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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 129 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 2561

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty using a measured resection and anterior referencing technique, the surgeon evaluates the gaps and finds that the extension gap is perfectly balanced, but the flexion gap is unacceptably tight. Which of the following adjustments is the best step to balance the knee?

. Decrease the size of the femoral component
. Recut the distal femur to remove more bone
. Release the posterior cruciate ligament completely
. Thicken the tibial polyethylene insert
. Release the superficial medial collateral ligament

Correct Answer & Explanation

. Decrease the size of the femoral component

Explanation

When using an anterior referencing system, decreasing the size of the femoral component (downsizing) will result in more posterior femoral condyle bone being resected. This opens up (increases) the flexion gap without affecting the extension gap, correcting the tight flexion gap.

Question 2562

Topic: 3. Adult Reconstruction (Hip & Knee)

When evaluating a patient for total hip arthroplasty (THA), a pre-operative seated to standing lateral radiograph series reveals a change in pelvic tilt (PT) of less than 10 degrees. This finding indicates:

. Normal spinopelvic mobility
. A hypermobile spinopelvic junction requiring a constrained liner
. A stiff spinopelvic junction increasing the risk of anterior dislocation in standing
. A stiff spinopelvic junction increasing the risk of posterior dislocation in sitting
. Sagittal spinal imbalance requiring spinal fusion prior to THA

Correct Answer & Explanation

. A stiff spinopelvic junction increasing the risk of posterior dislocation in sitting

Explanation

A change in pelvic tilt of <10 degrees from standing to sitting indicates a stiff spinopelvic junction. Because the pelvis fails to retrovert normally when sitting, the acetabular component does not open anteriorly, leading to anterior impingement and an increased risk of posterior dislocation during sitting.

Question 2563

Topic: 3. Adult Reconstruction (Hip & Knee)
A 50-year-old male with a metal-on-metal total hip arthroplasty placed 8 years ago presents with new-onset groin pain. Radiographs show a well-fixed implant without loosening. Aspiration yields sterile fluid with a predominance of lymphocytes. What type of hypersensitivity reaction is primarily responsible for this adverse local tissue reaction (ALTR)?
. Type I (IgE-mediated)
. Type II (Cytotoxic)
. Type III (Immune complex)
. Type IV (Delayed cell-mediated)
. Type V (Receptor-mediated)

Correct Answer & Explanation

. Type IV (Delayed cell-mediated)

Explanation

Adverse local tissue reactions (ALTR) or ALVAL (aseptic lymphocytic vasculitis-associated lesions) in metal-on-metal implants are characterized by a Type IV (delayed, cell-mediated) hypersensitivity reaction, leading to characteristic perivascular lymphocytic infiltration.

Question 2564

Topic: 3. Adult Reconstruction (Hip & Knee)

During the manufacturing of highly cross-linked polyethylene (HXLPE) for total hip arthroplasty, what is the primary purpose of thermal treatment (remelting or annealing) after gamma irradiation?

. To increase crystallinity of the polymer
. To induce additional cross-linking
. To extinguish residual free radicals
. To increase the overall molecular weight
. To sterilize the final implant

Correct Answer & Explanation

. To extinguish residual free radicals

Explanation

Gamma irradiation induces cross-linking in the polyethylene but leaves residual free radicals. Post-irradiation thermal treatment (either remelting above the melting temperature or annealing below it) is performed specifically to extinguish these free radicals, thereby preventing in vivo oxidative degradation.

Question 2565

Topic: Total Knee Arthroplasty (TKA)

In total knee arthroplasty, accurately establishing the femoral component rotation is critical for patellofemoral tracking and flexion gap balancing. Which of the following axes is defined by a line connecting the deepest part of the trochlear groove to the center of the intercondylar notch?

. Clinical transepicondylar axis
. Surgical transepicondylar axis
. Whiteside's line
. Posterior condylar axis
. Mechanical axis of the femur

Correct Answer & Explanation

. Whiteside's line

Explanation

Whiteside's line (the anteroposterior axis) is a crucial anatomical landmark used to establish femoral component rotation in TKA. It is defined by drawing a line from the deepest part of the trochlear groove anteriorly to the center of the intercondylar notch posteriorly. The femoral component is typically rotated externally so its posterior condyles are perpendicular to this line.

