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Infection, Pharmacology & VTE MCQs

Practice Set 26 of 68

This practice set contains high-yield board review questions covering key concepts in Infection, Pharmacology & VTE. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 501

Topic: Infection, Pharmacology & VTE

A medial approach is used to buttress a posteromedial tibial plateau fracture. The surgeon must dissect meticulously near the pes anserinus. From anterior/superior to posterior/inferior, what is the correct arrangement of the tendinous insertions of the pes anserinus?

. Semitendinosus, Gracilis, Sartorius
. Sartorius, Gracilis, Semitendinosus
. Gracilis, Sartorius, Semitendinosus
. Sartorius, Semitendinosus, Gracilis
. Semitendinosus, Sartorius, Gracilis

Correct Answer & Explanation

. Sartorius, Gracilis, Semitendinosus

Explanation

The pes anserinus inserts onto the anteromedial proximal tibia. The correct anatomical order from anterior to posterior (and superior to inferior) is Sartorius, Gracilis, and Semitendinosus (remembered by the mnemonic 'Say Grace before Tea').

Question 502

Topic: Infection, Pharmacology & VTE

The medial collateral ligament (MCL) of the knee has a superficial and deep component. The superficial MCL attaches distally to the medial aspect of the proximal tibia deep to which structure?

. Pes anserinus
. Semimembranosus tendon
. Medial patellofemoral ligament
. Popliteus tendon
. Iliotibial band

Correct Answer & Explanation

. Pes anserinus

Explanation

The superficial MCL inserts on the medial tibia approximately 4-5 cm distal to the joint line, situated deep to the pes anserinus tendons (sartorius, gracilis, and semitendinosus).

Question 503

Topic: Infection, Pharmacology & VTE
A 28-year-old skier sustains an isolated grade III medial collateral ligament (MCL) tear. An MRI is obtained to evaluate the injury. Which of the following MRI findings is associated with the highest rate of failure with nonoperative management?
. Avulsion from the medial femoral epicondyle
. Midsubstance tear at the joint line
. Avulsion from the tibial insertion with the distal end displaced superficial to the pes anserinus
. Associated medial meniscal tear
. Bone bruise on the lateral femoral condyle

Correct Answer & Explanation

. Avulsion from the tibial insertion with the distal end displaced superficial to the pes anserinus

Explanation

A Stener-like lesion of the MCL occurs when the tibial avulsion is displaced superficial to the pes anserinus, preventing healing. These lesions have a high failure rate with nonoperative management and generally require surgical repair.

Question 504

Topic: Infection, Pharmacology & VTE

A 28-year-old alpine skier sustains a severe valgus injury to the knee. MRI demonstrates a complete avulsion of the distal medial collateral ligament (MCL) that is flipped superficial to the pes anserinus tendons. Which of the following is the most appropriate management?

. Hinged knee brace locked in extension for 6 weeks
. Early functional rehabilitation with varus unloader bracing
. Acute surgical repair of the MCL
. Delayed MCL reconstruction utilizing hamstring autograft
. Corticosteroid injection into the pes anserinus bursa

Correct Answer & Explanation

. Acute surgical repair of the MCL

Explanation

A distal MCL avulsion that retracts and flips superficial to the pes anserinus tendons creates a Stener-like lesion. This soft tissue interposition prevents anatomic healing and is an established indication for acute surgical repair.

Question 505

Topic: Infection, Pharmacology & VTE

During a TKA for severe varus deformity, standard bone cuts have been made, and the deep medial collateral ligament (MCL) has been released. The knee remains tight medially in both flexion and extension. What is the next most appropriate step in the soft tissue release sequence?

. Release the pes anserinus
. Release the semimembranosus
. Epicondylar osteotomy
. Release the posterior cruciate ligament (PCL)
. Release the lateral collateral ligament (LCL)

Correct Answer & Explanation

. Release the semimembranosus

Explanation

In a tight medial compartment that persists after deep MCL release, the semimembranosus and posterior medial capsule should be released next. This helps balance a knee that is symmetrically tight in both flexion and extension.

