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1. General Principles & Basic Science MCQs

Practice Set 216 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 4301

Topic: Infection, Pharmacology & VTE

During a revision shoulder arthroplasty for a painful, stiff TSA, intraoperative cultures are obtained. At 10 days, the cultures grow Cutibacterium acnes. Which characteristic of this organism makes it particularly challenging to diagnose and treat in the setting of shoulder arthroplasty?

. It is a rapid-growing aerobic Gram-negative rod that resists standard prophylaxis.
. It produces a robust biofilm and typically lacks classic systemic inflammatory signs.
. It is uniformly resistant to penicillin, cephalosporins, and vancomycin.
. It presents acutely with high-grade fevers and purulent drainage within 2 weeks of index surgery.
. It obligatorily infects the subscapularis tendon matrix rather than the implant interface.

Correct Answer & Explanation

. It produces a robust biofilm and typically lacks classic systemic inflammatory signs.

Explanation

Cutibacterium acnes (formerly Propionibacterium acnes) is a slow-growing, Gram-positive, anaerobic rod commonly found in the sebaceous glands of the shoulder. It often causes indolent, low-grade periprosthetic joint infections lacking classic clinical signs (e.g., normal CRP/ESR, no fever, no erythema). Its ability to form a protective biofilm on implants makes both diagnosis (requiring extended culture times) and eradication challenging.

Question 4302

Topic: Surgical Anatomy & Approaches

A 24-year-old rugby player undergoes an open Latarjet procedure for recurrent anterior shoulder instability associated with 25% glenoid bone loss. In the recovery room, he exhibits marked weakness in elbow flexion and forearm supination. Which nerve was most likely injured during the procedure, and what is its normal anatomic relationship to the transferred coracoid?

. Axillary nerve; passes directly superior to the conjoined tendon
. Musculocutaneous nerve; enters the coracobrachialis medial and distal to the coracoid tip
. Musculocutaneous nerve; enters the short head of the biceps lateral and proximal to the coracoid base
. Median nerve; runs anterior to the axillary artery directly at the coracoid base
. Radial nerve; lies directly posterior and adherent to the coracoid process

Correct Answer & Explanation

. Musculocutaneous nerve; enters the coracobrachialis medial and distal to the coracoid tip

Explanation

The musculocutaneous nerve is at significant risk during the Latarjet procedure due to its proximity to the operative field. It typically enters the coracobrachialis muscle on its medial aspect, approximately 3 to 8 cm distal to the tip of the coracoid. Vigorous medial retraction of the conjoined tendon can cause a traction neuropraxia, presenting as weakness in the biceps and brachialis (elbow flexion and forearm supination).

Question 4303

Topic: 1. General Principles & Basic Science

A 32-year-old bodybuilder feels a sudden 'pop' in his anterior axilla while performing a heavy bench press. He presents with loss of the anterior axillary fold and profound weakness in internal rotation and adduction. MRI confirms a complete tear of the pectoralis major at the sternal head insertion. Which of the following describes the accurate anatomical footprint of the sternal head to guide an anatomic repair?

. It inserts deep and proximal to the clavicular head on the lateral lip of the bicipital groove.
. It inserts superficial and distal to the clavicular head on the lateral lip of the bicipital groove.
. It inserts on the medial lip of the bicipital groove, deep to the latissimus dorsi.
. It inserts onto the coracoid process, blending with the short head of the biceps.
. It blends directly with the anterior deltoid fascia without a distinct bony insertion.

Correct Answer & Explanation

. It inserts deep and proximal to the clavicular head on the lateral lip of the bicipital groove.

Explanation

The pectoralis major tendon undergoes a unique 180-degree twist before its insertion onto the lateral lip of the bicipital groove of the humerus. Due to this twist, the sternal (and abdominal) head fibers insert deep and proximal to the fibers of the clavicular head. Recognizing this layered footprint is essential for accurate anatomic footprint restoration during surgical repair.

Question 4304

Topic: Surgical Anatomy & Approaches

Which of the following nerve injuries is most likely to occur due to excessive medial retraction of the conjoined tendon during the deltopectoral approach for a total shoulder arthroplasty?

. Axillary nerve
. Musculocutaneous nerve
. Suprascapular nerve
. Radial nerve
. Median nerve

Correct Answer & Explanation

. Musculocutaneous nerve

Explanation

The musculocutaneous nerve enters the coracobrachialis approximately 3-8 cm distal to the coracoid process. Excessive or prolonged medial retraction of the conjoined tendon during a deltopectoral approach places this nerve at high risk for neuropraxia.

Question 4305

Topic: 1. General Principles & Basic Science

During a routine L4-L5 microdiscectomy, an incidental 4 mm dural tear occurs ventrolaterally, which is inaccessible for primary suture repair. Cerebrospinal fluid is actively pooling in the surgical field. What is the most appropriate next step in management?

