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1. General Principles & Basic Science MCQs

Practice Set 630 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 12581

Topic: Infection, Pharmacology & VTE

A patient's blood cultures come back positive for Methicillin-resistant Staphylococcus aureus (MRSA) from a confirmed spinal epidural abscess. The patient has no known allergies. Which antibiotic would be the most appropriate first-line targeted therapy?

. Ceftriaxone
. Piperacillin-tazobactam
. Vancomycin
. Ciprofloxacin
. Daptomycin

Correct Answer & Explanation

. Vancomycin

Explanation

Vancomycin is the cornerstone of treatment for MRSA infections, including spinal epidural abscesses, due to its reliable activity against methicillin-resistant strains. Ceftriaxone and Piperacillin-tazobactam lack MRSA coverage. Ciprofloxacin has some activity against S. aureus but is generally not preferred as first-line monotherapy for serious MRSA infections. Daptomycin is an alternative for MRSA, particularly in cases of vancomycin failure, intolerance, or in specific clinical scenarios, but vancomycin is typically first-line due to its established efficacy and cost-effectiveness.

Question 12582

Topic: Infection, Pharmacology & VTE

A patient with a prior lumbar fusion 6 months ago presents with worsening back pain, fever, and elevated inflammatory markers. Imaging suggests a deep surgical site infection involving the fusion hardware. What is the most appropriate initial management approach?

. Long-term suppressive oral antibiotics
. Urgent hardware removal, debridement, and IV antibiotics
. Percutaneous aspiration and antibiotic cement injection
. Continued observation and repeat imaging in 2 weeks
. High-dose steroids to reduce inflammation

Correct Answer & Explanation

. Urgent hardware removal, debridement, and IV antibiotics

Explanation

In the context of chronic or subacute deep surgical site infection involving spinal instrumentation, hardware removal, thorough debridement, and prolonged intravenous antibiotic therapy are often necessary to eradicate the infection. The biofilm formed on hardware makes antibiotic penetration difficult and typically prevents eradication without removal. Long-term suppressive antibiotics are rarely curative and typically reserved for patients who cannot undergo definitive surgery. Percutaneous aspiration may not be sufficient for extensive hardware-related infection. Observation is inappropriate. Steroids are contraindicated in active bacterial infection.

Question 12583

Topic: Infection, Pharmacology & VTE

Which class of antibiotics generally has poor penetration into the central nervous system and epidural space, making it less ideal as a primary monotherapy treatment for spinal epidural abscess?

. Fluoroquinolones
. Glycopeptides (e.g., Vancomycin)
. Beta-lactams (e.g., Ceftriaxone)
. Aminoglycosides
. Rifamycins

Correct Answer & Explanation

. Aminoglycosides

Explanation

Aminoglycosides (e.g., Gentamicin) generally have poor penetration into the central nervous system and epidural space. While they might be used in combination therapy for specific gram-negative organisms, they are not ideal as primary monotherapy agents for SEA due to this limited penetration and potential for nephrotoxicity and ototoxicity. Fluoroquinolones, beta-lactams, and rifamycins typically have better CNS penetration. Vancomycin's penetration is variable but it is still the primary choice for MRSA due to its efficacy and lack of superior alternatives for MRSA.

Question 12584

Topic: Infection, Pharmacology & VTE

Which of the following describes the typical MRI appearance of discitis?

. T1 hyperintense, T2 hypointense disc with no endplate changes
. T1 hypointense, T2 hyperintense disc with indistinct endplates and enhancement
. Normal disc signal with only mild vertebral body edema
. T1 hyperintense, T2 hyperintense disc with sharp endplate margins
. Diffuse vertebral body enhancement without disc involvement

Correct Answer & Explanation

. T1 hypointense, T2 hyperintense disc with indistinct endplates and enhancement

Explanation

Discitis typically presents on MRI with T1 hypointense and T2 hyperintense signal within the disc space, indicating increased fluid and inflammation. This is often accompanied by indistinct or irregular vertebral endplates and enhancement of both the disc and adjacent vertebral bodies after gadolinium administration, reflecting active infection and inflammation. Normal disc signal or sharp endplate margins would argue against active discitis. Diffuse vertebral body enhancement without disc involvement would be more typical of osteomyelitis without discitis, or other conditions.

