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2. Trauma MCQs

Practice Set 367 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 7321

Topic: 2. Trauma

When utilizing a proximal humerus locking plate for a comminuted surgical neck fracture, placement of the medial calcar screws is critical to prevent which of the following modes of construct failure?

. Varus collapse of the humeral head
. Valgus impaction of the humeral head
. Anterior translation of the greater tuberosity
. Nonunion of the lesser tuberosity
. Intra-articular screw penetration during elevation

Correct Answer & Explanation

. Varus collapse of the humeral head

Explanation

Placement of inferomedial calcar screws into the inferomedial quadrant of the humeral head provides critical mechanical support to the medial column. This resists the deforming forces of the pectoralis major and rotator cuff, significantly reducing the risk of varus collapse.

Question 7322

Topic: 2. Trauma

When evaluating a proximal humerus fracture, which of the following radiographic criteria is the strongest predictor of impending avascular necrosis (AVN) of the humeral head?

. Displacement of the greater tuberosity > 5mm
. Valgus impaction of the humeral head > 20 degrees
. Intra-articular extension into the anatomic neck
. A medial calcar segment attached to the articular surface measuring < 8 mm
. Diaphyseal extension of the fracture into the surgical neck

Correct Answer & Explanation

. Displacement of the greater tuberosity > 5mm

Explanation

Hertel's criteria for predicting ischemia of the humeral head include a short calcar length (< 8 mm) attached to the articular segment, disruption of the medial hinge, and basicervical fracture lines. These strongly correlate with high rates of AVN.

Question 7323

Topic: 2. Trauma

A 35-year-old man sustains a closed spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture). In the emergency department, he is noted to have an inability to extend his wrist and fingers. What is the most appropriate initial management?

. Immediate open reduction and internal fixation with radial nerve exploration
. Closed reduction and coaptation splinting
. External fixation
. Immediate primary nerve grafting
. Immediate amputation

Correct Answer & Explanation

. Immediate open reduction and internal fixation with radial nerve exploration

Explanation

A primary radial nerve palsy in the setting of a closed humeral shaft fracture is generally managed nonoperatively initially, as most palsies resolve spontaneously. Operative exploration is strictly indicated if a new palsy develops after an initially normal exam following closed reduction.

Question 7324

Topic: 2. Trauma

A 30-year-old man is evaluated in the emergency department after experiencing a first-time generalized tonic-clonic seizure. He has severe shoulder pain and his arm is locked in internal rotation. An AP radiograph shows a 'lightbulb' sign. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Anterior shoulder dislocation

Explanation

Posterior shoulder dislocations classically occur following seizures, electrocution, or severe trauma, presenting with the arm locked in internal rotation. The AP radiograph may show a 'lightbulb' sign due to internal rotation of the humeral head making it appear symmetrically spherical.

Question 7325

Topic: 2. Trauma

Which of the following radiographic criteria in a proximal humerus fracture is generally considered a strong indication for surgical intervention rather than nonoperative management?

. Greater tuberosity displacement of 3 mm
. Surgical neck angulation of 20 degrees
. Articular surface step-off of 1 mm
. Greater tuberosity displacement of 8 mm
. Shaft displacement of 10%

Correct Answer & Explanation

. Greater tuberosity displacement of 3 mm

Explanation

Displacement of the greater tuberosity greater than 5 mm is generally an indication for surgery in a proximal humerus fracture. Superior displacement of the tuberosity can lead to severe subacromial impingement and blocked external rotation.

Question 7326

Topic: 2. Trauma

A 42-year-old woman presents with a 7-month history of a painful midshaft humerus fracture initially treated with a functional brace. Radiographs show an atrophic nonunion with minimal callus. What is the most appropriate surgical treatment?

. Exchange intramedullary nailing
. Open reduction and internal fixation with compression plating and bone grafting
. Application of a fine-wire external fixator
. Pulsed electromagnetic field therapy
. Arthroscopic debridement of the fracture site

Correct Answer & Explanation

. Exchange intramedullary nailing

Explanation

Atrophic humeral shaft nonunions require rigid stability and biological stimulation. Open reduction with dynamic compression plating and autologous bone grafting is the gold standard, achieving very high union rates.

