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Infection, Pharmacology & VTE MCQs

Practice Set 28 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 541

Topic: Infection, Pharmacology & VTE

A 65-year-old diabetic patient presents with a deep, non-healing plantar midfoot ulcer. Radiographs show a bony prominence causing the ulcer, but MRI is equivocal for osteomyelitis. What is the gold standard for diagnosing osteomyelitis in this setting?

. Tagged white blood cell scan
. C-reactive protein
. Bone biopsy for histopathology and culture
. Three-phase bone scan
. Superficial swab culture of the ulcer

Correct Answer & Explanation

. Tagged white blood cell scan

Explanation

While imaging and clinical signs are helpful, a bone biopsy is the gold standard for definitively diagnosing osteomyelitis. It also provides reliable deep culture data to direct targeted antibiotic therapy in the diabetic foot.

Question 542

Topic: Infection, Pharmacology & VTE

A 60-year-old poorly controlled diabetic patient has a chronic plantar foot ulcer beneath the first metatarsal head. Which of the following clinical findings has the highest positive predictive value for underlying osteomyelitis?

. Erythema extending > 2 cm from the ulcer margin
. Visible tendon in the base of the ulcer
. A positive probe-to-bone test
. Erythrocyte sedimentation rate > 30 mm/hr
. Presence of purulent drainage

Correct Answer & Explanation

. Erythema extending > 2 cm from the ulcer margin

Explanation

A positive probe-to-bone test (palpating hard, gritty bone with a sterile metal probe) is highly predictive of underlying osteomyelitis in the setting of an infected diabetic foot ulcer. It significantly increases the probability of bone infection.

Question 543

Topic: Infection, Pharmacology & VTE

According to the Wagner classification system for diabetic foot ulcers, a lesion described as a deep ulcer with localized gangrene isolated to the great toe and forefoot is classified as:

. Grade 1
. Grade 2
. Grade 3
. Grade 4
. Grade 5

Correct Answer & Explanation

. Grade 1

Explanation

Wagner Grade 4 indicates localized gangrene (e.g., involving the forefoot, heel, or toes). Grade 3 involves a deep ulcer with osteomyelitis or abscess, while Grade 5 describes extensive gangrene of the entire foot.

Question 544

Topic: Infection, Pharmacology & VTE

Differentiating acute Charcot neuroarthropathy from osteomyelitis in the diabetic foot is challenging. On magnetic resonance imaging (MRI), which of the following findings is most specific for osteomyelitis rather than acute Charcot arthropathy?

. Subchondral bone marrow edema
. Diffuse subcutaneous soft tissue edema
. Presence of a significant joint effusion
. Extensive periarticular debris and fragmentation
. Presence of the "ghost sign" on T1-weighted images

Correct Answer & Explanation

. Subchondral bone marrow edema

Explanation

The "ghost sign" (where bone margins become invisible or indistinct on T1-weighted images but 'reappear' on T2/STIR images) is highly indicative of osteomyelitis. Charcot arthropathy typically demonstrates bone marrow edema strictly localized to the subchondral bone adjacent to affected joints.

Question 545

Topic: Infection, Pharmacology & VTE

A 60-year-old diabetic male has a chronic plantar ulcer under the first metatarsal head. On examination, a sterile metal probe easily advances through the ulcer base and palpably taps against a hard, gritty surface. What is the approximate positive predictive value of this clinical finding for underlying osteomyelitis?

. 10%
. 30%
. 60%
. 89%
. 100%

Correct Answer & Explanation

. 10%

Explanation

The "probe-to-bone" test has a high positive predictive value (approximately 89%) for diagnosing osteomyelitis in the presence of a clinically infected diabetic foot ulcer. It is a rapid, validated, and highly useful initial clinical evaluation tool.

Question 546

Topic: Infection, Pharmacology & VTE

A 50-year-old diabetic male has a chronic plantar midfoot ulcer overlying a rocker-bottom deformity. An MRI is ordered to differentiate chronic inactive Charcot osteoarthropathy from osteomyelitis. Which MRI finding is most specific for osteomyelitis rather than Charcot changes alone?

