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2. Trauma MCQs

Practice Set 390 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 7781

Topic: 2. Trauma

Recent anatomical studies and perfusion analyses (such as those by Hertel) regarding proximal humerus fractures have demonstrated that the primary blood supply to the humeral head is derived from which of the following?

. Ascending branch of the anterior humeral circumflex artery
. Posterior humeral circumflex artery
. Thoracoacromial artery
. Suprascapular artery
. Circumflex scapular artery

Correct Answer & Explanation

. Ascending branch of the anterior humeral circumflex artery

Explanation

Historically, the anterior humeral circumflex artery was considered the primary supply. However, recent studies demonstrate that the posterior humeral circumflex artery provides the majority of the blood supply to the humeral head.

Question 7782

Topic: 2. Trauma

Which of the following radiographic criteria is most strongly predictive of humeral head ischemia and avascular necrosis following a proximal humerus fracture?

. Metaphyseal head extension (calcar length) less than 8 mm
. Fracture of the greater tuberosity displaced > 5 mm
. Varus angulation of 10 degrees
. Intact medial hinge
. Fracture extending into the surgical neck only

Correct Answer & Explanation

. Metaphyseal head extension (calcar length) less than 8 mm

Explanation

Hertel described criteria predictive of humeral head ischemia, which include a metaphyseal head extension (calcar length) of less than 8 mm and disruption of the medial calcar hinge. These disrupt the critical blood supply.

Question 7783

Topic: 2. Trauma

A 35-year-old male presents to the emergency department after a generalized tonic-clonic seizure. His arm is locked in internal rotation and he has severe pain with any attempt at external rotation. Anteroposterior (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 commonly occur after seizures or electrical shocks due to the powerful internal rotators overpowering the external rotators. They clinically present with the arm locked in internal rotation and show a 'lightbulb' appearance on AP radiographs.

Question 7784

Topic: 2. Trauma

A 32-year-old male sustains a severe blunt trauma to his shoulder resulting in a scapular body fracture. Which of the following is considered an indication for open reduction and internal fixation of this fracture?

. 5 mm of medialization
. 10 degrees of angular deformity
. Medial/lateral displacement greater than 20 mm
. Presence of a concomitant non-displaced clavicle fracture
. Fracture extension into the scapular spine without displacement

Correct Answer & Explanation

. 5 mm of medialization

Explanation

Operative indications for extra-articular scapular body fractures include marked displacement, specifically medial/lateral translation greater than 20 mm or angular deformity greater than 45 degrees.

Question 7785

Topic: 2. Trauma

A 25-year-old male cyclist falls onto his shoulder and sustains a midshaft clavicle fracture. Which of the following findings is an absolute indication for acute operative intervention?

. 100% displacement without shortening
. 1.5 cm of shortening
. Impending open fracture with severe skin tenting and blanching
. Comminution with a butterfly fragment
. Concomitant non-displaced rib fractures

Correct Answer & Explanation

. 100% displacement without shortening

Explanation

Absolute indications for surgical fixation of a clavicle fracture include open fractures, neurovascular compromise, and impending open fractures (severe skin tenting with blanching/ischemia).

Question 7786

Topic: 2. Trauma

A 68-year-old woman sustains a proximal humerus fracture after a fall from standing height. Which of the following radiographic parameters is the most reliable predictor for the development of avascular necrosis (AVN) of the humeral head?

. Greater tuberosity displacement greater than 5 mm
. Varus angulation of 20 degrees
. Disruption of the medial hinge with a metaphyseal head extension (calcar length) of less than 8 mm
. Fracture extension into the surgical neck
. Presence of a concomitant nondisplaced lesser tuberosity fracture

Correct Answer & Explanation

. Greater tuberosity displacement greater than 5 mm

Explanation

Hertel criteria for predicting ischemia of the humeral head include a disrupted medial hinge and a short calcar segment (<8 mm attached to the articular segment). Disruption of these medial structures heavily compromises the ascending branch of the anterior humeral circumflex artery and intraosseous collateral blood supply.

Question 7787

Topic: Upper Extremity Trauma

A 28-year-old cyclist crashes over his handlebars and lands on his shoulder point. Radiographs reveal an acromioclavicular (AC) joint separation with the distal clavicle displaced superiorly by 150% compared to the acromion. Which two ligaments are primarily disrupted in this injury?

. Coracoacromial and acromioclavicular ligaments
. Conoid and trapezoid ligaments
. Coracohumeral and superior glenohumeral ligaments
. Transverse humeral and coracoacromial ligaments
. Sternoclavicular and costoclavicular ligaments

Correct Answer & Explanation

. Coracoacromial and acromioclavicular ligaments

Explanation

A Type III or higher AC separation involves complete disruption of both the acromioclavicular ligaments and the coracoclavicular (CC) ligaments. The CC ligaments consist of the medially based conoid ligament and the laterally based trapezoid ligament.

