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2. Trauma MCQs

Practice Set 458 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 9141

Topic: Upper Extremity Trauma
A 28-year-old male presents after a high-speed motorcycle collision with severe shoulder pain. Radiographs demonstrate an acromioclavicular (AC) joint separation with the clavicle displaced superiorly by 200% relative to the acromion. Based on the Rockwood classification, this is a Type V injury. Which of the following best describes the anatomical disruption in this specific injury type?
. Rupture of the AC ligaments with intact coracoclavicular (CC) ligaments.
. Rupture of the AC ligaments and CC ligaments, with an intact deltotrapezial fascia.
. Rupture of the AC ligaments and CC ligaments, with stripping of the deltotrapezial fascia from the distal clavicle.
. Inferior dislocation of the clavicle under the coracoid process.
. Posterior dislocation of the clavicle into the trapezius muscle.

Correct Answer & Explanation

. Rupture of the AC ligaments and CC ligaments, with stripping of the deltotrapezial fascia from the distal clavicle.

Explanation

The Rockwood classification categorizes AC joint injuries based on the degree and direction of displacement and the involved anatomical structures. A Type III injury involves rupture of both the AC and CC (conoid and trapezoid) ligaments, resulting in 25-100% superior displacement, but the deltotrapezial fascia remains largely intact. A Type V injury is a more severe variant characterized by >100% (often 100-300%) superior displacement of the clavicle. This extreme displacement is only possible because, in addition to the AC and CC ligament ruptures, there is extensive stripping and disruption of the deltotrapezial fascia from the distal clavicle. Type IV is posterior displacement into the trapezius. Type VI is inferior displacement under the coracoid.

Question 9142

Topic: 2. Trauma

A 28-year-old cyclist sustains a displaced midshaft clavicle fracture. On radiographic evaluation, the proximal fragment is displaced superiorly, and the distal fragment is displaced inferiorly and medially. Which muscle is primarily responsible for the superior displacement of the proximal fragment?

. Pectoralis major
. Deltoid
. Sternocleidomastoid
. Trapezius
. Subclavius

Correct Answer & Explanation

. Sternocleidomastoid

Explanation

Correct Answer: CThe characteristic displacement of a midshaft clavicle fracture is dictated by the muscular attachments on the clavicle. The proximal (medial) fragment is pulled superiorly and posteriorly by the unopposed action of the sternocleidomastoid (SCM) muscle. The distal (lateral) fragment is displaced inferiorly by the weight of the arm and the pull of the deltoid muscle, and it is pulled medially by the pectoralis major and latissimus dorsi muscles, leading to shortening of the shoulder girdle. The trapezius attaches to the distal third of the clavicle and does not cause the superior displacement of the proximal fragment. The subclavius lies inferior to the clavicle and depresses it.

Question 9143

Topic: 2. Trauma

The blood supply to the humeral head is a critical consideration in the management of proximal humerus fractures. While historically debated, recent anatomical studies emphasize the dominant role of the arcuate artery in perfusing the articular segment. From which primary vessel does the arcuate artery originate?

. Anterior humeral circumflex artery
. Posterior humeral circumflex artery
. Thoracoacromial artery
. Circumflex scapular artery
. Profunda brachii artery

Correct Answer & Explanation

. Posterior humeral circumflex artery

Explanation

Correct Answer: BHistorically, the anterior humeral circumflex artery (AHCA), specifically its ascending anterolateral branch running in the bicipital groove, was considered the primary blood supply to the humeral head. However, more recent quantitative anatomical studies (e.g., by Hettrich et al.) have demonstrated that the posterior humeral circumflex artery (PHCA) provides the majority (up to 64%) of the blood supply to the humeral head. The PHCA gives off the arcuate artery, which enters the posteromedial aspect of the proximal humerus and perfuses the articular segment. Disruption of the posteromedial hinge in proximal humerus fractures significantly compromises this blood supply, increasing the risk of avascular necrosis (AVN).