Question 12585

Topic: Infection, Pharmacology & VTE

A 55-year-old male with a history of chronic alcoholism and liver cirrhosis presents with several weeks of progressive back pain and fever. MRI shows diffuse L2 vertebral osteomyelitis. What organism should be particularly considered in this patient population?

. Staphylococcus aureus
. Streptococcus pneumoniae
. Klebsiella pneumoniae
. Mycobacterium avium complex
. Coagulase-negative Staphylococcus

Correct Answer & Explanation

. Klebsiella pneumoniae

Explanation

Patients with chronic alcoholism and liver cirrhosis are often immunocompromised and are at increased risk for infections with Gram-negative organisms, particularly Klebsiella pneumoniae, which can cause severe infections including vertebral osteomyelitis. While S. aureus is the most common cause overall, specific host factors broaden the differential for causative organisms. M. avium complex is seen in advanced HIV. S. pneumoniae is less common in vertebral osteomyelitis. Coagulase-negative Staph is usually associated with hardware or indolent infections.

Question 12586

Topic: Surgical Anatomy & Approaches

Which of the following statements regarding the posterior interosseous nerve (PIN) is TRUE?

. It provides sensory innervation to the dorsal forearm and hand.
. It is a branch of the median nerve.
. It innervates the brachioradialis and extensor carpi radialis longus muscles.
. It is purely a motor nerve after it branches from the radial nerve.
. It commonly causes 'wrist drop' when compressed at the elbow.

Correct Answer & Explanation

. It is purely a motor nerve after it branches from the radial nerve.

Explanation

The posterior interosseous nerve (PIN) is a purely motor nerve, branching from the radial nerve within the cubital fossa. It innervates the extrinsic extensors of the fingers and thumb, as well as the extensor carpi ulnaris and supinator. The superficial radial nerve provides sensory innervation. The radial nerve itself innervates the brachioradialis and ECRL (before it splits). A 'wrist drop' is typically associated with a more proximal radial nerve lesion, as the PIN lesion would preserve wrist extension through ECRL and ECPL (radial-innervated muscles before PIN branch).

Question 12587

Topic: Infection, Pharmacology & VTE

What is the most significant disadvantage of using a hinged external fixator for elbow instability?

. Inability to allow early range of motion
. High risk of infection at pin sites
. Requires open reduction for application
. Does not restore joint congruity
. Prolonged immobilization of the elbow

Correct Answer & Explanation

. High risk of infection at pin sites

Explanation

While hinged external fixators allow early range of motion, a significant disadvantage is the high risk of pin tract infection, which can lead to osteomyelitis or necessitate early removal. They are often used after closed or open reduction has restored joint congruity. They do not intrinsically prolong immobilization if designed to allow motion.

Question 12588

Topic: Infection, Pharmacology & VTE

How would you radiographically differentiate septic arthritis of the glenohumeral joint from advanced primary glenohumeral osteoarthritis in an 84-year-old lady?

. Septic arthritis presents with rapid, uniform joint space narrowing and early bone destruction
. Osteoarthritis shows more prominent subchondral cysts
. Septic arthritis always has a visible effusion
. Osteoarthritis causes greater periarticular osteopenia
. Septic arthritis typically shows large osteophytes

Correct Answer & Explanation

. Septic arthritis presents with rapid, uniform joint space narrowing and early bone destruction

Explanation

Septic arthritis is characterized by rapid, uniform (concentric) joint space narrowing due to cartilage destruction, along with early subchondral bone erosions and overall periarticular osteopenia. While effusion might be present, it's not always definitively visible on plain X-rays. Osteoarthritis, by contrast, has a slower progression, typically asymmetric joint space narrowing (often inferomedial), prominent osteophytes, subchondral sclerosis, and cysts, without the rapid, destructive pattern of infection.

