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Infection, Pharmacology & VTE MCQs

Practice Set 15 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 281

Topic: Infection, Pharmacology & VTE

In the management of a patient with a profoundly complex, multi-apical femoral deformity and a complex tibial deformity, the surgical team decides to stage the procedures, addressing the femur first and the tibia in a secondary operation several weeks later. Which of the following is the *most critical* advantage of this staged approach, particularly in a patient with compromised osteoporotic bone stock?

. It allows for immediate weight-bearing on the corrected femur, accelerating rehabilitation.
. It provides the surgeon an opportunity to dynamically adjust the subsequent tibial plan based on the femoral correction's outcome.
. It significantly reduces the overall cost of the surgical intervention by minimizing implant usage in a single setting.
. It completely eliminates the risk of systemic complications such as DVT and PE.
. It ensures that the patient's cosmetic outcome is prioritized over functional restoration.

Correct Answer & Explanation

. It provides the surgeon an opportunity to dynamically adjust the subsequent tibial plan based on the femoral correction's outcome.

Explanation

Correct Answer: BThe case highlights several critical advantages of staging procedures. While physiological tolerance and complication mitigation are important, the text specifically mentions: 'Intraoperative Adjustment: Provides the surgeon an opportunity to assess the clinical and radiographic outcome of the initial correction. If the femoral correction slightly alters the global limb length or mechanical axis unexpectedly, the subsequent tibial plan can be dynamically adjusted to compensate.' This ability to fine-tune the overall limb alignment based on the first stage's outcome is a paramount advantage in complex, multi-level corrections.Option A is incorrect; while early mobilization is a goal, immediate full weight-bearing after multi-level osteotomies in osteoporotic bone is unlikely and not the primary reason for staging. Option C is incorrect; staging procedures often increases overall costs due to multiple hospitalizations and anesthetic events. Option D is incorrect; staging reduces theriskof complications but does noteliminatethem. Option E is incorrect; functional restoration and biomechanical alignment are the primary goals, with cosmesis being a secondary benefit.

Question 282

Topic: Infection, Pharmacology & VTE

A 12-year-old patient with sequelae of neonatal septic arthritis of the hip presents with the radiographic findings shown below. The surgeon is planning a double-level pelvic support osteotomy. Based on the provided image and case description, which of the following is the most accurate description of the biomechanical consequence illustrated on the right side of the diagram?

. A. The mechanical axis passes centrally through the knee, leading to balanced compartment loading.
. B. The superior migration of the hip center causes the mechanical axis to shift laterally, inducing a valgus moment at the knee.
. C. The lateral shift of the hip's center of rotation causes the mechanical axis to deviate medially, inducing a varus moment at the knee.
. D. The anatomical axis of the femur is perfectly aligned with the mechanical axis, indicating no deformity.
. E. The joint line congruency angle (JLCA) is significantly increased, indicating severe patellofemoral instability.

Correct Answer & Explanation

. C. The lateral shift of the hip's center of rotation causes the mechanical axis to deviate medially, inducing a varus moment at the knee.

Explanation

Correct Answer: CThe case explicitly states and the image illustrates that in the sequelae of septic arthritis, the 'functional hip joint' is the unstable, superiorly and laterally migrated point of contact between the proximal femur and the ilium. This lateral shift of the hip's center of rotation causes the mechanical axis to deviate profoundly. The load-bearing line now falls far medial to the center of the knee, a condition known as Mechanical Axis Deviation (MAD), which induces a massive varus moment at the knee. This chronic varus force leads to lateral knee instability and medial compartment overload.Option A is incorrectas this describes a normal limb, not the pathological state shown on the right.Option B is incorrectbecause the mechanical axis shifts medially, not laterally, and induces a varus moment, not a valgus moment, at the knee.Option D is incorrectas the image clearly shows a significant deviation of the mechanical axis, indicating a severe deformity.Option E is incorrectbecause while knee pathology will develop, the primary biomechanical consequence illustrated by the mechanical axis deviation is the varus moment and subsequent medial compartment overload and lateral instability, not specifically an increased JLCA or patellofemoral instability as the direct consequence of the MAD shown.

