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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 136 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 2701

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary posterior-stabilized total knee arthroplasty (TKA), the surgeon evaluates the joint gaps after making the initial bony cuts. The knee is perfectly balanced and symmetric in full extension, but the flexion gap is unacceptably tight. What is the most appropriate surgical step to balance the knee?

. Release the posterior capsule
. Recut the distal femur to remove more bone
. Decrease the size of the femoral component using an anterior referencing system
. Increase the size of the femoral component
. Recut the proximal tibia with less posterior slope

Correct Answer & Explanation

. Decrease the size of the femoral component using an anterior referencing system

Explanation

A knee that is balanced in extension but tight in flexion requires an intervention that selectively increases the flexion gap. Decreasing the size of the femoral component (when using an anterior referencing system) will take more posterior condylar bone, thereby increasing the flexion gap without affecting the extension gap. Alternatively, increasing the posterior slope of the tibial cut increases the flexion gap more than the extension gap. Releasing the posterior capsule or cutting more distal femur would primarily affect the extension gap.

Question 2702

Topic: 3. Adult Reconstruction (Hip & Knee)

To minimize the risk of dislocation following primary total hip arthroplasty (THA), Lewinnek defined a "safe zone" for the orientation of the acetabular component. Which of the following represents the classic Lewinnek safe zone parameters for cup placement?

. 30 to 50 degrees of inclination and 5 to 25 degrees of retroversion
. 30 to 50 degrees of inclination and 5 to 25 degrees of anteversion
. 40 to 60 degrees of inclination and 10 to 30 degrees of anteversion
. 20 to 40 degrees of inclination and 0 to 15 degrees of anteversion
. 45 to 65 degrees of inclination and 15 to 35 degrees of retroversion

Correct Answer & Explanation

. 30 to 50 degrees of inclination and 5 to 25 degrees of anteversion

Explanation

Lewinnek's classic 'safe zone' for acetabular cup orientation is defined as 40 +/- 10 degrees of inclination (abduction angle) and 15 +/- 10 degrees of anteversion. Therefore, the range is 30 to 50 degrees of inclination and 5 to 25 degrees of anteversion. Implants placed outside this zone have traditionally been associated with a significantly higher risk of dislocation, though modern literature emphasizes combined anteversion and spinopelvic mobility as well.

Question 2703

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty using measured resection principles, the surgeon notes that the knee is well-balanced in extension but excessively tight in flexion. Which of the following is the most appropriate intraoperative adjustment?

. Increase the distal femoral resection
. Decrease the distal femoral resection
. Decrease the size of the femoral component using an anterior referencing system
. Upsize the femoral component
. Resect additional bone from the proximal tibia

Correct Answer & Explanation

. Decrease the size of the femoral component using an anterior referencing system

Explanation

A knee that is tight in flexion but balanced in extension has an isolated flexion gap mismatch (flexion gap is too tight). To increase the flexion gap without altering the extension gap, the surgeon can decrease the size of the femoral component. When using an anterior referencing system, downsizing the femoral component results in more posterior condylar bone resection, effectively opening the flexion gap.

Question 2704

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following bearing surface combinations in Total Hip Arthroplasty (THA) is associated with the lowest linear wear rate, but carries a unique risk of catastrophic fracture and 'squeaking'?

. Cobalt-chrome on highly cross-linked polyethylene
. Oxidized zirconium on highly cross-linked polyethylene
. Ceramic on ceramic
. Ceramic on conventional polyethylene
. Cobalt-chrome on cobalt-chrome

Correct Answer & Explanation

. Ceramic on ceramic

Explanation

Ceramic-on-ceramic (CoC) bearings have the lowest volumetric and linear wear rates among all bearing surfaces in THA. However, they carry specific complications not seen with metal-on-polyethylene, including the risk of catastrophic ceramic fracture and the phenomenon of 'squeaking' during range of motion.

Question 2705

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, after making the bone cuts and inserting trial components, the knee is found to be symmetrically tight in both full extension and 90 degrees of flexion. Which of the following is the most appropriate next step in management?

