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2. Trauma MCQs

Practice Set 638 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 12741

Topic: 2. Trauma
A 30-year-old male sustains a high-energy Pauwels type III femoral neck fracture. Based on the fracture morphology, why is this specific fracture pattern at a significantly higher risk for mechanical failure and nonunion compared to Pauwels type I fractures?
. Higher incidence of deep infection
. High shear forces causing varus collapse
. Increased baseline rates of osteoporosis in this demographic
. Greater risk of anterior hip dislocation
. Decreased vascularity to the femoral head compared to type I

Correct Answer & Explanation

. High shear forces causing varus collapse

Explanation

Pauwels type III fractures have a vertical orientation (fracture angle > 50 degrees). This steep angle converts physiological loads into profound shear forces, greatly increasing the risk of varus collapse, fixation failure, and nonunion.

Question 12742

Topic: Pelvic & Acetabular Trauma
A 40-year-old male presents in hemorrhagic shock following a crush injury to the pelvis. Anteroposterior pelvic radiograph demonstrates an anteroposterior compression type III (APC-III) pelvic ring injury with a widely displaced symphysis and completely disrupted sacroiliac joints. A pelvic binder is applied, and his blood pressure transiently improves. What is the predominant anatomic source of hemorrhage in this specific injury pattern?
. Superior gluteal artery
. Corona mortis
. Presacral venous plexus
. Internal pudendal artery
. Obturator artery

Correct Answer & Explanation

. Presacral venous plexus

Explanation

The presacral venous plexus and bleeding from fractured cancellous bone surfaces account for approximately 80% of hemorrhage in unstable pelvic ring fractures. Arterial bleeding occurs in a minority of cases, more typically involving branches of the internal iliac system such as the superior gluteal or internal pudendal arteries.

Question 12743

Topic: 2. Trauma

A 28-year-old male sustains a closed, highly comminuted midshaft tibia fracture treated with reamed intramedullary nailing. Twelve hours postoperatively, he requires rapidly escalating doses of intravenous opioids. His pain is severely exacerbated by passive stretch of the hallux, and the leg feels tense. If intra-compartmental pressures are measured, which of the following values is the most universally accepted threshold for diagnosing acute compartment syndrome?

. Absolute compartment pressure > 20 mmHg
. Absolute compartment pressure > 25 mmHg
. Diastolic blood pressure minus compartment pressure < 30 mmHg
. Mean arterial pressure minus compartment pressure > 40 mmHg
. Systolic blood pressure minus compartment pressure < 10 mmHg

Correct Answer & Explanation

. Diastolic blood pressure minus compartment pressure < 30 mmHg

Explanation

Acute compartment syndrome is most accurately diagnosed using the delta pressure, calculated as the patient's diastolic blood pressure minus the absolute compartment pressure. A delta pressure of less than 30 mmHg indicates critically impaired tissue perfusion and is the standard threshold for emergent fasciotomy.

Question 12744

Topic: 2. Trauma

A 35-year-old male is brought to the emergency department following a generalized tonic-clonic seizure. He complains of severe right shoulder pain and an inability to move the arm. On examination, the arm is locked in adduction and internal rotation. An axillary radiograph reveals a posterior shoulder dislocation. Which of the following osseous defects is most likely to be identified on advanced imaging?

. A compression fracture of the posterolateral aspect of the humeral head
. An avulsion fracture of the greater tuberosity
. A compression fracture of the anteromedial aspect of the humeral head
. An avulsion fracture of the anterior inferior glenoid rim
. A fracture of the coracoid process

Correct Answer & Explanation

. A compression fracture of the anteromedial aspect of the humeral head

Explanation

Correct Answer: CPosterior shoulder dislocations are classically associated with seizures, electrocution, or high-energy trauma with the arm in a flexed, adducted, and internally rotated position. The classic osseous lesion associated with a posterior dislocation is the reverse Hill-Sachs lesion, which is an impaction fracture of the anteromedial aspect of the humeral head caused by the posterior glenoid rim. A standard Hill-Sachs lesion (posterolateral) is seen in anterior dislocations.

