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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 294 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 5861

Topic: 3. Adult Reconstruction (Hip & Knee)

When is the use of long-term suppressive oral antibiotics (LTSA) most appropriate for a patient with a periprosthetic knee infection?

. As a primary treatment for acute PJI amenable to DAIR.
. For chronic PJI in young, active patients suitable for revision surgery.
. When surgical intervention is contraindicated due to severe comorbidities, or as a last resort after failed definitive treatments.
. To prevent PJI in high-risk patients post-operatively.
. As the sole treatment for recurrent acute PJI episodes.

Correct Answer & Explanation

. When surgical intervention is contraindicated due to severe comorbidities, or as a last resort after failed definitive treatments.

Explanation

Long-term suppressive oral antibiotics (LTSA) are generally reserved for patients with chronic PJI who are not surgical candidates due to severe comorbidities, or as a last resort after multiple failed definitive surgical treatments. The goal is to control the infection and symptoms rather than eradicate it, accepting the implant remains infected. It is not a primary treatment for acute PJI, nor for young, active patients who could benefit from revision. It is also not prophylactic or suitable as the sole treatment for recurrent acute episodes where surgical intervention is usually warranted.

Question 5862

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the recommended approach to managing PJI caused by culture-negative organisms, but with strong clinical and inflammatory marker evidence of infection?

. Treat empirically with broad-spectrum antibiotics and observe.
. Manage as aseptic loosening given the negative cultures.
. Proceed with implant removal, extensive debridement, and send multiple tissue samples for extended culture, fungal culture, mycobacterial culture, and broad-range PCR.
. Perform a knee fusion as a definitive solution.
. Order serum alpha-defensin and only proceed with surgery if positive.

Correct Answer & Explanation

. Proceed with implant removal, extensive debridement, and send multiple tissue samples for extended culture, fungal culture, mycobacterial culture, and broad-range PCR.

Explanation

Culture-negative PJI is a diagnostic and therapeutic challenge. When there is strong clinical suspicion and inflammatory evidence of PJI despite negative conventional cultures, it necessitates aggressive surgical intervention. This involves implant removal, extensive debridement, and sending multiple periprosthetic tissue samples for extended incubation (10-14 days), specialized media (e.g., fungal, mycobacterial), and molecular techniques like broad-range PCR, to identify the causative organism. Empirical antibiotic treatment without definitive diagnosis is prone to failure. Managing as aseptic loosening ignores the clear signs of infection. Fusion is a salvage, not initial diagnostic, procedure. Serum alpha-defensin is a diagnostic aid but doesn't replace definitive culture for guiding therapy or ruling out unusual pathogens.

Question 5863

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following scenarios carries the highest risk of PJI for a TKA patient?

. A 60-year-old male with well-controlled hypertension.
. A 70-year-old female undergoing revision TKA for aseptic loosening.
. A 55-year-old healthy active individual undergoing primary TKA.
. A 65-year-old diabetic male with an infected foot ulcer undergoing primary TKA.
. A 72-year-old female with osteoarthritis and a history of kidney stones.

Correct Answer & Explanation

. A 65-year-old diabetic male with an infected foot ulcer undergoing primary TKA.

Explanation

A patient with an active, untreated infection at a distant site (e.g., infected foot ulcer in a diabetic) undergoing a total joint arthroplasty is at extremely high risk for hematogenous seeding and subsequent PJI. All active infections should be completely resolved and treated before elective joint replacement. Revision TKA also carries a higher risk than primary TKA, but an active infection elsewhere is generally considered a strong contraindication to elective arthroplasty until resolved.

Question 5864

Topic: 3. Adult Reconstruction (Hip & Knee)

What percentage of surgical procedures for PJI eradication are typically considered successful with two-stage revision, allowing for reimplantation?

. Below 50%.
. 50-70%.
. 70-80%.
. 85-95%.
. Nearly 100%.

Correct Answer & Explanation

. 85-95%.

Explanation

The success rate for two-stage revision arthroplasty in eradicating infection, leading to successful reimplantation, is generally cited to be in the range of 85-95%. This makes it the gold standard for chronic PJI treatment. While not 100%, it offers the best chance of infection eradication and restoration of function compared to other methods.