Question 12589

Topic: Infection, Pharmacology & VTE

On an 84-year-old lady's shoulder X-ray, you observe localized areas of increased bone density, particularly beneath the articular cartilage in the glenohumeral joint. What term describes this finding, and what does it typically indicate?

. Osteopenia, indicating bone loss
. Sclerosis, indicating degenerative change
. Lucency, indicating an osteolytic lesion
. Sequestrum, indicating osteomyelitis
. Erosion, indicating inflammatory arthritis

Correct Answer & Explanation

. Sclerosis, indicating degenerative change

Explanation

Sclerosis refers to increased bone density, often seen as 'whiteness' on an X-ray. Subchondral sclerosis is a classic radiographic sign of degenerative joint disease (osteoarthritis), representing a response to increased stress on the underlying bone. Osteopenia is decreased bone density. Lucency is decreased density. Sequestrum is dead bone in osteomyelitis. Erosion is bone loss, often from inflammatory arthritis.

Question 12590

Topic: Infection, Pharmacology & VTE

An X-ray of an elderly shoulder shows a cyst-like lesion in the humeral head subchondral bone, with sclerotic margins, but no communication with the joint. How would you best describe this finding, and what is its typical etiology?

. Avascular necrosis
. Geode (subchondral cyst)
. Simple bone cyst
. Metastatic lesion
. Septic arthritis

Correct Answer & Explanation

. Geode (subchondral cyst)

Explanation

Geodes, also known as subchondral cysts, are common findings in osteoarthritis. They are fluid-filled cavities that form within the subchondral bone, often with sclerotic margins. While they can be large, they typically do not communicate with the joint space. Avascular necrosis shows collapse and increased density. A simple bone cyst is a different entity. Metastatic lesions would be more irregular. Septic arthritis causes destruction.

Question 12591

Topic: Physiology & Rehabilitation

A 50-year-old patient presents with lateral epicondylitis. An occupational therapist recommends an eccentric exercise program. What is the primary theoretical benefit of eccentric exercises in tendinopathy rehabilitation?

. To increase tendon length and flexibility.
. To reduce inflammation within the tendon.
. To induce collagen remodeling and strengthen the tendon.
. To increase concentric muscle strength for improved performance.
. To improve joint proprioception.

Correct Answer & Explanation

. To induce collagen remodeling and strengthen the tendon.

Explanation

The primary theoretical benefit of eccentric exercises in tendinopathy rehabilitation is to induce collagen remodeling, strengthen the tendon, and improve its load-bearing capacity. While they may contribute to flexibility and improved performance (by strengthening the entire muscle-tendon unit), the specific effect on tendon structure and resistance to injury is the key. They do not directly reduce inflammation, and proprioception is a secondary benefit. The progressive loading during the lengthening phase of muscle contraction is thought to stimulate fibroblast activity and collagen synthesis in a more organized fashion.

Question 12592

Topic: Surgical Anatomy & Approaches

Which nerve is at greatest risk of iatrogenic injury during surgical intervention for lateral epicondylitis?

. Median nerve
. Ulnar nerve
. Musculocutaneous nerve
. Superficial radial nerve
. Posterior interosseous nerve

Correct Answer & Explanation

. Posterior interosseous nerve

Explanation

During surgical intervention for lateral epicondylitis, especially with deeper dissection, the posterior interosseous nerve (PIN), a branch of the radial nerve, is at greatest risk. It winds around the radial neck and passes through the supinator muscle (Arcade of Frohse), near the surgical field for the common extensor origin. The superficial radial nerve is also a risk, but typically more distal and subcutaneous. Median, ulnar, and musculocutaneous nerves are more distant from the lateral epicondyle.