Question 7327

Topic: 2. Trauma

A 30-year-old male sustains a closed, spiral fracture of the distal third of the humeral shaft (Holstein-Lewis fracture) following an arm-wrestling match. On examination, he is unable to actively extend his wrist or fingers. Radiographs show acceptable alignment. What is the most appropriate initial management?

. Immediate open reduction and internal fixation with nerve exploration
. Application of a coaptation splint or functional brace and observation
. Electromyography (EMG) and nerve conduction studies
. Closed reduction under general anesthesia
. External fixation

Correct Answer & Explanation

. Immediate open reduction and internal fixation with nerve exploration

Explanation

Primary radial nerve palsy in the setting of a closed humeral shaft fracture is typically a neurapraxia and does not initially require surgical exploration. Expectant management with functional bracing and observation is standard, as >85% spontaneously recover.

Question 7328

Topic: 2. Trauma

A 68-year-old female presents with a 4-part proximal humerus fracture.

According to Hertel's criteria, which of the following radiographic findings is most predictive of humeral head ischemia and subsequent avascular necrosis?

. Greater tuberosity displacement > 5 mm
. Metaphyseal head extension (calcar length) < 8 mm
. Varus angulation > 20 degrees
. Comminution of the surgical neck
. Fracture of the lesser tuberosity

Correct Answer & Explanation

. Greater tuberosity displacement > 5 mm

Explanation

Hertel identified specific predictors for humeral head ischemia (AVN) following proximal humerus fractures. The most significant predictors include a metaphyseal calcar length < 8 mm, disruption of the medial hinge, and an anatomic neck fracture pattern.

Question 7329

Topic: 2. Trauma

An 8-month follow-up radiograph of a 45-year-old female treated nonoperatively for a midshaft humerus fracture shows a persistent fracture line with sclerotic, rounded bone ends and no bridging callus. Which of the following is the most appropriate surgical intervention for this atrophic nonunion?

. Intramedullary nailing without bone grafting
. Open reduction and internal fixation with compression plating and autogenous bone grafting
. Extracorporeal shock wave therapy
. Exchange casting with an functional brace
. External fixation

Correct Answer & Explanation

. Intramedullary nailing without bone grafting

Explanation

Atrophic nonunions lack adequate biological healing potential and require both rigid mechanical stability and biological augmentation. ORIF with compression plating and autogenous bone grafting (e.g., iliac crest) is the gold standard.

Question 7330

Topic: 2. Trauma

A 78-year-old female sustains a minimally displaced, 1-part proximal humerus fracture after a ground-level fall. Which of the following management strategies will best optimize her functional outcome and minimize complications?

. Strict immobilization in a sling for 6 weeks
. Sling immobilization for 1-2 weeks followed by early progressive range of motion
. Immediate open reduction and internal fixation with a locking plate
. Closed reduction and percutaneous pinning
. Hemiarthroplasty

Correct Answer & Explanation

. Strict immobilization in a sling for 6 weeks

Explanation

Minimally displaced proximal humerus fractures are treated nonoperatively. Early progressive range of motion (starting at 1-2 weeks) is crucial to prevent profound shoulder stiffness (adhesive capsulitis), which is the most common complication in this demographic.

Question 7331

Topic: 2. Trauma

During the insertion of a solid cortical screw for plate fixation, the surgeon notes that the screw resists fracture when subjected to high torque. The tensile strength of the screw, which dictates its resistance to fracture during insertion, is most directly determined by its:

. Major (outer) diameter
. Minor (core) diameter
. Pitch
. Lead
. Thread geometry

Correct Answer & Explanation

. Major (outer) diameter

Explanation

The minor (core) diameter is the solid central portion of the screw and determines its tensile strength and resistance to bending or breaking. The major (outer) diameter dictates the screw's pull-out strength.

Question 7332

Topic: 2. Trauma

Compared to conventional non-locking plates, locking compression plates (LCP) provide superior biomechanical stability in osteoporotic bone primarily because:

. They rely heavily on friction between the plate and the periosteum
. They function as fixed-angle devices that resist pullout and toggle
. They inherently have a higher area moment of inertia
. They induce primary bone healing exclusively via compression
. They dynamically increase the working length of the fracture construct

Correct Answer & Explanation

. They rely heavily on friction between the plate and the periosteum

Explanation

Locking plates utilize screws with threaded heads that lock into the plate, creating a fixed-angle construct. This relies on the combined strength of the screw-plate interface rather than bone-plate friction, making it superior for osteoporotic bone.

