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2. Trauma MCQs

Practice Set 243 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 4841

Topic: 2. Trauma

A 68-year-old female sustains a proximal humerus fracture. According to classic anatomic studies by Hertel et al., which combination of radiographic findings is the most reliable predictor of humeral head ischemia?

. Calcar length < 8 mm and disrupted medial hinge.
. Calcar length > 8 mm and intact medial hinge.
. Anatomic neck fracture with a displaced greater tuberosity.
. Surgical neck fracture with >45 degrees of angulation.
. Displaced lesser tuberosity with an intact calcar.

Correct Answer & Explanation

. Calcar length < 8 mm and disrupted medial hinge.

Explanation

Hertel et al. described predictors of humeral head ischemia after proximal humerus fractures. The most reliable predictors of AVN are a lack of metaphyseal head extension (calcar length less than 8 mm), disruption of the medial hinge, and a basicervical (anatomic neck) fracture pattern. When all three are present, the positive predictive value for ischemia is 97%.

Question 4842

Topic: 2. Trauma

A 22-year-old male motorcyclist is brought to the trauma bay after a high-speed collision. Chest radiograph shows lateral displacement of the left scapula with an intact clavicle but widely separated acromioclavicular and sternoclavicular joints. What is the most critical immediate step in evaluating this patient?

. MRI of the brachial plexus.
. CT angiogram of the upper extremity.
. Application of a figure-of-eight brace.
. Immediate closed reduction of the AC joint.
. EMG/NCS of the left upper extremity.

Correct Answer & Explanation

. CT angiogram of the upper extremity.

Explanation

The patient has a scapulothoracic dissociation, characterized by lateral displacement of the scapula and massive soft tissue injury. This represents a closed forequarter amputation. The most critical immediate concern is vascular injury (subclavian or axillary artery), which occurs in up to 80% of cases and can be rapidly fatal. CT angiography is the most critical immediate step.

Question 4843

Topic: 2. Trauma

In the development of acute compartment syndrome following a tibial shaft fracture, what is the initial microvascular event that triggers the cascade leading to muscle necrosis?

. Arterial vasospasm.
. Venous outflow obstruction.
. Arteriovenous shunting.
. Capillary endothelial damage leading to protein leak.
. Lymphatic occlusion.

Correct Answer & Explanation

. Venous outflow obstruction.

Explanation

The pathophysiology of acute compartment syndrome begins with an increase in intracompartmental pressure that surpasses local venous pressure. This leads to venous outflow obstruction, which causes a further increase in intracompartmental pressure, eventually collapsing the capillary bed. This eliminates the local tissue perfusion gradient, leading to ischemia. Arterial inflow is maintained until very late in the process.

Question 4844

Topic: 2. Trauma
A 25-year-old male sustains a vertically oriented (Pauwels Type III) femoral neck fracture. He undergoes closed reduction and internal fixation with three parallel cancellous screws. Which of the following biomechanical forces is the primary driver of failure (varus collapse and nonunion) in this specific fracture pattern?
. Compression forces.
. Shear forces.
. Tensile forces on the inferior neck.
. Rotational forces in external rotation.
. Distraction forces.

Correct Answer & Explanation

. Shear forces.

Explanation

Pauwels Type III femoral neck fractures are highly vertical (fracture angle >50 degrees from the horizontal). This vertical orientation converts vertical weight-bearing compressive forces into high shear forces across the fracture site. This predisposes the construct to varus collapse, loss of fixation, and nonunion when treated with simple parallel cancellous screws.

Question 4845

Topic: 2. Trauma

A 35-year-old female presents with a highly comminuted intra-articular distal femur fracture. CT scan reveals a coronal plane shear fracture of the lateral femoral condyle (Hoffa fracture). What is the optimal direction of lag screw placement for isolated fixation of this specific condylar fragment to maximize biomechanical stability?

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

Correct Answer & Explanation

. Anterior-to-posterior

Explanation

A Hoffa fracture is a coronal shear fracture of the femoral condyle. Biomechanical studies demonstrate that anterior-to-posterior lag screw fixation (often countersunk through the anterior articular cartilage or placed just proximal to the trochlea) provides the most stable construct to resist the posterior shear forces exerted by the gastrocnemius muscles.

