Menu

3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 256 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 5101

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a metal-on-polyethylene (MoP) THA presents 5 years postoperatively with sudden onset groin pain. Blood work reveals serum Cobalt levels significantly higher than Chromium levels. MRI with MARS sequencing shows a solid and cystic pseudotumor around the hip. What is the primary pathophysiologic mechanism for this failure?

. Type I immediate hypersensitivity reaction to titanium
. Mechanically assisted crevice corrosion at the head-neck junction
. Edge loading of the highly cross-linked polyethylene
. Third-body wear from residual cement mantles
. Galvanic corrosion at the stem-cement interface

Correct Answer & Explanation

. Type I immediate hypersensitivity reaction to titanium

Explanation

This presentation describes trunnionosis, which is caused by Mechanically Assisted Crevice Corrosion (MACC) at the modular head-neck junction. It classically presents with elevated serum Cobalt > Chromium (unlike bearing surface wear in Metal-on-Metal, where Co and Cr are elevated more equally) and can form Adverse Local Tissue Reactions (ALTR/pseudotumors) even in MoP bearings.

Question 5102

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a palpable, painful 'catch' and an audible pop during active extension of the knee from 40 degrees to 30 degrees following a posterior-stabilized (PS) Total Knee Arthroplasty (TKA). What is the most likely etiology?

. True patella baja resulting from joint line elevation
. Fibrous nodule at the superior pole of the patella engaging the intercondylar box
. Oversized tibial tray causing medial soft tissue impingement
. Excessive polyethylene wear of the tibial post
. Asymmetric gap balancing with a tight extension gap

Correct Answer & Explanation

. True patella baja resulting from joint line elevation

Explanation

This describes 'Patellar Clunk Syndrome', a complication unique to posterior-stabilized (PS) TKAs (especially earlier designs with a high intercondylar box ratio). It is caused by the formation of a fibrous nodule on the undersurface of the quadriceps tendon at the superior pole of the patella, which catches in the femoral intercondylar box during extension.

Question 5103

Topic: Total Knee Arthroplasty (TKA)

Intraoperatively during a primary TKA, the surgeon utilizes spacer blocks and finds that the flexion gap is excessively tight, but the extension gap is perfectly symmetric and balanced. Which of the following is the most appropriate surgical step to correct this kinematic mismatch?

. Resect an additional 2 mm of distal femur
. Release the posterior capsule
. Downsize the femoral component
. Increase the thickness of the polyethylene insert
. Perform an extensive release of the superficial MCL

Correct Answer & Explanation

. Resect an additional 2 mm of distal femur

Explanation

A tight flexion gap with a balanced extension gap means the AP dimension in flexion is too large. Downsizing the femoral component (which effectively resects more posterior femoral condyle when using anterior referencing) will increase the flexion gap without altering the extension gap.

Question 5104

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria for Periprosthetic Joint Infection (PJI), which of the following carries the highest diagnostic weight and qualifies as a definitive 'Major' criterion?

. Elevated synovial fluid alpha-defensin
. A single positive tissue culture for Staphylococcus epidermidis
. Positive synovial fluid leukocyte esterase (++ or greater)
. A sinus tract communicating with the joint
. Synovial fluid polymorphonuclear percentage (PMN%) > 80%

Correct Answer & Explanation

. Elevated synovial fluid alpha-defensin

Explanation

The 2018 ICM criteria establish two definitive (Major) criteria for PJI: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. The other options are minor criteria that contribute points toward the diagnosis.

Question 5105

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty, the surgeon utilizes a standard offset stem instead of a high offset stem, inadvertently decreasing the patient's native femoral offset by 15 mm. What is the most likely biomechanical consequence of this error?

. Increased abductor moment arm length
. Decreased joint reactive forces across the hip
. Increased stress on the medial femoral cortex
. Increased required abductor muscle force to maintain a level pelvis
. Decreased risk of prosthetic impingement

Correct Answer & Explanation

. Increased abductor moment arm length

Explanation

Decreasing femoral offset shortens the abductor moment arm. To maintain a level pelvis during the single-leg stance phase, the abductor muscles must generate significantly more force. This ultimately increases the overall joint reactive force across the hip and can lead to a Trendelenburg gait and increased wear.