. Cut additional distal femur
. Decrease the thickness of the tibial polyethylene insert
. Cut additional posterior femur
. Increase the posterior slope of the tibial cut
. Recut the tibia to increase varus alignment

Correct Answer & Explanation

. Decrease the thickness of the tibial polyethylene insert

Explanation

Symmetrical tightness in both flexion and extension indicates that the overall joint space is too small (both flexion and extension gaps are too tight). The most appropriate and simplest solution is to decrease the thickness of the tibial polyethylene insert or resect more tibial bone. Cutting additional distal femur would only address the extension gap.

Question 2706

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active male underwent a total hip arthroplasty using a ceramic-on-ceramic bearing surface. Two years postoperatively, he complains of an audible squeaking sound during hip flexion. Radiographic evaluation shows normal implant fixation. Which of the following component positions is most strongly associated with the development of squeaking in this bearing type?

. Excessive femoral anteversion
. Excessive acetabular cup anteversion
. Acetabular cup retroversion
. Decreased femoral offset
. Excessive acetabular cup inclination and edge loading

Correct Answer & Explanation

. Excessive acetabular cup inclination and edge loading

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is a well-documented complication. It is strongly associated with component malposition, specifically excessive acetabular cup inclination (steep cup) and extremes of anteversion/retroversion. This malposition leads to stripe wear, edge loading, and loss of fluid-film lubrication, culminating in the audible squeak.

Question 2707

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old woman presents with groin pain and a palpable mass 4 years after a metal-on-metal total hip arthroplasty. Serum cobalt and chromium levels are significantly elevated. A Metal Artifact Reduction Sequence (MARS) MRI shows a large cystic periarticular collection. Histologic analysis of the tissue during revision surgery would most likely demonstrate:

. Abundant neutrophils and Gram-positive cocci
. Birefringent particulate wear debris with macrophage infiltration
. Perivascular lymphocytic infiltrate with plasma cells and tissue necrosis
. Sheets of atypical plasma cells with kappa light chain restriction
. Non-caseating granulomas with Langhans giant cells

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate with plasma cells and tissue necrosis

Explanation

Adverse Local Tissue Reaction (ALTR) or Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions (ALVAL) in metal-on-metal hips is a type IV delayed hypersensitivity reaction. Histology characteristically shows a perivascular lymphocytic infiltrate, plasma cells, and tissue necrosis, unlike the predominantly macrophage-mediated response seen with polyethylene particulate wear.

Question 2708

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria for Periprosthetic Joint Infection (PJI), which of the following findings alone represents a major criterion confirming the diagnosis of PJI in a total knee arthroplasty?

. Elevated serum CRP > 10 mg/L and ESR > 30 mm/hr
. Synovial fluid WBC count of 4,000 cells/mcL
. A single positive intraoperative culture for Staphylococcus epidermidis
. A sinus tract communicating with the prosthesis
. Positive leukocyte esterase on a synovial fluid dipstick

Correct Answer & Explanation

. A sinus tract communicating with the prosthesis

Explanation

According to the ICM criteria, the two major criteria for PJI (either of which confirms the diagnosis alone) are: 1) A sinus tract communicating with the prosthesis, or 2) Two positive periprosthetic cultures with phenotypically identical organisms. The other options are minor criteria that contribute to a scoring system.

Question 2709

Topic: 3. Adult Reconstruction (Hip & Knee)

In posterior-stabilized (PS) total knee arthroplasty, the cam-and-post mechanism is designed to substitute for the resected posterior cruciate ligament (PCL). Which of the following best describes the intended kinematic effect of cam-post engagement during deep flexion?

. It forces anterior translation of the femur on the tibia
. It induces mandatory internal rotation of the femur on the tibia
. It induces posterior femoral rollback, increasing the moment arm of the quadriceps and improving maximal flexion
. It prevents varus/valgus lift-off during the swing phase of gait
. It acts as the primary constraint against anterior tibial translation in extension

Correct Answer & Explanation

. It induces posterior femoral rollback, increasing the moment arm of the quadriceps and improving maximal flexion

Explanation

In a PS TKA, the cam on the femoral component engages the post on the tibial polyethylene during knee flexion. This engagement drives the femur posteriorly on the tibia (posterior femoral rollback), preventing posterior impingement and increasing the moment arm of the extensor mechanism, which facilitates deep flexion.