Question 4846

Topic: 2. Trauma

A 35-year-old male sustains a posterior wall acetabular fracture with a concomitant posterior hip dislocation. During open reduction and internal fixation, an area of marginal impaction of the articular surface is identified. Which of the following surgical steps regarding this impacted fragment is most critical to prevent rapid onset of post-traumatic arthrosis?

. Excision of the impacted articular fragment to prevent mechanical catching
. Elevation of the impacted fragment and grafting of the underlying metaphyseal void
. Fixation of the impacted fragment in situ without elevation to preserve its blood supply
. Using a spring plate to compress the impacted fragment against the femoral head
. Performing a trochanteric flip osteotomy to visualize and bypass the impacted segment

Correct Answer & Explanation

. Elevation of the impacted fragment and grafting of the underlying metaphyseal void

Explanation

Marginal impaction refers to the depression of the osteochondral articular surface into the underlying cancellous bone of the acetabulum. Failure to recognize, elevate, and bone graft this impacted articular segment leads to incongruity of the joint surface, which is the most reliable predictor of poor clinical outcomes and rapid post-traumatic arthrosis following posterior wall acetabular fractures.

Question 4847

Topic: 2. Trauma

A 55-year-old female undergoes open reduction and internal fixation of a comminuted distal femur fracture (OTA/AO 33-C2) using a lateral locked plate. Which of the following technical errors during fixation most significantly increases the risk of asymmetric callus formation and subsequent nonunion?

. Use of a titanium rather than a stainless steel plate
. Leaving a gap of >2mm at the metaphyseal-diaphyseal junction
. Excessive rigidity of the diaphyseal construct resulting from an inadequate working length
. Placing the plate slightly anterior to the mid-axial line on the femoral shaft
. Applying a far-cortical locking screw configuration

Correct Answer & Explanation

. Excessive rigidity of the diaphyseal construct resulting from an inadequate working length

Explanation

Bridge plating of comminuted fractures relies on relative stability to promote secondary bone healing via callus formation. Excessive rigidity, commonly caused by using too many locking screws near the fracture site (inadequate working length), prevents the interfragmentary micro-motion necessary for callus formation, particularly on the far cortex. This leads to asymmetric callus and a high risk of nonunion and hardware failure.

Question 4848

Topic: 2. Trauma

A 30-year-old male presents 3 months after a conservatively managed, closed tibial shaft fracture with a progressive claw toe deformity of his lesser toes. He reports no pain but has difficulty fitting into shoes. Clinical examination reveals fixed flexion contractures at the distal interphalangeal joints of the lesser toes. Ischemic contracture of which of the following muscles is the most likely etiology?

. Flexor hallucis longus
. Extensor digitorum longus
. Flexor digitorum longus
. Tibialis posterior
. Lumbricals

Correct Answer & Explanation

. Flexor digitorum longus

Explanation

The patient is exhibiting signs of a missed deep posterior compartment syndrome of the leg. The deep posterior compartment contains the Tibialis posterior, Flexor digitorum longus (FDL), and Flexor hallucis longus (FHL). Ischemic contracture of the FDL leads to clawing of the lesser toes, whereas FHL contracture would lead to clawing of the great toe.

Question 4849

Topic: 2. Trauma

In the management of a 'floating shoulder' (ipsilateral displaced clavicle and scapular neck fractures), open reduction and internal fixation of the clavicle alone is often sufficient to indirectly reduce the scapular neck. However, operative fixation of the scapula is specifically indicated over clavicle-only fixation if the glenopolar angle (GPA) falls below what threshold?

. 10 degrees
. 22 degrees
. 35 degrees
. 45 degrees
. 60 degrees

Correct Answer & Explanation

. 22 degrees

Explanation

The glenopolar angle (GPA) assesses the rotational displacement of the glenoid in scapular neck fractures. The normal GPA is between 30 and 45 degrees. A severely decreased GPA (typically < 22 degrees) is associated with poor functional outcomes and is a recognized indication for direct operative fixation of the scapula, rather than relying on indirect reduction via clavicular fixation.

Question 4850

Topic: 2. Trauma

A 32-year-old motorcyclist is brought to the trauma bay following a high-speed collision. He presents with a flail, pulseless right upper extremity. An anteroposterior chest radiograph reveals a displaced clavicle fracture and a laterally displaced scapula compared to the contralateral side. Recognizing this pattern as a likely scapulothoracic dissociation, which of the following is the most appropriate next step to diagnose the extent of the most life- and limb-threatening associated injury?