. Convert to open laminectomy for primary repair
. Place a synthetic dural substitute, apply fibrin glue, and perform a tight fascial closure
. Insert a subarachnoid lumbar drain for 7 days
. Pack the defect with bone wax
. Leave a fascial drain on high wall suction

Correct Answer & Explanation

. Place a synthetic dural substitute, apply fibrin glue, and perform a tight fascial closure

Explanation

When a small dural tear occurs that is inaccessible for primary suture repair (such as a ventral or ventrolateral tear), the standard of care is to use dural patch/sealant techniques (like synthetic dural substitutes, muscle grafts, and fibrin glue) combined with a meticulous, watertight closure of the overlying fascia. Fascial drains on suction can create a continuous CSF fistula and should be avoided.

Question 4306

Topic: 1. General Principles & Basic Science

A 72-year-old female with profound osteoporosis presents with severe back pain 3 weeks after lifting a box. Imaging confirms an acute, isolated T12 osteoporotic vertebral compression fracture (VCF) with 30% anterior height loss and no retropulsion. Pain is not adequately controlled with oral analgesics and a brace. Which of the following is true regarding balloon kyphoplasty compared to non-operative management for this condition based on randomized controlled trials?

. Kyphoplasty has a lower risk of adjacent segment fracture.
. Kyphoplasty provides superior long-term (> 2 years) pain relief.
. Kyphoplasty provides faster early pain relief and functional improvement.
. Kyphoplasty significantly improves 1-year mortality rates.
. Kyphoplasty allows for complete restoration of vertebral height in chronic fractures.

Correct Answer & Explanation

. Kyphoplasty provides faster early pain relief and functional improvement.

Explanation

According to major randomized controlled trials (such as the FREE trial), balloon kyphoplasty provides faster and superior early pain relief and improvement in functional status compared to non-operative management during the first few months. However, by 1 to 2 years, the pain and functional outcomes between the operative and non-operative groups generally equalize. Cement augmentation carries a well-documented risk of adjacent segment fractures.

Question 4307

Topic: Infection, Pharmacology & VTE

A 45-year-old male with a history of intravenous drug use presents with severe back pain. Laboratory tests show elevated ESR and CRP. MRI with contrast reveals signal changes and enhancement of the L3-L4 disc space consistent with discitis/osteomyelitis. Blood cultures are negative. What is the most appropriate next step prior to initiating antibiotic therapy?

. Start empiric intravenous vancomycin and cefepime
. Obtain a CT-guided percutaneous biopsy of the disc space
. Perform an open surgical debridement
. Administer intra-articular steroid injections for pain relief
. Perform a gallium bone scan

Correct Answer & Explanation

. Obtain a CT-guided percutaneous biopsy of the disc space

Explanation

In cases of spontaneous pyogenic discitis/osteomyelitis with negative blood cultures and no neurologic deficit or instability, a CT-guided percutaneous biopsy should be performed to isolate the causative organism before initiating empiric antibiotics.

Question 4308

Topic: 1. General Principles & Basic Science

A 28-year-old gymnast sustains a superior peroneal retinaculum (SPR) tear, resulting in peroneal tendon subluxation. Which anatomical variation is most frequently associated with an increased risk of this specific pathology?

. A convex or shallow posterior fibular groove
. An anomalous peroneus tertius muscle
. A low-lying peroneus brevis muscle belly
. Hypertrophy of the peroneal tubercle
. Os peroneum

Correct Answer & Explanation

. A convex or shallow posterior fibular groove

Explanation

A convex, flat, or shallow retromalleolar fibular groove is a significant predisposing anatomic factor for peroneal tendon subluxation and dislocation. Surgical treatment often involves groove deepening procedures in addition to SPR repair. While a low-lying peroneus brevis muscle belly can contribute by overcrowding the space, the groove morphology is the most classic and surgically addressed structural risk factor.

Question 4309

Topic: Surgical Anatomy & Approaches

Recent literature regarding the fixation of posterior malleolus fractures in the setting of rotational ankle injuries emphasizes which of the following as the primary indication for open reduction and internal fixation of the posterior fragment?

. Fragment size greater than 25% of the articular surface
. Presence of an associated medial malleolus fracture
. Restoration of the incisura fibularis and syndesmotic stability
. Prevention of anterior talar translation
. Need to utilize a posterolateral surgical approach

Correct Answer & Explanation

. Restoration of the incisura fibularis and syndesmotic stability

Explanation

Historically, a fragment size >25-30% of the articular surface was the main indication for fixing the posterior malleolus. However, recent biomechanical and clinical studies emphasize that fixation of the posterior malleolus directly restores the posterior inferior tibiofibular ligament (PITFL) footprint, reconstituting the incisura fibularis and providing superior syndesmotic stability compared to trans-syndesmotic screws alone, regardless of the fragment's articular size.

