Menu

3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 120 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 2381

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with new-onset groin pain 6 years after a total hip arthroplasty using a dual-taper modular femoral stem with a cobalt-chromium head and highly cross-linked polyethylene liner. Serum cobalt levels are significantly elevated out of proportion to chromium. Aspirational fluid demonstrates a high macrophage count with black, metallic particulate debris but no organisms. What is the primary mechanism of failure?

. Polyethylene wear-induced osteolysis
. Mechanically assisted crevice corrosion (Trunnionosis)
. Aseptic loosening of the femoral stem secondary to stress shielding
. Unrecognized periprosthetic joint infection
. Metallosis due to recurrent component impingement

Correct Answer & Explanation

. Mechanically assisted crevice corrosion (Trunnionosis)

Explanation

The patient's presentation describes an adverse local tissue reaction (ALTR) secondary to trunnionosis. Trunnionosis (mechanically assisted crevice corrosion or MACC) occurs at the modular head-neck junction (trunnion). It is characterized by elevated serum cobalt levels (often disproportionately higher than chromium) and a characteristic local inflammatory response to the fretting and corrosion of the metallic debris. The absence of an alternative metal-on-metal articulation rules out classic bearing-surface metallosis.

Question 2382

Topic: Total Hip Arthroplasty (THA)

A 62-year-old man who underwent a primary ceramic-on-ceramic total hip arthroplasty two years ago presents with an audible 'squeaking' from his hip during normal ambulation. Radiographs show well-fixed components. Which of the following factors is most highly correlated with the development of squeaking in ceramic-on-ceramic bearings?

. Acetabular component placed in excessive anteversion and high inclination
. Decreased femoral offset
. Use of a 36-mm head instead of a 28-mm head
. Acetabular retroversion combined with a varus femoral stem
. Micro-motion of the uncemented femoral stem

Correct Answer & Explanation

. Acetabular component placed in excessive anteversion and high inclination

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasties is a well-documented phenomenon. It is most strongly associated with component malposition, specifically high acetabular inclination (abduction) and excessive anteversion. This malposition leads to 'edge loading,' where the mechanical contact forces are concentrated on the rim of the ceramic liner. Edge loading disrupts the fluid film lubrication, resulting in stripe wear, increased friction, and the generation of an audible squeak.

Question 2383

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty (TKA), after the bony cuts are made and trial components are placed, the surgeon evaluates the gaps. The knee is stable and symmetric in full extension, but in 90 degrees of flexion, the joint is symmetrically tight, making it difficult to insert the trial polyethylene insert. Utilizing an anterior referencing system, what is the most appropriate next step to balance the knee?

. Resect 2 mm more of the distal femur
. Upsize the femoral component
. Downsize the femoral component
. Increase the thickness of the tibial polyethylene insert
. Release the superficial medial collateral ligament

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is balanced in extension but tight in flexion requires an increase in the flexion gap without altering the extension gap. When using an anterior referencing system, the anterior cut remains flush with the anterior cortex. Downsizing the femoral component reduces the anterior-posterior (AP) dimension, which brings the posterior cut further anteriorly, thereby reducing posterior condylar offset and opening (enlarging) the flexion gap. Resecting more distal femur would increase the extension gap. Upsizing the femur would make it tighter in flexion.

Question 2384

Topic: Total Knee Arthroplasty (TKA)

Which of the following best describes the normal kinematics of the native knee that modern total knee arthroplasty (TKA) designs attempt to replicate?

. Femoral rollback with internal rotation of the tibia during flexion
. Femoral rollback with external rotation of the tibia during flexion
. Anterior femoral translation with tibial internal rotation during flexion
. Paradoxical anterior sliding of the femur during deep flexion
. Pure hinge motion with a single radius of curvature

Correct Answer & Explanation

. Femoral rollback with external rotation of the tibia during flexion

Explanation

Normal knee kinematics involve a 'screw-home' mechanism and 'femoral rollback'. As the knee goes from extension into flexion, the lateral femoral condyle rolls posteriorly more than the medial condyle, causing the femur to externally rotate relative to the tibia (or the tibia to internally rotate relative to the femur). Modern TKA designs, particularly posterior-stabilized or medial-pivot designs, attempt to recreate this native femoral rollback and tibial internal rotation to optimize flexion and patellar tracking.

