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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 125 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 2481

Topic: 3. Adult Reconstruction (Hip & Knee)

Aseptic loosening secondary to particulate wear debris remains a primary cause of late failure in total hip arthroplasty. Which specific cell type is primarily responsible for the phagocytosis of polyethylene particles and the subsequent initiation of the osteolytic cytokine cascade?

. Osteoblasts
. Osteoclasts
. Macrophages
. T-lymphocytes
. Polymorphonuclear leukocytes

Correct Answer & Explanation

. Macrophages

Explanation

Macrophages phagocytose submicron wear particles (0.1 to 10 micrometers) but cannot digest them. This results in the release of pro-inflammatory cytokines (IL-1, IL-6, TNF-alpha) that stimulate osteoclastic bone resorption, leading to osteolysis.

Question 2482

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman is evaluated for a painful total hip arthroplasty 10 years post-surgery. Radiographs show eccentric wear of the polyethylene liner and substantial osteolysis in Gruen zones 1 and 7. What is the primary biological mediator responsible for this osteolysis?

. Polymorphonuclear leukocytes
. Interleukin-10 (IL-10)
. Macrophage-derived tumor necrosis factor alpha (TNF-alpha)
. Osteoprotegerin (OPG)
. Cytotoxic T-lymphocytes

Correct Answer & Explanation

. Macrophage-derived tumor necrosis factor alpha (TNF-alpha)

Explanation

Periprosthetic osteolysis is primarily driven by a macrophage-mediated inflammatory response to particulate wear debris. Macrophages phagocytose the particles and release pro-inflammatory cytokines like TNF-alpha, IL-1, and IL-6, which stimulate osteoclastogenesis.

Question 2483

Topic: 3. Adult Reconstruction (Hip & Knee)

Six weeks after a total knee arthroplasty, a patient presents with persistent wound drainage and erythema. Aseptic aspiration yields a synovial fluid white blood cell count of 45,000 cells/uL with 92% neutrophils. What is the most appropriate surgical intervention?

. Suppressive antibiotic therapy alone
. One-stage revision arthroplasty
. Two-stage revision arthroplasty with an antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. Above-knee amputation

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange

Explanation

For acute periprosthetic joint infections occurring within 4 weeks of surgery or within 3 weeks of acute symptom onset, DAIR with modular component exchange is indicated. The implants are well-fixed, and the biofilm is immature, making salvage possible.

Question 2484

Topic: 3. Adult Reconstruction (Hip & Knee)

In the context of total hip arthroplasty, which of the following wear mechanisms is primarily responsible for the generation of submicron polyethylene particles when a roughened femoral head articulates with the liner?

. Adhesive wear
. Abrasive wear
. Fatigue wear
. Third-body wear
. Corrosive wear

Correct Answer & Explanation

. Abrasive wear

Explanation

Abrasive wear occurs when a hard, rough surface (like a scratched metallic femoral head) ploughs through a softer material (polyethylene), shaving away micro-particles. This is a primary generator of the debris that leads to osteolysis.

Question 2485

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, trial reduction reveals that the knee is well-balanced in flexion but tight in extension. Which of the following is the most appropriate intraoperative step to address this mismatch?

. Increase the posterior slope of the tibial cut
. Downsize the femoral component
. Release the posterior capsule and resect additional distal femur
. Upsize the femoral component
. Recut the proximal tibia to remove more bone

Correct Answer & Explanation

. Release the posterior capsule and resect additional distal femur

Explanation

A knee that is tight in extension but balanced in flexion requires an increase in the extension gap without altering the flexion gap. This is achieved by resecting more distal femur or releasing the posterior capsule.

Question 2486

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female presents with a painful popping sensation at the anterior aspect of her knee when extending from a flexed position, 12 months after a total knee arthroplasty. Which of the following implant designs is classically associated with this complication?

. Cruciate-retaining TKA
. Posterior-stabilized TKA
. Medial pivot TKA
. Unicompartmental knee arthroplasty
. Rotating hinge TKA

Correct Answer & Explanation

. Posterior-stabilized TKA

Explanation

Patellar clunk syndrome is typically associated with posterior-stabilized TKA designs. It occurs when a fibrous nodule forms at the superior pole of the patella and catches in the intercondylar box of the femoral component during extension.