Question 12745

Topic: 2. Trauma

A 35-year-old male presents to the emergency department after experiencing a first-time generalized tonic-clonic seizure. He complains of severe right shoulder pain and an inability to move the arm. On physical examination, his right arm is locked in internal rotation and adduction. Radiographs confirm a posterior glenohumeral dislocation. Which of the following osseous lesions is most commonly associated with this specific mechanism of injury?

. Anteroinferior glenoid rim fracture
. Posterolateral humeral head impaction fracture
. Anteromedial humeral head impaction fracture
. Greater tuberosity fracture
. Coracoid process fracture

Correct Answer & Explanation

. Anteromedial humeral head impaction fracture

Explanation

Correct Answer: Anteromedial humeral head impaction fracturePosterior shoulder dislocations are classically caused by seizures, electrical shocks, or high-energy trauma. The intense, uncoordinated muscle contractions during a seizure (where the stronger internal rotators overpower the external rotators) force the humeral head posteriorly. As the humeral head dislocates posteriorly, the anterior aspect of the humeral head impacts against the posterior glenoid rim, creating an anteromedial humeral head impaction fracture, known as a reverse Hill-Sachs lesion. A posterolateral impaction fracture (Hill-Sachs lesion) is seen in anterior dislocations.

Question 12746

Topic: 2. Trauma

A 45-year-old man presents to the emergency department with shoulder pain after a fall from a ladder. Anteroposterior (AP) radiographs of the shoulder reveal a "lightbulb" sign and a "trough line" sign. Which of the following is the most likely diagnosis?

. Anterior shoulder dislocation
. Posterior shoulder dislocation
. Inferior shoulder dislocation (luxatio erecta)
. Acromioclavicular joint separation
. Proximal humerus fracture

Correct Answer & Explanation

. Posterior shoulder dislocation

Explanation

Correct Answer: Posterior shoulder dislocationPosterior shoulder dislocations are notoriously missed on standard AP radiographs because the humeral head may appear to be in the glenoid. The "lightbulb" sign occurs because the humerus is locked in internal rotation, causing the humeral head to appear symmetric and rounded, resembling a lightbulb. The "trough line" sign represents the impaction fracture on the anteromedial humeral head (reverse Hill-Sachs lesion) created by the posterior glenoid rim. An axillary or scapular Y view is essential to confirm the posterior direction of the dislocation.

Question 12747

Topic: 2. Trauma

A 40-year-old electrician is evaluated in the emergency department following an electrocution injury. An AP shoulder radiograph reveals a 'trough line' sign. This radiographic finding corresponds to which of the following pathoanatomic lesions?

. Fracture of the posterior glenoid rim
. Impaction fracture of the posterolateral humeral head
. Impaction fracture of the anteromedial humeral head
. Avulsion fracture of the lesser tuberosity
. Avulsion fracture of the greater tuberosity

Correct Answer & Explanation

. Impaction fracture of the anteromedial humeral head

Explanation

The 'trough line' is an impaction fracture of the anteromedial aspect of the humeral head (reverse Hill-Sachs lesion). It is created when the anterior humeral head impacts the posterior glenoid rim during a posterior dislocation.

Question 12748

Topic: 2. Trauma

A 12-year-old pre-menarchal girl presents with a 2.0 cm leg length discrepancy due to a previously treated left femoral shaft fracture resulting in overgrowth. Her bone age matches her chronologic age. What is the most appropriate management to achieve equal leg lengths at maturity?

. Immediate contralateral distal femoral epiphysiodesis
. Observation until skeletal maturity followed by limb lengthening
. Contralateral proximal tibial epiphysiodesis at age 14
. Immediate ipsilateral femoral shortening osteotomy

Correct Answer & Explanation

. Immediate contralateral distal femoral epiphysiodesis

Explanation

A 12-year-old girl has approximately 2 years of growth remaining. A distal femoral epiphysiodesis arrests approximately 1 cm of growth per year, reliably correcting a 2.0 cm discrepancy by skeletal maturity.

Question 12749

Topic: 2. Trauma
A 45-year-old man presents with a Pauwels type III femoral neck fracture nonunion. A valgus-producing intertrochanteric osteotomy is planned. What is the primary biomechanical goal of this procedure?
. To increase the abductor moment arm
. To convert shear forces at the nonunion site into compressive forces
. To shift the mechanical axis medial to the knee joint
. To artificially increase the overall leg length

Correct Answer & Explanation

. To convert shear forces at the nonunion site into compressive forces

Explanation

A valgus osteotomy makes the fracture line more horizontal relative to the ground, decreasing the Pauwels angle. This mechanically converts destabilizing shear forces into stabilizing compressive forces, facilitating bony union.

