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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 121 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 2401

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria for periprosthetic joint infection (PJI), which of the following is considered a major criterion?

. Elevated serum CRP > 10 mg/L
. Positive leukocyte esterase strip test
. Two positive periprosthetic tissue cultures with identical organisms
. Synovial fluid WBC > 3000 cells/uL
. Elevated serum D-dimer

Correct Answer & Explanation

. Two positive periprosthetic tissue cultures with identical organisms

Explanation

The ICM criteria state that the presence of either a sinus tract communicating with the joint or two positive periprosthetic tissue/fluid cultures with phenotypically identical organisms serves as definitive (major) evidence of PJI. The other options are considered minor criteria.

Question 2402

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty utilizing the direct anterior approach (Smith-Petersen interval), the surgeon must be cautious of a nerve that typically exits the pelvis medial to the anterior superior iliac spine (ASIS) and crosses the surgical field.

Injury to this nerve will result in which of the following deficits?

. Weakness in hip abduction
. Weakness in knee extension
. Sensory loss over the lateral aspect of the thigh
. Sensory loss over the medial aspect of the thigh
. Weakness in hip external rotation

Correct Answer & Explanation

. Sensory loss over the lateral aspect of the thigh

Explanation

The lateral femoral cutaneous nerve (LFCN) is at risk during the direct anterior approach to the hip. It provides pure sensation to the lateral and anterolateral aspect of the thigh. It does not provide motor innervation. Weakness in hip abduction implies superior gluteal nerve injury, knee extension points to the femoral nerve, medial thigh sensation to the obturator nerve, and hip external rotation involves several short external rotators and associated nerves.

Question 2403

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female undergoes a primary posterior-stabilized total knee arthroplasty. Intraoperatively, the surgeon realizes that the knee is well-balanced in extension but unacceptably tight in flexion. Which of the following technical errors most frequently causes an isolated tight flexion gap?

. Excessive distal femoral resection
. Oversizing the femoral component in the anteroposterior (AP) dimension
. Undersizing the femoral component in the anteroposterior (AP) dimension
. Increasing the posterior slope of the tibial cut
. Recessing the joint line (patella alta)

Correct Answer & Explanation

. Oversizing the femoral component in the anteroposterior (AP) dimension

Explanation

The flexion gap in TKA is dictated primarily by the size of the posterior femoral condyles and the AP dimension of the femoral component. Oversizing the femoral component in the AP dimension (and specifically adding posterior offset) stuffs the posterior joint space, leading to a tight flexion gap. Excessive distal femoral resection affects the extension gap (making it loose). Increasing the posterior tibial slope would actually increase (loosen) the flexion gap.

Question 2404

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized Total Knee Arthroplasty (TKA), the surgeon uses spacer blocks to assess the flexion and extension gaps. The extension gap is symmetric and perfectly balanced. However, the flexion gap is unacceptably tight, preventing the knee from flexing past 80 degrees without lifting the joint off the tibia.

What is the most appropriate intraoperative adjustment to correct this mismatch?

. Resect an additional 2 mm of distal femur
. Decrease the femoral component size (using a posterior referencing system)
. Increase the thickness of the polyethylene insert
. Release the posterior capsule
. Resect an additional 2 mm of proximal tibia

Correct Answer & Explanation

. Decrease the femoral component size (using a posterior referencing system)

Explanation

A tight flexion gap with a balanced extension gap implies that the posterior condyles of the femur are projecting too far posteriorly, tightening the collateral ligaments only in flexion. Downsizing the femoral component using a posterior referencing system will result in a thicker posterior femoral cut, effectively opening the flexion gap without altering the distal femoral cut (which controls the extension gap). Resecting more proximal tibia would loosen both gaps equally. Resecting more distal femur would loosen only the extension gap.

Question 2405

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male with a metal-on-polyethylene total hip arthroplasty (THA) placed 8 years ago presents with insidious onset of anterior groin pain. Hip aspiration reveals cloudy fluid with normal leukocyte counts and negative cultures. MRI with metal artifact reduction sequence (MARS) demonstrates a cystic mass adjacent to the greater trochanter. Serum cobalt levels are markedly elevated, while chromium levels are normal. What is the most likely etiology of this patient's presentation?