Question 2566

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 a loud 'squeaking' noise from the hip with deep flexion. Which of the following is considered a significant risk factor for the development of squeaking in this bearing type?

. Increased femoral head size
. Use of a highly cross-linked polyethylene liner
. Acetabular component malposition (e.g., edge loading)
. Decreased body mass index (BMI)
. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)

Correct Answer & Explanation

. Acetabular component malposition (e.g., edge loading)

Explanation

Squeaking is a specific complication of ceramic-on-ceramic (CoC) bearings. Significant risk factors include acetabular component malposition (such as excessive inclination or anteversion), which leads to edge loading. Edge loading results in the loss of fluid film lubrication, stripe wear, and micro-separation, mechanically producing the audible squeak.

Question 2567

Topic: 3. Adult Reconstruction (Hip & Knee)
A patient with a metal-on-metal total hip arthroplasty presents with groin pain and a large cystic mass around the hip. A revision is performed, and tissue pathology reveals an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). This histological response is best characterized as which type of hypersensitivity reaction?
. Type I (IgE-mediated)
. Type II (Cytotoxic)
. Type III (Immune complex)
. Type IV (Delayed-type cell-mediated)
. Type V (Stimulatory autoantibody)

Correct Answer & Explanation

. Type IV (Delayed-type cell-mediated)

Explanation

ALVAL (Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion) is an adverse local tissue reaction associated predominantly with metal-on-metal implants. Histologically, it presents with a dense perivascular infiltrate of lymphocytes, characterizing it as a Type IV (delayed-type, cell-mediated) hypersensitivity reaction to metal ions (typically cobalt and chromium).

Question 2568

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a Metal-on-Metal (MoM) total hip arthroplasty presents with new-onset groin pain. Blood tests show elevated cobalt and chromium ions. Which imaging modality is considered the gold standard for diagnosing and assessing the extent of an adverse local tissue reaction (ALTR) or pseudotumor?

. Ultrasonography
. Technetium-99m bone scan
. Computed tomography (CT) with metal artifact reduction
. Metal artifact reduction sequence (MARS) MRI
. Fluoroscopic arthrogram

Correct Answer & Explanation

. Metal artifact reduction sequence (MARS) MRI

Explanation

Metal Artifact Reduction Sequence (MARS) MRI is the gold standard for evaluating adverse local tissue reactions (ALTR) or pseudotumors in symptomatic Metal-on-Metal THA patients. It accurately demonstrates the size, characteristics (solid vs. cystic), and extent of muscle necrosis or tissue damage, guiding the decision for revision surgery.

Question 2569

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary cruciate-retaining (CR) total knee arthroplasty, the surgeon evaluates the gaps with trial components. The extension gap is symmetric and perfectly balanced, but the flexion gap is excessively tight. Which of the following is the most appropriate next surgical step to address this imbalance?

. Recut the proximal tibia with increased posterior slope
. Recut the proximal tibia with decreased posterior slope
. Resect additional bone from the distal femur
. Downsize the tibial polyethylene insert
. Upsize the femoral component

Correct Answer & Explanation

. Recut the proximal tibia with decreased posterior slope

Explanation

A tight flexion gap with a balanced extension gap requires selective opening of the flexion space. Increasing the posterior slope of the tibial cut opens the flexion gap without significantly affecting the extension gap. Alternatively, anteriorizing the femoral component or recessing/releasing the PCL could also address a tight flexion gap. Resecting more distal femur only affects the extension gap.

Question 2570

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active man who underwent a total hip arthroplasty (THA) with a ceramic-on-ceramic bearing 2 years ago presents complaining of an audible, high-pitched squeak from his hip when he bends to tie his shoes. Radiographs reveal an acetabular cup inclination angle of 60 degrees. What is the primary pathophysiological mechanism responsible for this squeaking?

. Third-body wear from retained cement debris
. Cold flow of the articular bearing surface
. Stripe wear from edge loading of the ceramic liner
. Trunnionosis at the head-neck junction
. Impingement of the anterior capsule against the femoral neck

Correct Answer & Explanation

. Stripe wear from edge loading of the ceramic liner

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with component malposition, specifically excessive acetabular inclination or anteversion. This steep positioning leads to 'edge loading,' where the femoral head articulates with the rim of the ceramic liner. This concentrates stress, disrupts fluid-film lubrication, and causes 'stripe wear' on the ceramic head, generating the characteristic audible squeak.