Question 5865

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following statements regarding the role of C-reactive protein (CRP) in PJI management is most accurate?

. CRP is highly specific for PJI, rarely elevated in other conditions.
. CRP levels greater than 100 mg/L are diagnostic of PJI.
. Serial CRP measurements can be useful for monitoring treatment response after surgical debridement.
. CRP is not affected by systemic inflammatory conditions.
. A normal CRP level definitively rules out PJI.

Correct Answer & Explanation

. Serial CRP measurements can be useful for monitoring treatment response after surgical debridement.

Explanation

Serial CRP measurements are very useful for monitoring treatment response and trending infection resolution after surgical debridement (e.g., DAIR or first stage of two-stage revision). A declining CRP indicates effective treatment, while a persistently elevated or rising CRP suggests ongoing or recurrent infection. CRP is sensitive but not highly specific, as it can be elevated in many inflammatory conditions. No single cutoff is definitively diagnostic, although very high levels are highly suggestive. A normal CRP does not definitively rule out PJI, especially in low-grade or indolent infections.

Question 5866

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following techniques is most effective in preventing PJI during TKA surgery?

. Routine preoperative nasal swabbing for MRSA and decolonization.
. Exclusive use of laminar flow operating theaters.
. Postoperative administration of prophylactic antibiotics for 7 days.
. Strict adherence to sterile technique and appropriate prophylactic IV antibiotics for perioperative period.
. Routine use of antibiotic-loaded bone cement in all primary TKAs.

Correct Answer & Explanation

. Strict adherence to sterile technique and appropriate prophylactic IV antibiotics for perioperative period.

Explanation

Strict adherence to sterile technique throughout the surgical procedure, combined with appropriate perioperative prophylactic intravenous antibiotics, is the cornerstone of PJI prevention. Preoperative MRSA screening and decolonization is also highly recommended and shown to reduce risk, but it's part of a broader protocol and not the single most effective. Laminar flow is beneficial but not universally available or proven to be more critical than core sterile technique. Postoperative prophylactic antibiotics beyond 24 hours are not generally recommended due to increased resistance risk without clear benefit. Routine use of ALBC forprimaryTKA is debated and not as universally effective as core sterile technique and appropriate single-dose prophylaxis.

Question 5867

Topic: Total Knee Arthroplasty (TKA)

A patient with a chronically infected TKA caused by a sensitive Staphylococcus aureus is scheduled for a two-stage revision. What is the standard duration of antibiotic-free interval recommended before reimplantation to confirm eradication?

. Less than 72 hours.
. 1 to 2 weeks.
. 4 weeks.
. 6 weeks.
. No antibiotic-free interval is necessary.

Correct Answer & Explanation

. 1 to 2 weeks.

Explanation

To accurately assess for infection eradication during a two-stage revision, an antibiotic-free interval of at least 1 to 2 weeks (often 2 weeks is preferred) is recommended before performing repeat aspirations for culture. This 'antibiotic holiday' allows any remaining bacteria to regain metabolic activity, thus increasing the sensitivity of cultures and minimizing false negatives caused by antibiotic suppression. Less than 72 hours is too short, and longer periods may increase the risk of re-infection or spacer complications.

Question 5868

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary limitation of serum inflammatory markers (ESR, CRP) in diagnosing periprosthetic joint infection?

. They are specific only for fungal infections.
. They are often falsely low in acute infections.
. They lack specificity and can be elevated in various non-infectious inflammatory conditions.
. They require specialized laboratory equipment and are costly.
. They are only elevated in patients with systemic sepsis.

Correct Answer & Explanation

. They lack specificity and can be elevated in various non-infectious inflammatory conditions.

Explanation

The primary limitation of serum inflammatory markers like ESR and CRP in diagnosing PJI is their lack of specificity. They can be elevated in numerous non-infectious inflammatory conditions (e.g., rheumatoid arthritis flares, gout, trauma, other surgeries, obesity), leading to false positives. While sensitive, their non-specificity necessitates combining them with other diagnostic criteria. They are not specific to fungal infections, can be elevated in acute infections, are routine and inexpensive, and can be elevated locally without systemic sepsis.