Question 2385

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old active male presents with an audible squeak from his total hip arthroplasty, performed 4 years ago for osteoarthritis. He has a ceramic-on-ceramic bearing. Which of the following factors is most strongly associated with the development of this acoustic phenomenon?

. Femoral stem retroversion
. Edge loading due to acetabular component malpositioning
. Use of an oxidized zirconium femoral head
. Low body mass index (BMI)
. Polyethylene oxidation

Correct Answer & Explanation

. Edge loading due to acetabular component malpositioning

Explanation

Squeaking in a ceramic-on-ceramic (CoC) total hip arthroplasty is a well-documented phenomenon. It is most strongly associated with edge loading of the bearing surfaces, which typically occurs due to acetabular cup malpositioning (especially excessive abduction or anteversion). Edge loading leads to stripe wear and loss of fluid-film lubrication, culminating in the acoustic squeak. High BMI and younger, more active patients are also at higher risk, whereas oxidized zirconium and polyethylene are distinct bearing materials not associated with the classic CoC squeak.

Question 2386

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female is 1-year post-operative from a primary total knee arthroplasty (TKA). She complains of anterior knee pain and a feeling that her kneecap is 'popping out.' Examination and CT imaging demonstrate significant internal rotation of the femoral component relative to the epicondylar axis, as well as internal rotation of the tibial component relative to the tibial tubercle. This combined malrotation is most predictably associated with which of the following patellofemoral complications?

. Increased patellar height (patella alta)
. Medial patellar subluxation
. Lateral patellar subluxation
. Increased patellofemoral jump distance
. Patellar clunk syndrome

Correct Answer & Explanation

. Lateral patellar subluxation

Explanation

Internal rotation of the femoral and tibial components in TKA functionally increases the Q-angle. Internal rotation of the femoral component moves the trochlear groove medially, while internal rotation of the tibial component moves the tibial tubercle laterally relative to the trochlea. This lateralizes the extensor mechanism vector, reliably pulling the patella laterally and resulting in lateral patellar tracking, subluxation, or dislocation.

Question 2387

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old active female who underwent a ceramic-on-ceramic total hip arthroplasty 2 years ago presents with an audible "squeaking" sound from her hip during walking. She denies any pain, and her radiographs demonstrate well-fixed components with no evidence of loosening. What is the most likely biomechanical cause of this phenomenon?

. Aseptic loosening of the femoral stem
. Galvanic corrosion at the trunnion
. Edge loading due to component malposition
. Third-body wear from retained bone cement
. Impingement of the iliopsoas tendon

Correct Answer & Explanation

. Edge loading due to component malposition

Explanation

Squeaking is a known complication of ceramic-on-ceramic bearings. It is most strongly associated with edge loading of the bearing surfaces, which typically occurs due to component malposition, specifically an excessively steep (abducted) or excessively anteverted acetabular cup. It can also be related to stripe wear and micro-separation.

Question 2388

Topic: 3. Adult Reconstruction (Hip & Knee)

In posterior-stabilized (PS) total knee arthroplasty (TKA), the cam and post mechanism substitutes for the posterior cruciate ligament. The risk of posterior dislocation of the tibia on the femur is related to the 'jump distance'. Which of the following intraoperative modifications most effectively increases the jump distance?

. Increasing the posterior slope of the tibial cut
. Decreasing the posterior slope of the tibial cut
. Upsizing the femoral component
. Anterior translation of the femoral component
. External rotation of the tibial component

Correct Answer & Explanation

. Decreasing the posterior slope of the tibial cut

Explanation

Jump distance is the vertical distance the femoral cam must travel to clear the top of the tibial post. Decreasing the posterior slope of the tibial cut effectively increases the relative vertical height of the post relative to the femur, thereby increasing the jump distance and reducing the risk of cam-post dislocation. Conversely, increasing the posterior slope tilts the post backward, reducing its relative height and decreasing the jump distance.