Question 2571

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty (TKA), after making the standard bony cuts and placing the trial components, the surgeon assesses the gaps. The knee is perfectly balanced in full extension, but the joint is overly tight and fails to reach full flexion. Which of the following is the most appropriate surgical step to balance this knee?

. Release the posterior capsule
. Downsize the femoral component and use a thicker polyethylene insert
. Downsize the AP dimension of the femoral component
. Recut the distal femur to resect more bone
. Decrease the posterior slope of the tibial cut

Correct Answer & Explanation

. Downsize the AP dimension of the femoral component

Explanation

A knee that is balanced in extension but tight in flexion requires a selective increase in the flexion gap. Downsizing the anteroposterior (AP) dimension of the femoral component (when utilizing an anterior referencing system) resects more posterior condylar bone, opening the flexion gap without altering the extension gap. Increasing the posterior tibial slope is another option. Releasing the posterior capsule or recutting the distal femur would improperly affect the extension gap.

Question 2572

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female experiences recurrent posterior dislocations after a primary right total hip arthroplasty via a posterior approach. CT imaging demonstrates the acetabular cup is placed in 45 degrees of abduction and 5 degrees of retroversion. The femoral stem is in 10 degrees of anteversion. What is the primary cause of her instability?

. Excessive cup abduction
. Excessive femoral anteversion
. Acetabular cup retroversion
. Insufficient soft tissue tension
. Impingement of the greater trochanter

Correct Answer & Explanation

. Acetabular cup retroversion

Explanation

The safe zone for acetabular cup placement is historically 15 +/- 10 degrees of anteversion and 40 +/- 10 degrees of abduction. A retroverted cup (5 degrees retroversion) heavily predisposes the patient to posterior dislocation, particularly when combined with a posterior surgical approach.

Question 2573

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon performs a trial reduction and observes lateral tracking of the patella. Which of the following technical errors regarding component positioning is most likely responsible for this finding?

. Internal rotation of the femoral component
. External rotation of the tibial component
. External rotation of the femoral component
. Lateralization of the femoral component
. Medialization of the tibial tray

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of the femoral and/or tibial components increases the Q-angle, leading to lateral patellar maltracking. Conversely, appropriate external rotation of these components improves patellar tracking. Lateralization of the femoral or tibial components generally decreases the Q angle.

Question 2574

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man presents with a painful total knee arthroplasty 2 years after index surgery. Joint aspiration reveals a synovial WBC count of 3,500 cells/uL with 75% PMNs. Which of the following synovial fluid biomarkers is most specific for diagnosing a periprosthetic joint infection by targeting an antimicrobial peptide released by neutrophils?

. Leukocyte esterase
. C-reactive protein
. Alpha-defensin
. Interleukin-6
. Procalcitonin

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. It is highly sensitive and specific for periprosthetic joint infection (PJI). Leukocyte esterase is an enzyme released by neutrophils, useful but less specific than alpha-defensin.

Question 2575

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with groin pain. MRI reveals a large cystic mass around the hip joint. Histopathology of the periprosthetic tissue is most likely to show which of the following characterized by ALVAL (Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion)?

. Massive neutrophilic infiltration with positive alpha-defensin
. Extensive polymethylmethacrylate (PMMA) debris with foreign body giant cells
. Perivascular lymphocytic cuffing and extensive tissue necrosis
. Birefringent crystals under polarized light with monosodium urate
. Predominance of eosinophils and mast cells

Correct Answer & Explanation

. Perivascular lymphocytic cuffing and extensive tissue necrosis

Explanation

ALVAL is an adverse local tissue reaction (ALTR) associated with metal-on-metal arthroplasty (and corrosion in taper junctions). Histologically, it is a Type IV delayed hypersensitivity reaction characterized by perivascular lymphocytic cuffing, extensive tissue necrosis, and macrophages containing fine metallic wear debris.

Question 2576

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with new-onset groin pain 6 years after an uncomplicated primary metal-on-polyethylene total hip arthroplasty utilizing a large diameter modular femoral head. Radiographs show well-fixed components in acceptable alignment. Inflammatory markers are normal. Metal Artifact Reduction Sequence (MARS) MRI reveals a large cystic mass adjacent to the greater trochanter. What is the most likely diagnosis?

