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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 293 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 5841

Topic: 3. Adult Reconstruction (Hip & Knee)

A 79-year-old female with severe rheumatoid arthritis sustains a highly comminuted, intra-articular distal humerus fracture (AO type 13-C3). Which of the following is the primary advantage of performing a Total Elbow Arthroplasty (TEA) over Open Reduction Internal Fixation (ORIF) in this specific patient?

. Elimination of a permanent lifting restriction
. Immediate allowance for weight-bearing through the upper extremity
. A more predictable and rapid return of functional elbow range of motion
. Decreased incidence of postoperative ulnar neuropathy
. Lower lifetime probability of reoperation for aseptic loosening

Correct Answer & Explanation

. A more predictable and rapid return of functional elbow range of motion

Explanation

In elderly patients with poor bone quality (e.g., rheumatoid arthritis) and complex intra-articular distal humerus fractures, TEA offers a more reliable and immediate stable construct. This allows for early mobilization, leading to a more predictable return of functional range of motion compared to ORIF, which carries a high risk of fixation failure and stiffness. However, TEA necessitates a permanent 5-10 lb lifetime lifting restriction.

Question 5842

Topic: 3. Adult Reconstruction (Hip & Knee)

A 19-year-old rugby player presents to the emergency department after a direct blow to the medial aspect of his clavicle. He complains of severe pain and exhibits shortness of breath, mild stridor, and venous engorgement of his right upper extremity. A CT scan confirms a posterior sternoclavicular joint dislocation. What is the most appropriate next step in management?

. Immediate closed reduction in the emergency department using traction and a figure-of-eight brace
. Open reduction and internal fixation with K-wires across the sternoclavicular joint
. Closed reduction in the operating room with a cardiothoracic surgeon available on standby
. Observation and sling immobilization as these typically remodel in young patients
. Resection arthroplasty of the medial clavicle

Correct Answer & Explanation

. Closed reduction in the operating room with a cardiothoracic surgeon available on standby

Explanation

Posterior sternoclavicular dislocations are orthopedic emergencies if there are signs of mediastinal compression (dyspnea, dysphagia, stridor, venous congestion). Because the great vessels, trachea, and esophagus lie directly posterior to the medial clavicle, attempted closed reduction carries a risk of life-threatening hemorrhage if a vessel has been lacerated but tamponaded by the clavicle. Therefore, reduction must be performed in the operating room with a cardiothoracic surgeon on standby.

Question 5843

Topic: 3. Adult Reconstruction (Hip & Knee)

The primary blood supply to the proximal pole of the scaphoid enters the bone via which of the following anatomical regions?

. Volar tuberosity
. Dorsal ridge
. Scapholunate interosseous ligament
. Radioscaphocapitate ligament
. Proximal articular surface

Correct Answer & Explanation

. Dorsal ridge

Explanation

The major blood supply to the scaphoid enters through the dorsal ridge (accounting for 70-80% of perfusion) and courses in a retrograde fashion to the proximal pole. This retrograde blood flow is why proximal pole fractures have a notoriously high risk of avascular necrosis.

Question 5844

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old female presents with stage IV Eaton-Littler basal joint arthritis of the thumb, demonstrating pan-trapezial arthritis (CMC and STT joints). Which of the following procedures is absolutely contraindicated?

. Trapeziectomy alone
. Ligament reconstruction and tendon interposition (LRTI)
. Volar beak ligament reconstruction
. Arthrodesis of the CMC joint
. Trapeziectomy with hematoma distraction arthroplasty

Correct Answer & Explanation

. Volar beak ligament reconstruction

Explanation

Volar beak ligament reconstruction is indicated for early pre-arthritic hyperlaxity or Stage I disease. It is contraindicated in Stage IV pan-trapezial arthritis, where joint resection or salvage procedures (like LRTI or complete trapeziectomy) are required.

Question 5845

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoing two-stage revision for PJI has an articulating antibiotic-loaded cement spacer in place. Which type of antibiotic is generally preferred for incorporation into the cement spacer?