Question 2389

Topic: 3. Adult Reconstruction (Hip & Knee)

Articular cartilage provides a low-friction, load-bearing surface for synovial joints. Its biomechanical properties are derived from its specialized extracellular matrix. Which zone of normal articular cartilage contains the largest diameter collagen fibrils oriented strictly perpendicular to the joint surface to resist shear forces, and simultaneously possesses the highest concentration of proteoglycans?

. Superficial (tangential) zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified cartilage zone
. Tidemark

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone of articular cartilage represents about 30% of the cartilage volume. It contains the largest diameter type II collagen fibrils, which are oriented perpendicular to the subchondral bone to anchor the cartilage and resist shear forces. It also contains the highest concentration of proteoglycans (and therefore the lowest concentration of water), providing the highest compressive stiffness.

Question 2390

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female undergoes a primary total hip arthroplasty via a posterior approach. Postoperatively, she experiences recurrent posterior dislocations. Radiographic evaluation demonstrates an anteverted cup at 15 degrees and an abduction angle of 40 degrees, with the femoral stem in 5 degrees of retroversion. What is the most likely cause of her instability?

. Insufficient acetabular component abduction
. Excessive acetabular component anteversion
. Femoral component retroversion
. Impingement of the anterior capsule
. Weakness of the hip abductor musculature

Correct Answer & Explanation

. Femoral component retroversion

Explanation

Stability in total hip arthroplasty is largely dependent on the combined anteversion of the acetabular and femoral components, which should optimally be between 25 and 35 degrees (Widmer's criteria). In this case, the acetabular cup is anteverted 15 degrees, but the femoral stem is retroverted 5 degrees, resulting in a combined anteversion of only 10 degrees. This relative retroversion significantly increases the risk of posterior dislocation.

Question 2391

Topic: 3. Adult Reconstruction (Hip & Knee)
A 58-year-old female presents with groin pain and swelling three years after undergoing a metal-on-metal total hip arthroplasty. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) is suspected. Which of the following immunologic mechanisms is primarily responsible for the pathogenesis of this condition?
. Type I Hypersensitivity (IgE-mediated)
. Type II Hypersensitivity (Cytotoxic)
. Type III Hypersensitivity (Immune complex-mediated)
. Type IV Hypersensitivity (Delayed, T-cell mediated)
. Macrophage-induced osteolysis via particulate wear debris

Correct Answer & Explanation

. Type IV Hypersensitivity (Delayed, T-cell mediated)

Explanation

ALVAL (Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion) is a classic complication of metal-on-metal implants or corrosion at modular junctions (trunnionosis). It is driven by a Type IV (delayed, T-cell mediated) hypersensitivity reaction to metal ions (like cobalt and chromium). Histologically, it is characterized by a perivascular lymphocytic infiltrate. This distinguishes it from classic polyethylene wear debris, which is characterized by a macrophage-mediated foreign body response.

Question 2392

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty, trial components are placed, and gap balancing is assessed. The knee is found to be tight in 90 degrees of flexion but perfectly balanced in full extension. Which of the following femoral component adjustments will best correct this specific imbalance?

. Decrease the thickness of the polyethylene tibial insert
. Increase the distal femoral resection
. Downsize the femoral component (decrease AP dimension)
. Upsize the femoral component (increase AP dimension)
. Decrease the posterior slope of the tibial cut

Correct Answer & Explanation

. Downsize the femoral component (decrease AP dimension)

Explanation

In TKA gap balancing, the flexion gap is primarily controlled by the anteroposterior (AP) dimension of the femoral component, while the extension gap is controlled by the distal femoral resection. If the knee is tight in flexion but balanced in extension, the flexion gap needs to be increased without affecting the extension gap. Downsizing the femoral component decreases its AP dimension (specifically taking more posterior condyle), which opens up the flexion gap while leaving the extension gap unchanged.

Question 2393

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient complains of an audible "squeaking" sound from her total hip arthroplasty, which utilizes a ceramic-on-ceramic bearing surface. What surgical or mechanical factor is most strongly associated with the initiation of squeaking in modern ceramic-on-ceramic hips?

