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1. General Principles & Basic Science MCQs

Practice Set 631 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 12601

Topic: 1. General Principles & Basic Science

During an arthroscopic suprascapular nerve release for entrapment at the suprascapular notch, the surgeon must identify the transverse scapular ligament. To avoid vascular injury, the surgeon must be aware of the anatomic relationship of the neurovascular structures at this site. Which statement is correct?

. Both the suprascapular artery and nerve pass inferior to the ligament
. The suprascapular artery passes superior to the ligament, and the nerve passes inferior to it
. Both the suprascapular artery and nerve pass superior to the ligament
. The suprascapular nerve passes superior to the ligament, and the artery passes inferior to it
. The artery is deep to the nerve, and both pierce the ligament directly

Correct Answer & Explanation

. The suprascapular artery passes superior to the ligament, and the nerve passes inferior to it

Explanation

At the suprascapular notch, the transverse scapular ligament bridges the notch. The suprascapular artery passes over (superior to) the ligament, while the suprascapular nerve passes under (inferior to) the ligament through the notch. The classic mnemonic is 'Army (Artery) goes over the bridge, Navy (Nerve) goes under the bridge'.

Question 12602

Topic: Surgical Anatomy & Approaches

A 32-year-old male sustains a closed, mid-shaft humerus fracture. On initial presentation, his neurovascular exam is completely normal. A closed reduction is performed and a coaptation splint is applied. Immediately following the reduction, the patient is noted to have a complete wrist drop and inability to extend his fingers. What is the most appropriate next step in management?

. Clinical observation for 3 to 4 months followed by EMG if no recovery is noted
. Immediate surgical exploration of the radial nerve and rigid fracture fixation
. Immediate electromyography (EMG) and nerve conduction studies
. Switching from a coaptation splint to a Sarmiento functional fracture brace
. Administration of high-dose intravenous corticosteroids

Correct Answer & Explanation

. Immediate surgical exploration of the radial nerve and rigid fracture fixation

Explanation

While an initial (primary) radial nerve palsy in a closed humerus fracture is generally treated with observation, a secondary radial nerve palsy that developsimmediately aftera closed reduction attempt strongly suggests that the nerve has become entrapped or lacerated within the fracture site during the manipulation. This is a classic indication for immediate surgical exploration and internal fixation.

Question 12603

Topic: 1. General Principles & Basic Science

A 32-year-old male bodybuilder feels a 'pop' in his anterior chest while performing a heavy bench press. MRI confirms a complete rupture of the pectoralis major tendon at its insertion. Which of the following best describes the anatomic insertion of the pectoralis major tendon?

. The sternal head inserts superficial and proximal to the clavicular head on the lateral lip of the bicipital groove.
. The sternal head twists such that its lower fibers insert deep and proximal to the clavicular head on the lateral lip of the bicipital groove.
. The clavicular head inserts deep and proximal to the sternal head on the medial lip of the bicipital groove.
. The two heads merge to form a single untwisted tendon that inserts on the medial lip of the bicipital groove.
. The sternal head inserts onto the lesser tuberosity, while the clavicular head inserts onto the greater tuberosity.

Correct Answer & Explanation

. The sternal head twists such that its lower fibers insert deep and proximal to the clavicular head on the lateral lip of the bicipital groove.

Explanation

The pectoralis major inserts onto the lateral lip of the bicipital groove. The tendon is unique because it undergoes a 180-degree twist as it approaches the humerus. The clavicular head forms the anterior (superficial) lamina and inserts distally. The sternal/abdominal head forms the posterior (deep) lamina, twisting such that its lowest fibers insert most superiorly (proximally). Therefore, the sternal head inserts deep and proximal to the clavicular head.

Question 12604

Topic: 1. General Principles & Basic Science

During a Zone II flexor tendon repair, which of the following factors has been shown biomechanically to have the greatest influence on the ultimate tensile strength of the repair?

