatest biomechanical stability against the predominant deforming forces for this specific fracture pattern?
. Three parallel partially-threaded cancellous lag screws in an inverted triangle configuration
. A fixed-angle sliding hip screw with a supplemental derotation screw
. Two fully threaded cortical screws positioned centrally
. A standard trochanteric cephalomedullary nail
. Bipolar hemiarthroplasty

Correct Answer & Explanation

. A fixed-angle sliding hip screw with a supplemental derotation screw

Explanation

Pauwels type III femoral neck fractures are vertically oriented (>50 degrees) and are subject to high shear forces. Biomechanical studies have consistently demonstrated that a fixed-angle construct, such as a sliding hip screw (dynamic hip screw), provides superior stability against vertical shear stress compared to multiple cancellous lag screws. A supplemental derotation screw is often added to control rotational forces.

Question 8279

Topic: 2. Trauma
A 32-year-old construction worker sustains a Gustilo-Anderson Type IIIB open tibia fracture. He undergoes immediate irrigation and debridement, and skeletal stabilization with an external fixator. Following sequential debridements, the wound bed is deemed clean, but there is exposed diaphyseal bone devoid of periosteum requiring a free tissue transfer. To minimize the risk of deep infection and flap failure, soft-tissue coverage should ideally be performed within what timeframe from the initial injury?
. Within 24 hours
. Within 3 to 7 days
. Within 10 to 14 days
. Within 14 to 21 days
. After 3 weeks when healthy granulation tissue is fully formed

Correct Answer & Explanation

. Within 3 to 7 days

Explanation

Based on classic principles established by Godina and supported by subsequent orthoplastic literature, early soft-tissue coverage of open tibia fractures requiring flaps should ideally be performed within 72 hours, and generally no later than 7 days from the injury. Delayed coverage beyond 7 days significantly increases the rates of deep infection, flap failure, and eventual nonunion.

Question 8280

Topic: 2. Trauma

A 28-year-old man sustains a closed diaphyseal fracture of the tibia. Eight hours post-admission, he complains of worsening leg pain that is out of proportion to the injury and not relieved by intravenous opioids. Examination reveals tense calf compartments and excruciating pain with passive dorsiflexion of the hallux. His blood pressure is 110/70 mm Hg. Intracompartmental pressure monitoring is obtained. Which of the following pressure readings provides the strongest absolute indication for emergent fasciotomy?

. Absolute intracompartmental pressure of 25 mm Hg
. Absolute intracompartmental pressure of 30 mm Hg
. Delta pressure (Diastolic BP minus compartment pressure) of 20 mm Hg
. Delta pressure (Diastolic BP minus compartment pressure) of 45 mm Hg
. Delta pressure (Mean arterial pressure minus compartment pressure) of 40 mm Hg

Correct Answer & Explanation

. Delta pressure (Diastolic BP minus compartment pressure) of 20 mm Hg

Explanation

The most reliable and universally accepted threshold for diagnosing acute compartment syndrome in a borderline or uncooperative patient is the delta pressure (Delta P), calculated as the diastolic blood pressure minus the measured intracompartmental pressure. A Delta P of less than 30 mm Hg indicates critically impaired tissue perfusion and is an absolute indication for emergent fasciotomy. In this scenario, a Delta P of 20 mm Hg (indicating a compartment pressure of 50 mm Hg) clearly mandates surgical release.

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