. Excessive femoral head size (>36 mm)
. Use of a highly cross-linked polyethylene liner
. Component malpositioning leading to micro-separation and edge-loading
. Deep periprosthetic joint infection (PJI)
. Galvanic corrosion at the modular head-neck junction

Correct Answer & Explanation

. Component malpositioning leading to micro-separation and edge-loading

Explanation

Squeaking is a known complication unique to hard-on-hard bearing surfaces, most notably alumina ceramic-on-ceramic THA. The primary mechanical etiology is stripe wear caused by micro-separation during the swing phase of gait, leading to edge-loading when the head re-engages the rim of the cup. This is strongly associated with component malpositioning (particularly excessive cup anteversion or high inclination angles) that disrupts fluid film lubrication.

Question 2394

Topic: 3. Adult Reconstruction (Hip & Knee)

A healthy, highly active 40-year-old male falls from a ladder and sustains a displaced intracapsular fracture of the femoral neck (Garden IV). He is brought to the emergency department within 4 hours of the injury. What is the most appropriate surgical management for this specific patient?

. Urgent hemiarthroplasty of the hip
. Urgent total hip arthroplasty (THA)
. Closed or open reduction and internal fixation (CRIF/ORIF) as soon as possible
. Application of skeletal traction followed by delayed ORIF at 1 week
. Core decompression with fibular strut allografting

Correct Answer & Explanation

. Closed or open reduction and internal fixation (CRIF/ORIF) as soon as possible

Explanation

In a young, physiologically active patient (generally <60-65 years old), a displaced femoral neck fracture is an orthopedic urgency. The goal is head preservation despite the high risk of avascular necrosis (AVN) and nonunion. The standard of care is urgent closed or open reduction and internal fixation (using cannulated screws or a sliding hip screw device) to restore the native anatomy. Arthroplasty (hemi or THA) is reserved for older, lower-demand patients or cases of delayed presentation where head salvage is impossible.

Question 2395

Topic: Total Hip Arthroplasty (THA)

A 72-year-old male presents with recurrent posterior dislocations following a right total hip arthroplasty performed 2 months ago via a posterior approach. Radiographs show a well-fixed femoral stem and an acetabular component with 10 degrees of anteversion and 45 degrees of abduction. During revision surgery, the acetabular component is found to be solidly ingrown. Which of the following is the most appropriate surgical intervention to prevent further posterior dislocations?

. Increase femoral offset by changing to a longer femoral head.
. Revise the acetabular shell to increase anteversion.
. Apply a constrained acetabular liner into the existing shell.
. Revise the femoral stem to increase anteversion.
. Prescribe an abduction orthosis for 6 weeks.

Correct Answer & Explanation

. Revise the acetabular shell to increase anteversion.

Explanation

The ideal acetabular cup position in total hip arthroplasty is generally considered to be 15 to 20 degrees of anteversion and 40 to 45 degrees of abduction. An anteversion of 10 degrees is relatively retroverted, especially when a posterior approach is used, predisposing the patient to posterior instability. Since the cup is malpositioned, the most appropriate treatment is revision of the acetabular shell to correct the anteversion.

Question 2396

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old male with a history of a metal-on-metal total hip arthroplasty performed 8 years ago presents with progressive groin pain and swelling. Laboratory evaluation reveals significantly elevated serum cobalt and chromium ion levels. MRI demonstrates a large, thick-walled fluid collection. Histologic analysis of the periprosthetic tissue is most likely to show an adverse local tissue reaction (ALVAL) characterized by:

. Abundant neutrophils and intracellular gram-positive cocci
. A dense perivascular infiltrate of lymphocytes, indicative of a Type IV delayed hypersensitivity reaction
. Extensive sheets of foamy macrophages containing polyethylene debris
. A predominant eosinophilic infiltrate consistent with a Type I IgE-mediated allergy
. Myxoid degeneration and chondroid metaplasia

Correct Answer & Explanation

. A dense perivascular infiltrate of lymphocytes, indicative of a Type IV delayed hypersensitivity reaction

Explanation

Adverse Local Tissue Reaction (ALTR) or Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion (ALVAL) in response to metal wear debris from metal-on-metal implants is histologically characterized by a dense perivascular lymphocytic infiltrate. This represents a Type IV (cell-mediated) delayed hypersensitivity reaction to metal ions.

