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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 131 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 2601

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary posterior-stabilized total knee arthroplasty (TKA), the surgeon checks the flexion and extension gaps. The knee achieves full, symmetric extension but is significantly tight in flexion, preventing achieving 90 degrees of flexion. What is the most appropriate step to balance the knee?

. Recut the distal femur to resect more bone
. Release the posterior cruciate ligament completely
. Decrease the femoral component size and resect more posterior condyle
. Upsize the tibial polyethylene insert
. Recut the proximal tibia to increase the posterior slope

Correct Answer & Explanation

. Decrease the femoral component size and resect more posterior condyle

Explanation

When a TKA is tight in flexion but balanced and full in extension, the flexion gap needs to be enlarged without altering the extension gap. Decreasing the femoral component size (which resects more posterior femoral condyle with an anterior referencing system, or shifts the component anteriorly with a posterior referencing system while using a smaller size) effectively increases the flexion gap. Increasing the posterior slope of the tibia can also increase the flexion gap but alters tibial geometry and is limited by component constraints. Releasing the PCL is not the answer because it is a posterior-stabilized TKA, so the PCL has already been resected. Recutting the distal femur affects only the extension gap.

Question 2602

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following bearing surface combinations in total hip arthroplasty exhibits the lowest volumetric wear rate, but carries the highest risk of catastrophic failure due to fracture?

. Metal-on-highly cross-linked polyethylene
. Ceramic-on-polyethylene
. Metal-on-metal
. Ceramic-on-ceramic
. Oxinium-on-highly cross-linked polyethylene

Correct Answer & Explanation

. Ceramic-on-ceramic

Explanation

Ceramic-on-ceramic (CoC) bearing surfaces have the lowest volumetric wear rates of all bearing combinations. However, due to the brittle nature of the ceramic material, they carry a unique risk of catastrophic component fracture, as well as a risk of audible 'squeaking' during movement.

Question 2603

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, the surgeon performs gap balancing using tensioners. The knee is noted to be symmetric and well-balanced in full extension, but significantly tight in 90 degrees of flexion. Which of the following is the most appropriate intraoperative adjustment to achieve a balanced gap?

. Recut the distal femur to remove more bone
. Release the posterior cruciate ligament
. Downsize the femoral component
. Release the medial collateral ligament
. Increase the thickness of the polyethylene insert

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is tight in flexion but balanced in extension indicates an isolated tight flexion gap. Downsizing the femoral component (often utilizing an anterior referencing guide to avoid notching) decreases the anteroposterior dimension of the femur by taking more posterior condylar bone. This opens the flexion gap without altering the distal femoral cut (which controls the extension gap).

Question 2604

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old active male underwent a total hip arthroplasty using a ceramic-on-ceramic bearing surface two years ago. He now presents complaining of a high-pitched 'squeaking' sound emanating from the hip during walking, bending, and stair climbing. Which of the following component malpositions is most strongly associated with this phenomenon?

. Excessive cup anteversion and vertical cup inclination
. Cup retroversion and excessive cup adduction
. Femoral stem retroversion
. Excessive femoral offset
. Inadequate limb length restoration

Correct Answer & Explanation

. Excessive cup anteversion and vertical cup inclination

Explanation

Audible 'squeaking' is a unique complication of ceramic-on-ceramic (CoC) bearing surfaces. It is most strongly associated with edge-loading of the components, which disrupts fluid film lubrication. Edge-loading is most commonly caused by component malposition, specifically excessive cup abduction (steep vertical cup inclination) and/or excessive cup anteversion.

Question 2605

Topic: 3. Adult Reconstruction (Hip & Knee)
In total hip arthroplasty, periprosthetic osteolysis is primarily driven by a macrophage response to ultra-high-molecular-weight polyethylene (UHMWPE) wear particles. Which mechanism of wear is most responsible for generating the billions of submicron particles (0.1-1.0 micrometers) typically seen in a well-functioning metal-on-polyethylene articulation?
. Third-body wear
. Abrasive wear
. Adhesive wear
. Fatigue wear
. Corrosive wear

Correct Answer & Explanation

. Adhesive wear

Explanation

Adhesive wear is the primary mechanism generating the biologically active submicron polyethylene particles in a well-functioning THA. It occurs when micro-asperities on the metal or ceramic head temporarily weld to the polyethylene surface and shear off during motion. Abrasive wear creates larger particles, and fatigue wear leads to delamination.