Question 5106

Topic: Total Knee Arthroplasty (TKA)

Elevation of the joint line during TKA (often resulting from excessive distal femoral resection and using a thicker polyethylene insert) most commonly leads to which of the following complications?

. True patella alta
. Mid-flexion instability
. Hyperextension recurvatum
. Paradoxical anterior femoral sliding in extension
. A tight extension gap requiring posterior capsular release

Correct Answer & Explanation

. True patella alta

Explanation

Joint line elevation during TKA alters the isometry of the collateral ligaments. The ligaments become relatively lax in mid-flexion, causing mid-flexion instability. It also results in pseudo-patella baja (the patella is lower relative to the joint line, though the patellar tendon length is unchanged), which alters patellofemoral kinematics and can cause anterior knee pain.

Question 5107

Topic: 3. Adult Reconstruction (Hip & Knee)
A patient requires a femoral revision THA for aseptic loosening. Radiographs demonstrate extensive metaphyseal bone loss with the diaphyseal cortical bone remaining fully intact for only 3 cm distal to the tip of the current stem. According to the Paprosky femoral defect classification, what type of defect is present?
. Type II
. Type IIIA
. Type IIIB
. Type IV
. Type I

Correct Answer & Explanation

. Type IIIB

Explanation

In the Paprosky femoral defect classification: Type IIIA defects have >4 cm of intact diaphyseal bone available for distal fixation. Type IIIB defects have <4 cm of intact diaphyseal bone. Type IV defects have no functional diaphyseal bone (widened isthmus) requiring an extensively porous coated stem or impaction grafting. Since this patient has 3 cm intact, it is Type IIIB.

Question 5108

Topic: Total Hip Arthroplasty (THA)

Which of the following histological findings is pathognomonic for an Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion (ALVAL) in the setting of a failed metal-on-metal THA?

. Abundant neutrophils with intracellular bacteria
. Sheets of foamy macrophages containing birefringent polyethylene debris
. Perivascular lymphocytic infiltrates with tissue necrosis
. Non-caseating granulomas with giant cells
. Extensive acute fibrinoid necrosis entirely lacking lymphocytes

Correct Answer & Explanation

. Abundant neutrophils with intracellular bacteria

Explanation

ALVAL (Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion) is a Type IV delayed hypersensitivity reaction seen in metal-on-metal hip replacements. Histologically, it is defined by a heavy perivascular infiltrate of T-lymphocytes, macrophages, and varying degrees of tissue necrosis.

Question 5109

Topic: 3. Adult Reconstruction (Hip & Knee)

When evaluating a patient for a Unicompartmental Knee Arthroplasty (UKA), which of the following is considered a classic absolute contraindication?

. Age greater than 80 years
. Weight greater than 90 kg
. Absent anterior cruciate ligament (ACL)
. Patellofemoral chondromalacia without anterior knee pain
. A fixed flexion contracture of 10 degrees

Correct Answer & Explanation

. Age greater than 80 years

Explanation

Historically and classically, an absent or incompetent ACL is an absolute contraindication for a medial UKA because the altered kinematics lead to premature failure and progression of arthritis. Age and weight have been largely debunked as strict contraindications. Flexion contracture > 15 degrees is a contraindication (10 degrees is acceptable). Asymptomatic PF chondromalacia is not a contraindication.

Question 5110

Topic: Total Knee Arthroplasty (TKA)

Following a complete disruption of the extensor mechanism after TKA, a reconstruction utilizing synthetic mesh (e.g., Marlex) is performed. What is the critical recommended postoperative rehabilitation protocol to ensure construct survival?

. Immediate full active range of motion
. Immobilization in full extension for 6 to 8 weeks
. Immobilization in 30 degrees of flexion for 4 weeks
. Continuous passive motion (CPM) from 0 to 90 degrees starting on postoperative day 1
. Immediate active straight leg raises with hinged bracing

Correct Answer & Explanation

. Immediate full active range of motion

Explanation

Extensor mechanism reconstruction in the setting of a TKA (whether with Marlex mesh or allograft) relies heavily on host tissue ingrowth into the reconstructive material. The standard protocol requires strict immobilization in full extension for 6 to 8 weeks to prevent early catastrophic failure and allow for biologic incorporation.

