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2. Trauma MCQs

Practice Set 59 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 1161

Topic: 2. Trauma

A 30-year-old polytrauma patient undergoes damage control external fixation for a highly comminuted femoral shaft fracture. On day 5, his lactate has normalized. What is the maximum recommended time to convert the external fixator to an intramedullary nail to minimize infection risk?

. 7 days
. 14 days
. 21 days
. 28 days
. 35 days

Correct Answer & Explanation

. 14 days

Explanation

Conversion of a femoral external fixator to an intramedullary nail should ideally occur within 14 days. Delaying beyond two weeks significantly increases the risk of pin-tract colonization leading to deep intramedullary infection.

Question 1162

Topic: 2. Trauma

A 28-year-old male with a tibial shaft fracture develops disproportionate leg pain. Examination reveals tense calf compartments. Which parameter provides the most reliable objective threshold for diagnosing acute compartment syndrome?

. 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 (diastolic blood pressure minus absolute compartment pressure) is the most reliable indicator of compartment syndrome. A delta pressure of less than 30 mmHg necessitates urgent fasciotomy.

Question 1163

Topic: 2. Trauma

Six weeks after open reduction and internal fixation of a displaced talar neck fracture, a radiograph reveals subchondral radiolucency in the talar dome (Hawkins sign). What does this radiographic finding indicate?

. Onset of avascular necrosis
. Septic arthritis of the ankle joint
. Implant loosening
. Intact vascularity of the talar body
. Nonunion of the talar neck

Correct Answer & Explanation

. Intact vascularity of the talar body

Explanation

The Hawkins sign is a subchondral radiolucent band in the talar dome indicating subchondral osteopenia. It represents active bone resorption, which requires an intact blood supply, thereby indicating intact vascularity and a very low risk of AVN.

Question 1164

Topic: 2. Trauma
A 28-year-old male sustains a vertically oriented transcervical femoral neck fracture (Pauwels type III) in a motor vehicle accident. Which of the following fixation constructs provides the most biomechanical stability against shear forces for this specific fracture pattern?
. Three parallel cancellous screws placed in an inverted triangle
. A dynamic hip screw (DHS) with an anti-rotation screw
. A cephalomedullary nail
. Hemiarthroplasty
. Two parallel cancellous screws

Correct Answer & Explanation

. A dynamic hip screw (DHS) with an anti-rotation screw

Explanation

Pauwels type III fractures have a high degree of vertical shear instability. Biomechanical studies show that a sliding hip screw (DHS) combined with an anti-rotation screw provides superior resistance to shear forces compared to parallel cancellous screws.

Question 1165

Topic: 2. Trauma

A 40-year-old male sustains a coronal shear fracture of the lateral femoral condyle (Hoffa fracture). During open reduction and internal fixation, what is the biomechanically optimal direction for screw placement to capture the fracture fragment?

. Medial to lateral
. Lateral to medial
. Anterior to posterior
. Posterior to anterior
. Inferior to superior

Correct Answer & Explanation

. Anterior to posterior

Explanation

A Hoffa fracture is a coronal shear fracture of the femoral condyle. Anterior-to-posterior (AP) screw placement is biomechanically superior to PA placement for resisting the shear forces across the coronal fracture plane.

Question 1166

Topic: 2. Trauma

A 30-year-old male sustains a displaced talar neck fracture with subtalar subluxation but an intact tibiotalar joint (Hawkins Type II). At 8 weeks postoperatively, an AP radiograph of the ankle shows a subchondral radiolucent band in the talar dome. What does this radiographic finding indicate?

. Imminent avascular necrosis
. Presence of an intra-articular infection
. Nonunion of the talar neck
. Intact vascularity to the talar body
. Post-traumatic osteoarthritis

Correct Answer & Explanation

. Intact vascularity to the talar body

Explanation

A subchondral radiolucent band in the talar dome at 6-8 weeks is known as Hawkins sign. It represents subchondral atrophy (osteopenia) secondary to hyperemia, indicating intact vascular supply and a low risk of avascular necrosis.

Question 1167

Topic: Pelvic & Acetabular Trauma
A 45-year-old male arrives at the trauma bay hypotensive and tachycardic following a crush injury. Radiographs show a widened pubic symphysis (>3 cm) and disrupted sacroiliac joints. A pelvic binder is applied, and 2 units of packed RBCs are given, but his blood pressure remains 75/40 mmHg. A FAST exam is negative. What is the most appropriate next step?
. CT scan of the abdomen and pelvis
. Application of an external fixator
. Pre-peritoneal pelvic packing or angiography
. Exploratory laparotomy
. Administration of tranexamic acid and observation

Correct Answer & Explanation

. Pre-peritoneal pelvic packing or angiography

Explanation

In a hemodynamically unstable patient with a pelvic ring injury, negative FAST, and no response to initial resuscitation and binder application, the source of bleeding is likely retroperitoneal. Immediate pre-peritoneal pelvic packing or angioembolization is indicated.

Question 1168

Topic: Upper Extremity Trauma

Current anatomical and perfusion studies dictate that the primary blood supply to the articular segment (humeral head) in the proximal humerus is derived mainly from which of the following vessels?