Question 2487

Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old man undergoes a revision total hip arthroplasty for aseptic loosening. The femur exhibits a Paprosky Type IIIB defect, and the surgeon opts for a modular, fluted, tapered titanium stem. What is the primary biomechanical mechanism of diaphyseal fixation for this implant?
. It relies entirely on proximal metaphyseal cancellous bone for axial and rotational stability.
. It achieves rotational stability through diaphyseal splines and axial stability via the distal taper.
. It depends on cementation distal to the diaphyseal defect to ensure immediate weight-bearing.
. It prevents stress shielding by utilizing a highly rigid cobalt-chromium alloy.
. It requires an extensive porous coating to promote immediate osteoinduction in the sclerotic diaphysis.

Correct Answer & Explanation

. It achieves rotational stability through diaphyseal splines and axial stability via the distal taper.

Explanation

In severe metaphyseal bone loss (Paprosky IIIB), modular fluted tapered stems bypass the proximal deficiency to achieve stable diaphyseal fixation. The longitudinal flutes (splines) cut into the cortical bone to provide rotational stability, while the tapered design engages the diaphysis to provide axial stability and prevent subsidence.

Question 2488

Topic: 3. Adult Reconstruction (Hip & Knee)
During the FRCS (Tr & Orth) exam, a scenario is presented involving a 78-year-old patient with multiple comorbidities requiring a total hip arthroplasty. The examiner asks about the most appropriate method for assessing the patient's capacity to consent for surgery. Which of the following is the 'gold standard' principle to adhere to?
. A formal psychiatric assessment is always required for elderly patients.
. Capacity is a 'once-and-for-all' assessment, valid indefinitely.
. The patient must understand all potential complications, no matter how rare.
. Capacity is time- and decision-specific, assessed at the time of the decision.
. Family consent is legally binding if the patient is deemed vulnerable.

Correct Answer & Explanation

. Capacity is time- and decision-specific, assessed at the time of the decision.

Explanation

Capacity to consent is time- and decision-specific. This means it must be assessed in relation to the specific decision at hand (e.g., consenting for a total hip arthroplasty) and at the time the decision is being made, as capacity can fluctuate. A formal psychiatric assessment is not always required; the initial assessment is typically made by the treating clinician. Capacity is not a 'once-and-for-all' assessment. Patients need to understand the material information, including significant risks, but not every single rare complication. Family consent is not legally binding in an adult with capacity; it's only sought if the patient lacks capacity and is often for 'best interests' decisions, not consent in the legal sense.

Question 2489

Topic: 3. Adult Reconstruction (Hip & Knee)

A candidate is discussing common complications in orthopedic surgery. The examiner asks about the most effective single strategy for preventing venous thromboembolism (VTE) in high-risk orthopedic patients undergoing major lower limb surgery. Which of the following is considered most effective when used correctly?

. Early mobilization alone.
. Graduated compression stockings.
. Intermittent pneumatic compression devices.
. Low molecular weight heparin (LMWH) prophylaxis.
. Aspirin monotherapy.

Correct Answer & Explanation

. Low molecular weight heparin (LMWH) prophylaxis.

Explanation

For high-risk orthopedic patients undergoing major lower limb surgery, pharmacological prophylaxis (e.g., LMWH) is generally considered the most effective single strategy. While early mobilization, graduated compression stockings, and intermittent pneumatic compression devices are important adjuncts, pharmacological agents have the strongest evidence for significant reduction in VTE events in this population. Aspirin monotherapy has some evidence, particularly in specific settings like total knee arthroplasty, but LMWH or direct oral anticoagulants (DOACs) are often considered first-line for broader high-risk orthopedic procedures due to stronger efficacy data.

Question 2490

Topic: 3. Adult Reconstruction (Hip & Knee)

When performing a hip arthroplasty, the surgeon aims to restore native hip biomechanics. Which parameter is considered most critical to prevent impingement and dislocation?

. Leg length equality.
. Offset restoration.
. Cup inclination and anteversion.
. Stem size and version.
. Patient's post-operative activity level.

Correct Answer & Explanation

. Cup inclination and anteversion.

Explanation

Cup inclination and anteversion are paramount in preventing impingement and dislocation in total hip arthroplasty. Incorrect positioning can lead to either anterior or posterior instability. While offset restoration and leg length equality are important for gait, muscle function, and patient satisfaction, and stem size/version are also critical, the orientation of the acetabular component is arguably the most critical factor for stability in isolation. Patient activity level influences risk but is not a surgical parameter.