Question 9144

Topic: 2. Trauma

A 28-year-old male undergoes open reduction and internal fixation (ORIF) for a severely displaced midshaft clavicle fracture. During the anterior superior surgical approach, the surgeon must be cautious of a major neurovascular structure located directly posterior to the middle third of the clavicle, separated only by the subclavius muscle. Injury to the most anterior and medial aspect of this neurovascular bundle behind the clavicle would MOST likely involve which of the following?

. Suprascapular nerve
. Subclavian vein
. Brachial plexus trunks
. Axillary artery
. Phrenic nerve

Correct Answer & Explanation

. Subclavian vein

Explanation

Correct Answer: B (Subclavian vein)During ORIF of midshaft clavicle fractures, plunging drills or screws pose a significant risk to the underlying neurovascular structures. Directly posterior to the medial and middle thirds of the clavicle lies the subclavian vein, which is the most anterior and medial structure in the neurovascular bundle at this level. It is separated from the posterior cortex of the clavicle only by the thin subclavius muscle and fascia. The subclavian artery and the trunks of the brachial plexus lie posterior and slightly superior to the vein. The suprascapular nerve branches off the superior trunk further laterally. The axillary artery is the continuation of the subclavian artery distal to the lateral border of the first rib. The phrenic nerve lies on the anterior scalene muscle, deeper and more medial.

Question 9145

Topic: 2. Trauma

A 14-year-old male baseball pitcher feels a sudden "pop" on the medial side of his elbow during a pitch. Radiographs reveal an avulsion fracture of the medial epicondyle with 4 mm of displacement. If this injury is managed non-operatively and goes on to a symptomatic nonunion, which of the following biomechanical deficits is MOST likely to be observed during the late cocking and early acceleration phases of throwing?

. Diminished resistance to varus torque
. Diminished resistance to valgus torque
. Inability to actively extend the elbow
. Loss of forearm supination strength
. Excessive radiocapitellar compression

Correct Answer & Explanation

. Diminished resistance to valgus torque

Explanation

Correct Answer: B (Diminished resistance to valgus torque)The medial epicondyle serves as the origin for the flexor-pronator mass and the medial ulnar collateral ligament (MUCL). During the late cocking and early acceleration phases of throwing, the elbow is subjected to tremendous valgus stress. The MUCL is the primary static stabilizer against this valgus torque, and the flexor-pronator mass provides dynamic stabilization. An avulsion fracture of the medial epicondyle compromises both of these structures. If it progresses to a symptomatic nonunion, the medial side of the elbow becomes incompetent, leading to a diminished resistance to valgus torque, medial elbow instability, and pain during throwing. Varus torque is resisted by the lateral collateral ligament complex. Extension is controlled by the triceps (olecranon insertion). Supination is controlled by the biceps and supinator.

Question 9146

Topic: 2. Trauma

A 65-year-old female sustains a displaced 4-part proximal humerus fracture. The treating orthopedic surgeon elects to perform a hemiarthroplasty, citing a prohibitively high risk of avascular necrosis (AVN) of the humeral head if open reduction and internal fixation were attempted. Disruption of which of the following vessels is the primary anatomical basis for this high risk of AVN?

. Anterior humeral circumflex artery.
. Ascending branch of the anterior humeral circumflex artery.
. Arcuate branch of the posterior humeral circumflex artery.
. Circumflex scapular artery.
. Thoracoacromial artery.

Correct Answer & Explanation

. Arcuate branch of the posterior humeral circumflex artery.

Explanation

Correct Answer: Arcuate branch of the posterior humeral circumflex artery.Historically, the ascending branch of the anterior humeral circumflex artery (the anterolateral branch) was thought to be the primary blood supply to the humeral head. However, modern anatomical and perfusion studies (such as those by Brooks et al. and Hettrich et al.) have demonstrated that the posterior humeral circumflex artery, specifically via its arcuate branch, provides the majority (up to 64%) of the blood supply to the articular segment of the humeral head. In displaced 3- and 4-part proximal humerus fractures, especially those involving the anatomic neck or with significant medial hinge disruption, this posterior supply is severely compromised, leading to a high rate of avascular necrosis. The circumflex scapular and thoracoacromial arteries do not provide primary intraosseous supply to the humeral head.