Question 2397

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female is undergoing a primary posterior-stabilized total knee arthroplasty. During trialing, the surgeon notes that the knee is perfectly balanced in full extension, but the flexion gap is unacceptably tight, limiting flexion to 80 degrees and causing posterior lift-off of the tibial tray. Which of the following surgical adjustments is the most appropriate maneuver to balance the knee?

. Resect more distal femur
. Decrease the posterior slope of the tibial cut
. Upsize the femoral component
. Downsize the femoral component using an anterior referencing guide
. Release the posterior capsule

Correct Answer & Explanation

. Downsize the femoral component using an anterior referencing guide

Explanation

A tight flexion gap with a balanced extension gap means the AP dimension of the femoral component is too large, or the posterior tibial slope is inadequate. Downsizing the femoral component (when using an anterior referencing system) reduces the posterior condylar offset, thereby specifically opening the flexion gap without affecting the extension gap. Increasing (not decreasing) the posterior tibial slope would also be an option.

Question 2398

Topic: 3. Adult Reconstruction (Hip & Knee)
In the context of wear mechanisms in total joint arthroplasty, the generation of wear debris between the non-articulating backside of a polyethylene acetabular liner and the inner surface of a metallic acetabular shell is classified as which of the following?
. Mode I wear
. Mode II wear
. Mode III wear
. Mode IV wear
. Adhesive wear

Correct Answer & Explanation

. Mode IV wear

Explanation

Wear in total joint arthroplasty is categorized into four modes. Mode I occurs between two intended bearing surfaces (e.g., femoral head and polyethylene liner). Mode II occurs when a primary bearing surface rubs against a non-intended secondary surface (e.g., femoral head against metallic shell after liner wear-through). Mode III is third-body wear caused by loose particles. Mode IV wear occurs between two non-primary bearing surfaces rubbing against each other, such as backside wear between the polyethylene liner and the metallic acetabular shell.

Question 2399

Topic: 3. Adult Reconstruction (Hip & Knee)

In a posterior-stabilized total knee arthroplasty (TKA), the posterior cruciate ligament is resected. Which specific design feature of the implant is intended to substitute for the function of the posterior cruciate ligament by facilitating femoral rollback during knee flexion?

. The symmetric conformity of the polyethylene insert
. The posterior slope built into the tibial baseplate
. The interaction between the femoral cam and the polyethylene tibial post
. The extension of the anterior femoral flange
. The deep trochlear groove

Correct Answer & Explanation

. The interaction between the femoral cam and the polyethylene tibial post

Explanation

In a posterior-stabilized (PS) TKA, the native posterior cruciate ligament (PCL) is excised. To replicate its biomechanical role, the implant incorporates a central polyethylene post on the tibial insert and a metallic cam on the femoral component. As the knee flexes, the femoral cam engages the tibial post, forcibly driving the femur posteriorly (femoral rollback). This increases knee flexion clearance and improves the lever arm of the extensor mechanism.

Question 2400

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female undergoes a posterior approach total hip arthroplasty as shown in the postoperative radiograph.

She suffers a posterior dislocation 3 weeks postoperatively while rising from a low chair. Which of the following component positions increases the risk of posterior dislocation?

. Increased acetabular anteversion
. Decreased acetabular anteversion
. Increased acetabular inclination
. Increased femoral offset
. Increased femoral anteversion

Correct Answer & Explanation

. Decreased acetabular anteversion

Explanation

Posterior instability in total hip arthroplasty is exacerbated by positions of flexion, internal rotation, and adduction. Component malpositions that predispose to posterior dislocation include decreased acetabular anteversion (retroversion), decreased femoral anteversion, and insufficient femoral offset.

Test Yourself

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

On this Page