Question 2606

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male with a metal-on-metal total hip arthroplasty presents 5 years post-operatively with worsening groin pain and a palpable anterior soft tissue mass. Aspiration yields sterile, turbid fluid. Revision surgery is planned. Histological analysis of the pseudotumor (periprosthetic tissue) is most likely to demonstrate:

. Massive acute infiltration of polymorphonuclear leukocytes
. Birefringent particulate debris under polarized light with foreign body giant cells
. Extensive perivascular lymphocytic infiltration
. Sheets of lipid-laden macrophages (foam cells)
. Monoclonal B-cell proliferation

Correct Answer & Explanation

. Extensive perivascular lymphocytic infiltration

Explanation

The clinical scenario describes an Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion (ALVAL), a delayed Type IV hypersensitivity reaction uniquely associated with metal-on-metal bearings. The hallmark histological finding is a dense perivascular infiltrate of T-lymphocytes. Birefringent particles with giant cells are typical of polyethylene wear (macrophage-mediated osteolysis).

Question 2607

Topic: Total Hip Arthroplasty (THA)

A surgeon is templating for a primary Total Hip Arthroplasty (THA) and wishes to maximize the primary arc of motion to delay mechanical impingement of the components, thereby reducing dislocation risk. Which of the following geometric modifications to the implant will most effectively achieve this goal?

. Maximizing the head-to-neck ratio
. Minimizing the head-to-neck ratio
. Increasing the femoral neck diameter
. Using a skirted modular femoral head
. Decreasing the lateral femoral offset

Correct Answer & Explanation

. Maximizing the head-to-neck ratio

Explanation

The impingement-free primary arc of motion in a THA is mathematically driven by the head-to-neck ratio. Maximizing this ratio (by using a larger diameter femoral head and a smaller diameter femoral neck) allows for greater excursion of the neck before it contacts the acetabular rim. Skirted heads and thicker necks decrease this ratio, causing earlier impingement and increasing dislocation risk.

Question 2608

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old female with a history of a metal-on-metal total hip arthroplasty presents with groin pain and a palpable anterior mass. Aspiration yields sterile fluid, and revision surgery is performed. Histopathological examination of the periprosthetic tissue is most likely to reveal which of the following?

. Extensive polymorphonuclear leukocyte infiltration
. A dense monocyte/macrophage response laden with birefringent particles
. An aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Non-caseating granulomas with central necrosis
. Sheets of eosinophils and mast cells

Correct Answer & Explanation

. An aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-metal implants are characterized histologically by an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). This is a Type IV delayed hypersensitivity response to metal ions (cobalt and chromium), distinct from the macrophage-dominated response seen in traditional polyethylene wear (particle disease).

Question 2609

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male is evaluated for a medial unicompartmental knee arthroplasty (UKA) due to isolated medial compartment osteoarthritis. Which of the following is considered an absolute contraindication to proceeding with a medial UKA?

. Age greater than 55 years
. Body Mass Index of 30
. A flexible varus deformity of 5 degrees
. Inflammatory arthritis (e.g., Rheumatoid Arthritis)
. Intact anterior cruciate ligament (ACL)

Correct Answer & Explanation

. Inflammatory arthritis (e.g., Rheumatoid Arthritis)

Explanation

Absolute contraindications for unicompartmental knee arthroplasty (UKA) include inflammatory arthropathies (such as Rheumatoid Arthritis), absent or deficient anterior cruciate ligament (though some modern debate exists, historically it is an absolute contraindication), tri-compartmental arthritis, fixed varus deformity > 10 degrees, fixed valgus > 5 degrees, and flexion contracture > 15 degrees. An intact ACL is an indication, not a contraindication.

Question 2610

Topic: Total Hip Arthroplasty (THA)

A 60-year-old male undergoes a total hip arthroplasty using a ceramic-on-ceramic bearing. Two years postoperatively, he complains of an audible squeaking sound from the hip during walking, but denies pain. Which of the following factors is most strongly mechanically associated with squeaking in ceramic-on-ceramic THA?

. Acetabular component retroversion
. Use of a smaller diameter femoral head
. Impingement and edge loading
. Increased femoral stem offset
. Use of a highly cross-linked polyethylene liner

Correct Answer & Explanation

. Impingement and edge loading

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is multifactorial but is highly associated with edge loading due to component malposition, specifically acetabular cup malposition (steep cup inclination, excessive anteversion, or retroversion). This leads to impingement, micro-separation, and stripe wear, generating the characteristic squeaking sound.