Question 5869

Topic: 3. Adult Reconstruction (Hip & Knee)

In the presence of an infected TKA, which finding on plain radiographs would be most concerning for established chronic PJI with significant bone involvement?

. Soft tissue swelling around the joint.
. New heterotopic ossification.
. Periprosthetic lucencies greater than 2mm, progressive, or circumferential.
. Slight increase in joint space.
. Mild malalignment of components.

Correct Answer & Explanation

. Periprosthetic lucencies greater than 2mm, progressive, or circumferential.

Explanation

Periprosthetic lucencies greater than 2mm, progressive, or circumferential are highly concerning for established chronic PJI with bone involvement, often indicating loosening or osteolysis due to infection. These findings suggest bone resorption around the implant, a common manifestation of chronic infection. Soft tissue swelling and mild malalignment are less specific. Heterotopic ossification is not directly indicative of infection. An increase in joint space is unlikely with PJI and more likely with component dissociation.

Question 5870

Topic: Total Knee Arthroplasty (TKA)

For patients with an infected TKA who undergo a two-stage revision, what is generally the most important factor for maximizing patient satisfaction and functional outcomes after reimplantation?

. Use of the latest generation of prosthetic components.
. Early weight-bearing on the cement spacer.
. Aggressive physical therapy and rehabilitation to restore motion and strength.
. Prolonged systemic antibiotic therapy post-reimplantation.
. Strict adherence to a low-impact lifestyle.

Correct Answer & Explanation

. Aggressive physical therapy and rehabilitation to restore motion and strength.

Explanation

Aggressive physical therapy and rehabilitation to restore motion and strength are paramount for maximizing patient satisfaction and functional outcomes after reimplantation. While infection eradication is the primary goal, functional recovery depends heavily on regaining range of motion, strength, and confidence in the limb. Spacer choice (articulating), early mobilization, and dedicated rehab are critical. The latest components or prolonged antibiotics alone do not guarantee good function, and a low-impact lifestyle may be necessary but doesn't drive satisfaction as much as regained function.

Question 5871

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following interventions has the strongest evidence for reducing the incidence of PJI in the immediate perioperative period?

. Use of antibiotic-impregnated surgical drapes.
. Intraoperative pulsatile lavage with saline.
. Single dose intravenous prophylactic antibiotics administered within 60 minutes of incision.
. Routine blood transfusions to maintain hemoglobin levels.
. Extended postoperative antibiotic prophylaxis for 5-7 days.

Correct Answer & Explanation

. Single dose intravenous prophylactic antibiotics administered within 60 minutes of incision.

Explanation

Single-dose intravenous prophylactic antibiotics administered within 60 minutes prior to surgical incision has the strongest and most consistent evidence for reducing the incidence of PJI. This ensures adequate tissue levels of antibiotics at the time of potential contamination. Extended postoperative antibiotics are generally not recommended due to increased resistance risk without clear benefit. Pulsatile lavage efficacy is debated, antibiotic-impregnated drapes have some evidence but not as strong as systemic antibiotics. Blood transfusions are for anemia, not direct PJI prevention.

Question 5872

Topic: 3. Adult Reconstruction (Hip & Knee)

Which factor is most crucial in determining the type of antibiotic-loaded cement spacer (articulating vs. static) to be used during a two-stage revision for PJI?

. Patient's age.
. Body mass index (BMI).
. Quality of the remaining bone stock and integrity of the extensor mechanism/collateral ligaments.
. Type of previous prosthetic implant.
. Patient's preference for early weight-bearing.

Correct Answer & Explanation

. Quality of the remaining bone stock and integrity of the extensor mechanism/collateral ligaments.

Explanation

The quality of the remaining bone stock, the integrity of the extensor mechanism, and the status of the collateral ligaments are crucial in determining whether an articulating or static spacer can be used. Articulating spacers require sufficient bone and soft tissue integrity to maintain stability and allow motion. If there is significant bone loss or compromise to the extensor mechanism or ligaments, a static spacer may be necessary to provide stability and maintain the joint space. Patient's age or BMI are less direct determinants, and early weight-bearing preference is secondary to biomechanical stability.