Question 5111

Topic: Total Knee Arthroplasty (TKA)

A 72-year-old patient undergoes a primary TKA for severe valgus deformity. Intraoperatively, the medial collateral ligament (MCL) is found to be severely attenuated and incompetent, preventing varus-valgus stability with standard gap balancing, but the extensor mechanism and soft tissue envelope are otherwise intact. Which level of implant constraint is most appropriate as the next step?

. Cruciate retaining (CR)
. Posterior stabilized (PS)
. Constrained non-hinged (CCK)
. Rotating hinge
. Unicompartmental knee arthroplasty

Correct Answer & Explanation

. Cruciate retaining (CR)

Explanation

A Constrained Condylar Knee (CCK) utilizes a tall, thick tibial post and a deep femoral box to provide varus-valgus constraint. It is indicated when the collateral ligaments (especially the MCL) are attenuated or deficient, but a linked hinge is not yet required. A rotating hinge is reserved for complete collateral absence with global soft tissue failure or massive bone loss.

Question 5112

Topic: 3. Adult Reconstruction (Hip & Knee)
Radiographs of a failed THA demonstrate severe periprosthetic osteolysis. The acetabular component has migrated 4 cm superiorly and 2 cm medially past Kohler's line, and the radiographic teardrop is completely destroyed. Which Paprosky acetabular defect is present?
. Type IIA
. Type IIB
. Type IIC
. Type IIIA
. Type IIIB

Correct Answer & Explanation

. Type IIIB

Explanation

The Paprosky acetabular defect classification: Type IIIA indicates 'up and out' migration (>3 cm superior) with an intact Kohler's line. Type IIIB indicates 'up and in' migration (medial to Kohler's line, often with pelvic discontinuity) and destruction of the teardrop. Because the component has migrated past Kohler's line, it is a Type IIIB defect.

Question 5113

Topic: Total Knee Arthroplasty (TKA)

A patient presents 8 weeks after a primary TKA with severe stiffness. Despite aggressive, supervised physical therapy, their active and passive range of motion is limited to a painful arc from 15 degrees of extension to 75 degrees of flexion. What is the most appropriate next step in management?

. Immediate single-stage revision of the femoral and tibial components
. Arthroscopic lysis of adhesions
. Manipulation under anesthesia (MUA)
. Wait until 6 months postoperatively and reassess for MUA
. Open extensile lysis of adhesions

Correct Answer & Explanation

. Immediate single-stage revision of the femoral and tibial components

Explanation

For arthrofibrosis and significant stiffness following TKA that fails to improve with physical therapy, Manipulation Under Anesthesia (MUA) is highly effective if performed within the optimal window of 6 to 12 weeks postoperatively. Waiting until 6 months allows mature scar tissue to form, increasing the risk of periprosthetic fracture or tendon rupture during MUA.

Question 5114

Topic: 3. Adult Reconstruction (Hip & Knee)

During a standard Cruciate-Retaining (CR) Total Knee Arthroplasty, what is the primary consequence of an excessive posterior slope cut on the proximal tibia?

. Flexion gap becomes looser than the extension gap
. Extension gap becomes looser than the flexion gap
. Increased incidence of patellar clunk syndrome
. Anterior translation of the tibia in flexion
. Global instability of the knee construct

Correct Answer & Explanation

. Flexion gap becomes looser than the extension gap

Explanation

Increasing the posterior slope of the tibial cut increases the dimensions of the flexion gap without significantly affecting the extension gap, leading to a loose flexion gap. This can cause instability in flexion and poor kinematics.

Question 5115

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a metal-on-polyethylene total hip arthroplasty (large modular head) presents with insidious groin pain 5 years postoperatively. Blood tests reveal elevated cobalt levels and normal chromium. Aspiration is negative for infection.

What is the most likely diagnosis?

. Polyethylene wear and osteolysis
. Trunnionosis (mechanically assisted crevice corrosion)
. Psoas impingement syndrome
. Aseptic loosening of the acetabular cup
. Atypical mycobacterial periprosthetic joint infection

Correct Answer & Explanation

. Polyethylene wear and osteolysis

Explanation

Trunnionosis, or mechanically assisted crevice corrosion at the head-neck junction, can occur in non-Metal-on-Metal bearings, especially with large metal heads. It classically presents with elevated cobalt levels disproportionate to chromium, leading to an Adverse Local Tissue Reaction (ALTR).