. The type of suture material utilized for the core suture
. The use of a locking versus grasping peripheral epitendinous suture
. The number of core suture strands crossing the repair site
. The exact location of the epitendinous suture placement
. The caliber of the peripheral suture

Correct Answer & Explanation

. The number of core suture strands crossing the repair site

Explanation

Extensive biomechanical studies on flexor tendon repairs, notably by Tang and others, have demonstrated that the ultimate tensile strength of a flexor tendon repair is directly proportional to the number of core suture strands crossing the repair site. A 4-strand or 6-strand repair provides significantly greater strength than a 2-strand repair, allowing for safe early active motion protocols.

Question 12605

Topic: Surgical Anatomy & Approaches
A 60-year-old woman undergoes a ligament reconstruction and tendon interposition (LRTI) procedure for Eaton-Littler Stage III thumb carpometacarpal (CMC) arthritis via a dorsal approach. Which nerve is most at risk of injury during the surgical dissection down to the CMC joint capsule?
. Palmar cutaneous branch of the median nerve
. Deep motor branch of the ulnar nerve
. Superficial branch of the radial nerve
. Lateral antebrachial cutaneous nerve
. Posterior interosseous nerve

Correct Answer & Explanation

. Superficial branch of the radial nerve

Explanation

The dorsal surgical approach to the thumb CMC joint typically exploits the interval between the first extensor compartment (APL, EPB) and the third extensor compartment (EPL). The superficial branch of the radial nerve runs directly over this region to supply sensation to the dorsal-radial aspect of the hand and thumb, making it highly susceptible to iatrogenic injury or traction neuritis during CMC arthroplasty.

Question 12606

Topic: 1. General Principles & Basic Science

A patient presents with a jammed finger. To evaluate the integrity of the central slip of the extensor mechanism, Elson's test is performed. If the central slip is completely ruptured, what is the expected clinical finding when the patient attempts to extend the PIP joint against resistance from a 90-degree flexed position?

. The DIP joint remains completely flaccid and floppy.
. The PIP joint extends powerfully while the DIP flexes.
. The DIP joint goes into rigid extension.
. The lateral bands subluxate dorsally.
. The metacarpophalangeal joint hyperextends involuntarily.

Correct Answer & Explanation

. The DIP joint goes into rigid extension.

Explanation

In Elson's test, the PIP is bent to 90 degrees over a table edge. If the central slip is intact, extending against resistance directs force to the PIP, leaving the DIP floppy. If the central slip is torn, the force bypasses the PIP and is transmitted entirely through the lateral bands, which pulls the DIP into rigid extension.

Question 12607

Topic: 1. General Principles & Basic Science

The scapholunate interosseous ligament (SLIL) is the primary stabilizer of the scapholunate joint. It is divided into three anatomic regions. Which region is the thickest, strongest, and most critical for preventing scapholunate dissociation?

. Volar region
. Proximal (membranous) region
. Dorsal region
. Central region
. Radiocarpal region

Correct Answer & Explanation

. Dorsal region

Explanation

The dorsal region of the scapholunate interosseous ligament (SLIL) is the thickest and strongest component. It is the primary restraint to translation and diastasis of the scapholunate interval. In contrast, the volar portion is the thickest and strongest part of the lunotriquetral (LT) ligament.

Question 12608

Topic: 1. General Principles & Basic Science

In order to prevent bowstringing after a complex flexor tendon injury in zone II, which combination of annular pulleys is considered biomechanically critical to preserve or reconstruct?

. A1 and A2
. A2 and A4
. A3 and A5
. A1 and A5
. A2 and A3

Correct Answer & Explanation

. A2 and A4

Explanation

The A2 and A4 pulleys arise from the periosteum of the proximal and middle phalanges, respectively. They are the most critical pulleys for preventing tendon bowstringing and maintaining the mechanical advantage of flexor excursion.

Question 12609

Topic: Surgical Anatomy & Approaches

During a volar Henry approach to fix a distal radius fracture, the surgeon develops the interval between the flexor carpi radialis (FCR) and the radial artery. Which muscle must be elevated from the radius to directly expose the volar fracture fragments?

