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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 296 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 5901

Topic: 3. Adult Reconstruction (Hip & Knee)

Which factor is most predictive of early failure in medial unicompartmental knee arthroplasty (UKR)?

. Preoperative knee flexion contracture of 10 degrees
. Patient age over 75 years
. Postoperative mechanical axis of 3 degrees valgus
. Postoperative mechanical axis of 5 degrees varus
. BMI less than 25 kg/m^2

Correct Answer & Explanation

. Postoperative mechanical axis of 5 degrees varus

Explanation

Postoperative varus alignment (e.g., 5 degrees varus) in a medial UKR significantly increases the load on the medial compartment, leading to accelerated polyethylene wear and higher rates of early aseptic loosening and failure. UKRs typically aim for a slight varus or neutral mechanical axis to shift the load slightly to the lateral compartment. A 3-degree valgus alignment would shift too much load laterally and also be detrimental, but 5 degrees varus is a more direct cause of failure in amedialUKR. Other factors are less critical for early mechanical failure.

Question 5902

Topic: Total Knee Arthroplasty (TKA)

A TKA patient complains of a clunk and anterior knee pain. During surgical exploration, a fibrous nodule is found superior to the patellar component, within the quadriceps tendon. This is characteristic of:

. Patella alta
. Patella baja
. Patellar clunk syndrome
. Tibial component internal rotation
. Femoral component external rotation

Correct Answer & Explanation

. Patellar clunk syndrome

Explanation

This clinical description (clunk, anterior knee pain, fibrous nodule superior to the patellar component in the quadriceps tendon) is characteristic of 'patellar clunk syndrome.' It is more commonly associated with patellar baja or femoral component design issues that allow impingement of the suprapatellar pouch. Patella alta or rotational malalignment would typically present with different patellofemoral tracking issues rather than a specific fibrous nodule.

Question 5903

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a primary TKA is found to have polyethylene wear predominantly on the posterior aspect of the lateral tibial insert. What malalignment is most consistent with this pattern of wear?

. Excessive femoral component internal rotation
. Excessive tibial posterior slope
. Insufficient femoral external rotation
. Excessive femoral component external rotation
. Tibial component varus malposition

Correct Answer & Explanation

. Excessive femoral component external rotation

Explanation

Excessive femoral component external rotation can lead to an asymmetric flexion gap, often causing medial laxity and increased loading on the lateral compartment, particularly in flexion. This can result in increased wear on the posterior-lateral aspect of the tibial polyethylene. Excessive femoral internal rotation (or insufficient external rotation) would typically cause medial side issues and patellofemoral tracking. Excessive tibial posterior slope would cause anterior loading/impingement in flexion or hyperextension. Tibial varus would cause medial wear.

Question 5904

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary risk associated with a persistently tight medial compartment after TKA, despite appropriate bone cuts?

. Lateral compartment instability
. Patellofemoral tracking issues
. Increased polyethylene wear on the lateral side
. Early aseptic loosening of the medial tibial baseplate
. Limited knee flexion and potential MCL failure

Correct Answer & Explanation

. Limited knee flexion and potential MCL failure

Explanation

A persistently tight medial compartment can severely limit knee flexion due to impingement and can place excessive tension on the medial collateral ligament (MCL). This can lead to MCL failure (rupture) during surgery or postoperatively, or chronic MCL strain and pain. Lateral instability, patellofemoral issues, and increased lateral wear are more associated with a loose medial compartment or specific rotational errors. Early aseptic loosening is more common with varus malalignment.

Question 5905

Topic: Total Knee Arthroplasty (TKA)

When balancing the extension gap in a TKA, what is the ideal soft tissue tension?

. Visibly tight, no space can be created between components
. Just able to insert a thin feeler gauge (e.g., 2mm)
. Evenly balanced and stable, but not overtly tight or loose, allowing for a 1-2mm distraction with firm manual stress
. Loose enough to easily distract the joint by 5mm
. Variable, depending on patient's activity level

Correct Answer & Explanation

. Evenly balanced and stable, but not overtly tight or loose, allowing for a 1-2mm distraction with firm manual stress

Explanation

The ideal soft tissue tension in the extension gap should be evenly balanced and stable, but not overtly tight or loose. It should allow for 1-2mm of distraction with firm manual stress. This provides stability without restricting motion or causing impingement. Visibly tight or loose gaps are indicative of malalignment or inadequate balancing. The goal is to achieve a rectangular gap, equal to the flexion gap.