. Adverse local tissue reaction secondary to trunnionosis
. Polyethylene wear osteolysis
. Periprosthetic joint infection
. Aseptic loosening of the femoral stem
. Metal-on-metal articulation wear

Correct Answer & Explanation

. Adverse local tissue reaction secondary to trunnionosis

Explanation

The patient has a metal-on-polyethylene bearing but demonstrates systemic and local signs of metal toxicity (pseudotumor/ALTR). Elevated serum cobalt out of proportion to chromium in the setting of a non-metal-on-metal bearing is the hallmark of mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction. Polyethylene wear causes osteolysis but not elevated cobalt or classic ALTR cystic masses. Infection is ruled out by the negative aspirate.

Question 2406

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty (THA), the choice of bearing surface impacts the wear profile and complication risks. Which of the following bearing surface combinations is classically associated with the phenomenon of 'stripe wear' and an increased risk of audible squeaking during ambulation?

. Metal-on-highly crosslinked polyethylene
. Ceramic-on-polyethylene
. Metal-on-metal
. Ceramic-on-ceramic
. Oxinium-on-polyethylene

Correct Answer & Explanation

. Ceramic-on-ceramic

Explanation

Ceramic-on-ceramic (CoC) bearings offer extremely low wear rates and no risk of polyethylene osteolysis or metal ion toxicity. However, complications unique to CoC bearings include the risk of ceramic fracture, 'stripe wear' (linear wear patterns caused by edge loading during microseparation of the head and liner), and audible squeaking, which occurs in a small percentage of patients (up to 10% in some series) and can be highly distressing.

Question 2407

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old highly active man is scheduled for a total hip arthroplasty (THA). The surgeon considers utilizing a ceramic-on-ceramic bearing surface to maximize longevity. Which of the following is the most notable disadvantage or complication specific to a ceramic-on-ceramic bearing compared to ceramic-on-highly cross-linked polyethylene?

. A significantly higher rate of volumetric wear debris generation
. An increased risk of profound macrophage-mediated osteolysis
. Audible squeaking during hip articulation
. Severe adverse local tissue reactions (ALTR) mediated by a Type IV hypersensitivity
. Accelerated corrosion at the femoral head-neck trunnion

Correct Answer & Explanation

. Audible squeaking during hip articulation

Explanation

Ceramic-on-ceramic (CoC) bearings offer the lowest wear rates of all THA bearing couples and do not cause significant osteolysis or metal-related hypersensitivity. However, a well-documented unique complication of CoC bearings is audible squeaking during motion, occurring in up to 10-15% of patients in some series, often associated with micro-separation or impingement.

Question 2408

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty (TKA), the surgeon evaluates the flexion and extension gaps. Utilizing spacer blocks, the surgeon notes that the extension gap is symmetric and perfectly balanced, but the flexion gap is excessively tight. Assuming an anterior referencing sizing guide was used, which of the following surgical adjustments is the most appropriate next step to balance the knee?

. Increase the thickness of the distal femoral bone cut
. Perform a release of the posterior capsule
. Downsize the femoral component
. Decrease the posterior tibial slope
. Release the deep medial collateral ligament

Correct Answer & Explanation

. Downsize the femoral component

Explanation

When using an anterior referencing system, the anterior flange of all femoral components rests on the same cut surface. Downsizing the femoral component reduces its anteroposterior dimension by removing more bone from the posterior condyles. This specifically enlarges the flexion gap without altering the extension gap, thereby resolving an isolated tight flexion gap.

Question 2409

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty utilizing a measured resection technique, trial components are placed. Examination of the joint reveals that the knee is well-balanced and symmetric in 90 degrees of flexion, but it is excessively tight in full extension. Which of the following is the most appropriate next step to balance the knee?

. Release the posterior cruciate ligament (PCL)
. Resect additional proximal tibia
. Downsize the femoral component
. Resect additional distal femur
. Upsize the polyethylene insert

Correct Answer & Explanation

. Resect additional distal femur

Explanation

Gap balancing in TKA requires independent adjustment of the flexion and extension gaps. If the knee is balanced in flexion but tight in extension, the extension gap is too small. Resecting additional distal femur specifically opens the extension gap without affecting the flexion gap. Resecting more proximal tibia would open both gaps. Downsizing the femur increases the flexion gap. Upsizing the poly would make both gaps tighter.

Question 2410

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old female who underwent a metal-on-metal total hip arthroplasty 5 years ago presents with new-onset groin pain and a palpable mass. Aspiration yields sterile, cloudy fluid. Histopathological analysis of the periprosthetic tissue is most likely to demonstrate which of the following?

