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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 178 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 3541

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man with a metal-on-metal total hip arthroplasty presents with progressive groin pain and swelling 6 years after his index surgery. MRI with metal artifact reduction sequence (MARS) demonstrates a large, thick-walled cystic mass communicating with the joint space. Serum cobalt and chromium levels are elevated. If a biopsy of the periprosthetic tissue is performed, which of the following histologic findings is most characteristic of this patient's pathology?

. Massive infiltration of polymorphonuclear leukocytes with caseating granulomas
. Extensive perivascular lymphocytic infiltration
. Abundant foreign-body giant cells with birefringent polyethylene wear debris
. Florid woven bone formation with osteoblastic rimming
. Suppurative necrosis with a predominant eosinophilic infiltrate

Correct Answer & Explanation

. Extensive perivascular lymphocytic infiltration

Explanation

This patient has an adverse local tissue reaction (ALTR) or adverse reaction to metal debris (ARMD) associated with a metal-on-metal bearing. Histologically, this is often characterized by an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL), which features extensive perivascular lymphocytic infiltration. Giant cells with birefringent particles are seen in polyethylene wear disease.

Question 3542

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon performs a total knee arthroplasty using a measured resection technique. Postoperatively, the patient develops anterior knee pain and recurrent lateral patellar subluxation. A CT scan of the lower extremity is obtained to evaluate component rotation. Which of the following malpositions of the femoral component is most likely responsible for this complication?

. Excessive internal rotation
. Excessive external rotation
. Excessive flexion
. Excessive extension
. Medial translation

Correct Answer & Explanation

. Excessive internal rotation

Explanation

Internal rotation of the femoral component in total knee arthroplasty displaces the trochlear groove medially relative to the extensor mechanism, leading to a functional increase in the Q-angle. This promotes lateral patellar tilt, lateral tracking, and potential subluxation or dislocation of the patella.

Question 3543

Topic: 3. Adult Reconstruction (Hip & Knee)

In planning a total hip arthroplasty for a patient with severe osteoarthritis, the surgeon templates to medialize the center of rotation of the acetabular component relative to the native anatomy, without changing its superior-inferior position. What is the primary biomechanical effect of this medialization?

. Increases the abductor moment arm
. Decreases the body weight moment arm
. Increases the joint reactive force
. Increases the body weight moment arm
. Decreases the abductor moment arm

Correct Answer & Explanation

. Decreases the body weight moment arm

Explanation

Medializing the center of rotation of the hip moves the fulcrum closer to the body's center of gravity. This horizontal shift decreases the body weight moment arm. As a result, the abductor muscles must generate less force to maintain a level pelvis during single-leg stance, which ultimately decreases the total joint reactive force across the hip. Medialization alone does not significantly change the abductor moment arm unless combined with changes in femoral offset.

Question 3544

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents to the emergency department with a posterior dislocation of her total hip arthroplasty, which was performed via a posterior approach 6 weeks ago. After a successful closed reduction, component position is evaluated. Which of the following combinations of component positions would place her at the highest risk for recurrent posterior instability?

. Acetabular anteversion and femoral anteversion
. Acetabular retroversion and femoral retroversion
. Acetabular anteversion and femoral retroversion
. High hip center and increased femoral offset
. Acetabular retroversion and femoral anteversion

Correct Answer & Explanation

. Acetabular retroversion and femoral retroversion

Explanation

Posterior instability in total hip arthroplasty is strongly associated with component retroversion. A combination of acetabular retroversion and femoral retroversion results in a severe lack of anterior coverage and early impingement in flexion and internal rotation, which leverages the femoral head posteriorly out of the socket.

Question 3545

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with increasing pain and swelling in his total knee arthroplasty 3 years after the index surgery. Laboratory studies show an Erythrocyte Sedimentation Rate (ESR) of 55 mm/hr and a C-Reactive Protein (CRP) of 3.2 mg/dL. Knee aspiration yields a synovial fluid white blood cell (WBC) count of 5,500 cells/µL with 88% neutrophils. According to the 2018 International Consensus Meeting (ICM) criteria, what is the most appropriate definitive management for this patient?