Question 5906

Topic: Total Knee Arthroplasty (TKA)

A patient presents with a TKA reporting that their knee feels 'too tight' and they cannot fully flex. Radiographs show a well-aligned femoral component but a tibial component with an unusually steep posterior slope. What is the likely consequence of this tibial slope?

. Flexion contracture
. Hyperextension and anterior knee pain
. Anterior impingement and difficulty with terminal extension
. Loose flexion gap and posterior instability
. Increased patellofemoral contact forces

Correct Answer & Explanation

. Loose flexion gap and posterior instability

Explanation

An unusually steep (excessive) posterior slope of the tibial component creates a relatively loose flexion gap and can lead to posterior instability, particularly during flexion. It also predisposes to hyperextension. A flexion contracture is associated withinsufficientposterior slope or femoral component flexion. Anterior impingement is usually with insufficient slope. Increased patellofemoral forces are not directly caused by tibial slope, though instability can indirectly affect the patella.

Question 5907

Topic: Total Knee Arthroplasty (TKA)

What is the 'kinematic alignment' philosophy in TKA aiming to achieve regarding component placement?

. To restore a neutral mechanical axis of 0 degrees
. To align components such that the joint line is parallel to the floor in standing
. To reproduce the patient's pre-arthritic constitutional knee alignment
. To achieve an ideal 3 degrees of valgus for the femoral component
. To always use a measured resection technique

Correct Answer & Explanation

. To reproduce the patient's pre-arthritic constitutional knee alignment

Explanation

Kinematic alignment (KA) in TKA aims to reproduce the patient's pre-arthritic constitutional knee alignment and the native joint kinematics. This often results in a slight varus or valgus overall alignment, rather than a forced neutral mechanical axis. It contrasts with mechanical alignment (MA) which strives for a neutral mechanical axis. The goal is to avoid overstuffing or understuffing the joint based on individual anatomy.

Question 5908

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following describes the 'windshield wiper effect' in the context of TKA component malalignment?

. Degradation of the polyethylene due to oxidation
. Movement of the tibial component relative to the bone when not well-fixed, leading to osteolysis
. Movement of the patella over the femoral trochlea causing crepitus
. The cyclical rubbing of a tight soft tissue structure over a component edge, causing wear
. Rotation of the femoral component leading to differential wear

Correct Answer & Explanation

. Movement of the tibial component relative to the bone when not well-fixed, leading to osteolysis

Explanation

The 'windshield wiper effect' refers to the movement of the tibial component relative to the underlying bone, particularly at the keel or stem, when the component is not well-fixed. This micromotion can cause particulate wear, osteolysis, and eventual aseptic loosening. It's often associated with inadequate cementation, poor bone quality, or significant malalignment leading to high focal stresses.

Question 5909

Topic: Total Knee Arthroplasty (TKA)

In a TKA, a common cause of recurrent lateral patellar subluxation or dislocation is:

. Medial patellar component placement
. External rotation of the tibial component
. Internal rotation of the femoral component
. Insufficient posterior slope of the tibial component
. Valgus malalignment of the overall mechanical axis

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of the femoral component is a common cause of lateral patellar subluxation or dislocation. It effectively lateralizes the trochlear groove relative to the patella, predisposing to tracking issues. External rotation of the tibial component could also contribute but femoral rotational malalignment is a more potent factor. Medial patellar placement would tend to stabilize. Insufficient posterior slope and overall valgus malalignment are less directly linked to patellar tracking.

Question 5910

Topic: Total Knee Arthroplasty (TKA)

A TKA patient develops chronic anterior knee pain and a feeling of 'catch' or 'clunk' in mid-flexion. Radiographs are unremarkable. Which component malalignment would most likely be implicated in anterior impingement of the patella or extensor mechanism in flexion?

. Femoral component undersizing
. Excessive anterior position of the femoral component (e.g., inadequate anterior femoral cut)
. Excessive posterior slope of the tibial component
. Tibial component internal rotation
. Patellar component varus tilt

Correct Answer & Explanation

. Excessive anterior position of the femoral component (e.g., inadequate anterior femoral cut)

Explanation

Excessive anterior positioning of the femoral component (resulting from inadequate resection of the anterior femur or an oversized component) can lead to anterior impingement of the patella or extensor mechanism, causing a clunk or catch in mid-flexion. This effectively narrows the patellofemoral space. Undersizing might cause instability, not impingement. Excessive posterior tibial slope would cause posterior instability. Rotational or tilt issues lead to tracking problems, not typically anterior impingement in mid-flexion in this manner.