Question 7333

Topic: 2. Trauma

According to Perren's strain theory regarding fracture healing, what is the approximate maximum mechanical strain tolerated by granulation tissue during the initial inflammatory phase?

. 2%
. 10%
. 30%
. 100%
. 200%

Correct Answer & Explanation

. 2%

Explanation

Perren's strain theory dictates the type of tissue that can survive at a fracture site. Granulation tissue can tolerate up to 100% strain, allowing it to bridge highly mobile fracture gaps, whereas bone can only form when strain is reduced below 2%.

Question 7334

Topic: Lower Extremity Trauma

In orthopedic implant biomechanics, the bending stiffness of a solid cylindrical intramedullary nail is proportional to its radius raised to which power?

. Radius to the first power
. Radius squared
. Radius cubed
. Radius to the fourth power
. Radius to the fifth power

Correct Answer & Explanation

. Radius to the first power

Explanation

The bending stiffness of a solid cylinder is determined by the area moment of inertia, which is proportional to the radius to the fourth power (r^4). Therefore, a small increase in the radius significantly increases the nail's resistance to bending.

Question 7335

Topic: 2. Trauma

A 45-year-old man presents with a hypertrophic nonunion of a midshaft femur fracture 8 months after intramedullary nailing. What is the primary underlying cause of this specific type of nonunion?

. Avascularity at the fracture site
. Inadequate mechanical stability
. Chronic bacterial infection
. Interposition of soft tissue
. Systemic metabolic bone disease

Correct Answer & Explanation

. Avascularity at the fracture site

Explanation

A hypertrophic nonunion typically has adequate biology and blood supply, as evidenced by exuberant callus formation (the "elephant shoe" appearance). The failure to bridge the fracture gap is primarily due to inadequate mechanical stability.

Question 7336

Topic: 2. Trauma

Which of the following conditions is most likely to result in primary bone healing without callus formation?

. Intramedullary nailing of a femur fracture
. Casting of a tibial shaft fracture
. Bridge plating of a comminuted radius fracture
. Absolute stability achieved by anatomic reduction and dynamic compression plating
. External fixation of a pelvic ring injury

Correct Answer & Explanation

. Intramedullary nailing of a femur fracture

Explanation

Primary bone healing occurs via cutting cones crossing the fracture site. It requires absolute stability and anatomic reduction, typically achieved with rigid internal fixation like dynamic compression plating.

Question 7337

Topic: Lower Extremity Trauma

How does doubling the diameter of a solid intramedullary nail affect its torsional rigidity?

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

Correct Answer & Explanation

. Increases it by a factor of 2

Explanation

Torsional rigidity of a solid cylinder is proportional to the radius to the fourth power. Therefore, doubling the diameter increases the torsional rigidity by a factor of 16.

Question 7338

Topic: 2. Trauma

When placing a tension band construct on a transverse olecranon fracture, on which surface of the bone should the tension band be applied to be biomechanically effective?

. Compression side
. Tension side
. Neutral axis
. Medial surface
. Lateral surface

Correct Answer & Explanation

. Compression side

Explanation

A tension band must be applied to the tension side of a fractured bone. It acts dynamically to convert tensile forces on the convex side into compressive forces across the fracture site on the concave side.

Question 7339

Topic: 2. Trauma

Increasing the "working length" of an intramedullary nail or a plate construct has which of the following biomechanical effects?

. Increases the torsional stiffness of the construct
. Decreases the bending stiffness, making the construct more flexible
. Increases the axial compression across the fracture
. Decreases the strain on the hardware, increasing the risk of breakage
. Promotes primary bone healing

Correct Answer & Explanation

. Increases the torsional stiffness of the construct

Explanation

The working length is the distance between the two closest points of fixation across a fracture. Increasing it decreases the bending stiffness, making the construct more flexible and promoting secondary bone healing.

Question 7340

Topic: Lower Extremity Trauma

If the radius of a solid intramedullary nail is increased by a factor of two, its theoretical bending stiffness increases by a factor of:

. 2
. 4
. 8
. 16
. 32

Correct Answer & Explanation

. 2

Explanation

The bending stiffness of a solid cylinder is proportional to its area moment of inertia, which scales with the radius to the fourth power. Therefore, doubling the radius increases the theoretical bending stiffness by a factor of 16.

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