Question 283

Topic: Infection, Pharmacology & VTE

A 20-year-old patient is undergoing preoperative planning for an Ilizarov double-level pelvic support osteotomy for sequelae of septic arthritis. The surgeon has identified the desired point of contact between the proximal femur and the lateral wall of the pelvis (ischium) as the new functional hip center. According to Paley's principles, what is the significance of this point in planning the proximal osteotomy?

. A. It defines the Mechanical Proximal Tibial Angle (MPTA) for the distal osteotomy.
. B. It serves as the Center of Rotation of Angulation (CORA) for the proximal osteotomy.
. C. It dictates the Joint Line Congruency Angle (JLCA) for the knee joint.
. D. It is the primary reference for calculating the leg length discrepancy (LLD) at skeletal maturity.
. E. It determines the optimal site for the distal varus-lengthening osteotomy.

Correct Answer & Explanation

. B. It serves as the Center of Rotation of Angulation (CORA) for the proximal osteotomy.

Explanation

Correct Answer: BThe case states, 'The Center of Rotation of Angulation (CORA) is the geometric heart of any deformity correction... However, in the case of an absent femoral head, there is no proximal anatomical landmark to define the proximal axis. The surgeon must therefore define a new, functional hip center. This is achieved by determining the desired point of contact between the proximal femur and the lateral wall of the pelvis—specifically, the ischium. The CORA for the pelvic support osteotomy is then planned at this exact level.'Option A is incorrectbecause MPTA relates to the proximal tibia, not the hip CORA.Option C is incorrectbecause JLCA relates to the knee joint line congruency, not the hip CORA.Option D is incorrectbecause while LLD is a component, the CORA is specifically for angular correction planning, not LLD prediction.Option E is incorrectbecause the CORA for the proximal osteotomy is distinct from the planning of the distal osteotomy site, although they are related in the overall correction strategy.

Question 284

Topic: Infection, Pharmacology & VTE

A patient with a long-standing hip flexion contracture due to septic arthritis sequelae is undergoing preoperative planning for a double-level Ilizarov reconstruction. The surgeon notes significant compensatory lumbar lordosis. Which component of the proximal osteotomy is specifically designed to address this sagittal plane deformity and its associated symptoms?

. A. The valgus component, to provide pelvic support.
. B. The varus component, to correct mechanical axis deviation.
. C. The extension component, to correct the hip flexion contracture.
. D. The distraction component, to lengthen the limb.
. E. The rotational component, to address femoral anteversion.

Correct Answer & Explanation

. C. The extension component, to correct the hip flexion contracture.

Explanation

Correct Answer: CThe case explicitly addresses sagittal plane analysis: 'Patients almost always present with a significant hip flexion contracture... Therefore, the proximal osteotomy must be a multiplanar valgus-extension osteotomy. The extension component is calculated from a careful clinical examination (Thomas test) and sagittal radiographs. Correcting the flexion contracture allows the patient to stand fully upright, eliminating the severe compensatory lumbar lordosis that causes chronic back pain in these patients.'Option A is incorrectbecause the valgus component primarily addresses pelvic instability and abductor tensioning in the coronal plane.Option B is incorrectbecause a varus component is part of thedistalosteotomy, not the proximal, and its role is to correct lateral MAD, not hip flexion contracture.Option D is incorrectbecause distraction is part of thedistalosteotomy for limb lengthening, not the proximal osteotomy's acute correction of flexion contracture.Option E is incorrectbecause while rotational deformities can exist, the extension component specifically addresses the flexion contracture and lumbar lordosis.