. Subchondral bone marrow edema
. Joint effusion in the tarsometatarsal joints
. Presence of a sinus tract extending to the bone
. Ligamentous disruption
. Thickening of the plantar fascia

Correct Answer & Explanation

. Subchondral bone marrow edema

Explanation

Both osteomyelitis and Charcot arthropathy exhibit bone marrow edema on MRI. However, the presence of a sinus tract, adjacent soft tissue ulceration, or the 'ghost sign' (indistinct bone margins on T1) are highly specific for osteomyelitis.

Question 547

Topic: Infection, Pharmacology & VTE

Which of the following magnetic resonance imaging (MRI) findings is the most sensitive and specific for distinguishing osteomyelitis from acute Charcot neuroarthropathy in the diabetic foot?

. Diffuse subchondral bone marrow edema on STIR sequences
. Joint subluxation, debris, and fragmentation
. Intramuscular edema in the intrinsic foot muscles
. Replacement of subchondral fat signal with low T1 signal in a focal geographic pattern extending from an ulcer
. High signal intensity in the deep subcutaneous tissues

Correct Answer & Explanation

. Diffuse subchondral bone marrow edema on STIR sequences

Explanation

Replacement of the normal marrow fat signal (low T1) that extends contiguously from a skin ulcer is highly indicative of osteomyelitis. Acute Charcot typically exhibits periarticular subchondral marrow edema but preserves the geographic marrow fat signal away from the joint.

Question 548

Topic: Infection, Pharmacology & VTE

A 58-year-old diabetic male presents with a deep plantar ulcer extending to the joint capsule, but with no bone involvement, no abscess, and no gangrene. According to the Wagner classification, what grade is this ulcer?

. Grade 0
. Grade 1
. Grade 2
. Grade 3
. Grade 4

Correct Answer & Explanation

. Grade 0

Explanation

Wagner Grade 2 ulcers are deep ulcers penetrating to the tendon, bone, or joint capsule but without deep infection or osteomyelitis. Grade 1 is superficial, and Grade 3 involves deep infection such as osteomyelitis or abscess.

Question 549

Topic: Infection, Pharmacology & VTE

A 62-year-old diabetic patient with a chronic midfoot ulcer presents with erythema and swelling. Radiographs show bone destruction. Which of the following is the most reliable imaging modality to differentiate acute Charcot neuroarthropathy from osteomyelitis?

. Three-phase bone scan
. Indium-111 labeled WBC scan combined with Technetium-99m marrow scan
. Computed tomography (CT)
. Plain radiographs
. Ultrasound

Correct Answer & Explanation

. Three-phase bone scan

Explanation

Differentiating Charcot arthropathy from osteomyelitis is clinically challenging. A combined Indium-111 WBC scan and Tc-99m marrow scan is highly specific and sensitive for diagnosing osteomyelitis in the setting of Charcot foot.

Question 550

Topic: Infection, Pharmacology & VTE

A diabetic patient presents with a midfoot ulcer and deep soft tissue swelling. Which of the following MRI findings is most indicative of osteomyelitis rather than acute Charcot neuroarthropathy?

. Diffuse bone marrow edema involving multiple contiguous midfoot bones
. Focal, confluent marrow replacement (low T1 signal) directly contiguous with the skin ulcer
. Extensive subchondral cyst formation around the ankle joint
. Diffuse soft tissue edema that resolves with elevation
. Thickening of the plantar fascia without cortical destruction

Correct Answer & Explanation

. Diffuse bone marrow edema involving multiple contiguous midfoot bones

Explanation

Osteomyelitis typically presents on MRI as focal marrow abnormality (low T1, high T2) that is spatially contiguous with a skin ulcer or sinus tract. Acute Charcot typically exhibits periarticular marrow edema across multiple bones (the "ghost sign") without direct continuity to an ulcer.

Question 551

Topic: Infection, Pharmacology & VTE

Rivaroxaban, an oral anticoagulant commonly prescribed for DVT prophylaxis following total joint arthroplasty, exerts its therapeutic effect by directly inhibiting:

. Factor IIa (Thrombin)
. Factor Xa
. Antithrombin III
. Vitamin K epoxide reductase
. Cyclooxygenase-1

Correct Answer & Explanation

. Factor IIa (Thrombin)

Explanation

Rivaroxaban and apixaban are direct oral anticoagulants that reversibly inhibit Factor Xa. This interrupts both the intrinsic and extrinsic pathways of the coagulation cascade.