Question 5873

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old male with multiple comorbidities is diagnosed with a chronic PJI of the knee. He is deemed too frail for a two-stage revision, but the infection is causing severe pain and intermittent draining. Which of the following is the most appropriate palliative option?

. DAIR procedure with long-term oral antibiotics.
. Long-term suppressive oral antibiotics with implant retention.
. Knee arthrodesis.
. Above-knee amputation.
. Single-stage revision arthroplasty.

Correct Answer & Explanation

. Long-term suppressive oral antibiotics with implant retention.

Explanation

Given that the patient is too frail for a definitive two-stage revision, long-term suppressive oral antibiotics with implant retention is the most appropriate palliative option. The goal is to manage symptoms, reduce pain, and control the infection without attempting complete eradication through surgery. DAIR is typically for acute infections or early chronic infections in healthier patients. Arthrodesis and amputation are definitive surgical solutions, which the patient is too frail for. Single-stage revision is also a definitive surgical procedure, not palliative.

Question 5874

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the recommended treatment for a TKA infection caused by Mycobacterium tuberculosis?

. DAIR with standard 6-week anti-TB drug regimen.
. Two-stage revision with implant removal, extensive debridement, and prolonged multi-drug anti-TB therapy (typically 12-18 months).
. Single-stage revision with topical anti-TB agents.
. Long-term suppressive oral antibiotics indefinitely.
. Arthrodesis as the primary treatment due to high recurrence rates.

Correct Answer & Explanation

. Two-stage revision with implant removal, extensive debridement, and prolonged multi-drug anti-TB therapy (typically 12-18 months).

Explanation

Tuberculosis PJI is a rare but severe form of infection. It requires aggressive surgical management, typically a two-stage revision with complete implant removal and thorough debridement, combined with prolonged multi-drug anti-TB therapy, usually for 12-18 months. DAIR is generally ineffective for mycobacterial infections. Single-stage revision has a high failure rate. Long-term suppressive antibiotics are not curative. Arthrodesis is a salvage option, not the primary treatment.

Question 5875

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is the most accurate statement regarding synovial fluid leukocyte esterase for PJI diagnosis?

. It is a highly sensitive and specific test, superior to alpha-defensin.
. A negative result definitively rules out PJI.
. It can be performed rapidly at the point of care and has high negative predictive value.
. It is useful only for differentiating between Gram-positive and Gram-negative infections.
. Its accuracy is significantly affected by prior antibiotic use.

Correct Answer & Explanation

. It can be performed rapidly at the point of care and has high negative predictive value.

Explanation

Synovial fluid leukocyte esterase (LE) is a rapid, point-of-care test that has a high negative predictive value (NPV) for PJI. This means a negative result makes PJI highly unlikely. While not as specific as alpha-defensin, its rapid nature and high NPV make it a valuable screening tool. Its accuracy can be affected by blood contamination or recent antibiotic use, but its high NPV is a key advantage. It does not differentiate between Gram-positive and Gram-negative bacteria and is not superior to alpha-defensin.

Question 5876

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the most appropriate management for a patient with a chronically infected TKA and significant knee pain who refuses any further surgical intervention?

. Referral for psychological counseling only.
. Initiate long-term suppressive oral antibiotics, along with pain management and functional bracing if needed.
. Recommend immediate amputation as it's the only non-surgical option.
. Insist on a two-stage revision, explaining the risks of non-compliance.
. Physical therapy alone to improve range of motion.

Correct Answer & Explanation

. Initiate long-term suppressive oral antibiotics, along with pain management and functional bracing if needed.

Explanation

If a patient with chronic PJI refuses further surgical intervention, the most appropriate management is palliative. This typically involves initiating long-term suppressive oral antibiotics to control the infection and reduce symptoms, coupled with aggressive pain management, and functional bracing or orthoses if mechanical instability is an issue. This approach aims to maximize comfort and function while accepting the presence of the infection. Amputation is a surgical option and a last resort. Insisting on surgery is unethical if the patient has capacity and refuses. Physical therapy alone is insufficient for infection control.

Question 5877

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old male undergoes TKA. On post-operative day 5, he develops a fever of 39.5°C and severe pain. The wound is erythematous and draining purulent fluid. What is the most likely pathogen?