Question 7788

Topic: 2. Trauma

A 22-year-old cyclist sustains a completely displaced midshaft clavicle fracture. Which of the following findings serves as an absolute indication for immediate open reduction and internal fixation?

. 15 mm of shortening
. Severe pain with crepitus
. Skin tenting without blanching
. An associated open wound over the fracture site
. A Z-type butterfly fragment

Correct Answer & Explanation

. 15 mm of shortening

Explanation

Absolute indications for operative management of clavicle fractures include open fractures, neurovascular compromise, and severe skin tenting causing ischemia (blanching). Shortening and simple skin tenting are considered relative indications.

Question 7789

Topic: 2. Trauma

A 68-year-old female sustains a 4-part proximal humerus fracture. According to Hertel's criteria, which of the following radiographic features is the most reliable predictor for the development of humeral head avascular necrosis?

. Metaphyseal head extension length less than 8 mm
. An intact medial periosteal hinge
. Greater tuberosity displacement over 1 cm
. Valgus impaction of the head
. Displacement of the surgical neck > 5 mm

Correct Answer & Explanation

. Metaphyseal head extension length less than 8 mm

Explanation

Hertel's criteria for high AVN risk include a short calcar segment (metaphyseal extension <8 mm), a disrupted medial hinge, and an anatomic neck fracture line. Conversely, an intact medial hinge is strongly protective against ischemia.

Question 7790

Topic: Upper Extremity Trauma

A 24-year-old male falls directly onto his shoulder. Examination shows a prominent distal clavicle, and radiographs confirm a Rockwood Type V acromioclavicular (AC) joint separation with 150% superior displacement. What is the recommended management?

. Broad arm sling for 6 weeks
. Excision of the distal clavicle
. Hook plate fixation alone
. Surgical reconstruction of the coracoclavicular ligaments
. Acromioclavicular joint arthrodesis

Correct Answer & Explanation

. Broad arm sling for 6 weeks

Explanation

Type V AC joint injuries, characterized by severe superior displacement and stripping of the deltotrapezial fascia, generally require surgical reconstruction of the coracoclavicular ligaments to restore anatomy and function.

Question 7791

Topic: 2. Trauma

A 45-year-old man falls on his outstretched hand and presents with a displaced, comminuted fracture of the middle third of the clavicle with 2.5 cm of shortening. What is the most significant long-term consequence of nonoperative management of this specific fracture pattern?

. High risk of neurovascular compromise
. Decreased shoulder strength and endurance
. Scapular winging
. Glenohumeral arthritis
. Rotator cuff arthropathy

Correct Answer & Explanation

. High risk of neurovascular compromise

Explanation

Clavicle fractures with significant shortening (>2 cm) alter the resting mechanics of the shoulder girdle. This leads to symptomatic nonunion or malunion characterized by decreased shoulder strength, endurance, and altered scapular kinematics.

Question 7792

Topic: 2. Trauma

A 65-year-old woman sustains a highly displaced 4-part proximal humerus fracture. Which of the following radiographic parameters described by Hertel is the most reliable predictor of humeral head ischemia?

. Greater tuberosity displacement > 5 mm
. Lesser tuberosity comminution
. Angulation of the surgical neck > 45 degrees
. Metaphyseal head extension (calcar length) less than 8 mm
. Disruption of the anterior humeral circumflex artery

Correct Answer & Explanation

. Greater tuberosity displacement > 5 mm

Explanation

Hertel described predictors of humeral head ischemia in proximal humerus fractures. The most reliable predictors include a metaphyseal head extension (calcar segment) < 8 mm, disruption of the medial hinge (> 2 mm), and an anatomic neck fracture pattern.

Question 7793

Topic: 2. Trauma

A 25-year-old cyclist sustains a completely displaced midshaft clavicle fracture. Which of the following findings is considered an absolute indication for operative fixation?

. Shortening of 2 cm
. Z-type fracture comminution
. 100% superior displacement of the medial fragment
. Open fracture
. Presence of a cosmetic "bump" deformity

Correct Answer & Explanation

. Shortening of 2 cm

Explanation

Absolute indications for operative fixation of a clavicle fracture include open fractures, neurovascular compromise (e.g., subclavian artery injury), and symptomatic nonunion. Displacement, shortening (> 2 cm), and severe comminution are considered relative indications.