. Immediate operative exploration of the brachial plexus via a supraclavicular approach
. CT angiography (CTA) of the upper extremity
. Magnetic Resonance Imaging (MRI) of the cervical spine
. Electromyography (EMG) of the upper extremity
. Diagnostic laparoscopy

Correct Answer & Explanation

. CT angiography (CTA) of the upper extremity

Explanation

Scapulothoracic dissociation is a devastating closed forequarter amputation characterized by lateral displacement of the scapula, clavicle fracture or AC/SC joint disruption, and severe neurovascular injury. Vascular injury (subclavian or axillary artery) occurs in up to 88% of cases and is life-threatening. Therefore, an immediate CT angiogram (or formal angiography) is the most critical next step to evaluate for vascular injury in a pulseless extremity.

Question 4851

Topic: 2. Trauma
A 30-year-old male sustains a high-energy vertically oriented (Pauwels type III) displaced femoral neck fracture. Which of the following fixation constructs provides the most biomechanically stable construct against vertical shear forces?
. Three parallel cannulated screws
. Sliding hip screw with a derotation screw
. Dynamic condylar screw
. Proximal femoral nail with a single lag screw
. Cephalomedullary nail with dual lag screws

Correct Answer & Explanation

. Sliding hip screw with a derotation screw

Explanation

Pauwels III fractures experience high vertical shear forces. A sliding hip screw (fixed-angle construct) combined with an anti-rotation screw provides superior biomechanical stability against shear compared to multiple parallel cannulated screws.

Question 4852

Topic: 2. Trauma
A 45-year-old construction worker sustains a Gustilo-Anderson Type IIIB open tibia fracture. According to current evidence, what is the most critical initial factor in preventing a deep infection?
. Pulsatile lavage with 9 liters of normal saline
. Soft tissue coverage within 24 hours
. Time to administration of systemic antibiotics
. Use of local antibiotic beads at the fracture site
. Immediate internal fixation rather than external fixation

Correct Answer & Explanation

. Time to administration of systemic antibiotics

Explanation

The most significant independent factor in reducing infection rates in open fractures is the early administration of systemic antibiotics, ideally within 1 hour of injury. Timing of soft tissue coverage is also important but secondary to immediate antibiotic prophylaxis.

Question 4853

Topic: Upper Extremity Trauma

During a surgical reconstruction for a chronic Type V acromioclavicular (AC) joint separation, the surgeon aims to reconstruct the coracoclavicular ligaments. What is the approximate anatomic distance from the distal clavicle to the normal insertion of the conoid ligament?

. 1.5 cm
. 3.0 cm
. 4.5 cm
. 6.0 cm
. 7.5 cm

Correct Answer & Explanation

. 4.5 cm

Explanation

The conoid ligament inserts approximately 4.5 cm medial to the distal articular end of the clavicle, while the trapezoid ligament inserts approximately 3.0 cm medial to it. Knowledge of this anatomy is crucial for accurate tunnel placement during reconstruction.

Question 4854

Topic: 2. Trauma

A 32-year-old male develops acute compartment syndrome of the leg following a tibial plateau fracture. Which clinical finding specifically isolates involvement of the deep posterior compartment?

. Weakness in ankle dorsiflexion
. Decreased sensation in the first web space
. Pain with passive extension of the great toe
. Loss of eversion strength
. Decreased sensation over the lateral border of the foot

Correct Answer & Explanation

. Pain with passive extension of the great toe

Explanation

The deep posterior compartment contains the flexor hallucis longus (FHL), flexor digitorum longus (FDL), and tibialis posterior. Pain with passive extension of the toes (which stretches the FHL and FDL) is a classic sign of deep posterior compartment ischemia.

Question 4855

Topic: 2. Trauma

A 65-year-old female presents with a displaced 4-part proximal humerus fracture. According to the Hertel criteria, which radiographic finding is the most reliable predictor of humeral head ischemia?