. Pronator teres
. Flexor pollicis longus
. Pronator quadratus
. Brachioradialis
. Flexor digitorum superficialis

Correct Answer & Explanation

. Pronator quadratus

Explanation

The pronator quadratus natively covers the volar aspect of the distal radius. In the volar Henry approach, an L-shaped incision is made to release the pronator quadratus from its radial and distal borders, reflecting it ulnarly to expose the bone.

Question 12610

Topic: 1. General Principles & Basic Science

A 62-year-old female presents with severe base of thumb pain. Radiographs reveal Eaton-Littler Stage IV carpometacarpal (CMC) joint arthritis. By definition, Stage IV disease involves advanced osteoarthritic changes at the trapeziometacarpal joint and which other articulation?

. Scaphotrapezialtrapezoid (STT) joint
. Radiolunate joint
. Trapezoid-capitate joint
. Scapholunate joint
. Metacarpophalangeal (MCP) joint

Correct Answer & Explanation

. Scaphotrapezialtrapezoid (STT) joint

Explanation

Eaton-Littler Stage IV thumb CMC arthritis is characterized by pantrapezial arthritis, which involves both the trapeziometacarpal joint and the scaphotrapezialtrapezoid (STT) joint. This makes isolated CMC arthrodesis or replacement less favorable.

Question 12611

Topic: 1. General Principles & Basic Science

A patient with long-standing rheumatoid arthritis has severe, fixed forefoot deformities. During the non-weightbearing examination, you attempt to correct the forefoot abduction, but it remains rigid. This finding suggests:

. The deformity is primarily due to soft tissue contracture.
. The patient is guarding due to pain.
. There is significant bony adaptation or joint fusion in the midfoot and forefoot.
. The patient has an underlying neurological deficit.
. The plantar plate of the MTP joints is intact.

Correct Answer & Explanation

. There is significant bony adaptation or joint fusion in the midfoot and forefoot.

Explanation

A rigid, uncorrectable forefoot abduction (splaying) or other fixed deformities in the non-weightbearing state strongly suggests significant bony adaptation, irreversible joint destruction, or even auto-fusion of joints in the midfoot and forefoot. Soft tissue contractures can cause some rigidity, but complete bony fixation implies severe, chronic structural changes that will likely require bony procedures for correction. It's a critical distinction for surgical planning.

Question 12612

Topic: Infection, Pharmacology & VTE

A patient with a chronically infected TKA caused by methicillin-resistant Staphylococcus aureus (MRSA) is undergoing two-stage revision. During the first stage, extensive debridement is performed. What is the most appropriate empirical intravenous antibiotic regimen to initiate while awaiting definitive culture sensitivities?

. Cefazolin and Gentamicin.
. Vancomycin and Rifampin.
. Ciprofloxacin and Clindamycin.
. Ampicillin/Sulbactam.
. Piperacillin/Tazobactam.

Correct Answer & Explanation

. Vancomycin and Rifampin.

Explanation

For known or suspected MRSA PJI, vancomycin is the cornerstone of empirical treatment because of its reliable activity against MRSA. Rifampin is a potent anti-biofilm agent and is often added as a synergistic agent, particularly for staphylococcal infections, but it should never be used as monotherapy due to rapid resistance development. Cefazolin is ineffective against MRSA. Ciprofloxacin, clindamycin, ampicillin/sulbactam, and piperacillin/tazobactam are generally not reliably effective against MRSA. The combination of Vancomycin and Rifampin provides excellent coverage for MRSA and biofilm activity while awaiting sensitivities, although rifampin should be used with caution due to drug interactions and resistance potential.

Question 12613

Topic: 1. General Principles & Basic Science

Which of the following is an advantage of using an articulating antibiotic-loaded cement spacer compared to a static spacer in a two-stage revision?

. Higher antibiotic elution concentration.
. Provides greater mechanical stability and prevents bony overgrowth.
. Allows for earlier knee range of motion and maintains soft tissue envelope.
. Easier to remove during the second stage.
. Eliminates the need for systemic antibiotics.