. A bacteriostatic antibiotic with low heat stability.
. An antibiotic with high systemic absorption and short half-life.
. A heat-stable, broad-spectrum, bactericidal antibiotic that elutes well from cement.
. An antibiotic specifically targeting Gram-negative organisms only.
. An antibiotic that requires frequent dosing for effective plasma levels.

Correct Answer & Explanation

. A heat-stable, broad-spectrum, bactericidal antibiotic that elutes well from cement.

Explanation

The ideal antibiotic for incorporation into bone cement should be heat-stable (to withstand the exothermic polymerization process), broad-spectrum (to cover common PJI pathogens, at least initially), bactericidal (for definitive killing), and demonstrate good elution characteristics from the cement. Aminoglycosides (e.g., gentamicin, tobramycin) and vancomycin are commonly used because they meet these criteria. Bacteriostatic antibiotics are generally less preferred for severe infections. High systemic absorption is undesirable for local delivery, and short half-life would require higher loading. Focusing solely on Gram-negative organisms would miss Gram-positive cocci, which are the most common cause of PJI.

Question 5846

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following organisms is most commonly implicated in late chronic periprosthetic joint infections (PJI) (>1 year post-op)?
. Staphylococcus aureus.
. Coagulase-negative Staphylococci (CoNS).
. Pseudomonas aeruginosa.
. Streptococcus pyogenes.
. Escherichia coli.

Correct Answer & Explanation

. Coagulase-negative Staphylococci (CoNS).

Explanation

Coagulase-negative Staphylococci (CoNS), particularly Staphylococcus epidermidis, are the most common organisms implicated in late chronic PJIs. These organisms are typically low-virulence and often present with indolent symptoms that manifest months to years after the initial surgery. While Staphylococcus aureus is also common, it tends to cause more acute and subacute infections. Pseudomonas and Enterobacteriaceae are less common but can cause severe infections, often associated with healthcare-associated exposures or immunocompromised hosts. Streptococcus pyogenes typically causes acute, aggressive infections.

Question 5847

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the typical success rate of a well-executed two-stage revision arthroplasty for chronic PJI?

. 30-40%.
. 50-60%.
. 65-75%.
. 85-95%.
. Less than 20%.

Correct Answer & Explanation

. 85-95%.

Explanation

The typical success rate for eradicating infection with a well-executed two-stage revision arthroplasty for chronic PJI ranges from 85% to 95%. This is considered the gold standard for chronic PJI treatment due to its high efficacy in eliminating the infection while maintaining joint function. The other options represent significantly lower or impossibly high success rates for this complex surgical intervention. While a 100% success rate is not achievable, this method offers the best chance for infection eradication and functional restoration.

Question 5848

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following factors would most strongly contraindicate a DAIR (Debridement, Antibiotics, and Implant Retention) procedure for a periprosthetic joint infection?

. Symptom duration of 4 weeks.
. Positive Gram stain for Gram-positive cocci.
. Presence of a draining sinus tract.
. Systemic fever and elevated CRP.
. Patient age of 75 years.

Correct Answer & Explanation

. Presence of a draining sinus tract.

Explanation

The presence of a draining sinus tract communicating with the joint prosthesis is an absolute contraindication to DAIR. A sinus tract indicates a chronic, well-established infection with significant biofilm formation, making implant retention highly unlikely to succeed. In such cases, a two-stage revision is typically required. Symptom duration of 4 weeks is at the upper limit but still potentially acceptable for DAIR. Positive Gram stain and systemic signs of infection are consistent with PJI and would prompt DAIR if other criteria are met. Patient age is not a contraindication to DAIR.

Question 5849

Topic: 3. Adult Reconstruction (Hip & Knee)

In the setting of a two-stage revision for PJI, what is the recommended minimum 'antibiotic holiday' period before performing repeat aspirations to confirm infection eradication prior to the second stage?

. No holiday is needed; aspirate while on antibiotics.
. 2-3 days.
. 1-2 weeks.
. 4 weeks.
. 3 months.

Correct Answer & Explanation

. 1-2 weeks.