Question 12593

Topic: Surgical Anatomy & Approaches

An examiner asks you to describe post-operative complications following shoulder arthroscopy. Which of the following is a recognized, albeit rare, neurological complication specific to the beach-chair position?

. Axillary nerve injury.
. Musculocutaneous nerve injury.
. Brachial plexus traction injury.
. Suprascapular nerve injury.
. Ulnar nerve compression neuropathy.

Correct Answer & Explanation

. Brachial plexus traction injury.

Explanation

Brachial plexus traction injury, particularly involving the lower trunk (C8-T1), is a recognized, albeit rare, complication associated with the beach-chair position during shoulder arthroscopy. This typically occurs due to excessive traction on the arm, often compounded by factors like neck lateral flexion or rotation. While other nerve injuries can occur, brachial plexus traction is a specific concern related to positioning and traction application. Axillary nerve injury is more common with deltoid dissection, and musculocutaneous or suprascapular nerve injuries are more likely with direct iatrogenic injury or retraction.

Question 12594

Topic: Surgical Anatomy & Approaches

An examiner asks you about the 'quadrilateral space syndrome'. Which nerve and artery are primarily compressed in this syndrome?

. Suprascapular nerve and suprascapular artery.
. Axillary nerve and posterior circumflex humeral artery.
. Musculocutaneous nerve and anterior circumflex humeral artery.
. Radial nerve and profunda brachii artery.
. Ulnar nerve and ulnar artery.

Correct Answer & Explanation

. Axillary nerve and posterior circumflex humeral artery.

Explanation

The quadrilateral space is an anatomical space bounded by the teres minor (superiorly), teres major (inferiorly), long head of triceps (medially), and surgical neck of the humerus (laterally). The axillary nerve and posterior circumflex humeral artery pass through this space. Compression of these structures, often due to fibrous bands or trauma, can lead to quadrilateral space syndrome, characterized by posterior shoulder pain, paresthesia, and deltoid weakness. The other options involve different anatomical structures and locations.

Question 12595

Topic: Surgical Anatomy & Approaches

An examiner asks about a patient with a proximal humerus fracture and suspected axillary nerve injury. What clinical finding would be most indicative of this nerve injury?

. Weakness in wrist extension.
. Loss of sensation over the medial forearm.
. Inability to abduct the arm beyond 90 degrees due to deltoid weakness.
. Weakness in elbow flexion.
. Paresthesia in the thumb, index, and middle fingers.

Correct Answer & Explanation

. Inability to abduct the arm beyond 90 degrees due to deltoid weakness.

Explanation

The axillary nerve innervates the deltoid and teres minor muscles and provides sensory supply to the 'regimental badge' area over the lateral shoulder. Therefore, inability to abduct the arm (due to deltoid weakness) combined with sensory loss over the lateral shoulder would be most indicative of an axillary nerve injury. The other options describe symptoms related to different nerve distributions.

Question 12596

Topic: 1. General Principles & Basic Science

A 32-year-old bodybuilder experiences a sharp pop and sudden pain in his anterior chest wall while performing a heavy bench press. He is diagnosed with a complete pectoralis major rupture. Regarding the normal anatomy of the pectoralis major tendon insertion on the humerus, which of the following statements is true?

. The clavicular head inserts deep and proximal to the sternocostal head.
. The sternocostal head inserts deep and proximal to the clavicular head.
. Both heads insert as a single intertwined layer on the lesser tuberosity.
. The sternocostal head inserts distally on the medial lip of the bicipital groove.
. The clavicular head forms the posterior lamina of the tendon.

Correct Answer & Explanation

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

Explanation

The pectoralis major tendon has a unique twisted insertion on the lateral lip of the bicipital groove. The clavicular head inserts anteriorly (superficial) and distally. The sternocostal head twists upon itself so that its most inferior fibers insert superiorly, resulting in the sternocostal head inserting deep and proximal to the clavicular head. It is the sternocostal head that is most commonly ruptured during a bench press.