Question 2491

Topic: 3. Adult Reconstruction (Hip & Knee)

Which structure is most vulnerable to injury during a standard posterior approach to the hip (e.g., for total hip arthroplasty)?

. Femoral nerve.
. Obturator nerve.
. Sciatic nerve.
. Superior gluteal nerve.
. Inferior gluteal artery.

Correct Answer & Explanation

. Sciatic nerve.

Explanation

The sciatic nerve is the most vulnerable major nerve during a standard posterior approach to the hip. It lies in close proximity to the posterior aspect of the hip joint, superficial to the short external rotators (which are often detached and reattached). Care must be taken during dissection, retraction, and component placement to avoid traction or direct injury. The femoral and obturator nerves are anterior, and the gluteal nerves/vessels are more superior or anterior-superior.

Question 2492

Topic: 3. Adult Reconstruction (Hip & Knee)

A 12-year-old boy presents with an acute-on-chronic slipped upper femoral epiphysis (SUFE). He is unable to weight-bear even with crutches. According to the Loder classification, what is his primary risk regarding complications?

. A 50% risk of chondrolysis regardless of treatment
. A lower risk of avascular necrosis (AVN) compared to stable SUFE
. A high risk of early-onset osteoarthritis without AVN
. An up to 47% risk of avascular necrosis (AVN) of the femoral head
. Femoral nerve palsy secondary to hematoma

Correct Answer & Explanation

. An up to 47% risk of avascular necrosis (AVN) of the femoral head

Explanation

Inability to weight-bear defines an unstable SUFE in the Loder classification. Unstable slips carry a high risk of avascular necrosis (typically 20-47%), significantly altering the prognosis compared to stable slips.

Question 2493

Topic: 3. Adult Reconstruction (Hip & Knee)

In an Adult Pathology viva, you are asked about Periprosthetic Joint Infection (PJI). According to the 2018 International Consensus Meeting (ICM) criteria, which of the following is considered a major criterion for diagnosing PJI?

. Two positive periprosthetic cultures with phenotypically identical organisms
. Elevated serum C-reactive protein (CRP) and D-dimer
. Positive leukocyte esterase on synovial fluid dipstick
. Elevated synovial fluid polymorphonuclear (PMN) percentage
. A single positive tissue culture with a virulent organism

Correct Answer & Explanation

. Two positive periprosthetic cultures with phenotypically identical organisms

Explanation

The ICM major criteria for PJI are the presence of a sinus tract communicating with the prosthesis or two positive tissue/fluid cultures isolating the same organism. Minor criteria include elevated inflammatory markers and synovial white cell counts.

Question 2494

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman presents with acute onset knee pain, swelling, and erythema 3 weeks after an uncomplicated total knee arthroplasty. Her CRP is 180 mg/L. Joint aspirate yields turbid fluid with 65,000 WBCs/mcL (90% neutrophils). Which of the following is the most appropriate initial management?

. Intravenous antibiotics for 6 weeks followed by single-stage revision
. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. Immediate two-stage revision arthroplasty
. Suppressive oral antibiotic therapy
. Arthroscopic washout and drainage

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange

Explanation

For acute periprosthetic joint infections occurring within 4 weeks of index surgery, Debridement, Antibiotics, and Implant Retention (DAIR) with modular component exchange is the treatment of choice. This provides a balance of eradicating infection while minimizing the morbidity of a full revision.

Question 2495

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty for a severe valgus deformity, you find that the lateral structures remain tight in extension after bone cuts. Which of the following structures should be released first to correct the valgus deformity in extension?

. Medial collateral ligament
. Posterior cruciate ligament
. Iliotibial (IT) band
. Popliteus tendon
. Lateral collateral ligament

Correct Answer & Explanation

. Iliotibial (IT) band

Explanation

In a valgus knee, the iliotibial (IT) band is the primary tether to correction in extension. Sequential release of the lateral structures typically begins with the IT band (or lateral capsule), followed by the popliteus, and then the LCL if necessary.

Question 2496

Topic: 3. Adult Reconstruction (Hip & Knee)

In the adult elective orthopedics viva, you are shown a radiograph of a 45-year-old patient who underwent a total hip arthroplasty with a ceramic-on-ceramic bearing. They now complain of a new-onset squeaking noise when walking. Which of the following factors is most strongly associated with this phenomenon?