Question 5911

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the most common consequence of significant varus malalignment of the femoral component in TKA?

. Lateral collateral ligament (LCL) laxity
. Medial collateral ligament (MCL) laxity
. Increased polyethylene wear on the lateral side
. Increased polyethylene wear on the medial side
. Patellar subluxation

Correct Answer & Explanation

. Lateral collateral ligament (LCL) laxity

Explanation

Significant varus malalignment of the femoral component leads to lateral collateral ligament (LCL) laxity, particularly in extension, and can result in varus instability. It effectively opens up the lateral compartment. Valgus malalignment of the femoral component would lead to MCL laxity. Increased wear typically occurs on the side of increased loading, which is medial with varustibialor overall limb malalignment, but for femoralcomponentvarus, the LCL becomes loose.

Question 5912

Topic: Total Knee Arthroplasty (TKA)

When assessing the sagittal alignment of the femoral component on a true lateral radiograph, which line should be parallel to the anterior femoral cortex?

. Posterior femoral condylar line
. Anterior femoral condylar line (of the component)
. Transepicondylar axis
. Whiteside's line
. Mechanical axis of the femur

Correct Answer & Explanation

. Anterior femoral condylar line (of the component)

Explanation

On a true lateral radiograph, the anterior femoral condylar line of the component should be parallel to the anterior femoral cortex. This indicates proper sagittal positioning of the femoral component, avoiding notching or anterior impingement. The posterior condylar line indicates flexion/extension relative to the shaft. The other options are for rotational or overall mechanical alignment.

Question 5913

Topic: Total Knee Arthroplasty (TKA)

What is the primary technical goal of using a 'gap balancing' technique in TKA?

. To ensure bone cuts are perpendicular to the mechanical axis
. To achieve equal and rectangular flexion and extension gaps
. To restore the constitutional alignment of the patient's knee
. To minimize blood loss during surgery
. To avoid notching of the femoral cortex

Correct Answer & Explanation

. To achieve equal and rectangular flexion and extension gaps

Explanation

The primary technical goal of the 'gap balancing' technique in TKA is to achieve equal and rectangular flexion and extension gaps. This is done by assessing the soft tissue tension in both flexion and extension and making bone resections and soft tissue releases to create balanced, symmetrical gaps of the same dimension. This ensures stability throughout the range of motion. While mechanical axis restoration is a goal, gap balancing focuses on the soft tissue envelopes.

Question 5914

Topic: Total Knee Arthroplasty (TKA)

A patient with a TKA reports chronic posterior knee pain and a feeling of instability during staircase ascent. A lateral radiograph shows slight posterior subluxation of the femoral component on the tibial tray. Which malalignment is most likely?

. Excessive anterior slope of the tibial component (reversed slope)
. Insufficient posterior slope of the tibial component
. Excessive posterior slope of the tibial component
. Femoral component undersizing
. Internal rotation of the tibial component

Correct Answer & Explanation

. Excessive posterior slope of the tibial component

Explanation

Excessive posterior slope of the tibial component creates a relatively loose flexion gap and can lead to posterior subluxation of the femoral component on the tibial tray, particularly during activities like staircase ascent which involve high flexion and posterior shear forces. It effectively allows the femur to slide posteriorly. Insufficient posterior slope would cause tightness in flexion. Femoral undersizing might cause instability, but posterior subluxation is highly indicative of excessive posterior slope.

Question 5915

Topic: Total Knee Arthroplasty (TKA)

When templating for TKA, what is the most important measurement to ensure proper restoration of limb length and joint line?

. Preoperative knee flexion range of motion
. Preoperative patellar height
. Distal femoral resection amount relative to epicondylar axis
. Overall mechanical axis deviation
. Preoperative distal femoral length and proximal tibial length relative to fixed landmarks

Correct Answer & Explanation

. Preoperative distal femoral length and proximal tibial length relative to fixed landmarks

Explanation

To ensure proper restoration of limb length and joint line, it is crucial to measure the preoperative distal femoral length and proximal tibial length relative to fixed anatomical landmarks (e.g., femoral head, ankle joint, fibular head). This helps guide bone resections to avoid either lengthening or shortening the limb significantly and to maintain the natural joint line, preventing patella baja or alta. Other options are important but not directly forbothlimb length and joint line restoration.