Question 9147

Topic: Upper Extremity Trauma

A 28-year-old male sustains a Type V acromioclavicular (AC) joint separation during a rugby match. The surgeon plans an open reduction and anatomical reconstruction of the coracoclavicular (CC) ligaments using a tendon allograft. To accurately recreate the native biomechanics, the surgeon must understand the anatomical footprints of the CC ligaments. Which of the following best describes the anatomical footprint of the conoid ligament relative to the trapezoid ligament on the undersurface of the clavicle?

. Medial and posterior.
. Medial and anterior.
. Lateral and posterior.
. Lateral and anterior.
. Directly inferior and central.

Correct Answer & Explanation

. Medial and posterior.

Explanation

Correct Answer: Medial and posterior.The coracoclavicular (CC) ligaments are the primary restraints to superior and posterior translation of the clavicle relative to the acromion. They consist of two distinct bands: the conoid and the trapezoid. The conoid ligament is the more medial and posterior of the two. It originates from the posteromedial base of the coracoid process and inserts onto the conoid tubercle on the posteromedial undersurface of the distal clavicle. The trapezoid ligament is located lateral and anterior to the conoid. It originates from the superior aspect of the coracoid process and inserts onto the trapezoid line on the anterolateral undersurface of the distal clavicle. Understanding this spatial relationship is critical for anatomical CC ligament reconstruction techniques.

Question 9148

Topic: 2. Trauma

A 70-year-old osteoporotic female sustains a displaced proximal humerus fracture. According to Hertel's criteria, which of the following radiographic findings is the most reliable predictor of humeral head ischemia?

. Greater tuberosity displacement greater than 5 mm
. Metaphyseal head extension (calcar length) less than 8 mm
. Angulation of the humeral head greater than 45 degrees
. Disruption of the lateral periosteal hinge
. Presence of a surgical neck fracture line

Correct Answer & Explanation

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

Explanation

Hertel established that a metaphyseal head extension (calcar length) of less than 8 mm, disruption of the medial hinge, and an anatomic neck fracture are the strongest predictors of humeral head ischemia following proximal humerus fractures.

Question 9149

Topic: Upper Extremity Trauma

A 21-year-old collegiate baseball pitcher presents with medial elbow pain and diminished throwing velocity. MRI arthrogram demonstrates an avulsion of the anterior bundle of the medial ulnar collateral ligament (MUCL). At which anatomic landmark does this critical stabilizing structure insert?

. Coronoid process of the ulna
. Medial epicondyle of the humerus
. Sublime tubercle of the proximal ulna
. Olecranon process
. Radial notch of the ulna

Correct Answer & Explanation

. Sublime tubercle of the proximal ulna

Explanation

The anterior bundle of the MUCL is the primary restraint to valgus stress at the elbow during throwing. It originates on the anterior undersurface of the medial epicondyle and inserts on the sublime tubercle of the anteromedial coronoid facet.

Question 9150

Topic: 2. Trauma

A 25-year-old cyclist sustains a completely displaced midshaft clavicle fracture with 2.5 cm of shortening. Compared to non-operative management, open reduction and internal fixation (ORIF) of this specific fracture pattern is most likely to result in which of the following?

. Decreased rate of nonunion
. Increased superior shoulder strength
. Decreased risk of adhesive capsulitis
. Higher rate of complex regional pain syndrome
. Lower rate of reoperation

Correct Answer & Explanation

. Lower rate of reoperation

Explanation

ORIF of completely displaced midshaft clavicle fractures with >2 cm of shortening significantly decreases the rate of nonunion and symptomatic malunion compared to non-operative treatment. However, ORIF carries a higher overall reoperation rate, largely due to symptomatic hardware removal.

Question 9151

Topic: 2. Trauma

A 65-year-old female sustains a 3-part proximal humerus fracture. According to Hertel's criteria, which of the following radiographic findings is the most reliable predictor of subsequent avascular necrosis of the humeral head?