Question 2710

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with groin pain and swelling. A MARS MRI demonstrates a cystic soft tissue mass around the hip. A revision is performed, and histologic examination of the tissue reveals aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL). This histological finding is primarily characterized by:

. Sheets of polymorphonuclear neutrophils
. Perivascular lymphocytic infiltrate and tissue necrosis
. Extensive caseating granulomas with Langhans giant cells
. Birefringent polyethylene wear debris within macrophages
. Malignant spindle cells with high mitotic figures

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate and tissue necrosis

Explanation

ALVAL (Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion) is a delayed type IV hypersensitivity reaction to metal ions (cobalt and chromium) seen in metal-on-metal hip arthroplasty or trunnionosis. Histologically, it is characterized by a perivascular lymphocytic infiltrate, macrophage accumulation, and varying degrees of tissue necrosis.

Question 2711

Topic: 3. Adult Reconstruction (Hip & Knee)

In the design of a posterior-stabilized (PS) total knee arthroplasty (TKA), the tibial polyethylene insert features a central post that interacts with a cam on the femoral component. What is the primary biomechanical purpose of the cam-and-post mechanism during deep knee flexion?

. To prevent varus and valgus instability
. To substitute for the anterior cruciate ligament
. To enforce posterior femoral rollback
. To restrict knee hyperextension
. To increase the patellofemoral moment arm

Correct Answer & Explanation

. To enforce posterior femoral rollback

Explanation

In a posterior-stabilized (PS) TKA, the posterior cruciate ligament (PCL) is resected. The central cam on the femoral component engages the tibial post during flexion (usually around 70 degrees) to substitute for the PCL. This engagement mechanically drives the femur posteriorly on the tibia (enforcing posterior femoral rollback), which improves maximal knee flexion and prevents posterior subluxation of the tibia.

Question 2712

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female presents with an audible 'squeaking' sound coming from her hip 3 years after a Total Hip Arthroplasty. Radiographs show a well-fixed, ceramic-on-ceramic bearing surface. Which of the following component position factors is most strongly associated with the development of this phenomenon?

. Decreased acetabular component anteversion
. Increased femoral stem offset
. Acetabular component retroversion
. Acetabular component malposition, specifically excessive inclination leading to edge loading
. Femoral stem retroversion

Correct Answer & Explanation

. Acetabular component malposition, specifically excessive inclination leading to edge loading

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading of the bearing surfaces. Edge loading is most frequently caused by acetabular component malposition, particularly excessive inclination (abduction) or version abnormalities, leading to loss of fluid film lubrication and stripe wear on the ceramic.

Question 2713

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized Total Knee Arthroplasty, trial reduction reveals that the knee is well-balanced in full extension but is excessively tight in 90 degrees of flexion. Which of the following is the most appropriate intraoperative option to exclusively address this imbalance?

. Resect additional distal femur
. Upsize the femoral component
. Downsize the femoral component (decrease anteroposterior dimension)
. Use a thinner polyethylene insert
. Release the posterior capsule

Correct Answer & Explanation

. Downsize the femoral component (decrease anteroposterior dimension)

Explanation

When the flexion gap is tight but the extension gap is balanced, the surgeon must increase the flexion gap independently. Downsizing the femoral component (which decreases the anteroposterior dimension of the femur) increases the flexion gap without altering the extension gap. Using a thinner insert would create instability in extension.

Question 2714

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female presents with progressive groin pain 4 years after undergoing a metal-on-metal total hip arthroplasty. Inflammatory markers are normal, and radiographs show no loosening. A MARS MRI reveals a solid-cystic pseudotumor in the periprosthetic soft tissues. Serum cobalt and chromium levels are elevated. What histological finding is most characteristic of this condition?

. Extensive neutrophil infiltration with intracellular bacteria
. Massive sheet-like proliferation of polyethylene wear debris
. Perivascular lymphocytic infiltrate with high endothelial venules
. Non-caseating granulomas with Langhans giant cells
. Plasmacytosis with prominent Russell bodies

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate with high endothelial venules

Explanation

Adverse Local Tissue Reaction (ALTR) or ALVAL (Aseptic Lymphocytic Vasculitis-Associated Lesion) is characteristic of metal-on-metal hypersensitivity. Histology typically demonstrates a diffuse perivascular infiltrate of T-lymphocytes, high endothelial venules, and soft tissue necrosis. Neutrophils suggest acute infection, whereas non-caseating granulomas suggest sarcoid or mycobacterial infection.