Question 5916

Topic: 3. Adult Reconstruction (Hip & Knee)

A TKA patient develops severe pain, swelling, and warmth 3 months postoperatively. Aspiration confirms acute periprosthetic joint infection. What component malalignment, if present, might have indirectly contributed to this infection risk?

. Overall neutral mechanical axis
. Femoral component external rotation
. Patella alta
. Any significant malalignment causing chronic soft tissue irritation or instability
. Tibial component varus alignment

Correct Answer & Explanation

. Any significant malalignment causing chronic soft tissue irritation or instability

Explanation

While direct causation is rare, any significant component malalignment leading to chronic soft tissue irritation, persistent effusions, pain, or instability can compromise the local biological environment, potentially increasing the risk of infection. Chronic inflammation, repeated injections, and potentially compromised vascularity due to abnormal mechanics can be contributing factors. Neutral alignment, specific rotations or patella alta do not inherently increase infection risk unless they are symptomatic and lead to other interventions or complications.

Question 5917

Topic: Total Knee Arthroplasty (TKA)

When performing TKA, the anterior femoral cortex is accidentally 'notched' during distal femoral resection. What malalignment or surgical error predisposes to this?

. Femoral component undersizing
. Excessive posterior slope of the femoral component
. Using an overly anterior entry point for the intramedullary guide rod
. Insufficient distal femoral resection
. Excessive external rotation of the femoral component

Correct Answer & Explanation

. Using an overly anterior entry point for the intramedullary guide rod

Explanation

Notching of the anterior femoral cortex occurs when the intramedullary guide rod for distal femoral resection is placed with an overly anterior entry point, leading to an oblique cut that compromises the anterior cortex. This can predispose to periprosthetic fracture. It is not directly related to femoral component sizing, slope, or rotation, but rather to the distal femoral cutting block's positioning. Insufficient distal femoral resection would lead to a tight extension gap, not notching.

Question 5918

Topic: Total Knee Arthroplasty (TKA)

Which intraoperative assessment confirms adequate rotational alignment of the tibial component relative to the femoral component in flexion?

. The tibial component is parallel to the mechanical axis of the tibia on a long leg view
. The patella tracks centrally in the femoral trochlea during flexion-extension
. The femoral component is 3-5 degrees externally rotated to the posterior condyles
. The medial and lateral flexion gaps are equal and rectangular when evaluated with a spacer block
. The tibial component has a 3-degree posterior slope

Correct Answer & Explanation

. The medial and lateral flexion gaps are equal and rectangular when evaluated with a spacer block

Explanation

Adequate rotational alignment of the tibial component relative to the femoral component, especially in flexion, is confirmed when the medial and lateral flexion gaps are equal and rectangular when evaluated with a spacer block. This indicates that the tibiofemoral articulation is balanced and symmetrical in the rotational plane. While central patellar tracking is a good sign, the gap assessment is a direct measure of tibiofemoral rotation. Other options describe different aspects of alignment.

Question 5919

Topic: Total Knee Arthroplasty (TKA)

What is the potential consequence of restoring the joint line too proximally in TKA?

. Patella alta
. Patella baja
. Increased risk of extensor mechanism impingement
. Increased range of motion
. Reduced risk of quadriceps weakness

Correct Answer & Explanation

. Patella baja

Explanation

Restoring the joint line too proximally (i.e., making the distal femoral cut and/or proximal tibial cut more proximally than the native joint line) can lead to patella baja (low-riding patella). This shortens the patellar tendon moment arm, increases patellofemoral contact forces, can cause anterior knee pain, crepitus, and potentially patellar clunk syndrome. Patella alta is due to a more distally restored joint line.

Question 5920

Topic: Total Knee Arthroplasty (TKA)

What is a characteristic symptom of symptomatic patella baja after TKA?

. Lateral patellar subluxation and a 'J' sign
. Difficulty initiating knee flexion and increased patellofemoral pressure
. Hyperextension and instability
. Posterior knee pain and clunking in deep flexion
. Effusion without pain

Correct Answer & Explanation

. Difficulty initiating knee flexion and increased patellofemoral pressure

Explanation

Symptomatic patella baja (low-riding patella) after TKA typically manifests as difficulty initiating knee flexion, increased patellofemoral contact pressure, anterior knee pain, crepitus, and sometimes patellar clunk syndrome. It can also lead to a functional shortening of the quadriceps moment arm. Lateral patellar subluxation and a 'J' sign are more indicative of patella alta or rotational malalignment. Hyperextension is related to tibial slope. Posterior knee pain and clunking in deep flexion often relate to posterior impingement or loose bodies.

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