. Abundant neutrophils and bacterial organisms
. Sheets of lipid-laden macrophages
. Perivascular lymphocytic infiltrate
. Birefringent polymeric wear debris under polarized light
. Extensive caseating granulomas

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate

Explanation

Adverse local tissue reaction (ALTR) or Aseptic Lymphocytic Vasculitis-Associated Lesions (ALVAL) is a Type IV delayed hypersensitivity reaction to metal ions (cobalt and chromium). Histologically, ALVAL is characterized by extensive perivascular lymphocytic infiltrates. Birefringent wear debris is typical of polyethylene wear, not metal-on-metal.

Question 2411

Topic: Total Hip Arthroplasty (THA)

A 55-year-old male who underwent a ceramic-on-ceramic total hip arthroplasty 3 years ago reports a new 'squeaking' noise from his hip during specific movements. He denies pain, and radiographs show no gross loosening. Which of the following component position factors is most strongly associated with the development of squeaking in ceramic-on-ceramic bearings?

. Decreased femoral offset
. Excessive acetabular cup anteversion
. Insufficient acetabular cup abduction
. Femoral stem retroversion
. Edge loading due to cup malposition

Correct Answer & Explanation

. Edge loading due to cup malposition

Explanation

Squeaking in ceramic-on-ceramic THA is most strongly associated with edge loading, which often results from cup malposition (such as excessive abduction or extremes of version). Edge loading leads to loss of fluid-film lubrication, stripe wear, and micro-separation during the swing phase, producing the characteristic high-frequency squeak.

Question 2412

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male who underwent an uncomplicated total hip arthroplasty (THA) 3 years ago presents to the clinic complaining of a high-pitched squeaking noise coming from his hip when he walks or bends over. He denies any pain, instability, or trauma. Based on this presentation, what bearing surface combination was most likely utilized in his THA?

. Metal-on-polyethylene
. Ceramic-on-ceramic
. Metal-on-metal
. Ceramic-on-polyethylene
. Oxinium-on-polyethylene

Correct Answer & Explanation

. Ceramic-on-ceramic

Explanation

Squeaking is a known, unique complication associated with ceramic-on-ceramic (CoC) bearing surfaces in total hip arthroplasty, occurring in up to 10% of cases. The exact etiology is multifactorial, potentially involving stripe wear, edge loading, microseparation, or third-body debris. Squeaking typically does not occur with polyethylene or metal-on-metal bearing surfaces.

Question 2413

Topic: Total Hip Arthroplasty (THA)

A 68-year-old female presents with recurrent posterior dislocations following a primary total hip arthroplasty performed 6 months ago.

A recent CT scan evaluating component positioning reveals an acetabular component inclination of 45 degrees and an anteversion of 0 degrees. The femoral stem has 15 degrees of anteversion. What is the most likely underlying cause of her recurrent instability?

. Acetabular retroversion
. Excessive acetabular anteversion
. Excessive femoral stem anteversion
. Vertical inclination of the acetabular component
. Abductor mechanism deficiency

Correct Answer & Explanation

. Acetabular retroversion

Explanation

The 'safe zone' for acetabular component placement, historically described by Lewinnek, is 15° ± 10° of anteversion and 40° ± 10° of inclination. An acetabular anteversion of 0 degrees means the cup is placed in relative retroversion compared to normal native anatomy. Acetabular retroversion heavily predisposes a THA patient to posterior dislocation, particularly when the hip is placed in flexion, adduction, and internal rotation.

Question 2414

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon evaluates the gaps after initial bony resections. The extension gap is symmetric and perfectly balanced, but the flexion gap is tight medially and loose laterally. What is the most appropriate next step to balance the knee?

. Release the superficial medial collateral ligament
. Release the posterior cruciate ligament
. Externally rotate the femoral component
. Downsize the femoral component
. Resect more distal femur

Correct Answer & Explanation

. Externally rotate the femoral component

Explanation

A flexion gap that is tight medially and loose laterally indicates relative internal rotation of the femoral component. Externally rotating the femoral component will loosen the medial side in flexion and tighten the lateral side in flexion without affecting the extension gap.

Question 2415

Topic: 3. Adult Reconstruction (Hip & Knee)

Which bearing surface combination in Total Hip Arthroplasty (THA) is associated with the lowest volumetric wear rate in laboratory simulator studies?