Explanation

To accurately assess for infection eradication during a two-stage revision, it is recommended to have an 'antibiotic holiday' of at least 1-2 weeks (typically 2 weeks is preferred) before performing repeat aspirations. This period allows any residual bacteria to become metabolically active and increases the sensitivity of cultures by minimizing false negatives due to antibiotic suppression. Aspirating while on antibiotics significantly increases the risk of false-negative results, leading to premature reimplantation and high rates of recurrence.

Question 5850

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient develops a PJI after TKA caused by Cutibacterium acnes (formerly Propionibacterium acnes). This organism is typically associated with which type of PJI presentation?

. Fulminant acute infection with rapid joint destruction.
. Late-onset, indolent, low-grade infection with subtle symptoms.
. Systemic sepsis with multiple organ involvement.
. Acute infection with severe local inflammation within days of surgery.
. Necrotizing fasciitis around the knee.

Correct Answer & Explanation

. Late-onset, indolent, low-grade infection with subtle symptoms.

Explanation

Cutibacterium acnes (formerly P. acnes) is a common skin commensal that can cause low-grade, indolent, late-onset periprosthetic joint infections. These infections are often characterized by subtle symptoms, delayed diagnosis, and may require extended culture incubation times (e.g., 10-14 days) to detect the organism. They typically do not cause fulminant acute infections or systemic sepsis. This organism is more commonly associated with shoulder PJI but can occur in the knee.

Question 5851

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the recommended range for the concentration of vancomycin often incorporated into antibiotic-loaded bone cement for spacers in PJI treatment?

. 0.1 - 0.5 grams per 40g cement pack.
. 1 - 2 grams per 40g cement pack.
. 4 - 8 grams per 40g cement pack.
. 10 - 20 grams per 40g cement pack.
. More than 20 grams per 40g cement pack.

Correct Answer & Explanation

. 4 - 8 grams per 40g cement pack.

Explanation

For antibiotic-loaded bone cement (ALBC) spacers, especially in a two-stage revision, high doses of antibiotics are typically incorporated to achieve maximal local elution. For vancomycin, a common concentration range is 4-8 grams per 40g cement pack. Some may use up to 10g depending on the situation, but going much higher can compromise the mechanical properties of the cement. The lower doses (0.1-2g) are more typical for prophylactic ALBC used in primary TKA, not for treating established infection.

Question 5852

Topic: 3. Adult Reconstruction (Hip & Knee)

When considering a single-stage revision for chronic PJI, which of the following scenarios would be the most suitable indication?

. Infection caused by multi-drug resistant Pseudomonas.
. Chronic infection with extensive bone loss requiring major reconstruction.
. A well-characterized, sensitive organism, good soft tissue envelope, and healthy host.
. Presence of an active draining sinus tract.
. Multiple prior failed attempts at infection eradication.

Correct Answer & Explanation

. A well-characterized, sensitive organism, good soft tissue envelope, and healthy host.

Explanation

Single-stage revision for chronic PJI is a viable option in highly selected cases. The ideal candidate has a well-characterized, susceptible organism (e.g., sensitive Staph aureus, CoNS), good soft tissue envelope, healthy host (Cierny-Mader Type A), minimal bone loss, and no active draining sinus tract. Infections caused by multi-drug resistant organisms, extensive bone loss, active sinus tracts, or multiple prior failures typically necessitate a two-stage approach for higher success rates. A single-stage procedure requires meticulous debridement and confident eradication in one setting.

Question 5853

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient develops a PJI 2 years after TKA with Staphylococcus aureus. He undergoes a DAIR procedure with polyethylene exchange and receives appropriate IV and oral antibiotics. 6 months later, he presents with recurrent knee pain and elevated inflammatory markers. What is the most likely reason for the failure of DAIR in this case?

. Inadequate duration of oral antibiotic therapy.
. Too early presentation of PJI for DAIR.
. Poor penetration of antibiotics into the biofilm.
. Failure to exchange the femoral and tibial components.
. Misdiagnosis of PJI.

Correct Answer & Explanation

. Poor penetration of antibiotics into the biofilm.