Question 285

Topic: Infection, Pharmacology & VTE

A 14-year-old patient, as seen in the clinical image, presents with the sequelae of neonatal septic arthritis of the hip. The surgeon is performing the proximal valgus-extension osteotomy as part of a double-level Ilizarov reconstruction. Which of the following statements accurately describes a critical aspect of the operative workflow for this specific osteotomy?

. A. The osteotomy is performed distally at the level of the knee joint to allow for acute correction of the valgus deformity.
. B. The osteotomy is performed percutaneously using a high-energy oscillating saw to ensure rapid bone division.
. C. The osteotomy site must be precisely at the level of the ischial tuberosity when the leg is pulled down to its maximal length under traction.
. D. The correction of the valgus and extension components is performed gradually over several weeks using distraction osteogenesis.
. E. The primary goal of this osteotomy is to correct the leg length discrepancy via acute shortening.

Correct Answer & Explanation

. C. The osteotomy site must be precisely at the level of the ischial tuberosity when the leg is pulled down to its maximal length under traction.

Explanation

Correct Answer: CThe case states, 'The proximal osteotomy is performed first and is typically corrected acutely on the operating table. Level of Osteotomy: The osteotomy site is paramount. It must be performed precisely at the level of the ischial tuberosity when the leg is pulled down to its maximal length under traction. This ensures the apex of the angulation will sit perfectly against its intended bony buttress.'Option A is incorrectbecause the proximal osteotomy is performed proximally, at the level of the ischial tuberosity, not distally at the knee.Option B is incorrectbecause the case specifies a 'percutaneous, low-energy osteotomy is performed using a multiple drill-hole and osteotome technique. This preserves the periosteum and the vital endosteal blood supply necessary for rapid bone healing,' directly contradicting the use of a high-energy oscillating saw.Option D is incorrectbecause the proximal osteotomy is typically correctedacutelyon the operating table, not gradually over weeks. Gradual correction is for the distal lengthening osteotomy.Option E is incorrectbecause the primary goal of the proximal osteotomy is pelvic support and correction of hip instability/flexion contracture, not LLD correction via acute shortening (which is generally avoided in lengthening procedures).

Question 286

Topic: Infection, Pharmacology & VTE

Why do neonates and infants younger than 18 months have a significantly higher risk of concurrent metaphyseal osteomyelitis and septic arthritis of the hip compared to older children?

. They have an immature blood-brain barrier
. They possess transphyseal blood vessels connecting the metaphysis to the epiphysis
. Their acetabular cartilage is highly vascularized
. They have a higher prevalence of Kingella kingae infections
. Their innate immune system lacks functioning macrophages

Correct Answer & Explanation

. They possess transphyseal blood vessels connecting the metaphysis to the epiphysis

Explanation

In infants under 18 months, transphyseal vessels cross the cartilaginous physis, allowing infection to easily spread from the metaphysis directly into the epiphysis and the joint space.

Question 287

Topic: Infection, Pharmacology & VTE

A 6-year-old boy in an endemic region presents with a massive knee effusion and a refusal to bear weight. He has a low-grade fever, ESR of 30, and CRP of 1.8 mg/dL. Synovial fluid aspiration reveals a WBC count of 55,000 cells/mm3 with 85% neutrophils. Which diagnosis must be strongly considered and differentiated from bacterial septic arthritis?

. Transient synovitis
. Lyme arthritis
. Juvenile Idiopathic Arthritis
. Pigmented Villonodular Synovitis
. Hemophilic arthropathy

Correct Answer & Explanation

. Lyme arthritis

Explanation

Lyme arthritis often mimics septic arthritis with high synovial fluid WBC counts (often 50,000-60,000), but patients typically exhibit less severe systemic toxicity. Lyme serology is crucial in endemic areas.