Question 552

Topic: Infection, Pharmacology & VTE

The superficial medial collateral ligament (sMCL) is a key static stabilizer of the knee. Proximal to its primary attachment on the medial epicondyle, where does its distal tibial attachment firmly insert?

. Anterior to the pes anserinus, approximately 2-3 cm distal to the joint line
. Deep to the pes anserinus tendons, approximately 4-5 cm distal to the joint line
. Posterior to the direct arm of the semimembranosus
. Directly on the Gerdy tubercle
. Superficial to the pes anserinus, 8-10 cm distal to the joint line

Correct Answer & Explanation

. Anterior to the pes anserinus, approximately 2-3 cm distal to the joint line

Explanation

The primary distal attachment of the superficial MCL is located deep to the pes anserinus tendons, roughly 4-5 cm distal to the medial joint line. This broad footprint provides significant valgus stability.

Question 553

Topic: Infection, Pharmacology & VTE

A patient sustains a high-energy knee dislocation (KD-III). Vascular surgery is consulted due to an absent dorsalis pedis pulse. The popliteal artery is exceptionally prone to traction injury in this scenario because it is tethered at which two anatomical landmarks?

. Proximally at the adductor hiatus and distally at the soleal arch
. Proximally at the femoral triangle and distally at the medial malleolus
. Proximally at the popliteal fossa midpoint and distally at the fibular neck
. Proximally at the superior genicular branches and distally at the pes anserinus
. Proximally at the adductor longus and distally at the superficial posterior compartment

Correct Answer & Explanation

. Proximally at the adductor hiatus and distally at the soleal arch

Explanation

The popliteal artery is rigidly fixed proximally as it exits the adductor hiatus (Hunter's canal) and distally as it passes under the tendinous arch of the soleus. This lack of mobility makes it highly susceptible to stretch and intimal tearing during gross knee dislocations.

Question 554

Topic: Infection, Pharmacology & VTE

An 82-year-old female with a history of atrial fibrillation presents with a displaced left femoral neck fracture. She takes apixaban 5 mg twice daily, with her last dose 12 hours ago. Renal function is normal. What is the recommended timing for surgical intervention?

. Proceed immediately to surgery
. Wait 24-48 hours from the last dose of apixaban before surgery
. Administer Vitamin K and FFP, then proceed to surgery
. Delay surgery for 7 days to ensure complete washout
. Perform surgery under general anesthesia only, ignoring the apixaban

Correct Answer & Explanation

. Proceed immediately to surgery

Explanation

For patients on direct oral anticoagulants like apixaban with normal renal function, a delay of 24 to 48 hours is recommended to allow clearance and reduce bleeding risks. Reversal agents are typically reserved for life-threatening hemorrhage.

Question 555

Topic: Infection, Pharmacology & VTE

A 45-year-old male sustains a high-energy closed pilon fracture. A spanning external fixator is placed on the day of injury. When planning definitive open reduction and internal fixation (ORIF), which of the following is the most reliable clinical indicator that the soft tissue envelope is ready for surgery?

. Normalization of erythrocyte sedimentation rate (ESR)
. Appearance of epithelialized fracture blisters
. Presence of a positive wrinkle test
. Exactly 14 days post-injury
. Resolution of deep venous thrombosis (DVT)

Correct Answer & Explanation

. Normalization of erythrocyte sedimentation rate (ESR)

Explanation

The wrinkle test indicates that tissue edema has subsided enough to allow safe surgical incision and wound closure. Operating before this sign appears significantly increases the risk of wound dehiscence and deep infection.

Question 556

Topic: Infection, Pharmacology & VTE

A 72-year-old male presents with acute pain and swelling in his dominant hand. He has a history of a cat bite to the dorsum of his hand 24 hours prior. Examination reveals erythema, warmth, and exquisite tenderness, particularly over the MCP joint of the index finger. He has limited range of motion due to pain. Which of the following is the MOST appropriate initial management?