Question 12750

Topic: Lower Extremity Trauma

At skeletal maturity, a healthy, asymptomatic patient is diagnosed with a projected leg length discrepancy of 1.5 cm. What is the most appropriate initial management?

. Observation and reassurance.
. Prescription of a 1.5 cm shoe lift.
. Contralateral distal femoral epiphysiodesis.
. Femoral shortening osteotomy.
. Tibial lengthening over an intramedullary nail.

Correct Answer & Explanation

. Observation and reassurance.

Explanation

Limb length discrepancies less than 2.0 cm at skeletal maturity are typically asymptomatic and well-tolerated. Observation without any active intervention or shoe lift is the most appropriate management.

Question 12751

Topic: Lower Extremity Trauma

In evaluating sagittal plane deformities of the proximal tibia, what is the normal posterior proximal tibial angle (PPTA)?

. 70 degrees
. 81 degrees
. 90 degrees
. 95 degrees
. 100 degrees

Correct Answer & Explanation

. 81 degrees

Explanation

The normal posterior proximal tibial angle (PPTA) is 81 degrees (range 77-84 degrees). This parameter describes the normal posterior slope of the tibial plateau in the sagittal plane.

Question 12752

Topic: Lower Extremity Trauma

During deformity planning for a varus knee, the Joint Line Convergence Angle (JLCA) is measured at 7 degrees medially convergent. The normal JLCA is 0 to 2 degrees. What does this abnormal JLCA strongly imply?

. An extra-articular bony deformity of the distal femur.
. An extra-articular bony deformity of the proximal tibia.
. A primary valgus alignment of the mechanical axis.
. Fixed medial compartment cartilage loss or lateral collateral ligament laxity.
. Normal physiologic bowing in a skeletal mature patient.

Correct Answer & Explanation

. Fixed medial compartment cartilage loss or lateral collateral ligament laxity.

Explanation

An abnormal JLCA indicates an intra-articular source of deformity. In a varus knee with a medially convergent JLCA, this is typically due to asymmetric medial joint space narrowing (cartilage loss) or lateral ligamentous laxity.

Question 12753

Topic: Lower Extremity Trauma

A 10-year-old girl with a predicted leg length discrepancy of 3 cm at skeletal maturity is scheduled for a distal femoral epiphysiodesis. According to the Menelaus method and Green-Anderson growth data, approximately how much lower extremity growth per year is expected specifically from the distal femur?

. 6 mm/year
. 10 mm/year
. 13 mm/year
. 16 mm/year
. 20 mm/year

Correct Answer & Explanation

. 10 mm/year

Explanation

The distal femur contributes approximately 10 mm (3/8 inch) of growth per year until skeletal maturity. In contrast, the proximal tibia contributes approximately 6 mm (1/4 inch) per year.

Question 12754

Topic: Lower Extremity Trauma

The Menelaus method is a simplified arithmetic rule used to estimate remaining growth for timing epiphysiodesis in leg length discrepancies. This method assumes that lower extremity growth ceases at what ages for girls and boys, respectively?

. 12 and 14 years
. 13 and 15 years
. 14 and 16 years
. 16 and 18 years
. 18 and 21 years

Correct Answer & Explanation

. 14 and 16 years

Explanation

The Menelaus arithmetic method simplifies growth remaining calculations by assuming growth ceases at age 14 for girls and age 16 for boys. It applies standard growth rates of 10 mm/yr for the distal femur and 6 mm/yr for the proximal tibia during these remaining years.

Question 12755

Topic: 2. Trauma

The Taylor Spatial Frame utilizes six independent struts to correct multidirectional deformities simultaneously. This external fixation system is based mathematically on which of the following kinematic models?