. Open debridement, antibiotics, and implant retention (DAIR)
. Single-stage revision arthroplasty in all cases
. Two-stage exchange arthroplasty
. Suppressive antibiotic therapy alone
. Aseptic revision of the tibial insert

Correct Answer & Explanation

. Two-stage exchange arthroplasty

Explanation

The patient has a chronic periprosthetic joint infection (PJI), indicated by symptom onset years after surgery, elevated inflammatory markers (ESR >30 mm/hr, CRP >1.0 mg/dL), and a synovial WBC >3,000 cells/µL with >80% PMNs. The standard of care for chronic PJI in the United States is a two-stage exchange arthroplasty. DAIR is reserved for acute postoperative or acute hematogenous infections (typically within 4 weeks of symptom onset or surgery).

Question 3546

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman presents with anterior knee pain and a sensation of giving way 1 year after a primary total knee arthroplasty. Radiographs reveal lateral patellar subluxation. A CT scan is performed to evaluate component rotation. Which of the following component malpositions is the most likely cause of this complication?

. External rotation of the femoral component and external rotation of the tibial component
. Internal rotation of the femoral component and internal rotation of the tibial component
. External rotation of the femoral component and internal rotation of the tibial component
. Internal rotation of the femoral component and external rotation of the tibial component
. Excessive valgus alignment of the femoral component

Correct Answer & Explanation

. Internal rotation of the femoral component and internal rotation of the tibial component

Explanation

Patellar maltracking and lateral subluxation or dislocation after total knee arthroplasty are most frequently caused by internal rotation of the femoral and/or tibial components. Internal rotation of the femoral component translates the trochlear groove medially, increasing the Q angle. Internal rotation of the tibial component lateralizes the tibial tubercle, further increasing the Q angle and the lateral vector on the patella. Combined internal rotation of both components synergistically exacerbates patellar maltracking.

Question 3547

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old man presents with a painful total hip arthroplasty 4 years after his index procedure. His ESR is 45 mm/hr and CRP is 22 mg/L. Joint aspiration is performed. According to the 2018 International Consensus Meeting (ICM) criteria, which of the following synovial fluid results strongly supports the diagnosis of a chronic periprosthetic joint infection?

. WBC count of 1,500 cells/µL with 55% neutrophils
. WBC count of 2,500 cells/µL with 65% neutrophils
. WBC count of 3,500 cells/µL with 85% neutrophils
. WBC count of 4,000 cells/µL with 75% neutrophils
. Presence of numerous calcium pyrophosphate crystals

Correct Answer & Explanation

. WBC count of 3,500 cells/µL with 85% neutrophils

Explanation

The 2018 International Consensus Meeting (ICM) criteria for chronic periprosthetic joint infection (PJI) rely on a scoring system based on major and minor criteria. For minor criteria in chronic PJI (>90 days postoperatively), a synovial fluid WBC count greater than 3,000 cells/µL and a polymorphonuclear (PMN) percentage greater than 80% are strongly indicative of infection. Only option C meets both established thresholds to yield the maximum score for these biomarkers.

Question 3548

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man presents with progressive groin pain and swelling 6 years after a metal-on-metal total hip arthroplasty. A MARS MRI demonstrates a large cystic mass adjacent to the greater trochanter. Aspiration reveals sterile, cloudy fluid. If a tissue biopsy of the pseudotumor were analyzed, what would be the most characteristic histological finding?