. Oral antibiotics and observation
. Application of warm compresses and elevation
. Emergency irrigation and debridement of the wound and joint, followed by intravenous antibiotics
. Corticosteroid injection into the MCP joint
. Close monitoring with serial radiographs

Correct Answer & Explanation

. Oral antibiotics and observation

Explanation

A cat bite to the hand carries a high risk of severe infection, particularly due to Pasteurella multocida and potential for joint penetration, leading to septic arthritis or osteomyelitis. The patient's acute presentation with erythema, warmth, exquisite tenderness over the MCP joint, and limited range of motion are highly indicative of septic arthritis or cellulitis progressing to deeper infection. Given the mechanism and signs of severe infection, emergency surgical irrigation and debridement of the wound and joint (if joint penetration is confirmed or suspected), followed by broad-spectrum intravenous antibiotics, is the MOST appropriate immediate management. Oral antibiotics alone are insufficient for deep hand infections. Warm compresses and elevation are supportive but not definitive. Corticosteroid injections are contraindicated in infection. Close monitoring is inadequate for a rapidly progressing infection.

Question 557

Topic: Infection, Pharmacology & VTE

A patient with severe osteoarthritis of the knee is prescribed an NSAID. What is the primary mechanism of action of NSAIDs?

. Inhibition of leukotriene synthesis.
. Selective blockade of TNF-alpha.
. Inhibition of cyclooxygenase enzymes (COX-1 and COX-2).
. Stimulation of opioid receptors.
. Enhancement of cartilage repair.

Correct Answer & Explanation

. Inhibition of leukotriene synthesis.

Explanation

Non-steroidal anti-inflammatory drugs (NSAIDs) primarily exert their analgesic and anti-inflammatory effects by inhibiting cyclooxygenase (COX) enzymes (COX-1 and COX-2). This inhibition reduces the synthesis of prostaglandins, which are key mediators of pain and inflammation. They do not selectively block TNF-alpha (biologics do), stimulate opioid receptors, or directly enhance cartilage repair. Some NSAIDs also inhibit leukotriene synthesis, but COX inhibition is the main mechanism.

Question 558

Topic: Infection, Pharmacology & VTE

Which antibiotic class is commonly used for prophylactic coverage in orthopedic surgery, particularly against Gram-positive bacteria like Staphylococcus aureus?

. Fluoroquinolones (e.g., Ciprofloxacin)
. Aminoglycosides (e.g., Gentamicin)
. First or second-generation Cephalosporins (e.g., Cefazolin)
. Macrolides (e.g., Azithromycin)
. Tetracyclines (e.g., Doxycycline)

Correct Answer & Explanation

. Fluoroquinolones (e.g., Ciprofloxacin)

Explanation

First or second-generation cephalosporins, such as Cefazolin, are the antibiotics of choice for surgical prophylaxis in most orthopedic procedures. They provide excellent coverage against common surgical site infection pathogens, particularly Gram-positive bacteria like Staphylococcus aureus, while having a relatively narrow spectrum compared to broader agents. Fluoroquinolones and aminoglycosides have broader spectrums and are typically reserved for established infections or specific indications. Macrolides and tetracyclines are generally not first-line for surgical prophylaxis.

Question 559

Topic: Infection, Pharmacology & VTE

A patient is undergoing revision hip arthroplasty due to a suspected infection. Which laboratory marker is most sensitive for detecting chronic osteomyelitis?

. White Blood Cell (WBC) count
. Erythrocyte Sedimentation Rate (ESR)
. C-Reactive Protein (CRP)
. Procalcitonin
. Serum Creatinine

Correct Answer & Explanation

. White Blood Cell (WBC) count

Explanation

While both ESR and CRP are elevated in infection, ESR tends to remain elevated for a longer duration in chronic infections like osteomyelitis compared to CRP, which normalizes more rapidly. CRP is generally more sensitive for acute infections. WBC count is often normal in chronic osteomyelitis. Procalcitonin is typically used for severe systemic bacterial infections (sepsis). Serum creatinine assesses renal function.

Question 560

Topic: Infection, Pharmacology & VTE

What is the most common organism responsible for acute hematogenous osteomyelitis in healthy children?

. Escherichia coli
. Pseudomonas aeruginosa
. Staphylococcus aureus
. Streptococcus pyogenes
. Kingella kingae

Correct Answer & Explanation

. Escherichia coli

Explanation

Staphylococcus aureus is by far the most common causative organism for acute hematogenous osteomyelitis across all age groups, including healthy children. While Kingella kingae is increasingly recognized in young children, S. aureus remains the dominant pathogen. E. coli and Pseudomonas are more common in neonates or immunocompromised patients. Streptococcus pyogenes is less common in bone infections.

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