. Anterior circumflex humeral artery
. Posterior circumflex humeral artery
. Suprascapular artery
. Thoracoacromial artery
. Profunda brachii artery

Correct Answer & Explanation

. Posterior circumflex humeral artery

Explanation

While historically the anterior circumflex humeral artery was thought to be the primary supply, recent anatomical studies demonstrate that the posterior circumflex humeral artery provides the majority (up to 64%) of the blood supply to the humeral head.

Question 1169

Topic: Pelvic & Acetabular Trauma
In the initial trauma bay management of a hemodynamically unstable patient with an anteroposterior compression (APC-III) pelvic ring injury, where should the pelvic binder be centered for optimal mechanical advantage?
. Anterior superior iliac spines
. Greater trochanters
. Iliac crests
. Symphysis pubis
. Sacral promontory

Correct Answer & Explanation

. Greater trochanters

Explanation

Pelvic binders should be centered directly over the greater trochanters to effectively close the pelvic ring and reduce pelvic volume. Placement over the iliac crests is incorrect and less mechanically effective.

Question 1170

Topic: 2. Trauma
A 28-year-old male sustains a high-energy Pauwels type III (vertical) femoral neck fracture. Which of the following fixation constructs provides the most biomechanically stable construct for this fracture pattern?
. Three inverted parallel cancellous screws
. Dynamic hip screw (sliding hip screw) with a derotational screw
. Cephalomedullary nail
. Hemiarthroplasty
. Two parallel cancellous screws

Correct Answer & Explanation

. Dynamic hip screw (sliding hip screw) with a derotational screw

Explanation

Vertical (Pauwels type III) femoral neck fractures in young adults experience high shear forces. A sliding hip screw combined with a derotational screw provides superior biomechanical stability compared to multiple cancellous screws.

Question 1171

Topic: 2. Trauma
According to current guidelines, what is the most appropriate initial antibiotic prophylaxis for a 45-year-old male presenting with a Gustilo-Anderson Type IIIA open tibia fracture resulting from a motorcycle accident?
. First-generation cephalosporin alone
. First-generation cephalosporin and an aminoglycoside
. First-generation cephalosporin, aminoglycoside, and high-dose penicillin
. Vancomycin and piperacillin-tazobactam
. Fluoroquinolone alone

Correct Answer & Explanation

. First-generation cephalosporin and an aminoglycoside

Explanation

For Gustilo Type III open fractures, standard prophylaxis historically and commonly on board exams includes a first-generation cephalosporin (for Gram-positives) plus an aminoglycoside (for Gram-negatives). Penicillin is added only if there is farm soil contamination.

Question 1172

Topic: 2. Trauma

A 30-year-old male with a comminuted tibial shaft fracture complains of severe pain out of proportion to his injury. Physical exam shows tense compartments. Blood pressure is 120/80 mmHg. What is the absolute threshold for delta pressure that mandates immediate four-compartment 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 (Diastolic BP minus absolute compartment pressure) is the most reliable indicator for acute compartment syndrome. A delta pressure of less than 30 mmHg is an indication for immediate fasciotomy.

Question 1173

Topic: 2. Trauma

A 70-year-old female on prolonged bisphosphonate therapy presents with thigh pain. Radiographs reveal lateral cortical thickening and a transverse radiolucent line in the subtrochanteric femur. If prophylactic intramedullary nailing is planned, what is the most critical technical objective to prevent iatrogenic fracture completion?

. Use of a flexible reamer
. Over-reaming the canal by 1.5 to 2.0 mm larger than the nail diameter
. Using an unreamed solid nail
. Fixation in 10 degrees of varus
. Restricting fixation to a sliding hip screw

Correct Answer & Explanation

. Over-reaming the canal by 1.5 to 2.0 mm larger than the nail diameter

Explanation

Atypical femur fractures in bisphosphonate users have hard, brittle bone and an increased anterolateral bow. Over-reaming the canal (by 1.5-2.0mm) is critical to prevent iatrogenic fracture during nail insertion.

Question 1174

Topic: 2. Trauma
A 25-year-old male sustains a displaced Pauwels type III (high shear angle) femoral neck fracture during a motor vehicle collision. Which of the following internal fixation constructs provides the most biomechanically stable fixation for this specific fracture pattern?
. Three parallel cannulated screws in an inverted triangle configuration.
. A fixed-angle sliding hip screw with an additional derotation screw.
. A dynamic condylar screw system.
. Hemiarthroplasty of the hip.
. A single large-diameter intramedullary nail.

Correct Answer & Explanation

. A fixed-angle sliding hip screw with an additional derotation screw.

Explanation

Pauwels type III femoral neck fractures have a highly vertical orientation, subjecting them to extreme shear forces. A fixed-angle sliding hip screw with a supplemental derotation screw provides superior biomechanical stability against shear and varus collapse compared to multiple parallel cannulated screws.

