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1. General Principles & Basic Science MCQs

Practice Set 643 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 12841

Topic: 1. General Principles & Basic Science
A 16-year-old baseball pitcher sustains an AC joint injury. On examination, a 'step-off' deformity is evident, and the distal clavicle is very prominent. Radiographs reveal complete disruption of the AC ligaments and coracoclavicular ligaments, with marked superior displacement of the clavicle, measuring twice the normal coracoclavicular distance on the contralateral side. The deltoid and trapezius muscles are stripped from the distal clavicle. What Rockwood type best describes this injury?
. Type II
. Type III
. Type IV
. Type V
. Type VI

Correct Answer & Explanation

. Type V

Explanation

This describes a Rockwood Type V injury. Key features include complete disruption of both AC and CC ligaments, severe superior displacement of the clavicle (significantly greater than Type III, often quantified as 100% or more of acromial height or twice the contralateral CC distance), and critically, extensive stripping of the deltoid and trapezius muscles from the distal clavicle. Type III has complete AC and CC tears but less severe displacement and typically intact deltoid/trapezius fascia.

Question 12842

Topic: Infection, Pharmacology & VTE

What is the appropriate management for a Rockwood Type I AC joint injury?

. Surgical repair of the AC ligaments.
. Coracoclavicular ligament reconstruction.
. Sling immobilization for 4-6 weeks with no active motion.
. Symptomatic treatment including ice, analgesics, and early protected range of motion.
. Distal clavicle excision (Mumford procedure).

Correct Answer & Explanation

. Symptomatic treatment including ice, analgesics, and early protected range of motion.

Explanation

Rockwood Type I AC joint injuries are managed conservatively with symptomatic treatment. This typically includes rest, ice, oral analgesics (NSAIDs), and a short period of sling immobilization for comfort, followed by early initiation of protected range of motion exercises as pain allows. Surgical intervention or prolonged immobilization is not indicated for Type I injuries.

Question 12843

Topic: 1. General Principles & Basic Science
When interpreting radiographs for an AC joint injury, what characteristic finding indicates a Type III injury?
. Normal AC and CC distances.
. Widened AC joint space with normal CC distance.
. Widened AC joint space and increased CC distance (>25% compared to contralateral side).
. Posterior displacement of the clavicle.
. Inferior displacement of the clavicle.

Correct Answer & Explanation

. Widened AC joint space and increased CC distance (>25% compared to contralateral side).

Explanation

A Rockwood Type III injury is characterized by complete disruption of both the AC and CC ligaments. Radiographically, this manifests as a widened AC joint space and a significantly increased coracoclavicular (CC) distance (typically >25% greater than the contralateral uninjured side). Normal distances indicate Type I. Widened AC space with normal CC distance would be more indicative of Type II. Posterior or inferior displacement points to Type IV or VI, respectively.

Question 12844

Topic: 1. General Principles & Basic Science

What is the primary concern if a patient with an AC joint injury develops a significant posterior displacement of the clavicle (Rockwood Type IV)?

. Risk of impingement syndrome.
. Compromise of the neurovascular structures (e.g., brachial plexus, subclavian vessels).
. Higher likelihood of post-traumatic osteoarthritis.
. Difficulty in achieving reduction with closed manipulation.
. Increased cosmetic deformity.

Correct Answer & Explanation

. Compromise of the neurovascular structures (e.g., brachial plexus, subclavian vessels).

Explanation

Posterior displacement of the clavicle, as seen in Rockwood Type IV injuries, pushes the distal clavicle into the trapezius muscle, often placing the underlying neurovascular structures (brachial plexus and subclavian vessels) at significant risk of compression or injury. This necessitates prompt and careful evaluation and typically surgical management for reduction. While cosmetic deformity and difficulty in reduction are true, the neurovascular compromise is the most critical immediate concern.