. Polyethylene wear osteolysis
. Adverse local tissue reaction secondary to trunnionosis
. Periprosthetic joint infection
. Iliopsoas impingement
. Aseptic component loosening

Correct Answer & Explanation

. Adverse local tissue reaction secondary to trunnionosis

Explanation

The patient has an adverse local tissue reaction (ALTR) resulting from mechanically assisted crevice corrosion at the modular head-neck junction, known as trunnionosis. This can occur even in metal-on-polyethylene articulations, particularly when a large diameter head is used, as it increases the torque and fretting corrosion at the trunnion.

Question 2577

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty (TKA), the surgeon trials the components and notes that the knee is well-balanced in full extension but excessively tight in 90 degrees of flexion. Which of the following is the most appropriate next step to balance the knee?

. Release the posterior capsule
. Upsize the femoral component
. Downsize the femoral component and use a posterior referencing system
. Increase the thickness of the polyethylene insert
. Mill more bone from the distal femur

Correct Answer & Explanation

. Downsize the femoral component and use a posterior referencing system

Explanation

A tight flexion gap with a balanced extension gap implies that the anteroposterior dimension of the femoral component, specifically the posterior condyles, is too large. Downsizing the femoral component using a posterior referencing system will decrease the posterior condylar offset, thereby enlarging the flexion gap without affecting the extension gap.

Question 2578

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon notes that the knee is well-balanced in full extension, but the flexion gap is excessively tight both medially and laterally. What is the most appropriate next step to balance the knee?

. Resect additional distal femur
. Increase the anteroposterior size of the femoral component
. Decrease the anteroposterior size of the femoral component
. Thicken the polyethylene tibial insert
. Release the superficial medial collateral ligament

Correct Answer & Explanation

. Decrease the anteroposterior size of the femoral component

Explanation

A tight flexion gap with a balanced extension gap indicates the posterior condyles are too prominent or the space is too small in flexion. Decreasing the anteroposterior (AP) size of the femoral component increases the flexion gap without affecting the extension gap. Increasing posterior tibial slope or recessing the PCL (if retaining) are alternative solutions.

Question 2579

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman undergoes a total hip arthroplasty via a direct anterior approach. Postoperatively, she complains of numbness and a burning sensation over the anterolateral aspect of her thigh. Which nerve is most likely injured, and between which two muscles does it typically pass near the anterior superior iliac spine?

. Femoral nerve; Psoas and Iliacus
. Lateral femoral cutaneous nerve; Tensor fasciae latae and Sartorius
. Lateral femoral cutaneous nerve; Gluteus medius and Tensor fasciae latae
. Obturator nerve; Adductor longus and Brevis
. Ilioinguinal nerve; Internal and External oblique

Correct Answer & Explanation

. Lateral femoral cutaneous nerve; Tensor fasciae latae and Sartorius

Explanation

The lateral femoral cutaneous nerve (LFCN) is at highest risk during the direct anterior approach to the hip. It provides sensation to the anterolateral thigh. Anatomically, it typically exits the pelvis medial to the ASIS and courses distally in the interval between the tensor fasciae latae (TFL) and the sartorius muscle.

Question 2580

Topic: 3. Adult Reconstruction (Hip & Knee)

During the trial phase of a cruciate-retaining (CR) total knee arthroplasty, the knee is found to be stable and symmetric in extension, but it is unacceptably tight in flexion, causing anterior liftoff of the tibial tray. Assuming the posterior cruciate ligament (PCL) has already been appropriately managed and recessed, what is the best surgical option to balance the knee?

. Decrease the posterior tibial slope
. Increase the posterior tibial slope
. Resect more distal femur
. Use a thicker polyethylene insert
. Upsize the femoral component

Correct Answer & Explanation

. Increase the posterior tibial slope

Explanation

A tight flexion gap with a balanced extension gap implies that the space in flexion needs to be selectively increased without altering the extension gap. Increasing the posterior slope of the tibial cut effectively lowers the posterior aspect of the tibia, opening up the flexion gap while having a minimal effect on the extension gap. Resecting more distal femur would exclusively open the extension gap. Upsizing the femoral component would decrease the flexion gap, worsening the problem. Using a thicker insert would tighten both flexion and extension gaps.

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