Question 506

Topic: Infection, Pharmacology & VTE

A 70-year-old man presents with a chronic prosthetic joint infection 2 years after THA. Aspiration grows methicillin-resistant Staphylococcus aureus (MRSA). You plan a two-stage exchange. What antibiotic should be predominantly mixed into the temporary polymethylmethacrylate (PMMA) spacer?

. Cefazolin
. Vancomycin
. Gentamicin
. Rifampin
. Clindamycin

Correct Answer & Explanation

. Vancomycin

Explanation

Vancomycin provides targeted elution against MRSA. While an aminoglycoside like tobramycin or gentamicin is often added for synergistic broad-spectrum coverage and to improve elution properties, Vancomycin is the critical agent against the known organism.

Question 507

Topic: Infection, Pharmacology & VTE

A patient undergoing treatment for an implant-associated orthopedic infection develops sudden Achilles tendon pain. The antibiotic utilized is known to inhibit DNA gyrase. Which medication was most likely prescribed?

. Rifampin
. Vancomycin
. Ciprofloxacin
. Linezolid
. Gentamicin

Correct Answer & Explanation

. Ciprofloxacin

Explanation

Fluoroquinolones, such as ciprofloxacin, work by inhibiting bacterial DNA gyrase (topoisomerase II) and topoisomerase IV. They carry a black box warning for tendinopathy and tendon rupture, which most commonly affects the Achilles tendon.

Question 508

Topic: Infection, Pharmacology & VTE

A 65-year-old male is treated with a specific antibiotic adjunct due to a staphylococcal prosthetic joint infection, chosen for its unique ability to penetrate mature biofilm. What is the mechanism of action of this drug?

. Inhibits cell wall synthesis by binding to D-alanyl-D-alanine
. Inhibits DNA-dependent RNA polymerase
. Inhibits protein synthesis by binding to the 30S ribosomal subunit
. Inhibits protein synthesis by binding to the 50S ribosomal subunit
. Disrupts the bacterial cell membrane via lipopeptide insertion

Correct Answer & Explanation

. Inhibits DNA-dependent RNA polymerase

Explanation

Rifampin is highly effective against biofilm-producing organisms like Staphylococcus species in prosthetic joint infections. Its primary mechanism of action is the inhibition of bacterial DNA-dependent RNA polymerase, thereby halting RNA transcription.

Question 509

Topic: Infection, Pharmacology & VTE
Rivaroxaban is utilized for venous thromboembolism (VTE) prophylaxis following total joint arthroplasty. What is its exact mechanism of action?
. Direct thrombin (Factor IIa) inhibitor
. Vitamin K antagonist
. Direct Factor Xa inhibitor
. Activates antithrombin III
. Inhibits ADP receptors on platelets

Correct Answer & Explanation

. Direct Factor Xa inhibitor

Explanation

Rivaroxaban is an oral anticoagulant that directly inhibits Factor Xa. This interrupts both the intrinsic and extrinsic pathways of the blood coagulation cascade, preventing thrombin formation.

Question 510

Topic: Infection, Pharmacology & VTE

A patient develops a methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. Vancomycin is initiated. What is the specific mechanism of action of this antibiotic?

. Binds reversibly to the 50S ribosomal subunit
. Inhibits DNA gyrase leading to DNA strand breakage
. Binds to D-alanyl-D-alanine termini of peptidoglycan precursors
. Inhibits cross-linking by binding penicillin-binding proteins (PBPs)
. Disrupts the bacterial cell membrane via depolarization

Correct Answer & Explanation

. Binds to D-alanyl-D-alanine termini of peptidoglycan precursors

Explanation

Vancomycin is a glycopeptide antibiotic that inhibits bacterial cell wall synthesis by binding to the D-alanyl-D-alanine terminus of cell wall precursors. This prevents the cross-linking of peptidoglycan chains, unlike beta-lactams which bind directly to PBPs.