. Abundant neutrophils and fibrinous exudate
. Perivascular lymphocytic infiltrate and tissue necrosis
. Massive presence of polyethylene wear debris with foreign body giant cells
. Sheets of plasma cells and Russell bodies
. Spindle cells with a high mitotic index and osteoid formation

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate and tissue necrosis

Explanation

Adverse local tissue reaction (ALTR) or aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) is a well-recognized complication of metal-on-metal (MoM) hip arthroplasty. Histologically, ALVAL is characterized by a perivascular lymphocytic infiltrate (primarily T cells), macrophage infiltration, and varying degrees of tissue necrosis. This is considered a delayed-type (Type IV) hypersensitivity reaction to metal ions, specifically cobalt and chromium.

Question 3549

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is widely considered an absolute contraindication for a medial unicompartmental knee arthroplasty (UKA)?

. Age greater than 80 years
. Weight greater than 90 kg
. Anterior cruciate ligament (ACL) deficiency
. Flexion contracture of 10 degrees
. Inflammatory arthritis

Correct Answer & Explanation

. Inflammatory arthritis

Explanation

Inflammatory arthritis (e.g., rheumatoid arthritis) is universally considered an absolute contraindication for unicompartmental knee arthroplasty (UKA) due to the pan-articular nature of the disease, which will predictably progress to involve the unresurfaced compartments. Age > 80 and weight > 90 kg were historically considered contraindications but are now considered relative or non-contraindications. ACL deficiency is a relative contraindication (some fixed-bearing UKAs are performed in this setting). A flexion contracture of < 15 degrees is generally acceptable.

Question 3550

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman undergoes a posterior approach total hip arthroplasty. Six weeks postoperatively, she sustains a posterior dislocation while bending over to tie her shoes. Radiographs demonstrate the acetabular component is placed in 55 degrees of inclination and 5 degrees of retroversion. Which of the following most accurately describes the biomechanical etiology of her instability?

. Anterior impingement causing posterior subluxation
. Insufficient offset resulting in abductor weakness
. Posterior impingement causing anterior subluxation
. Cam impingement from a retained femoral neck
. Excessive combined anteversion

Correct Answer & Explanation

. Anterior impingement causing posterior subluxation

Explanation

The 'safe zone' for acetabular component positioning is historically described as 40 ± 10 degrees of inclination and 15 ± 10 degrees of anteversion. This patient's cup is retroverted (5 degrees of retroversion). Retroversion of the acetabular component leads to anterior impingement of the femoral neck against the anterior rim of the socket during hip flexion and internal rotation (such as bending over to tie shoes). This anterior impingement acts as a fulcrum, levering the femoral head out posteriorly and resulting in a posterior dislocation.

Question 3551

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman presents with an inability to actively extend her knee 3 years after a primary total knee arthroplasty. Clinical examination and ultrasound confirm a chronic, retracted patellar tendon rupture. Infection has been definitively ruled out, and the remaining prosthetic components are well-fixed. What is the most appropriate and durable reconstructive option?

. Primary end-to-end repair using non-absorbable sutures
. Primary repair augmented with autologous hamstring tendons
. Reconstruction using a synthetic mesh (e.g., Marlex) or an extensor mechanism allograft
. Arthrodesis of the knee joint
. Revision to a hinged total knee arthroplasty

Correct Answer & Explanation

. Reconstruction using a synthetic mesh (e.g., Marlex) or an extensor mechanism allograft

Explanation

Chronic patellar tendon rupture following TKA is a severely debilitating complication. Primary repair, even when augmented with local autograft, is associated with unacceptably high failure rates (often exceeding 70%) due to compromised tissue quality and the high mechanical demands placed over a relatively avascular prosthetic joint. The most reliable and durable options for restoring active extension in this setting are reconstruction using synthetic mesh (e.g., Marlex mesh, utilizing the technique described by the Mayo Clinic) or a complete extensor mechanism allograft (incorporating the tibial tubercle, patellar tendon, patella, and quadriceps tendon).

Question 3552

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old man presents with anterior knee pain and a feeling of instability when descending stairs, 1 year after a posterior-stabilized total knee arthroplasty (TKA). Radiographs demonstrate that the femoral component was placed in excessive internal rotation. What is the primary kinematic consequence of this specific component malposition?