Question 4310

Topic: 1. General Principles & Basic Science

A 16-year-old female presents with medial midfoot pain exacerbated by shoe wear. Radiographs demonstrate an ossicle located medial to the navicular body, separated by a synchondrosis. If conservative management fails, surgical excision of the ossicle usually requires detachment and reattachment of which of the following tendons?

. Tibialis anterior
. Tibialis posterior
. Flexor hallucis longus
. Flexor digitorum longus
. Peroneus longus

Correct Answer & Explanation

. Tibialis posterior

Explanation

The patient has a symptomatic accessory navicular (Type II). The tibialis posterior tendon commonly inserts, at least partially, into the accessory ossicle. Excision of the ossicle (the Kidner procedure) frequently requires advancing and reattaching the tibialis posterior tendon to the remaining native navicular to restore medial longitudinal arch dynamic support.

Question 4311

Topic: 1. General Principles & Basic Science

A patient with diabetes and a plantar midfoot ulcer presents with significant midfoot swelling and erythema. Plain radiographs show diffuse midfoot bone destruction. Which imaging modality has the highest specificity for differentiating acute Charcot neuroarthropathy from superimposed osteomyelitis?

. Three-phase Technetium-99m bone scan
. Gallium-67 scan
. Indium-111 labeled leukocyte scan combined with Technetium-99m marrow scan
. Standard MRI with gadolinium
. Ultrasound

Correct Answer & Explanation

. Indium-111 labeled leukocyte scan combined with Technetium-99m marrow scan

Explanation

Differentiating Charcot neuroarthropathy from osteomyelitis can be challenging on MRI due to reactive marrow edema. The combination of an Indium-111 leukocyte scan and a Tc-99m sulfur colloid marrow scan provides the highest specificity for diagnosing osteomyelitis in this setting.

Question 4312

Topic: Surgical Anatomy & Approaches

A 22-year-old man presents with severe crush injury to his right forearm and is diagnosed with acute compartment syndrome. A volar approach for fasciotomy (extensile Henry approach) is planned. During deep dissection, which critical neurovascular structure must be carefully protected as it passes between the two heads of the pronator teres?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve
. Median nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Median nerve

Explanation

The median nerve classically runs between the humeral and ulnar heads of the pronator teres muscle in the proximal forearm. During the volar forearm fasciotomy (which utilizes the Henry approach extending from the distal humerus to the wrist), careful identification and release of the pronator teres aponeurosis and the FDS arch is necessary to thoroughly decompress the deep volar compartment and prevent secondary median nerve entrapment.

Question 4313

Topic: Surgical Anatomy & Approaches

A 40-year-old man undergoes a single-incision anterior approach for repair of a complete acute distal biceps tendon rupture using a cortical button technique. Postoperatively, he complains of burning pain and numbness over the radial aspect of the mid-to-distal volar forearm. His motor function is completely intact. Which nerve was most likely injured during the surgical approach?

. Superficial radial nerve
. Posterior interosseous nerve
. Lateral antebrachial cutaneous nerve
. Medial antebrachial cutaneous nerve
. Anterior interosseous nerve

Correct Answer & Explanation

. Lateral antebrachial cutaneous nerve

Explanation

The lateral antebrachial cutaneous nerve (LABC), the terminal sensory branch of the musculocutaneous nerve, exits the deep fascia lateral to the biceps tendon and runs near the cephalic vein. It provides sensation to the radial half of the volar forearm. It is highly susceptible to traction or transection injury during the anterior single-incision approach to the distal biceps. The posterior interosseous nerve (PIN) is at risk during a two-incision approach or with deep retractors, but it provides motor innervation (which is intact here).

Question 4314

Topic: Surgical Anatomy & Approaches
A 28-year-old male sustains a sharp complete transection of his radial nerve at the mid-humeral level. Within 24-48 hours post-injury, Wallerian degeneration begins. Which of the following best describes the pathophysiological process of Wallerian degeneration distal to the injury site?
. Schwann cells undergo rapid apoptosis and are completely cleared by local macrophages
. Axons and myelin degrade while macrophages clear the debris, and Schwann cells proliferate to form Bands of Bรผngner
. Complete loss of the endoneurial tubes occurs, requiring surgical grafting to direct regenerating axons
. Degeneration proceeds in a proximal-to-distal direction solely driven by osteoclastic enzyme release
. Retrograde degeneration extends entirely back to the spinal cord, leading to death of the anterior horn cell

Correct Answer & Explanation

. Axons and myelin degrade while macrophages clear the debris, and Schwann cells proliferate to form Bands of Bรผngner

Explanation

Wallerian degeneration occurs in the distal stump of a transected nerve. The axons and myelin sheath rapidly degrade, and macrophages migrate in to clear the debris. Crucially, the Schwann cells do not die; rather, they dedifferentiate, proliferate, and align to form longitudinal columns known as Bands of Bรผngner within the preserved endoneurial tubes. These bands secrete neurotrophic factors and provide a physical pathway to guide regenerating axonal sprouts from the proximal stump.