Question 1175

Topic: Pelvic & Acetabular Trauma
A 42-year-old male is brought to the trauma bay after a crush injury. He has an anteroposterior compression (APC) type III pelvic ring injury and remains hypotensive despite aggressive fluid resuscitation and application of a pelvic binder. What is the most common anatomical source of major hemorrhage in unstable pelvic ring injuries?
. Posterior pelvic venous plexus
. Superior gluteal artery
. Internal pudendal artery
. External iliac artery
. Obturator artery

Correct Answer & Explanation

. Posterior pelvic venous plexus

Explanation

While arterial bleeding (such as from the superior gluteal artery or internal pudendal artery) can cause life-threatening hemorrhage, approximately 80-90% of bleeding in pelvic trauma originates from the pre-sacral and pre-vesical venous plexuses or the fractured cancellous bone surfaces.

Question 1176

Topic: 2. Trauma

A 22-year-old male undergoes intramedullary nailing for a closed comminuted tibial shaft fracture. Postoperatively, he requires increasing doses of opioids and has severe pain with passive toe extension. His blood pressure is 100/65 mmHg. Intracompartmental pressure monitoring reveals an absolute anterior compartment pressure of 42 mmHg. What is the most appropriate next step in management?

. Immediate four-compartment fasciotomy of the leg.
. Remove all dressings, elevate the leg above heart level, and reassess in 4 hours.
. Observation, as the absolute compartment pressure is less than 45 mmHg.
. Intravenous administration of mannitol and serial examinations.
. Perform a CT angiogram of the lower extremity to rule out arterial injury.

Correct Answer & Explanation

. Immediate four-compartment fasciotomy of the leg.

Explanation

Compartment syndrome is diagnosed clinically but confirmed when the Delta P (diastolic blood pressure minus absolute compartment pressure) is less than 30 mmHg. Here, the Delta P is 23 mmHg (65 - 42), mandating an emergent four-compartment fasciotomy to prevent irreversible muscle necrosis.

Question 1177

Topic: Lower Extremity Trauma

What is the most common anatomical location for a Non-Ossifying Fibroma?

. Vertebral body
. Diaphysis of long bones
. Epiphysis of long bones
. Metaphysis of long bones
. Small bones of the hand and foot

Correct Answer & Explanation

. Metaphysis of long bones

Explanation

Correct Answer: DNOFs almost exclusively occur in the metaphysis of long bones, with the distal femur, proximal tibia, and distal tibia being the most frequently affected sites. They originate in the cortex and grow into the medullary cavity.

Question 1178

Topic: 2. Trauma

Which statement regarding the cortical involvement of Non-Ossifying Fibroma is most accurate in predicting pathological fracture risk?

. Any cortical involvement, regardless of percentage, mandates prophylactic surgery.
. Fracture risk is directly proportional to the lesion's length along the bone, not its cortical involvement.
. Lesions involving more than 50% of the cortical diameter are considered high risk for pathological fracture.
. Cortical thickening is a sign of impending fracture.
. Fracture risk is only present if the lesion is located in the diaphysis.

Correct Answer & Explanation

. Lesions involving more than 50% of the cortical diameter are considered high risk for pathological fracture.

Explanation

Correct Answer: CThe most widely accepted criterion for increased pathological fracture risk in NOF is involvement of more than 50% of the cortical diameter. This significantly weakens the bone. Cortical thinning is more common than thickening. Length along the bone is less critical than cross-sectional cortical involvement. NOFs are metaphyseal, not diaphyseal, and fracture risk is directly related to structural weakening.

Question 1179

Topic: 2. Trauma

A 9-year-old boy sustains a minimally displaced pathologic fracture through a 4 cm non-ossifying fibroma in the distal femur after a minor fall. What is the most appropriate initial management?

. Immediate curettage and bone grafting with internal fixation
. Cast immobilization or bracing until the fracture heals
. Wide resection and endoprosthetic reconstruction
. Intralesional corticosteroid injection
. Preoperative radiation followed by curettage

Correct Answer & Explanation

. Cast immobilization or bracing until the fracture heals

Explanation

Pathologic fractures through a non-ossifying fibroma (NOF) are typically treated non-operatively with cast immobilization to allow the fracture to heal. As the fracture heals, the NOF often ossifies; if the lesion persists and remains mechanically weak after healing, curettage and grafting can be considered later.

Question 1180

Topic: 2. Trauma

A 12-year-old boy is incidentally found to have a large non-ossifying fibroma in the distal tibia. Which of the following radiographic parameters is the most widely accepted threshold indicating a significantly increased risk of pathologic fracture, potentially warranting prophylactic surgical intervention?

. Lesion occupying greater than 50% of the bone diameter
. Lesion length greater than 2 cm
. Presence of a thick, continuous sclerotic margin
. Extension of the lesion into the secondary ossification center
. The presence of a single, solid lamellated periosteal reaction

Correct Answer & Explanation

. Lesion occupying greater than 50% of the bone diameter

Explanation

Prophylactic curettage and bone grafting for an NOF is generally considered when the lesion occupies >50% of the transverse diameter of the bone or is >33 mm in length, as these parameters strongly correlate with an increased risk of pathologic fracture.

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