Question 7794

Topic: 2. Trauma

A 40-year-old male sustains an isolated extra-articular scapular neck fracture in a motor vehicle collision. Which of the following parameters represents an accepted indication for open reduction and internal fixation?

. Medial/lateral translation of 5 mm
. Glenopolar angle of 40 degrees
. Angulation of the structural neck > 40 degrees
. Intra-articular step-off of 2 mm
. 10% involvement of the glenoid fossa

Correct Answer & Explanation

. Medial/lateral translation of 5 mm

Explanation

Operative indications for extra-articular scapular neck/body fractures include > 40 degrees of angulation, medial/lateral translation > 1 cm (10 mm), and a glenopolar angle < 22 degrees. These thresholds identify significant displacement that may impair shoulder mechanics if left untreated.

Question 7795

Topic: 2. Trauma

A 55-year-old female undergoes open reduction and internal fixation of a proximal humerus fracture with a locking plate. Three months postoperatively, she develops new-onset pain, and radiographs demonstrate intra-articular screw penetration. What is the most common mechanical cause for this complication?

. Use of excessively long screws during the index procedure
. Loss of medial column support leading to varus collapse
. Avascular necrosis of the humeral head
. Unrecognized preoperative glenohumeral arthritis
. Failure of the greater tuberosity to heal

Correct Answer & Explanation

. Use of excessively long screws during the index procedure

Explanation

The most common cause of secondary screw penetration into the glenohumeral joint after locked plating of a proximal humerus fracture is varus collapse. This typically occurs due to a failure to surgically restore medial column support, such as inadequate placement of inferior calcar screws.

Question 7796

Topic: Upper Extremity Trauma

A 25-year-old male falls directly onto his acromion. Radiographs reveal 150% superior displacement of the distal clavicle relative to the acromion, and an axillary view shows the clavicle displaced posteriorly into the trapezius fascia. What is the Rockwood classification of this acromioclavicular joint injury?

. Type II
. Type III
. Type IV
. Type V
. Type VI

Correct Answer & Explanation

. Type II

Explanation

A Rockwood Type IV AC joint injury is characterized by posterior displacement of the distal clavicle into or through the trapezius fascia. Type V injuries feature >100-300% superior displacement but without the hallmark posterior fascial displacement seen in Type IV.

Question 7797

Topic: Lower Extremity Trauma

A solid cylindrical intramedullary nail has a radius of 'r'. If the radius is doubled to '2r', the bending stiffness of the solid nail 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 (r^4). Therefore, doubling the radius increases the bending stiffness by a factor of 16 (2^4).

Question 7798

Topic: 2. Trauma

An orthopedic surgeon is selecting a non-locking cortical screw for fracture fixation. Which of the following design modifications will most significantly increase the screw's pullout strength from bone?

. Increasing the inner (root) diameter
. Decreasing the outer thread diameter
. Decreasing the thread pitch
. Increasing the screw core diameter
. Decreasing the thread depth

Correct Answer & Explanation

. Increasing the inner (root) diameter

Explanation

Pullout strength is directly proportional to the outer diameter and the length of engagement, and inversely proportional to thread pitch (a finer pitch increases the number of threads engaged in the bone). Increasing the core (root) diameter increases the tensile/fatigue strength of the screw itself, not its pullout strength.

Question 7799

Topic: 2. Trauma

When applying a bridge plate to a comminuted femoral shaft fracture, intentionally increasing the working length of the plate will have which of the following biomechanical effects?

. Increase the torsional stiffness of the construct
. Decrease the interfragmentary strain to < 2%
. Decrease the bending stiffness of the construct
. Increase the risk of plate failure in direct tension
. Increase the stress shielding of the underlying intact bone

Correct Answer & Explanation

. Increase the torsional stiffness of the construct

Explanation

The working length of a plate is the longitudinal distance between the two closest screws on either side of the fracture. Increasing this distance decreases the overall bending stiffness of the construct, allowing more flexible fixation which stimulates secondary bone healing.

Question 7800

Topic: 2. Trauma

In a highly osteoporotic distal femur fracture treated with a modern locking plate, the stability of the construct relies primarily on:

. Friction generated between the undersurface of the plate and the bone
. Cortical purchase of the screw threads in the far cortex
. The fixed-angle threaded interface between the screw head and the plate
. Dynamic compression of the fracture gap via eccentric drilling
. The use of fully threaded cancellous screws acting as lag screws

Correct Answer & Explanation

. Friction generated between the undersurface of the plate and the bone

Explanation

Unlike conventional plates that rely on friction generated by compressing the plate tightly against the bone, locking plates function as fixed-angle devices. Stability is achieved through the rigid threaded interface between the screw head and the plate hole, preventing individual screw toggle or pullout.

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