Question 12845

Topic: 1. General Principles & Basic Science
Which of the following imaging modalities offers the best resolution for visualizing the AC joint capsule and surrounding soft tissues, helpful in differentiating subtle Type II from Type III injuries?
. Plain radiographs (AP, Zanca, Axillary)
. CT scan
. Ultrasound
. MRI
. Bone scan

Correct Answer & Explanation

. MRI

Explanation

Magnetic Resonance Imaging (MRI) offers superior soft tissue contrast and resolution compared to other modalities, making it the best choice for visualizing the AC joint capsule, surrounding musculature (deltoid, trapezius), and the coracoclavicular ligaments. This detailed view can be crucial in cases where plain radiographs are equivocal, helping to precisely delineate the extent of ligamentous injury and aiding in the differentiation of Type II from Type III injuries. CT is better for bone, ultrasound for dynamic, bone scan for metabolic activity.

Question 12846

Topic: 1. General Principles & Basic Science

The coracoclavicular ligaments consist of two distinct bundles. Which one is located more medially and is typically trapezoidal in shape?

. Conoid ligament
. Trapezoid ligament
. Acromial ligament
. Coracoacromial ligament
. Deltoid ligament

Correct Answer & Explanation

. Conoid ligament

Explanation

The coracoclavicular ligaments are comprised of the conoid and trapezoid ligaments. The conoid ligament is the more medial and posterior of the two, typically conical or trapezoidal in shape. The trapezoid ligament is more lateral and anterior, and quadrilateral in shape. Both originate from the coracoid process and insert onto the clavicle, providing vertical stability to the AC joint.

Question 12847

Topic: 1. General Principles & Basic Science

For Rockwood Type VI AC joint dislocations, which structure is the clavicle most commonly displaced beneath?

. Acromion
. Glenoid
. Coracoid process
. Scapular spine
. Humeral head

Correct Answer & Explanation

. Coracoid process

Explanation

Rockwood Type VI is a rare injury where the distal clavicle is displaced inferiorly. The most common location for this displacement is beneath the coracoid process (subcoracoid). It can also occur, though less commonly, beneath the acromion (subacromial). This type of injury often involves significant force and can be associated with neurovascular compromise.

Question 12848

Topic: 1. General Principles & Basic Science
What is the approximate percentage of AC joint injuries that fall into Rockwood Types I-III, as mentioned in the provided text?
. 50%
. 75%
. 85%
. 98%
. 100%

Correct Answer & Explanation

. 98%

Explanation

The provided content explicitly states: 'Types I–III account for 98% of these injuries.' This is a direct recall from the provided text.

Question 12849

Topic: 1. General Principles & Basic Science

What is the main purpose of the conoid and trapezoid ligaments collectively?

. To prevent anterior translation of the humeral head.
. To stabilize the sternoclavicular joint.
. To provide horizontal stability to the AC joint.
. To provide vertical stability to the AC joint.
. To limit external rotation of the humerus.

Correct Answer & Explanation

. To provide vertical stability to the AC joint.

Explanation

The conoid and trapezoid ligaments, which together form the coracoclavicular (CC) ligaments, are the primary stabilizers against vertical displacement (superior migration) of the distal clavicle relative to the acromion. They suspend the scapula and upper extremity from the clavicle.

Question 12850

Topic: 1. General Principles & Basic Science

What is the typical timeframe for initiating protected active range of motion exercises following a conservatively managed Rockwood Type II AC joint injury?

. Immediately post-injury (day 1-3).
. After 2-3 weeks of sling immobilization.
. After 6-8 weeks of strict immobilization.
. Only after radiographs confirm complete healing (typically 3 months).
. Never, as it risks further injury.

Correct Answer & Explanation

. After 2-3 weeks of sling immobilization.