Question 12597

Topic: 1. General Principles & Basic Science

A 32-year-old male tears his pectoralis major while performing a maximal bench press. Which of the following represents the typical sequence of tearing of the pectoralis major tendon at its humeral insertion?

. Clavicular head tears first, followed by the sternal head
. Sternal head tears first, followed by the clavicular head
. Both heads tear simultaneously due to equivalent load distribution
. The muscular junction tears prior to any tendon involvement
. The short head of the biceps always ruptures prior to the pectoralis major

Correct Answer & Explanation

. Sternal head tears first, followed by the clavicular head

Explanation

The sternal head of the pectoralis major inserts deep and proximal to the clavicular head. During a bench press (specifically at the lowest point of the lift when the arm is extended, abducted, and externally rotated), the sternal head is placed under maximum tension and is predictably the first part of the tendon to rupture, followed by the clavicular head if the force continues.

Question 12598

Topic: 1. General Principles & Basic Science

A 28-year-old weightlifter feels a 'pop' in his anterior chest wall while performing a bench press. MRI confirms a complete tear of the pectoralis major tendon at its insertion. Regarding the normal anatomy of the pectoralis major insertion, which of the following statements is true?

. The sternal head inserts deep and proximal to the clavicular head.
. The sternal head inserts superficial and distal to the clavicular head.
. The clavicular head inserts deep and distal to the sternal head.
. The sternal head inserts deep and distal to the clavicular head.
. Both heads insert at the exact same level with parallel fibers.

Correct Answer & Explanation

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

Explanation

The pectoralis major tendon undergoes a 180-degree twist before inserting onto the lateral lip of the bicipital groove. Because of this twist, the lower fibers of the muscle (sternal/abdominal head) become the posterior lamina and insert highest (most proximal) and deep. The upper fibers (clavicular head) form the anterior lamina and insert more inferiorly (distal) and superficial.

Question 12599

Topic: 1. General Principles & Basic Science

A 19-year-old football player presents to the emergency department after a direct blow to the anteromedial clavicle. He complains of chest pain, difficulty swallowing (dysphagia), and a choking sensation. Clinical exam reveals a sunken appearance of the medial clavicle. What is the most appropriate next step in management?

. Immediate closed reduction under procedural sedation in the ED
. Urgent CT scan of the chest and formal closed reduction in the OR with cardiothoracic surgery available
. Discharge with a sling and outpatient orthopedic follow-up
. Immediate open reduction and internal fixation with a hook plate
. Figure-of-eight brace and admission for observation

Correct Answer & Explanation

. Urgent CT scan of the chest and formal closed reduction in the OR with cardiothoracic surgery available

Explanation

The patient has a posterior sternoclavicular dislocation, which is an orthopedic emergency due to the risk of compression to the trachea, esophagus, and great vessels. An urgent CT assesses the mediastinum. Reduction should be performed in the operating room with a cardiothoracic surgeon available in case of a catastrophic vascular tear during reduction.

Question 12600

Topic: 1. General Principles & Basic Science

A 30-year-old male bodybuilder feels a sudden 'pop' in his anterior axilla while performing heavy bench press exercises. Examination reveals ecchymosis, swelling, and loss of the normal anterior axillary fold. If surgical repair is pursued, understanding the anatomy of the pectoralis major footprint is critical. Which of the following statements regarding the sternal head insertion is accurate?

. It inserts deep and proximal to the clavicular head
. It inserts superficial and distal to the clavicular head
. It inserts superficial and proximal to the clavicular head
. It inserts deep and distal to the clavicular head
. It merges completely with the clavicular head prior to insertion, making them indistinguishable

Correct Answer & Explanation

. It inserts deep and distal to the clavicular head

Explanation

At its humeral footprint, the pectoralis major tendon undergoes a 180-degree twist. The clavicular head descends to insert anteriorly (superficial) and distally. The sternal head twists behind it to insert posteriorly (deep) and proximally. Tears most commonly involve the sternal head failing during eccentric contraction.

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