Question 288

Topic: Infection, Pharmacology & VTE
A 4-year-old boy presents with right hip pain, a limp, and refusal to bear weight. Temperature is 38.8°C. Blood tests show an ESR of 55 mm/hr and WBC of 14,000/mm³. According to the Kocher criteria, what is the approximate probability that this child has septic arthritis rather than transient synovitis?
. 40%
. 71%
. 83%
. 93%
. 99%

Correct Answer & Explanation

. 99%

Explanation

The Kocher criteria include non-weight-bearing, temperature >38.5°C, ESR >40 mm/hr, and WBC >12,000/mm³. Having all four predictors yields a 99% probability of septic arthritis.

Question 289

Topic: Infection, Pharmacology & VTE
A 2-year-old girl is diagnosed with a septic hip. Gram stain is negative, but PCR and BACTEC blood culture systems eventually isolate a fastidious Gram-negative coccobacillus. Which of the following organisms is most likely responsible?
. Staphylococcus aureus
. Streptococcus pneumoniae
. Kingella kingae
. Haemophilus influenzae type B
. Neisseria gonorrhoeae

Correct Answer & Explanation

. Kingella kingae

Explanation

Kingella kingae is a fastidious Gram-negative organism increasingly recognized as a leading cause of pediatric septic arthritis in toddlers (6 months to 4 years). It is best isolated using PCR or inoculation into aerobic BACTEC blood culture vials.

Question 290

Topic: Infection, Pharmacology & VTE

A 3-year-old child presents with suspected septic arthritis of the hip. The child holds the hip in a characteristic "resting position." This position minimizes intracapsular pressure to reduce the risk of avascular necrosis. What is this classic position?

. Extension, adduction, and internal rotation
. Flexion, abduction, and external rotation
. Flexion, adduction, and internal rotation
. Extension, abduction, and external rotation
. Neutral flexion, neutral abduction, and internal rotation

Correct Answer & Explanation

. Flexion, abduction, and external rotation

Explanation

The hip capsule has its maximum volume in flexion, abduction, and external rotation. Children with joint effusions from septic arthritis reflexively hold the hip in this position to minimize pressure and pain.

Question 291

Topic: Infection, Pharmacology & VTE

In the evaluation of a limping child with hip pain, a C-reactive protein (CRP) value greater than what threshold is considered the strongest independent laboratory predictor of septic arthritis versus transient synovitis?

. 0.5 mg/dL
. 1.0 mg/dL
. 2.0 mg/dL
. 5.0 mg/dL
. 10.0 mg/dL

Correct Answer & Explanation

. 2.0 mg/dL

Explanation

Studies (e.g., Caird et al.) demonstrated that a CRP > 2.0 mg/dL is a strong independent predictor of septic arthritis. It is often considered more reliable than ESR in the acute setting due to its rapid rise and fall.

Question 292

Topic: Infection, Pharmacology & VTE

A 2-week-old neonate born at 32 weeks gestation is evaluated for decreased movement of the right leg. The infant is afebrile but demonstrates pain with diaper changes. Ultrasound shows a right hip effusion. What is the most common causative organism for septic arthritis in this specific age group?

. Kingella kingae
. Streptococcus pyogenes
. Staphylococcus aureus
. Pseudomonas aeruginosa
. Salmonella typhi

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Even in neonates, Staphylococcus aureus is the most common cause of septic arthritis. Group B Streptococcus and Gram-negative enteric bacilli are also prevalent but less common than S. aureus. Neonates often lack fever, presenting instead with pseudoparalysis.

Question 293

Topic: Infection, Pharmacology & VTE
A 4-year-old boy presents with right hip pain and refusal to bear weight. His temperature is 38.8°C (101.8°F). Laboratory studies reveal a WBC count of 13,500/mm³ and an ESR of 55 mm/hr. According to the Kocher criteria, what is the approximate probability that this child has septic arthritis of the hip?
. 0.2%
. 9.5%
. 40.0%
. 93.0%
. 99.6%

Correct Answer & Explanation

. 99.6%

Explanation

The Kocher criteria for differentiating septic arthritis from transient synovitis include: non-weight bearing, temperature >38.5°C, ESR >40 mm/hr, and WBC >12,000/mm³. The probability of septic arthritis with 4 criteria present is approximately 99.6%.