. Posteromedial hinge displacement > 2 mm
. Calcar length < 8 mm
. Head-split fracture pattern
. Greater tuberosity displacement > 5 mm
. Initial angulation > 45 degrees

Correct Answer & Explanation

. Calcar length < 8 mm

Explanation

Hertel identified specific radiographic predictors for humeral head ischemia, with a metaphyseal head extension (calcar length) of less than 8 mm being a highly reliable predictor of avascular necrosis. An intact medial hinge and anatomical neck fractures are also critical determinants in assessing the vascular viability of the humeral head.

Question 9152

Topic: 2. Trauma

A 40-year-old female sustains a coronal shear fracture of the distal humerus involving the capitellum and the lateral aspect of the trochlea (Bryan and Morrey Type IV). Which surgical approach provides the most optimal visualization for anatomic reduction and fixation of this specific articular fracture?

. Posterior approach with olecranon osteotomy
. Extended lateral (extensile lateral) approach
. Medial approach with pronator-flexor mass elevation
. Anterior approach through the brachialis
. Posterior approach with triceps-splitting

Correct Answer & Explanation

. Extended lateral (extensile lateral) approach

Explanation

The extended lateral approach provides excellent direct visualization of the anterior articular surface of the capitellum and lateral trochlea, which is strictly required for accurate reduction of coronal shear fractures. Olecranon osteotomies provide excellent posterior visualization but poor access to the anterior articular surface.

Question 9153

Topic: 2. Trauma

A 25-year-old male cyclist falls and sustains a midshaft clavicle fracture. Which of the following radiographic parameters is the strongest absolute indication for operative fixation over non-operative management to prevent nonunion and symptomatic malunion?

. >1 cm of initial fracture shortening
. Presence of a single butterfly fragment
. >100% displacement of the fracture ends
. Superior displacement of the medial fragment by 5 mm
. Z-deformity with horizontal fragment orientation

Correct Answer & Explanation

. >100% displacement of the fracture ends

Explanation

Complete displacement (>100%) and significant shortening (historically >2 cm) are strong absolute or relative indications for operative fixation of midshaft clavicle fractures. Current literature supports fixation for completely displaced fractures to decrease nonunion rates and improve early functional recovery compared to non-operative treatment.

Question 9154

Topic: Upper Extremity Trauma

During an anatomic coracoclavicular (CC) ligament reconstruction for a chronic Type V acromioclavicular joint separation, the surgeon aims to accurately recreate the insertions of the conoid and trapezoid ligaments on the clavicle. Which of the following best describes the anatomic footprints of these ligaments?

. The conoid inserts anterolaterally and the trapezoid inserts posteromedially
. The conoid inserts posteromedially and the trapezoid inserts anterolaterally
. Both ligaments insert on the anterior border of the distal clavicle
. The conoid inserts on the superior clavicle and the trapezoid inserts on the inferior clavicle
. The conoid and trapezoid share a single conjoined insertion 10 mm medial to the AC joint

Correct Answer & Explanation

. The conoid inserts posteromedially and the trapezoid inserts anterolaterally

Explanation

In the native anatomy of the coracoclavicular ligaments, the conoid ligament footprint is located posteromedially on the conoid tubercle, approximately 45 mm from the distal clavicle. The trapezoid ligament footprint is located more anterolaterally, approximately 25 mm from the distal clavicle.

Question 9155

Topic: 2. Trauma

A 68-year-old patient with a history of severe protein-calorie malnutrition presents with a long-standing tibial nonunion. Which nutrient deficiency is most directly linked to impaired collagen synthesis, a critical component of fracture healing?

. Vitamin D
. Calcium
. Vitamin C
. Vitamin K
. Zinc

Correct Answer & Explanation

. Vitamin C

Explanation

Vitamin C (ascorbic acid) is an essential cofactor for the hydroxylation of proline and lysine residues in collagen synthesis. A deficiency in Vitamin C leads to impaired collagen cross-linking and synthesis, compromising the structural integrity of the newly formed bone matrix. While other nutrients are important, Vitamin C directly impacts collagen. Vitamin D and Calcium are crucial for mineralization. Zinc is involved in enzymatic reactions, and Vitamin K in carboxylation of bone proteins.