Explanation

For a conservatively managed Rockwood Type II AC joint injury, a short period of sling immobilization (typically 1-2 weeks for comfort) is followed by the initiation of protected active and passive range of motion exercises within pain limits. The goal is to prevent stiffness while allowing initial ligament healing. Prolonged strict immobilization is typically avoided for Type II injuries as it can lead to stiffness without significant benefit.

Question 12851

Topic: 1. General Principles & Basic Science

When interpreting AP radiographs for AC joint injury, what is a normal range for the coracoclavicular distance in adults?

. 5-8 mm
. 9-12 mm
. 13-16 mm
. 17-20 mm
. 21-25 mm

Correct Answer & Explanation

. 9-12 mm

Explanation

The normal coracoclavicular distance in adults typically ranges from 11-13 mm, but commonly cited ranges can vary slightly, with 10-13 mm being standard. Therefore, 9-12 mm is the closest and most appropriate option provided. A difference of more than 25% compared to the contralateral side is generally considered indicative of a CC ligament tear and superior displacement.

Question 12852

Topic: 1. General Principles & Basic Science

What is the most accurate way to assess for horizontal instability of the AC joint on physical examination?

. Direct palpation of the AC joint.
. Applying an anterior-posterior shear force to the distal clavicle while stabilizing the scapula.
. Cross-body adduction test.
. Empty can test.
. Speed's test.

Correct Answer & Explanation

. Applying an anterior-posterior shear force to the distal clavicle while stabilizing the scapula.

Explanation

Assessing for horizontal instability (anterior-posterior shear) of the AC joint involves applying a direct anterior-posterior force to the distal clavicle while stabilizing the scapula (or acromion). This maneuver directly tests the integrity of the AC joint capsule and ligaments against shear forces. While cross-body adduction causes compression and can elicit pain, it doesn't directly assess AP translation. The other tests are for different pathologies.

Question 12853

Topic: 1. General Principles & Basic Science

For a Rockwood Type V AC joint injury, what is the generally accepted management strategy?

. Symptomatic conservative treatment only.
. Prolonged immobilization in a spica cast.
. Always surgical repair/reconstruction.
. Distal clavicle excision without stabilization.
. Trial of conservative management followed by surgery if pain persists.

Correct Answer & Explanation

. Always surgical repair/reconstruction.

Explanation

Rockwood Type V AC joint injuries, due to their severe displacement, complete disruption of AC and CC ligaments, and extensive stripping of the deltoid and trapezius, are nearly always managed surgically. Surgical repair or reconstruction is necessary to restore anatomical alignment, stability, and optimize functional outcomes. Conservative management is generally considered inadequate for such severe injuries.

Question 12854

Topic: 1. General Principles & Basic Science
Which type of AC joint dislocation involves the clavicle being displaced inferiorly, often tearing through the coracoid and musculature?
. Type III
. Type IV
. Type V
. Type VI
. Type II

Correct Answer & Explanation

. Type VI

Explanation

Rockwood Type VI AC joint dislocation is characterized by inferior displacement of the distal clavicle, typically beneath the coracoid process or less commonly, beneath the acromion. This is a rare but severe injury pattern requiring substantial force. The other types involve superior or posterior displacement.

Question 12855

Topic: 1. General Principles & Basic Science

In the context of AC joint injuries, what does the term 'acromial height' refer to when assessing superior displacement?

. The vertical distance from the acromion to the greater tuberosity.
. The vertical distance from the superior aspect of the acromion to the inferior border of the scapula.
. The vertical dimension of the acromion itself, used as a reference for quantifying clavicle displacement.
. The distance from the AC joint to the glenoid.
. The height of the acromion relative to the humeral head.

Correct Answer & Explanation

. The vertical dimension of the acromion itself, used as a reference for quantifying clavicle displacement.

Explanation

When assessing superior displacement, particularly in Rockwood Type V injuries, the 'acromial height' or width is often used as a reference measurement. A Type V injury is described as having 100% or more superior displacement of the clavicle relative to the acromial height, meaning the clavicle is displaced by at least the full height of the acromion. It provides a standardized way to quantify the severity of the superior migration.