Question 4315

Topic: 1. General Principles & Basic Science

A 45-year-old male sustains a bicondylar tibial plateau fracture with a displaced, large posteromedial coronal split fragment. A posteromedial surgical approach is chosen for optimal buttress plating. This approach develops an internervous plane between which of the following muscle groups?

. Medial head of the gastrocnemius and the pes anserinus
. Semimembranosus and semitendinosus
. Popliteus and soleus
. Tibialis posterior and flexor digitorum longus
. Tibialis anterior and extensor hallucis longus

Correct Answer & Explanation

. Medial head of the gastrocnemius and the pes anserinus

Explanation

The posteromedial approach to the tibial plateau is critical for addressing posteromedial shear fragments, which cannot be adequately buttressed from an anteromedial approach. The correct anatomic interval is between the medial head of the gastrocnemius (retracted laterally/posteriorly) and the pes anserinus tendons (retracted medially/anteriorly).

Question 4316

Topic: 1. General Principles & Basic Science

Which zone of articular cartilage has the highest concentration of proteoglycans, features collagen fibrils arranged perpendicular to the joint surface, and is primarily responsible for resisting compressive forces?

. Superficial (tangential) zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified zone
. Tidemark

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone of articular cartilage is characterized by the highest concentration of proteoglycans and the lowest water content. Its collagen fibrils (primarily Type II) are arranged perpendicular to the articular surface, making this zone critical for resisting compressive loads.

Question 4317

Topic: 1. General Principles & Basic Science

Which type of collagen acts as the primary cross-linking molecule between Type II collagen fibrils in articular cartilage, effectively linking the fibrils to the extracellular matrix and providing structural stability?

. Type I
. Type VI
. Type IX
. Type X
. Type XI

Correct Answer & Explanation

. Type IX

Explanation

Type IX collagen is a non-fibrillar collagen that covalently binds to the surface of Type II collagen fibrils. It acts as an essential cross-linking molecule that connects the fibril network to the surrounding proteoglycan extracellular matrix.

Question 4318

Topic: 1. General Principles & Basic Science

In the early pathogenesis of osteoarthritis, which biochemical change occurs first in the articular cartilage extracellular matrix?

. Increase in total proteoglycan content
. Decrease in water content
. Increase in water content and decrease in proteoglycan concentration
. Cleavage of type I collagen by MMP-1
. Chondrocyte apoptosis as the primary initial event

Correct Answer & Explanation

. Increase in water content and decrease in proteoglycan concentration

Explanation

The earliest biochemical change in osteoarthritis is the damage to the Type II collagen meshwork, which allows the hydrophilic proteoglycans to swell. This leads to an overall increase in water content and a relative decrease in proteoglycan concentration, resulting in decreased stiffness of the cartilage.

Question 4319

Topic: 1. General Principles & Basic Science

Which of the following characteristics best describes the deep (radial) zone of articular cartilage compared to the superficial zone?

. Highest water content and collagen fibers parallel to the joint surface
. Lowest proteoglycan content and highest chondrocyte density
. Highest proteoglycan content and collagen fibers oriented perpendicular to the joint surface
. Predominantly Type I collagen oriented parallel to the joint surface
. Highest water content and random collagen fiber orientation

Correct Answer & Explanation

. Highest proteoglycan content and collagen fibers oriented perpendicular to the joint surface

Explanation

The deep (radial) zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. Its collagen fibers (primarily Type II) are arranged perpendicular to the articular surface to maximize resistance to compressive loads. In contrast, the superficial zone has the highest water content, lowest proteoglycan content, and collagen fibers parallel to the joint surface to resist shear forces.

Question 4320

Topic: 1. General Principles & Basic Science

Biomechanical studies have demonstrated that an unrepaired complete radial tear of the posterior medial meniscus root alters knee joint contact pressures to a state most similar to which of the following conditions?

. An intact meniscus
. A partial meniscectomy of less than 30%
. A total meniscectomy
. An ACL-deficient knee
. An isolated posterior horn longitudinal tear

Correct Answer & Explanation

. A total meniscectomy

Explanation

A complete radial tear or avulsion of the posterior medial meniscus root completely disrupts the circumferential hoop stresses of the meniscus. Biomechanically, this renders the meniscus functionally incompetent, causing extrusion and increasing peak tibiofemoral contact pressures to levels equivalent to those seen after a total meniscectomy. This strongly predisposes the joint to rapid articular cartilage degeneration.

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