Explanation

The most likely reason for DAIR failure in this scenario, especially with a recurrence after a seemingly appropriate initial attempt, is the inherent limitation of antibiotics to fully eradicate established biofilm. Biofilm, a protective matrix produced by bacteria, significantly reduces antibiotic penetration and makes bacteria highly resistant to systemic therapy. While the other options could contribute to failure, biofilm resistance is a fundamental challenge to DAIR success in chronic or recurrent infections. DAIR is less effective for late-onset chronic PJI (>3 months) and is prone to failure in recurrent infections. Exchanging femoral and tibial components is part of a revision, not DAIR. Inadequate antibiotic duration is a possibility, but biofilm resistance is more fundamental.

Question 5854

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient presenting with suspected PJI, what is the most sensitive and specific test available for diagnosis before surgical intervention?

. Erythrocyte Sedimentation Rate (ESR).
. C-Reactive Protein (CRP).
. Serum D-dimer.
. Synovial fluid alpha-defensin.
. Plain radiographs.

Correct Answer & Explanation

. Synovial fluid alpha-defensin.

Explanation

Synovial fluid alpha-defensin has emerged as a highly sensitive and specific diagnostic marker for PJI, even in equivocal cases or when patients are on antibiotics. It is particularly useful for differentiating between aseptic loosening and PJI. ESR and CRP are useful inflammatory markers but lack the specificity of alpha-defensin and can be elevated in non-infectious conditions. Serum D-dimer is primarily for DVT exclusion. Plain radiographs are important for assessing hardware and bone but are not specific for infection.

Question 5855

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active male develops chronic PJI secondary to a highly resistant Staphylococcus epidermidis. After multiple failed two-stage revisions, he desires a definitive solution, but a further revision is deemed too risky due to extensive bone loss and poor soft tissues. What is the most appropriate salvage procedure?

. Long-term suppressive oral antibiotics with implant retention.
. Knee arthrodesis.
. Amputation above the knee.
. Further attempts at two-stage revision with custom implants.
. Removal of components with no further intervention (excision arthroplasty).

Correct Answer & Explanation

. Knee arthrodesis.

Explanation

Knee arthrodesis (fusion) is a recognized salvage procedure for failed periprosthetic joint infection, especially when eradication is difficult, and the patient has significant bone loss, poor soft tissues, or has failed multiple prior revisions. It provides a stable, pain-free limb, though function is compromised. Amputation is a last resort, usually for intractable, limb-threatening infections. Long-term suppressive antibiotics are for patients who cannot tolerate surgery or for whom infection cannot be eradicated, but fusion offers a more definitive mechanical solution. Excision arthroplasty (Girdlestone knee) typically results in a flail, painful, unstable knee. Further revisions might be considered but were stated as too risky in the prompt.

Question 5856

Topic: 3. Adult Reconstruction (Hip & Knee)

Which type of periprosthetic joint infection is most commonly associated with a hematogenous spread from a distant source?

. Acute post-operative infection (within 3 months).
. Early chronic infection (3-12 months post-op).
. Late chronic infection (>12 months post-op).
. Intraoperative contamination.
. Early acute infection (within 1 month).

Correct Answer & Explanation

. Late chronic infection (>12 months post-op).

Explanation

Late chronic infections (>12 months post-op) are most commonly associated with hematogenous seeding from a distant source (e.g., urinary tract infection, dental abscess, skin infection). Bacteria travel through the bloodstream and colonize the implant surface. Acute post-operative infections and early acute infections are more commonly due to intraoperative contamination or early wound complications. Early chronic infections can be a mix of both but are often indolent intraoperative contaminants.

Question 5857

Topic: 3. Adult Reconstruction (Hip & Knee)
Which risk factor is considered the most modifiable patient-specific risk factor for reducing the incidence of PJI in patients undergoing TKA?
. Advanced age.
. Type 2 Diabetes Mellitus with uncontrolled HbA1c.
. Obesity (BMI >40 kg/mยฒ).
. History of inflammatory arthritis.
. Male gender.

Correct Answer & Explanation

. Type 2 Diabetes Mellitus with uncontrolled HbA1c.