Question 511

Topic: Infection, Pharmacology & VTE
A patient is prescribed enoxaparin for deep vein thrombosis prophylaxis following total hip arthroplasty. Which of the following best describes its mechanism of action?
. Direct inhibition of factor Xa
. Direct inhibition of thrombin (Factor IIa)
. Vitamin K antagonism
. Potentiation of antithrombin III with a higher affinity for Factor Xa than thrombin
. Irreversible inhibition of cyclooxygenase in platelets

Correct Answer & Explanation

. Potentiation of antithrombin III with a higher affinity for Factor Xa than thrombin

Explanation

Low-molecular-weight heparins (LMWH) like enoxaparin bind to antithrombin III to enhance its activity. Due to their shorter chain length compared to unfractionated heparin, they preferentially inhibit Factor Xa over thrombin (Factor IIa).

Question 512

Topic: Infection, Pharmacology & VTE
Rivaroxaban is commonly prescribed for deep vein thrombosis prophylaxis following total joint arthroplasty. Which of the following best describes its mechanism of action?
. Direct thrombin inhibitor
. Vitamin K antagonist
. Direct Factor Xa inhibitor
. Antithrombin III activator
. Plasminogen activator

Correct Answer & Explanation

. Direct Factor Xa inhibitor

Explanation

Rivaroxaban is an oral anticoagulant that directly inhibits free and clot-bound Factor Xa. This interrupts the intrinsic and extrinsic pathway of the blood coagulation cascade, preventing thrombin generation.

Question 513

Topic: Infection, Pharmacology & VTE
Fondaparinux is an anticoagulant frequently prescribed for venous thromboembolism prophylaxis following major orthopedic surgery. What is the exact mechanism of action of this synthetic pentasaccharide?
. Direct, reversible inhibition of thrombin (Factor IIa)
. Irreversible antagonism of Vitamin K epoxide reductase
. Direct, competitive inhibition of Factor Xa
. Indirect inhibition of Factor Xa via binding to antithrombin III
. Irreversible inhibition of ADP-induced platelet aggregation

Correct Answer & Explanation

. Indirect inhibition of Factor Xa via binding to antithrombin III

Explanation

Fondaparinux binds exclusively to antithrombin III, inducing a conformational change that dramatically accelerates its natural inhibition of Factor Xa. Unlike apixaban or rivaroxaban, which are direct inhibitors, fondaparinux requires antithrombin III to exert its anticoagulant effect.

Question 514

Topic: Infection, Pharmacology & VTE
A patient is prescribed rivaroxaban for DVT prophylaxis following a total knee arthroplasty. What is the mechanism of action of this pharmacological agent?
. Directly inhibits thrombin (Factor IIa)
. Directly inhibits Factor Xa
. Binds to antithrombin III to inhibit Factor Xa
. Inhibits vitamin K epoxide reductase
. Inhibits ADP binding to the P2Y12 receptor

Correct Answer & Explanation

. Directly inhibits Factor Xa

Explanation

Rivaroxaban and apixaban are direct oral anticoagulants that work by specifically and reversibly binding to and inhibiting free and clot-bound Factor Xa. Unlike heparin, they do not require antithrombin III to exert their effect.

Question 515

Topic: Infection, Pharmacology & VTE

During a massive rotator cuff repair, a patient receives an interscalene block and subsequently develops seizures followed by cardiac arrest. The anesthesiologist diagnoses severe bupivacaine toxicity. What is the most appropriate specific treatment to reverse the cardiotoxicity?

. Intravenous epinephrine push
. Intravenous 20% lipid emulsion
. High-dose intravenous naloxone
. Intravenous calcium gluconate
. Intravenous flumazenil

Correct Answer & Explanation

. Intravenous 20% lipid emulsion

Explanation

Bupivacaine is highly lipophilic and can cause catastrophic, refractory cardiac arrhythmias if injected intravascularly. Intravenous 20% lipid emulsion therapy is the standard of care to create a "lipid sink" that rapidly extracts the local anesthetic from the myocardial tissues.