Correct Answer & Explanation

. Allows for earlier knee range of motion and maintains soft tissue envelope.

Explanation

Articulating antibiotic-loaded cement spacers offer several advantages over static spacers, primarily allowing for earlier and greater knee range of motion, which helps maintain the soft tissue envelope, prevent arthrofibrosis, and improve functional outcomes. While both spacer types elute antibiotics, articulating spacers are generally not superior in terms of elution concentration. Static spacers often provide more stability and are easier to mold. Neither eliminates the need for systemic antibiotics. Removing articulating spacers can sometimes be more challenging than static ones if they become ingrown or fractured.

Question 12614

Topic: Infection, Pharmacology & VTE

Which imaging modality is most sensitive for detecting early osteomyelitis or loosening in a periprosthetic infection setting when plain radiographs are inconclusive?

. Conventional X-rays.
. Computed Tomography (CT) scan.
. Magnetic Resonance Imaging (MRI).
. Technetium-99m bone scan with Gallium-67 scan or Indium-111 labeled leukocyte scan.
. Ultrasound.

Correct Answer & Explanation

. Technetium-99m bone scan with Gallium-67 scan or Indium-111 labeled leukocyte scan.

Explanation

While MRI offers good soft tissue and bone marrow assessment, it is severely limited by artifact from metal implants. Nuclear medicine scans (Technetium-99m bone scan combined with Gallium-67 scan or Indium-111 labeled leukocyte scan) are generally considered the most sensitive and specific imaging modalities for detecting early osteomyelitis, implant loosening, and differentiating between aseptic loosening and septic loosening in the presence of metallic implants. Plain radiographs are initial, but often inconclusive. CT is good for bone detail but less sensitive for early infection. Ultrasound is useful for fluid collections but not osteomyelitis or loosening.

Question 12615

Topic: Infection, Pharmacology & VTE

What is the primary role of rifampin in the treatment regimen for staphylococcal periprosthetic joint infections?

. As a stand-alone agent for eradication.
. To provide broad-spectrum coverage against Gram-negative organisms.
. To enhance bone penetration of other antibiotics.
. To act synergistically with other antibiotics by disrupting bacterial biofilm.
. To reduce systemic inflammatory response.

Correct Answer & Explanation

. To act synergistically with other antibiotics by disrupting bacterial biofilm.

Explanation

Rifampin is highly effective in disrupting bacterial biofilms, particularly those formed by staphylococci. It is used synergistically with other antistaphylococcal agents (e.g., fluoroquinolones, vancomycin, beta-lactams) and should never be used as monotherapy due to the rapid development of resistance. It does not primarily cover Gram-negative organisms, and its main role is not bone penetration (though it has good penetration) but rather biofilm eradication. It does not directly reduce systemic inflammation as its primary action.

Question 12616

Topic: Infection, Pharmacology & VTE

What is the primary goal of extensive debridement during the first stage of a two-stage revision for PJI?

. To prepare the bone for cement spacer placement.
. To remove all infected and necrotic soft tissue and biofilm.
. To resect additional bone for lengthening the limb.
. To harvest healthy tissue for wound closure.
. To expose blood vessels for local antibiotic delivery.

Correct Answer & Explanation

. To remove all infected and necrotic soft tissue and biofilm.

Explanation

The primary goal of extensive debridement during the first stage of a two-stage revision is to remove all infected and necrotic soft tissue, granulation tissue, and bacterial biofilm from the periprosthetic space and bone. This reduction of bacterial load is crucial for successful infection eradication. While preparing the bone for a spacer is a secondary outcome, the main focus is on meticulously cleaning the entire infected bed. Bone resection for lengthening is not a goal, and harvesting tissue is for closure, not debridement itself. Exposing vessels is not the primary goal.

Question 12617

Topic: Infection, Pharmacology & VTE

A 60-year-old male develops a PJI 1 year post-TKA due to coagulase-negative Staphylococcus. He undergoes a DAIR procedure. Which of the following oral antibiotics is most commonly used in combination with rifampin for suppressive or prolonged post-DAIR therapy for Staphylococcal PJI?