Explanation

Uncontrolled Type 2 Diabetes Mellitus, particularly with an elevated HbA1c (>7.5-8.0%), is a highly modifiable risk factor. Preoperative optimization of glycemic control has been shown to significantly reduce the risk of PJI. While obesity is also modifiable, achieving significant weight loss prior to surgery can be challenging. Advanced age and inflammatory arthritis are non-modifiable. Male gender is a less significant or inconsistent risk factor compared to diabetes or obesity.

Question 5858

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a TKA develops a Candida albicans PJI. Which of the following is the most appropriate management strategy?

. DAIR with polyethylene exchange and oral fluconazole.
. Single-stage revision TKA with intravenous fluconazole.
. Two-stage revision TKA with aggressive debridement and prolonged systemic antifungal therapy (e.g., amphotericin B or echinocandin initially, then fluconazole).
. Arthrodesis as first-line treatment.
. Long-term suppressive oral antifungals only.

Correct Answer & Explanation

. Two-stage revision TKA with aggressive debridement and prolonged systemic antifungal therapy (e.g., amphotericin B or echinocandin initially, then fluconazole).

Explanation

Fungal PJI, especially due to Candida, is challenging to treat. It requires aggressive surgical debridement and implant removal (two-stage revision is preferred) in conjunction with prolonged, targeted systemic antifungal therapy. Initial therapy often involves potent agents like amphotericin B or an echinocandin, followed by a prolonged course of fluconazole once sensitivity is confirmed and the patient is stable. DAIR is almost always ineffective for fungal PJI. Single-stage revision carries high failure rates. Arthrodesis is a salvage procedure, not first-line. Long-term suppressive therapy without implant removal is unlikely to eradicate the infection.

Question 5859

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary advantage of using a static antibiotic-loaded cement spacer over an articulating spacer in certain complex PJI cases?

. Allows for earlier weight-bearing and functional recovery.
. Better preservation of joint mechanics.
. Provides greater stability, potentially more space for debridement, and easier fabrication in severe bone loss.
. Significantly higher local antibiotic concentration.
. Reduces the risk of subsequent aseptic loosening.

Correct Answer & Explanation

. Provides greater stability, potentially more space for debridement, and easier fabrication in severe bone loss.

Explanation

Static antibiotic-loaded cement spacers, while limiting joint motion, offer advantages in complex PJI cases, particularly those with severe bone loss, poor soft tissue coverage, or instability. They provide greater mechanical stability, can be custom-molded to fill large defects, allow for extensive debridement without concern for subsequent articulation, and are often simpler to fabricate. They also prevent bony overgrowth into the joint space. Articulating spacers are better for functional recovery and joint mechanics. Antibiotic elution concentrations are similar. Neither directly reduces the risk of aseptic loosening in the long term, as the goal is infection eradication.

Question 5860

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old male with a 10-year-old TKA presents with sudden onset excruciating knee pain, swelling, and fever. Synovial fluid analysis shows 80,000 WBC/ยตL, 92% neutrophils. Gram stain is negative. What is the most appropriate next step given the clinical scenario?

. Start empirical oral antibiotics and observe.
. Perform a repeat synovial fluid aspiration for fungal and mycobacterial cultures.
. Proceed directly to urgent surgical debridement with tissue samples for culture, even with negative Gram stain.
. Order a Technetium-99m bone scan.
. Administer anti-inflammatory medications and re-evaluate in 24 hours.

Correct Answer & Explanation

. Proceed directly to urgent surgical debridement with tissue samples for culture, even with negative Gram stain.

Explanation

Given the acute presentation, high fever, and highly inflammatory synovial fluid analysis (very high WBC and PMN%), this is an acute PJI until proven otherwise, even with a negative Gram stain. A negative Gram stain does not rule out infection, as its sensitivity is low. Urgent surgical debridement, washout, and collection of multiple periprosthetic tissue samples for aerobic, anaerobic, fungal, and mycobacterial cultures are crucial. Delaying surgery for further aspirations or imaging risks worsening infection and irreversible damage. Empirical oral antibiotics alone are insufficient for acute PJI.

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