. The Ilizarov tension-stress effect
. The Paley multiplier method
. The Stewart-Gough platform
. The Euler buckling theorem
. The Menelaus arithmetic rule

Correct Answer & Explanation

. The Stewart-Gough platform

Explanation

The Taylor Spatial Frame (TSF) is a hexapod external fixator based on the Stewart-Gough platform mechanism. This mathematical model provides six degrees of freedom, allowing for precise, simultaneous correction of complex multidirectional deformities.

Question 12756

Topic: 2. Trauma

A 45-year-old male sustained a severe traumatic brain injury and an associated acetabular fracture. To prevent heterotopic ossification (HO) following open reduction internal fixation, which of the following regimens is most appropriate while minimizing fracture nonunion risk?

. High-dose Indomethacin for 6 weeks
. Single fraction 700 cGy radiation therapy postoperatively
. Etidronate for 12 weeks
. Low-dose Indomethacin for 3 days
. Methotrexate for 2 weeks

Correct Answer & Explanation

. Single fraction 700 cGy radiation therapy postoperatively

Explanation

Single fraction radiation (700-800 cGy) given within 24-48 hours post-op is highly effective for HO prophylaxis. NSAIDs like Indomethacin risk impaired fracture healing, which is especially concerning in multitrauma patients.

Question 12757

Topic: 2. Trauma
Following a severe traumatic brain injury and subsequent open reduction internal fixation of an acetabular fracture, a 35-year-old male develops significant stiffness in the affected hip. Radiographs reveal bone bridging the pelvis and the proximal femur, resulting in apparent hip ankylosis. According to the Brooker classification, what grade is this heterotopic ossification?
. Grade I
. Grade II
. Grade III
. Grade IV
. Grade V

Correct Answer & Explanation

. Grade IV

Explanation

The Brooker classification describes heterotopic ossification of the hip. Grade I is islands of bone; Grade II has >1 cm between opposing bone surfaces; Grade III has <1 cm between opposing surfaces; and Grade IV represents true radiographic bone ankylosis.

Question 12758

Topic: 2. Trauma

A 45-year-old male sustains an acetabular fracture requiring open reduction and internal fixation. The surgeon plans to prescribe indomethacin for heterotopic ossification prophylaxis. Which of the following is the most significant musculoskeletal risk associated with this therapy?

. Increased risk of deep vein thrombosis
. Avascular necrosis of the femoral head
. Nonunion of the fracture
. Premature closure of the triradiate cartilage
. Chondrolysis of the hip joint

Correct Answer & Explanation

. Nonunion of the fracture

Explanation

Indomethacin, a non-selective NSAID, inhibits COX enzymes, which are necessary for the normal inflammatory phase of fracture healing. Its use for HO prophylaxis significantly increases the risk of fracture nonunion and is generally contraindicated when simultaneous long bone or pelvic fracture healing is required.

Question 12759

Topic: 2. Trauma

A 25-year-old patient presents with a distal femur fracture after a minor fall. An AP radiograph is shown.

The radiograph reveals an "Erlenmeyer flask" deformity and an "endobone" appearance. What is the fundamental defect leading to this metaphyseal flaring?

. Defective metaphyseal osteoclastic remodeling
. Hyperactive physeal chondrocyte proliferation
. Excessive periosteal appositional bone growth
. Failure of primary mineralization of the osteoid matrix
. Avascular necrosis of the distal femoral epiphysis

Correct Answer & Explanation

. Defective metaphyseal osteoclastic remodeling

Explanation

The Erlenmeyer flask deformity in osteopetrosis is caused by defective osteoclastic modeling of the metaphysis. Normal bone requires osteoclasts to narrow the metaphysis as it transitions into the diaphysis.

Question 12760

Topic: 2. Trauma

A 4-year-old boy with a history of severe anemia presents with a subtrochanteric femur fracture. Radiographs show a "bone-within-a-bone" appearance.

What is the most severe neurological complication associated with this condition?

. Syringomyelia
. Atlantoaxial instability
. Cranial nerve palsies leading to blindness and deafness
. Basilar invagination
. Central sleep apnea

Correct Answer & Explanation

. Cranial nerve palsies leading to blindness and deafness

Explanation

Osteopetrosis causes diffuse osteosclerosis that narrows neural foramina. This leads to cranial nerve entrapment, most commonly resulting in blindness (optic nerve) and deafness (vestibulocochlear nerve).

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