Question 516

Topic: Infection, Pharmacology & VTE

Nonsteroidal anti-inflammatory drugs (NSAIDs) are often withheld following fractures or spinal fusions due to concerns of impaired bone healing. NSAIDs interfere with bone healing primarily by inhibiting which of the following?

. Interleukin-1 (IL-1) synthesis
. Vascular endothelial growth factor (VEGF) production
. Cyclooxygenase (COX) enzymes, leading to decreased prostaglandin E2 (PGE2)
. Transforming growth factor-beta (TGF-beta) activation
. Tumor necrosis factor-alpha (TNF-alpha)

Correct Answer & Explanation

. Interleukin-1 (IL-1) synthesis

Explanation

NSAIDs inhibit COX enzymes, thereby blocking the synthesis of prostaglandins (especially PGE2). Prostaglandins are essential in the early inflammatory phase of fracture healing for mediating angiogenesis and recruiting osteogenic cells.

Question 517

Topic: Infection, Pharmacology & VTE

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to potentially impair fracture healing. This adverse effect is primarily mediated by the inhibition of which enzyme?

. Lipoxygenase (LOX)
. Phospholipase A2
. Cyclooxygenase-2 (COX-2)
. Thromboxane synthase
. Nitric oxide synthase

Correct Answer & Explanation

. Lipoxygenase (LOX)

Explanation

NSAIDs inhibit COX-1 and COX-2 enzymes. The inhibition of COX-2 specifically reduces the production of prostaglandins (like PGE2) that are critical for the early inflammatory phase and subsequent osteoblast differentiation.

Question 518

Topic: Infection, Pharmacology & VTE

The pes anserinus is frequently utilized as a harvest site for autograft in anterior cruciate ligament reconstruction. From anterior to posterior, what is the anatomical arrangement of these tendinous insertions on the proximal medial tibia?

. Gracilis, Sartorius, Semitendinosus
. Sartorius, Gracilis, Semitendinosus
. Semitendinosus, Gracilis, Sartorius
. Sartorius, Semitendinosus, Gracilis
. Gracilis, Semitendinosus, Sartorius

Correct Answer & Explanation

. Gracilis, Sartorius, Semitendinosus

Explanation

The correct anterior-to-posterior order of the pes anserinus tendons is Sartorius, Gracilis, and Semitendinosus (mnemonic: "Say Grace before Tea").

Question 519

Topic: Infection, Pharmacology & VTE

A patient sustains a traumatic knee dislocation and undergoes immediate reduction. Vascular evaluation is required due to the high risk of popliteal artery injury. Between which two distinct anatomical structures is the popliteal artery firmly tethered, making it susceptible to shear stress?

. Inguinal ligament and pes anserinus
. Adductor hiatus and the tendinous arch of the soleus
. Sciatic notch and the popliteus tendon
. Femoral triangle and the interosseous membrane
. Linea aspera and the fibular head

Correct Answer & Explanation

. Inguinal ligament and pes anserinus

Explanation

The popliteal artery is rigidly tethered proximally at the adductor hiatus (Hunter's canal) and distally at the tendinous arch of the soleus. This anatomic tethering predisposes it to traction injury during knee dislocations.

Question 520

Topic: Infection, Pharmacology & VTE

A 40-year-old male suffers a valgus knee injury. An MRI is obtained, revealing a distal avulsion of the superficial medial collateral ligament (MCL). The torn distal end is flipped superficial to the pes anserinus tendons (a Stener-like lesion). What is the recommended management?

. Hinged knee brace and early range of motion
. Cast immobilization for 6 weeks
. Corticosteroid injection and physical therapy
. Surgical repair of the MCL
. Isolated physical therapy with no bracing

Correct Answer & Explanation

. Hinged knee brace and early range of motion

Explanation

Unlike proximal and mid-substance MCL tears which generally heal well non-operatively, a distal tibial avulsion of the MCL that is displaced superficial to the pes anserinus cannot spontaneously reattach to its footprint. This Stener-like lesion requires surgical repair.

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