Question 12856

Topic: 1. General Principles & Basic Science

A 30-year-old weightlifter feels a sharp 'pop' in his anterior axilla while performing a heavy bench press. Exam reveals an asymmetrical chest wall contour and weakness with internal rotation. Which specific portion of the affected muscle is most commonly ruptured first in this mechanism?

. Clavicular head at the musculotendinous junction
. Clavicular head at its insertion
. Sternal head at its insertion
. Sternal head at the musculotendinous junction
. Abdominal head at its origin

Correct Answer & Explanation

. Sternal head at its insertion

Explanation

Pectoralis major ruptures typically occur during eccentric loading (e.g., bench press). The sternal head, which inserts deep and proximal to the clavicular head, experiences the greatest tension in the extended and externally rotated position and usually ruptures first at its insertion.

Question 12857

Topic: 1. General Principles & Basic Science

Recent quantitative anatomic studies have redefined the predominant vascular supply to the humeral head. Which of the following vessels is now recognized as providing the primary blood supply to the humeral head?

. Anterior humeral circumflex artery
. Posterior humeral circumflex artery
. Thoracoacromial artery
. Subscapular artery
. Circumflex scapular artery

Correct Answer & Explanation

. Posterior humeral circumflex artery

Explanation

Historically, the anterior humeral circumflex artery was thought to be the primary supply via the arcuate artery. However, recent studies (e.g., Hettrich et al.) demonstrate that the posterior humeral circumflex artery provides the vast majority (up to 64%) of the blood supply to the humeral head.

Question 12858

Topic: 1. General Principles & Basic Science

During surgical repair of an acute pectoralis major rupture, understanding the insertional anatomy is critical. Which of the following statements accurately describes the insertion of the pectoralis major tendon on the humerus?

. The sternal head inserts deep and proximal to the clavicular head
. The clavicular head inserts deep and proximal to the sternal head
. Both heads insert as a single inseparable tendon at the same level
. The sternal head inserts exclusively into the lesser tuberosity
. The clavicular head inserts deep and distal to the sternal head

Correct Answer & Explanation

. The sternal head inserts deep and proximal to the clavicular head

Explanation

The pectoralis major tendon twists 180 degrees before inserting on the lateral lip of the bicipital groove. Consequently, the sternal head inserts deep (posterior) and proximal relative to the clavicular head.

Question 12859

Topic: Surgical Anatomy & Approaches

Compression in the quadrilateral space typically leads to atrophy of the teres minor and deltoid. Which artery travels through this space alongside the affected nerve?

. Anterior humeral circumflex artery
. Circumflex scapular artery
. Poster humeral circumflex artery
. Profunda brachii artery
. Suprascapular artery

Correct Answer & Explanation

. Poster humeral circumflex artery

Explanation

The quadrilateral space contains the axillary nerve and the posterior humeral circumflex artery. It is bordered by the teres minor (superior), teres major (inferior), long head of the triceps (medial), and surgical neck of the humerus (lateral).

Question 12860

Topic: Surgical Anatomy & Approaches

During a total hip arthroplasty using the direct anterior approach (DAA), the surgeon exploits the internervous plane between the sartorius and the tensor fasciae latae (TFL). Which nerve provides the motor innervation to the muscle located immediately lateral to this interval?

. Femoral nerve
. Superior gluteal nerve
. Inferior gluteal nerve
. Obturator nerve
. Sciatic nerve

Correct Answer & Explanation

. Superior gluteal nerve

Explanation

The direct anterior approach to the hip utilizes the internervous plane between the sartorius (medial) and the tensor fasciae latae (lateral). The sartorius is innervated by the femoral nerve. The tensor fasciae latae (TFL), located lateral to the interval, is innervated by the superior gluteal nerve. Understanding this plane prevents denervation of the key abductor musculature.

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