. Angulation of the surgical neck > 45 degrees
. Displacement of the greater tuberosity > 1 cm
. A metaphyseal head extension (calcar length) of less than 8 mm
. Disruption of the lateral periosteal hinge
. Presence of a head-split fracture

Correct Answer & Explanation

. A metaphyseal head extension (calcar length) of less than 8 mm

Explanation

Hertel et al. identified that a metaphyseal head extension (calcar length) of < 8 mm, disruption of the medial hinge, and an anatomical neck fracture pattern are the most highly predictive factors for humeral head ischemia. A short calcar length indicates loss of critical vascular supply from the anterior humeral circumflex artery.

Question 4856

Topic: 2. Trauma
Osteonecrosis of the femoral head after intramedullary nailing in children is thought to be the result of injury to the
. artery within the ligamentum teres.
. medial femoral circumflex artery.
. lateral ascending cervical artery.
. lateral femoral circumflex artery.
. intraosseous blood supply.

Correct Answer & Explanation

. lateral ascending cervical artery.

Explanation

All of these are possible explanations for the development of osteonecrosis following intramedullary nailing in children. However, the lateral ascending cervical artery, which supplies the epiphysis, is much more vulnerable to injury in children because it lies in the trochanteric fossa.

Question 4857

Topic: 2. Trauma
A 10.5-year-old boy sustained the injury shown in Figure 72 when he fell out of a tree. This is a closed, neurologically intact injury and the patient has no head injury or loss of consciousness. He weighs 115 pounds and is otherwise healthy. What is the optimal treatment option for this injury?
. Immediate spica casting
. Flexible intramedullary nail placement
. Traction and casting
. External fixation
. Solid intramedullary nail fixation via the greater trochanter

Correct Answer & Explanation

. Solid intramedullary nail fixation via the greater trochanter

Explanation

Although flexible intramedullary nails are a good treatment alternative for femoral shaft fractures in older children, patients weighing more than 100 pounds have a higher incidence of complications that include bending of the nails. Therefore, transtrochanteric solid intramedullary nail fixation is most likely the best option for this patient. Using a greater trochanteric entry point avoids the piriformis fossa and the possibility of osteonecrosis.

Question 4858

Topic: 2. Trauma
A 25-year-old left hand-dominant man has severe left shoulder pain after being involved in a high-speed motor vehicle accident. Examination reveals that he is unable to move the left shoulder. His neurovascular status is intact in the entire left upper extremity. A radiograph is shown in Figure 19. What is the most appropriate surgical management of this injury?
. Arthroscopic reduction and fixation
. Percutaneous pinning
. Open reduction and internal fixation
. Hemiarthroplasty with tuberosity reconstruction
. Reverse shoulder arthroplasty

Correct Answer & Explanation

. Open reduction and internal fixation

Explanation

DISCUSSION: In this young patient, every attempt must be made to retain the native proximal humerus; therefore, open reduction and internal fixation should be attempted of both the articular segment and tuberosities to the humeral shaft. This is best accomplished through an open approach. Shoulder arthroplasty should be reserved for the elderly and for failed internal fixation.

Question 4859

Topic: 2. Trauma
Reamed femoral intramedullary nailing is associated with a higher rate of which of the following, as compared to nonreamed nailing for distal femur fractures?
. Malalignment
. Pulmonary complications
. Need for transfusion
. Iatrogenic fracture
. Union

Correct Answer & Explanation

. Union

Explanation

DISCUSSION: Reamed intramedullary femoral nailing is associated with a higher rate of union than nonreamed femoral nailing. The reference by the Canadian group randomized 224 patients to reamed vs. unreamed femoral nails and found that the relative risk of nonunion was 4.5x greater without reaming, and nonunion was also greater with the use of a small-diameter nail.

Question 4860

Topic: Upper Extremity Trauma

During reconstruction of the acromioclavicular joint, a graft is used to recreate the conoid and trapezoid ligaments. Which of the following best describes the anatomic footprint and biomechanical role of the conoid ligament?

. Inserts on the anterolateral clavicle and resists posterior translation
. Inserts on the posteromedial clavicle and primarily resists superior translation
. Inserts on the posterolateral clavicle and primarily resists anterior translation
. Inserts on the anteromedial clavicle and resists inferior translation
. Inserts on the distal clavicle and acts as the primary restraint to axial rotation

Correct Answer & Explanation

. Inserts on the posteromedial clavicle and primarily resists superior translation

Explanation

The conoid ligament inserts on the posteromedial aspect of the distal clavicle and is the primary restraint to superior translation. The trapezoid ligament inserts anterolaterally and resists posterior translation.

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