. Cephalexin.
. Doxycycline.
. Levofloxacin.
. Clindamycin.
. Metronidazole.

Correct Answer & Explanation

. Levofloxacin.

Explanation

For staphylococcal PJI (including coagulase-negative Staphylococci), a fluoroquinolone (like ciprofloxacin or levofloxacin) is often chosen to combine with rifampin for oral suppressive or prolonged post-DAIR therapy, due to its good bone penetration and synergy with rifampin against biofilm. However, given the options, Levofloxacin is the appropriate fluoroquinolone. Doxycycline can also be used but Levofloxacin is a more common and robust choice in this context. Cephalexin and clindamycin are typically less preferred for suppressive therapy with rifampin due to resistance profiles or less optimal synergy. Metronidazole has no activity against staphylococci.

Question 12618

Topic: Infection, Pharmacology & VTE

What is the recommended minimum duration of antibiotic therapy for a low-virulence PJI (e.g., CoNS) treated with DAIR and polyethylene exchange?

. 1 week IV + 2 weeks oral.
. 2 weeks IV + 4 weeks oral.
. 2-4 weeks IV + 3-6 months oral.
. 6-8 weeks IV only.
. 12 months oral only.

Correct Answer & Explanation

. 2-4 weeks IV + 3-6 months oral.

Explanation

For low-virulence organisms treated with DAIR, the typical recommendation is 2-4 weeks of targeted intravenous antibiotics, followed by a prolonged course of oral antibiotics for 3-6 months. This extended duration of oral suppressive therapy is crucial to prevent recurrence given the challenges of eradicating biofilm with implant retention. Shorter durations are associated with higher failure rates.

Question 12619

Topic: Infection, Pharmacology & VTE

What is the primary concern regarding the use of systemic fluoroquinolones (e.g., ciprofloxacin, levofloxacin) in combination with rifampin for Staphylococcal PJI?

. Lack of efficacy against Staphylococci.
. High incidence of renal toxicity.
. Rapid development of resistance if used as monotherapy and drug interactions with rifampin.
. Poor bone penetration.
. High rates of anaphylaxis.

Correct Answer & Explanation

. Rapid development of resistance if used as monotherapy and drug interactions with rifampin.

Explanation

While fluoroquinolones are effective against many Staphylococci and have good bone penetration, the primary concern when used in combination with rifampin is the rapid development of resistance if the fluoroquinolone is used as monotherapy, or if rifampin is not introduced simultaneously with a companion drug. Also, rifampin is a potent inducer of cytochrome P450 enzymes, leading to numerous drug-drug interactions that must be carefully managed. Renal toxicity is more associated with aminoglycosides and vancomycin. Anaphylaxis is not a primary concern for fluoroquinolones. Lack of efficacy is incorrect as they are often used in this setting.

Question 12620

Topic: Surgical Anatomy & Approaches

What is the recommended approach for managing a PJI caused by multiple organisms (polymicrobial infection) versus a monomicrobial infection?

. Polymicrobial infections are generally easier to treat due to broader antibiotic susceptibility.
. Polymicrobial infections typically require a more aggressive surgical approach (e.g., two-stage revision) and broader antibiotic coverage.
. Monomicrobial infections always require implant removal, whereas polymicrobial can be treated with DAIR.
. The choice of antibiotics is simpler for polymicrobial infections.
. Polymicrobial infections carry a better prognosis than monomicrobial.

Correct Answer & Explanation

. Polymicrobial infections typically require a more aggressive surgical approach (e.g., two-stage revision) and broader antibiotic coverage.

Explanation

Polymicrobial infections are generally more challenging to treat than monomicrobial infections and are associated with a poorer prognosis. They often require a more aggressive surgical approach (typically two-stage revision) and broader, carefully selected antibiotic coverage to target all identified organisms. Their complexity makes them harder to eradicate. DAIR is less likely to succeed. Monomicrobial infections by virulent organisms can also necessitate implant removal. The choice of antibiotics is more complex, not simpler.

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