Question 2611

Topic: Total Knee Arthroplasty (TKA)

Which of the following best describes the intended biomechanical advantage of femoral roll-back in a posterior stabilized (PS) total knee arthroplasty?

. It increases the patellofemoral contact forces.
. It anteriorly displaces the axis of rotation to improve extension.
. It improves maximum knee flexion by clearing the posterior femur from the posterior tibia.
. It allows the collateral ligaments to loosen in deep flexion.
. It prevents anterior tibial translation during early flexion.

Correct Answer & Explanation

. It improves maximum knee flexion by clearing the posterior femur from the posterior tibia.

Explanation

Femoral roll-back refers to the posterior translation of the femoral condyles on the tibial plateau during knee flexion. In a posterior stabilized (PS) TKA, the cam-post mechanism enforces this roll-back. The primary biomechanical advantage is that it shifts the contact point posteriorly, delaying impingement of the posterior femoral shaft on the posterior tibia, thereby increasing the maximum achievable knee flexion arc.

Question 2612

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a metal-on-polyethylene total hip arthroplasty (titanium stem, large-diameter cobalt-chromium head) performed 6 years ago presents with groin pain and a large hip effusion. Aspiration is negative for infection but reveals dark, blackish debris. Serum cobalt levels are significantly elevated, while serum chromium levels are normal. What is the most likely diagnosis?

. Aseptic loosening of the acetabular component
. Mechanically assisted crevice corrosion at the head-neck junction
. Polyethylene wear-induced osteolysis
. Galvanic corrosion at the stem-cement interface
. Undiagnosed low-virulence periprosthetic joint infection

Correct Answer & Explanation

. Mechanically assisted crevice corrosion at the head-neck junction

Explanation

The clinical presentation of a symptomatic effusion, black tissue debris, and a high cobalt/normal chromium ratio in a metal-on-polyethylene THA is classic for trunnionosis—specifically mechanically assisted crevice corrosion (MACC) at the modular head-neck junction (the trunnion). It is more common with large femoral heads on titanium stems.

Question 2613

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, the trial reduction reveals that the knee is well-balanced and symmetric in extension, but it is too tight in flexion, preventing adequate range of motion. Which of the following surgical modifications is the most appropriate next step to balance the knee?

. Perform a more aggressive distal femoral resection
. Downsize the femoral component utilizing an anterior referencing system
. Upsize the femoral component utilizing a posterior referencing system
. Release the posterior capsule from the femur
. Use a thicker polyethylene insert

Correct Answer & Explanation

. Downsize the femoral component utilizing an anterior referencing system

Explanation

A knee that is tight in flexion but balanced in extension requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component using anterior referencing will remove more bone from the posterior condyles, effectively increasing the flexion gap while leaving the distal cut (extension gap) unaffected.

Question 2614

Topic: Total Hip Arthroplasty (THA)

A 55-year-old man who underwent a ceramic-on-ceramic total hip arthroplasty 3 years ago complains of a loud squeaking noise from his hip with bending and walking. Radiographs are unremarkable. Which of the following component positions is most strongly associated with this phenomenon?

. Acetabular component inclination of 35 degrees
. Acetabular component inclination of 55 degrees
. Femoral stem retroversion of 10 degrees
. Femoral stem anteversion of 15 degrees
. Increased lateral femoral offset

Correct Answer & Explanation

. Acetabular component inclination of 55 degrees

Explanation

Squeaking in ceramic-on-ceramic (CoC) THA is strongly correlated with edge loading and subsequent stripe wear of the ceramic components. Edge loading is most frequently caused by malpositioning of the acetabular component, particularly cup inclination greater than 45-50 degrees, or excessive anteversion/retroversion. An inclination of 55 degrees significantly increases the risk of edge loading and squeaking.

Question 2615

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, the trial components are inserted. The surgeon notes that the knee is well-balanced and stable in full extension, but the joint is excessively tight and difficult to bring past 90 degrees of flexion. Which of the following intraoperative maneuvers is the most appropriate next step to resolve this specific kinematic mismatch?