. Cobalt-chrome on highly cross-linked polyethylene
. Ceramic on highly cross-linked polyethylene
. Cobalt-chrome on conventional polyethylene
. Ceramic on ceramic
. Metal on metal

Correct Answer & Explanation

. Ceramic on ceramic

Explanation

Ceramic-on-ceramic (CoC) bearing surfaces exhibit the lowest volumetric wear rates of any bearing combination (typically < 1 cubic mm/year). However, they carry unique risks, such as squeaking and catastrophic ceramic fracture. Modern highly cross-linked polyethylene also has very low wear and is more commonly used clinically to avoid the risks of CoC.

Question 2416

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male who underwent a metal-on-metal total hip arthroplasty 8 years ago presents with groin pain and a palpable anterior mass. Serum cobalt and chromium levels are significantly elevated. A MARS MRI shows a thick-walled, cystic mass communicating with the joint. What is the characteristic histological finding associated with this condition?

. Abundant acute inflammatory infiltrate with neutrophils
. Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions (ALVAL)
. Monoclonal sheets of plasma cells
. Multinucleated foreign body giant cells containing birefringent polyethylene debris
. Malignant spindle cells with high mitotic activity

Correct Answer & Explanation

. Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions (ALVAL)

Explanation

The clinical picture describes an adverse local tissue reaction (ALTR) or 'pseudotumor' associated with metal-on-metal bearing surfaces. Histologically, this immune-mediated delayed-type hypersensitivity response (Type IV) to metal debris is characterized by Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions (ALVAL), demonstrating a robust perivascular lymphocytic infiltrate and tissue necrosis.

Question 2417

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty (TKA), the surgeon determines the rotational alignment of the femoral component. If the surgeon chooses to use the surgical epicondylar axis (SEA) to establish rotation, what specific anatomical landmarks must be connected?

. The medial epicondylar sulcus and the most prominent point of the lateral epicondyle
. The most prominent point of the medial epicondyle and the most prominent point of the lateral epicondyle
. The center of the trochlear groove and the apex of the intercondylar notch
. The posterior-most aspects of the medial and lateral femoral condyles
. The medial collateral ligament insertion and the fibular head

Correct Answer & Explanation

. The medial epicondylar sulcus and the most prominent point of the lateral epicondyle

Explanation

Establishing correct femoral rotation is critical for patellar tracking and flexion gap balance in TKA. The Surgical Epicondylar Axis (SEA) connects the sulcus on the medial epicondyle (the origin of the deep MCL) to the most prominent point on the lateral epicondyle. This differs from the Clinical Epicondylar Axis, which connects the most prominent points of both the medial and lateral epicondyles.

Question 2418

Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old male who underwent a metal-on-metal total hip arthroplasty 6 years ago presents with new-onset groin pain and a palpable mass. Workup reveals an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). Which type of hypersensitivity reaction is the primary driver of this pathology?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type IV

Explanation

ALVAL (aseptic lymphocyte-dominated vasculitis-associated lesion), also known clinically as a pseudotumor in the context of metal-on-metal hip replacements, is primarily mediated by a Type IV (delayed, T-cell mediated) hypersensitivity reaction to metal wear debris (usually cobalt and chromium ions).

Question 2419

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty (TKA), after making all bone cuts and placing trial components, the surgeon assesses the gaps. The knee is noted to be perfectly balanced and appropriately tensioned in full extension but is excessively tight in 90 degrees of flexion. Which of the following component adjustments is the most appropriate to correct this mismatch?

. Downsize the femoral component and translate it anteriorly.
. Upsize the femoral component and translate it posteriorly.
. Release the posterior capsule.
. Downsize the femoral component while maintaining the anterior referencing.
. Increase the thickness of the polyethylene tibial insert.

Correct Answer & Explanation

. Downsize the femoral component while maintaining the anterior referencing.

Explanation

A knee that is balanced in extension but tight in flexion requires an isolated increase in the flexion gap. This is achieved by downsizing the femoral component, which selectively decreases the posterior condylar offset. Anterior referencing must be maintained to avoid notching the anterior femur. Releasing the posterior capsule primarily opens the extension gap.

Question 2420

Topic: Total Hip Arthroplasty (THA)

A 68-year-old female undergoes a primary THA via a posterior approach. Postoperatively, she suffers a posterior dislocation. Which of the following component malpositions most likely contributed to this complication?

. Excessive acetabular anteversion
. Decreased femoral offset
. Excessive acetabular abduction
. Acetabular retroversion
. Excessive femoral anteversion

Correct Answer & Explanation

. Acetabular retroversion

Explanation

Posterior dislocation following THA is most commonly associated with acetabular retroversion or insufficient femoral anteversion. Excessive acetabular anteversion typically leads to anterior dislocation.

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