Question 294

Topic: Infection, Pharmacology & VTE

A 12-year-old patient presents with a severe varus deformity of the proximal tibia, with the CORA located just below the knee joint line. The surgeon plans a gradual correction using an external fixator. To avoid violating the joint capsule with hardware while still adhering to Paley's geometric principles, a specialized construct is employed, as shown in the image below. What is the primary purpose of this specific hardware assembly?

. To allow for acute correction of the deformity without distraction osteogenesis.
. To facilitate the placement of the osteotomy directly at the CORA, even within the joint.
. To position the mechanical hinge precisely at the CORA in space, while keeping the physical ring distal to the joint.
. To prevent any translation at the osteotomy site, ensuring a pure angular correction.
. To enable simultaneous correction of rotational and angular deformities with a single hinge.

Correct Answer & Explanation

. To position the mechanical hinge precisely at the CORA in space, while keeping the physical ring distal to the joint.

Explanation

Correct Answer: CThe image displays a juxta-articular hinge assembly, specifically designed for deformities located in close proximity to a joint (juxta-articular deformities) where the CORA is near the joint line. As explained in the case, placing a full circular external fixator ring or transfixion wires/half-pins across the joint capsule is contraindicated due to the high risk of septic arthritis. This sophisticated construct allows the surgeon to apply the proximal reference ring at a safe distance distal to the joint capsule. Specialized outriggers, threaded rods, and hinge plates are then used to build the mechanical hingeupwards(proximally) from the reference ring, positioning its pivot point precisely at the level of the anatomical CORA in space, which lies superior to the physical ring itself. This configuration places the correction under Osteotomy Rule 2, allowing for perfect angular correction with predictable translation, without compromising the joint.Option A is incorrect; this system is typically used for gradual distraction osteogenesis. Option B is incorrect; the primary goal is to avoid violating the joint, so the osteotomy is performeddistalto the CORA, not at it within the joint. Option D is incorrect; this setup inherently involves predictable translation (Rule 2). Option E is incorrect; while external fixators can address multi-planar deformities, the specific purpose of this hinge assembly is related to juxta-articular CORA placement, not necessarily simultaneous rotation correction with a single hinge.

Question 295

Topic: Infection, Pharmacology & VTE

A patient undergoing tibial lengthening presents to the clinic 4 weeks postoperatively with erythema, localized pain, and serous discharge at a single pin site. There is no evidence of pin loosening or systemic illness. What is the most appropriate initial management?

. Immediate surgical removal of the pin.
. Intravenous vancomycin and hospital admission.
. Oral antibiotics and optimization of local pin site care.
. Surgical debridement of the pin tract.
. Complete revision of the external fixator frame.

Correct Answer & Explanation

. Oral antibiotics and optimization of local pin site care.

Explanation

This presentation is consistent with a minor (Checketts-burns Grade 1 or 2) pin tract infection. The standard of care is local pin care optimization and a short course of oral antibiotics covering skin flora. Pin removal is reserved for loose pins or refractory deep infections.

Question 296

Topic: Infection, Pharmacology & VTE

During a TKA for a severe varus deformity with a tight medial compartment, sequential soft tissue releases are required to balance the knee in extension. What is the standard correct sequence of medial release?

. Superficial MCL, then deep MCL, then semimembranosus
. Deep MCL, then posteromedial capsule, then superficial MCL as needed
. Pes anserinus, then superficial MCL, then deep MCL
. Posteromedial capsule, then PCL, then deep MCL
. Superficial MCL completely off the tibial metaphysis as the first step

Correct Answer & Explanation

. Deep MCL, then posteromedial capsule, then superficial MCL as needed

Explanation

The classic sequence for medial release in a varus knee begins with removal of osteophytes, followed by release of the deep MCL and posteromedial capsule. If further release is needed, the superficial MCL is progressively elevated.