. Resect additional bone from the distal femur
. Downsize the femoral component and use a thicker polyethylene insert
. Downsize the femoral component
. Release the posterior cruciate ligament
. Recut the proximal tibia with less posterior slope

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is balanced in extension but tight in flexion has a tight flexion gap. To increase the flexion gap without affecting the extension gap, the surgeon must either downsize the femoral component (which decreases the anterior-posterior dimension and thus the posterior condylar offset) or increase the posterior slope of the tibial cut. Since the knee is a posterior-stabilized design, the PCL is already resected. Resecting more distal femur would loosen the extension gap. Simply downsizing the femoral component effectively opens the flexion gap.

Question 2616

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male underwent a primary total hip arthroplasty utilizing a ceramic-on-ceramic bearing. At 2-year follow-up, he complains of an audible 'squeaking' noise when walking, though he has no pain. Which factor is most strongly associated with the development of squeaking in this specific bearing couple?

. Increased femoral offset
. Acetabular component retroversion or malposition
. Use of a 28 mm rather than 36 mm femoral head
. Titanium femoral stem
. Excessive polyethylene wear

Correct Answer & Explanation

. Acetabular component retroversion or malposition

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading caused by acetabular component malposition (e.g., excessive anteversion, retroversion, or high inclination angles), which leads to loss of fluid film lubrication and subsequent stripe wear.

Question 2617

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon utilizes tensioners and notes that the knee is excessively tight in flexion but correctly balanced in extension. Which of the following steps is the most appropriate maneuver to correct this isolated flexion gap imbalance?

. Increase the distal femoral resection
. Decrease the posterior slope of the tibial cut
. Resect more posterior femoral condyle (downsize the femoral component)
. Release the posterior cruciate ligament completely
. Recut the tibia with increased varus

Correct Answer & Explanation

. Resect more posterior femoral condyle (downsize the femoral component)

Explanation

An isolated tight flexion gap indicates that too much bone or implant is occupying the space when the knee is flexed. Because the extension gap is fine, the distal femur and tibial cuts are correct in those planes. To selectively enlarge the flexion gap, the surgeon can downsize the femoral component (which resects more posterior condylar bone), increase the posterior slope of the tibial cut, or release the PCL if it is retained.

Question 2618

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary biological advantage of using highly cross-linked polyethylene (HXLPE) compared to conventional polyethylene in total hip arthroplasty?

. Increased resistance to fatigue crack propagation
. Decreased generation of submicron-sized wear debris
. Increased ultimate tensile strength
. Enhanced oxidative stability without the need for thermal treatment
. Decreased risk of catastrophic liner dissociation

Correct Answer & Explanation

. Decreased generation of submicron-sized wear debris

Explanation

The primary advantage of highly cross-linked polyethylene is the significant reduction in volumetric wear and the consequent decrease in the generation of submicron wear debris, which is the primary driver of macrophage-induced osteolysis. However, the cross-linking and subsequent remelting processes decrease its fatigue crack resistance, ductility, and ultimate tensile strength.

Question 2619

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 making the initial bone cuts and removing all medial osteophytes. Which of the following medial structures should be released next to balance the gaps symmetrically?

. Superficial medial collateral ligament (sMCL)
. Deep medial collateral ligament (dMCL)
. Pes anserinus tendons
. Semimembranosus tendon
. Posterior cruciate ligament (PCL)

Correct Answer & Explanation

. Superficial medial collateral ligament (sMCL)

Explanation

In a stepwise medial release for a varus knee, osteophytes are removed first. If the joint remains tight in both flexion and extension, the deep MCL (which is often inherently released during a standard medial tibial exposure) and the posteromedial capsule are addressed next. The superficial MCL (sMCL) is preserved initially and is only progressively released off its tibial insertion if tightness persists after deep MCL/posteromedial corner release.

Question 2620

Topic: 3. Adult Reconstruction (Hip & Knee)
Which method of cross-linking and sterilization for ultra-high-molecular-weight polyethylene (UHMWPE) components is most associated with late oxidative degradation, subsurface delamination, and premature failure in total hip arthroplasty?
. Gamma irradiation in an inert gas environment
. Gamma irradiation in air
. Ethylene oxide sterilization
. Gas plasma sterilization
. Electron beam irradiation with post-irradiation remelting

Correct Answer & Explanation

. Gamma irradiation in air

Explanation

Gamma irradiation in air produces free radicals within the polyethylene. When exposed to oxygen in vivo or during shelf storage, these free radicals lead to chain scission and oxidative degradation. This process severely weakens the mechanical properties of the polyethylene, causing subsurface delamination, pitting, and premature wear.

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