Question 2715

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty for a valgus knee, trial implants are placed. The knee is balanced in flexion but remains significantly tight on the lateral side in full extension. Which of the following structures is the primary tether and should be released to address this specific asymmetry?

. Popliteus tendon
. Iliotibial band
. Lateral collateral ligament
. Posterior cruciate ligament
. Lateral gastrocnemius head

Correct Answer & Explanation

. Iliotibial band

Explanation

In the valgus knee, the iliotibial band (ITB) acts as a primary lateral tether in extension. If the knee is tight laterally in extension but balanced in flexion, the ITB should be released or lengthened (e.g., via pie-crusting). The popliteus is a primary lateral stabilizer in flexion; releasing it would affect the flexion gap more than the extension gap.

Question 2716

Topic: Total Hip Arthroplasty (THA)

In complex total hip arthroplasty, a dual mobility articulation may be utilized to decrease the risk of dislocation. The primary biomechanical mechanism by which a dual mobility construct prevents instability is:

. Decreased volumetric wear compared to standard bearings
. Increased jump distance
. Elimination of backside wear
. Increased lateral offset without modularity
. Prevention of trunnionosis

Correct Answer & Explanation

. Increased jump distance

Explanation

A dual mobility construct consists of a small femoral head captive within a larger polyethylene liner, which itself articulates freely within a highly polished metallic acetabular shell. This effectively increases the effective head size (the large poly liner acts as the head during extreme range of motion), thereby massively increasing the 'jump distance' required for the construct to dislocate.

Question 2717

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria for Periprosthetic Joint Infection (PJI), which of the following findings is considered a MAJOR criterion that independently confirms the diagnosis of PJI?

. Elevated serum C-reactive protein (CRP) > 10 mg/L
. Purulence in the affected joint observed intraoperatively
. A single positive intraoperative tissue culture
. A sinus tract communicating with the joint
. Elevated synovial white blood cell count > 3,000 cells/uL

Correct Answer & Explanation

. A sinus tract communicating with the joint

Explanation

The 2018 ICM criteria establish two major criteria for definitive diagnosis of PJI: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. Purulence, elevated inflammatory markers, and a single positive culture serve only as minor criteria.

Question 2718

Topic: Total Hip Arthroplasty (THA)

A 65-year-old man undergoes primary THA with a ceramic-on-ceramic bearing. At 2-year follow-up, he complains of a reproducible squeaking noise when walking. Which of the following factors is most strongly associated with squeaking in ceramic-on-ceramic total hip arthroplasty?

. Femoral offset less than 35mm
. Cup anteversion of 15 degrees
. Edge loading due to component malposition
. Use of a 28mm femoral head
. Body mass index less than 25

Correct Answer & Explanation

. Edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which typically occurs due to acetabular component malposition (such as steep inclination or improper anteversion). This leads to microseparation and stripe wear, producing the characteristic squeak.

Question 2719

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman presents 1 year after a posterior-stabilized total knee arthroplasty with a painful catching sensation when extending her knee from a flexed position. What is the most likely diagnosis?

. Patellar maltracking
. Patellar clunk syndrome
. Popliteus tendon impingement
. Aseptic loosening of the tibial tray
. Polyethylene wear

Correct Answer & Explanation

. Patellar clunk syndrome

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA. A fibrotic nodule forms on the undersurface of the quadriceps tendon and catches in the intercondylar box of the femoral component during active extension from a flexed position, producing a painful clunk.

Question 2720

Topic: 3. Adult Reconstruction (Hip & Knee)

According to Lewinnek, what is the historically described 'safe zone' for acetabular component positioning in total hip arthroplasty to minimize the risk of dislocation?

. 30° ± 10° inclination and 10° ± 10° anteversion
. 40° ± 10° inclination and 15° ± 10° anteversion
. 45° ± 10° inclination and 25° ± 10° anteversion
. 50° ± 10° inclination and 15° ± 10° anteversion
. 40° ± 10° inclination and 30° ± 10° anteversion

Correct Answer & Explanation

. 40° ± 10° inclination and 15° ± 10° anteversion

Explanation

The classic Lewinnek safe zone for acetabular cup placement is 40° ± 10° of lateral opening (inclination) and 15° ± 10° of anteversion. Cups placed outside this zone historically have a higher rate of dislocation, although recent literature questions the absolute validity of a single safe zone for all patients.

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