. An undersized femoral stem causing micro-motion.
. Excessive acetabular cup anteversion and edge loading.
. Use of an un-cemented instead of a cemented stem.
. Incomplete seating of the ceramic liner leading to malseating.
. The use of a larger femoral head size (e.g., 36mm).

Correct Answer & Explanation

. Excessive acetabular cup anteversion and edge loading.

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is strongly associated with edge loading, often due to component malposition such as excessive cup steepness or anteversion. This leads to stripe wear and disruption of the fluid film lubrication.

Question 2497

Topic: 3. Adult Reconstruction (Hip & Knee)

In the context of bearing surfaces in total hip arthroplasty, which of the following best describes the toughening mechanism utilized in Zirconia-Toughened Alumina (ZTA) ceramics?

. Phase transformation from tetragonal to monoclinic structure
. Cross-linking via gamma irradiation
. Increased grain size leading to crack deflection
. Transformation from monoclinic to cubic structure
. Sacrificial surface oxidation preventing crack propagation

Correct Answer & Explanation

. Phase transformation from tetragonal to monoclinic structure

Explanation

Zirconia-Toughened Alumina (ZTA) ceramics utilize a mechanism known as 'phase transformation toughening'. When a micro-crack begins to propagate through the material, the localized stress at the crack tip induces the metastable tetragonal zirconia particles to transform into a monoclinic phase. This transformation is accompanied by a 4-5% volume expansion, which places the crack tip under compressive stress and halts its propagation, significantly increasing the fracture toughness of the bearing.

Question 2498

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty for a severe varus deformity, the knee remains tight medially in both flexion and extension after removal of the osteophytes. According to standard sequential medial release techniques, which structure should be released first?

. Pes anserinus
. Deep medial collateral ligament (MCL)
. Superficial medial collateral ligament (MCL)
. Posteromedial corner capsule
. Semimembranosus insertion

Correct Answer & Explanation

. Deep medial collateral ligament (MCL)

Explanation

In the standard sequential release for a varus knee during TKA, osteophytes are removed first. If the knee remains tight in both flexion and extension, the deep MCL (meniscotibial ligament) is typically the first structure released off the proximal medial tibia. If further release is needed, the posteromedial capsule is released (tight in extension), followed by the semimembranosus. The superficial MCL is released last, usually starting from its distal insertion, if severe varus persists. The pes anserinus is generally preserved unless extreme release is required.

Question 2499

Topic: 3. Adult Reconstruction (Hip & Knee)

The scaphoid bone is highly susceptible to avascular necrosis due to its tenuous blood supply. The primary vascular supply to the proximal pole of the scaphoid is derived from the dorsal carpal branch of the radial artery. Where does this branch typically enter the scaphoid?

. Directly into the proximal pole articular cartilage
. Through the volar tubercle
. Along the dorsal ridge, distal to the waist
. Via the scapholunate interosseous ligament
. At the distal articular surface near the trapezium

Correct Answer & Explanation

. Along the dorsal ridge, distal to the waist

Explanation

The primary blood supply to the scaphoid comes from the dorsal carpal branch of the radial artery, which accounts for 70-80% of the bone's vascularity. This vessel enters the scaphoid through a series of foramina located along the dorsal ridge, which is distal to the waist of the scaphoid. The blood then flows in a retrograde fashion to supply the proximal pole. Fractures through the waist interrupt this retrograde flow, putting the proximal pole at high risk for avascular necrosis.

Question 2500

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) has significantly reduced the rate of osteolysis compared to conventional polyethylene. Which of the following manufacturing processes is utilized to eliminate free radicals and improve the oxidation resistance of HXLPE, albeit at the cost of decreasing its fatigue strength?

. Cold irradiation in an oxygen-rich environment
. Remelting the polyethylene above its melting temperature
. Annealing the polyethylene below its melting temperature
. Addition of barium sulfate during extrusion
. Ethylene oxide sterilization

Correct Answer & Explanation

. Remelting the polyethylene above its melting temperature

Explanation

Irradiation of polyethylene causes cross-linking, which improves wear resistance but also generates free radicals that can lead to oxidation and degradation. To eliminate these free radicals, the polyethylene is thermally treated. Remelting (heating above the melting point, ~135 degrees Celsius) eliminates all free radicals but decreases crystallinity and fatigue strength. Annealing (heating below the melting point) preserves fatigue strength but leaves some trapped free radicals.

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