Question 9156

Topic: 2. Trauma

In secondary fracture healing, what interfragmentary gap size is generally considered optimal for the formation of a robust cartilaginous callus?

. Less than 0.1 mm
. 0.1 mm to 0.5 mm
. 0.5 mm to 2 mm
. 2 mm to 5 mm
. Greater than 5 mm

Correct Answer & Explanation

. 0.5 mm to 2 mm

Explanation

An interfragmentary gap of 0.5 mm to 2 mm (and often up to 5mm) is generally considered optimal for secondary fracture healing, allowing for sufficient interfragmentary motion (strain) to stimulate chondrogenesis and subsequent endochondral ossification, while not being so large as to impede callus bridging. Gaps less than 0.1mm are suitable for primary healing. Larger gaps can lead to nonunion due to inadequate bridging.

Question 9157

Topic: 2. Trauma

Vascular compromise at the fracture site, such as in scaphoid waist fractures or femoral neck fractures, is a significant risk factor for nonunion. What is the primary consequence of compromised vascularity on fracture healing?

. Excessive fibrous tissue formation
. Reduced mechanical stability
. Inadequate delivery of oxygen, nutrients, and repair cells
. Accelerated osteoclast activity
. Increased inflammatory cytokine release

Correct Answer & Explanation

. Inadequate delivery of oxygen, nutrients, and repair cells

Explanation

Compromised vascularity directly impairs fracture healing by preventing the adequate delivery of oxygen, nutrients, and essential repair cells (e.g., mesenchymal stem cells, inflammatory cells) to the fracture site. This leads to tissue necrosis, an inability to form a viable callus, and ultimately a high risk of nonunion. While fibrous tissue may form, it's a consequence of the underlying biological failure, not the primary consequence.

Question 9158

Topic: 2. Trauma

Compared to closed fractures, open fractures have a higher risk of delayed union and nonunion. What is the main reason for this increased risk?

. More extensive soft tissue damage and contamination leading to infection
. Less pain, leading to early weight-bearing and destabilization
. Increased systemic inflammatory response
. Higher incidence of comminution, promoting primary healing
. Reduced production of systemic growth factors

Correct Answer & Explanation

. More extensive soft tissue damage and contamination leading to infection

Explanation

Open fractures typically involve more extensive soft tissue damage, periosteal stripping, and contamination, which significantly increase the risk of infection and further compromise vascularity. Infection is a potent inhibitor of fracture healing. While comminution can be present, the main differentiating factor and risk for impaired healing in open fractures is the soft tissue injury and contamination.

Question 9159

Topic: 2. Trauma

Which of the following fracture locations is notoriously prone to nonunion due to its precarious blood supply?

. Distal radius
. Proximal humerus
. Tibial plateau
. Scaphoid waist
. Calcaneus

Correct Answer & Explanation

. Scaphoid waist

Explanation

The scaphoid waist, particularly after a fracture, has a high risk of nonunion and avascular necrosis due to its retrograde blood supply. The blood vessels enter distally, meaning a waist fracture can interrupt the blood supply to the proximal pole, which then becomes avascular. Other fractures listed generally have more robust blood supplies, though nonunion can occur for various reasons.

Question 9160

Topic: 2. Trauma

A delayed union is defined as a fracture that has not healed within which time frame, though still having the potential to heal without intervention?

. Within 3 months of injury
. Within 6 months of injury
. Within 9 months of injury
. Within 1 year of injury
. Beyond 1 year with no progression towards healing

Correct Answer & Explanation

. Within 6 months of injury

Explanation

A delayed union is generally defined as a fracture that has not healed within 6 months of injury, but still shows radiographic or clinical evidence of progress toward union and is expected to heal with continued immobilization or conservative treatment. Nonunion is typically defined as a fracture that has not healed within 6-9 months and shows no further signs of progression towards healing, or has failed to unite 3 months after reaching biological union time for that specific bone.

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