Question 297

Topic: Infection, Pharmacology & VTE

During a repeat diagnostic arthrocentesis, 45 cc of dark, opaque, reddish-brown fluid was aspirated from the patient's knee. The fluid was negative for crystals, and cultures were negative. Which classic description is often used to characterize the appearance of synovial fluid in Pigmented Villonodular Synovitis (PVNS)?

. Clear, straw-colored
. Turbid, purulent
. Resembling 'crankcase oil' or liquid chocolate
. Highly viscous, mucinous
. Cloudy, yellow with urate crystals

Correct Answer & Explanation

. Resembling 'crankcase oil' or liquid chocolate

Explanation

Correct Answer: C - Resembling 'crankcase oil' or liquid chocolateThe case explicitly states that the aspirated fluid was "dark, opaque, reddish-brown fluid, often classically described as resembling 'crankcase oil' or liquid chocolate." This distinctive appearance is due to the chronic presence of blood and hemosiderin within the joint, a hallmark of PVNS.A. Clear, straw-colored:This describes normal synovial fluid or a non-inflammatory effusion, which is not consistent with the patient's presentation.B. Turbid, purulent:This is characteristic of septic arthritis, which was ruled out by negative cultures and Gram stain.D. Highly viscous, mucinous:This can be seen in conditions like synovial chondromatosis or early osteoarthritis, but not the dark, bloody fluid of PVNS.E. Cloudy, yellow with urate crystals:This is characteristic of gout, which was ruled out by crystal analysis.

Question 298

Topic: Infection, Pharmacology & VTE

A 28-year-old female presents with a chronic, mildly painful, swollen knee without any history of preceding trauma. Aspiration of the joint yields a thick, dark brown, "chocolate-like" fluid that does not clear with sequential aspiration. Which of the following is the most likely diagnosis?

. Gouty arthritis
. Synovial osteochondromatosis
. Pigmented villonodular synovitis (PVNS)
. Septic arthritis
. Hemochromatosis arthropathy

Correct Answer & Explanation

. Pigmented villonodular synovitis (PVNS)

Explanation

Aspiration of dark brown or "chocolate" colored fluid from a non-traumatized, chronically swollen knee is classic for PVNS. The color is due to heavy hemosiderin deposition from repeated microscopic bleeding of the hyperplastic synovium.

Question 299

Topic: Infection, Pharmacology & VTE

A patient presents with an atraumatic, swollen, and painful shoulder. Aspiration of the joint is performed to rule out infection. The fluid aspirated is dark brown and opaque ('chocolate fluid'). Cultures are negative. What is the most likely diagnosis?

. Septic arthritis
. Rheumatoid arthritis
. Gouty arthropathy
. Pigmented villonodular synovitis (PVNS)
. Osteoarthritis

Correct Answer & Explanation

. Pigmented villonodular synovitis (PVNS)

Explanation

Aspiration of a joint affected by PVNS typically yields dark brown or serosanguineous 'chocolate' fluid. This coloration is secondary to chronic recurrent hemarthrosis and extensive hemosiderin deposition within the synovial fluid and lining.

Question 300

Topic: Infection, Pharmacology & VTE

During routine follow-up for a patient with an Ilizarov frame, you note erythema, serous drainage, and mild tenderness around a tibial half-pin. The pin remains rigidly fixed to the bone without loosening. What is the most appropriate initial management?

. Immediate removal of the pin in the clinic
. Surgical debridement and exchange of the pin to a different site
. Intravenous vancomycin and hospital admission
. Local pin site care and a course of oral antibiotics
. Cessation of all distraction adjustments until the erythema resolves

Correct Answer & Explanation

. Local pin site care and a course of oral antibiotics

Explanation

This presentation is consistent with a minor pin tract infection (Checketts-burns grade 1 or 2). Standard management includes increased local pin care and oral antibiotics. Pin removal is reserved for loose pins or deep osteomyelitis.

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