Question 5116

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old female presents with a feeling of instability when going down stairs one year after a primary TKA. Clinical exam reveals stability in full extension and at 90 degrees of flexion, but excessive AP laxity at 30-45 degrees of flexion. Which of the following technical errors is the most likely cause?

. Undersized femoral component
. Excessive distal femoral resection
. Joint line elevation
. Excessive posterior slope
. Internal rotation of the tibial component

Correct Answer & Explanation

. Undersized femoral component

Explanation

Mid-flexion instability typically occurs when the joint line is elevated. The collateral ligaments become relatively lax in mid-flexion due to altered isometry, even if the gaps at 0 and 90 degrees are perfectly balanced.

Question 5117

Topic: 3. Adult Reconstruction (Hip & Knee)

In diagnosing Periprosthetic Joint Infection (PJI), the 2018 ICM criteria include Alpha-defensin as a major synovial fluid biomarker. What is the primary cellular source of Alpha-defensin in the context of PJI?

. Macrophages
. Lymphocytes
. Neutrophils
. Fibroblasts
. Synovial lining cells

Correct Answer & Explanation

. Macrophages

Explanation

Alpha-defensin is a highly specific antimicrobial peptide released predominantly by human neutrophils in response to pathogens, making it an excellent biomarker for diagnosing periprosthetic joint infection.

Question 5118

Topic: Total Hip Arthroplasty (THA)

A 55-year-old female underwent THA with a ceramic-on-ceramic bearing. At her 2-year follow-up, she complains of a loud squeaking noise from her hip when bending to tie her shoes. Which of the following factors is most strongly associated with squeaking in ceramic-on-ceramic THA?

. Use of a larger femoral head (>36 mm)
. Cup anteversion greater than 20 degrees
. Edge loading due to component malposition or impingement
. High body mass index (>35 kg/m2)
. Uncorrected limb length discrepancy

Correct Answer & Explanation

. Use of a larger femoral head (>36 mm)

Explanation

Squeaking in ceramic-on-ceramic hips is multifactorial but is most strongly correlated with edge loading and stripe wear. This frequently results from component malposition (such as excessive cup inclination) or impingement causing micro-separation.

Question 5119

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man who underwent a Posterior Stabilized (PS) Total Knee Arthroplasty 18 months ago complains of a painful 'catch' or 'pop' when extending his knee from 40 degrees of flexion. Which of the following is the most likely pathophysiologic mechanism for this condition?

. Entrapment of the popliteus tendon against the lateral femoral condyle
. Hypertrophic fibrous nodule at the superior pole of the patella catching in the intercondylar notch
. Impingement of the unresurfaced patella on an oversized femoral component
. Subluxation of the patella laterally due to excessive internal rotation of the tibial tray
. A retained loose body impinging in the medial gutter

Correct Answer & Explanation

. Entrapment of the popliteus tendon against the lateral femoral condyle

Explanation

Patellar clunk syndrome occurs primarily in PS knees when a hypertrophic fibrous nodule forms at the superior pole of the patella. During extension from deep flexion, the nodule catches within the intercondylar box of the femoral component.

Question 5120

Topic: 3. Adult Reconstruction (Hip & Knee)

To reduce polyethylene wear rates in THA, highly cross-linked polyethylene (HXLPE) is widely used. What is the primary purpose of the post-irradiation thermal treatment (melting or annealing) in the manufacturing of HXLPE?

. To increase the crystalline content and stiffness
. To eliminate residual free radicals and reduce oxidative degradation
. To enhance the elastic modulus and yield strength
. To increase the ultimate tensile strength to prevent rim fracture
. To lower the friction coefficient against ceramic heads

Correct Answer & Explanation

. To increase the crystalline content and stiffness

Explanation

Irradiation creates cross-links to improve wear resistance but leaves behind free radicals that can cause long-term oxidative degradation. Thermal treatment (melting or annealing) eliminates or reduces these free radicals.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page