. Staphylococcus epidermidis.
. Cutibacterium acnes.
. Staphylococcus aureus.
. Candida albicans.
. Escherichia coli.

Correct Answer & Explanation

. Staphylococcus aureus.

Explanation

An acute, virulent infection developing within days to a week post-operatively, presenting with high fever, severe pain, and purulent drainage, is most characteristic of Staphylococcus aureus. S. aureus is a highly virulent pathogen often associated with acute, rapidly progressing infections. S. epidermidis and Cutibacterium acnes typically cause more indolent, late-onset infections. Candida and E. coli are less common but can cause acute infections, though S. aureus is the most likely in this classic scenario.

Question 5878

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following describes a key principle for successful DAIR (Debridement, Antibiotics, Implant Retention) in PJI?

. Applicable to all PJI cases, regardless of onset or pathogen.
. Relies on complete removal of all prosthetic components.
. Requires symptom duration <3-6 weeks, stable implants, and sensitive organisms.
. Involves indefinite systemic antibiotic monotherapy.
. Primarily used for fungal and mycobacterial infections.

Correct Answer & Explanation

. Requires symptom duration <3-6 weeks, stable implants, and sensitive organisms.

Explanation

DAIR is a treatment option for acute PJI, but its success depends on strict criteria: 1) short symptom duration (<3-6 weeks), 2) stable implants, 3) a sensitive, low-virulence organism (e.g., sensitive Staph aureus, streptococci), and 4) intact soft tissues. It relies on meticulous debridement, exchange of modular components (polyethylene liner), and prolonged targeted antibiotic therapy. It does not involve complete removal of all components and is not applicable to all PJI cases, especially chronic or those with virulent/resistant pathogens, or fungal/mycobacterial infections. Indefinite monotherapy is inappropriate.

Question 5879

Topic: 3. Adult Reconstruction (Hip & Knee)

In the context of PJI diagnostics, what is the role of histopathological analysis of periprosthetic tissues?

. It identifies the specific bacterial species causing the infection.
. It quantifies antibiotic susceptibility of the pathogen.
. It can detect inflammatory infiltrates consistent with infection, even in culture-negative cases.
. It is only useful for differentiating between aseptic and septic loosening in the absence of radiographs.
. It is primarily used to assess bone quality before reimplantation.

Correct Answer & Explanation

. It can detect inflammatory infiltrates consistent with infection, even in culture-negative cases.

Explanation

Histopathological analysis of periprosthetic tissues (e.g., frozen sections or permanent sections) is a valuable diagnostic tool. It can identify inflammatory infiltrates (e.g., >5 neutrophils per high-power field in 5 fields) that are highly suggestive of infection, even in culture-negative cases. It does not identify specific bacterial species or quantify antibiotic susceptibility (that's microbiology's role) but provides morphological evidence of an inflammatory response indicative of infection. While it helps differentiate between septic and aseptic loosening, it's not the sole criterion and can't replace culture for guiding antibiotic choice.

Question 5880

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a chronically infected TKA has failed multiple surgical revisions. He develops persistent sepsis, severe soft tissue breakdown, and intractable pain. What is the definitive salvage procedure to consider?

. Repeat two-stage revision with a different antibiotic regimen.
. Long-term suppressive oral antibiotics.
. Above-knee amputation.
. Knee arthrodesis.
. Excision arthroplasty (Girdlestone knee).

Correct Answer & Explanation

. Above-knee amputation.

Explanation

In cases of intractable, limb-threatening infection with persistent sepsis, severe soft tissue breakdown, and failed multiple surgical revisions, above-knee amputation becomes the definitive salvage procedure. While arthrodesis is also a salvage procedure for failed infection, amputation is considered when the limb is no longer salvageable and poses a threat to the patient's life or quality of life due to persistent infection. Excision arthroplasty (Girdlestone) provides a flail, unstable, painful limb, often requiring eventual amputation. Repeat revisions are not feasible if already failed multiple times with severe local complications. Long-term suppressive antibiotics are palliative, not curative, and insufficient for severe sepsis and tissue breakdown.

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