. Medial-lateral instability in full extension
. Lateral patellar tracking and patellofemoral instability
. Increased lateral flexion gap resulting in mid-flexion instability
. Patella baja due to altered joint line height
. Excessive external rotation of the tibia during the swing phase of gait

Correct Answer & Explanation

. Lateral patellar tracking and patellofemoral instability

Explanation

Internal rotation of the femoral component in TKA effectively medializes the trochlear groove relative to the extensor mechanism, which increases the Q-angle. This alteration leads to lateral patellar tracking, anterior knee pain, and potential patellar subluxation or dislocation. It also abnormally tightens the medial flexion gap while loosening the lateral flexion gap, creating asymmetric kinematics during flexion, rather than extension instability.

Question 3553

Topic: 3. Adult Reconstruction (Hip & Knee)
A 65-year-old man presents with chronic pain in his right total hip arthroplasty, which was performed 3 years ago. Joint aspiration yields synovial fluid with a white blood cell count of 3,500 cells/µL with 75% polymorphonuclear neutrophils (PMNs). An alpha-defensin test is positive. Serum CRP is 15 mg/L, and ESR is 35 mm/hr. There is no sinus tract. According to the 2018 International Consensus Meeting (ICM) criteria, what is the most accurate diagnostic classification for this patient?
. Definitive PJI based on major criteria
. Definitive PJI based on minor criteria scoring
. Probable PJI, requiring repeat aspiration
. Indeterminate PJI, requiring tissue biopsy
. Aseptic loosening, as PMNs are below 80%

Correct Answer & Explanation

. Definitive PJI based on minor criteria scoring

Explanation

The 2018 ICM criteria utilize a scoring system when major criteria (sinus tract or two positive cultures with the same organism) are absent. A score of ≥ 6 indicates definitive PJI. The scoring is as follows: Positive alpha-defensin (3 points), elevated synovial WBC count > 3,000 cells/µL (3 points), elevated CRP > 10 mg/L (2 points), and elevated ESR > 30 mm/hr (1 point). Elevated PMN % > 80% would be 2 points, but in this case, it is 75% (0 points). The total score is 3 + 3 + 2 + 1 = 9 points. Because the score is ≥ 6, this patient has a definitive diagnosis of periprosthetic joint infection (PJI) based on minor criteria scoring.

Question 3554

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man complains of groin pain and a palpable mass 8 years following a metal-on-metal hip resurfacing arthroplasty. MRI demonstrates an extensive solid and cystic periarticular mass. Serum metal ion levels are Cobalt = 15 ppb and Chromium = 12 ppb. Aspiration yields no bacterial growth. Revision surgery is planned, and extensive soft tissue necrosis is encountered. Which of the following is the characteristic histologic finding of the pseudo-capsule in this condition?

. Dense infiltration of neutrophils with foreign body giant cells
. Perivascular lymphocytic infiltrate (ALVAL) and extensive tissue necrosis
. Abundant sheets of foamy macrophages containing birefringent polyethylene debris
. Non-caseating granulomas with multinucleated giant cells
. Palisading granulomas surrounded by dense eosinophilic infiltration

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate (ALVAL) and extensive tissue necrosis

Explanation

The clinical scenario describes an adverse local tissue reaction (ALTR) or adverse reaction to metal debris (ARMD), which is typically associated with metal-on-metal bearings. The characteristic histologic finding of this reaction is Aseptic Lymphocytic Vasculitis-Associated Lesion (ALVAL). ALVAL is identified by a delayed-type hypersensitivity reaction featuring perivascular lymphocytic infiltration, macrophage infiltration, and areas of extensive soft tissue necrosis. In contrast, polyethylene wear typically induces a macrophage-mediated foreign-body response without the pronounced lymphocytic vasculitis.

Question 3555

Topic: 3. Adult Reconstruction (Hip & Knee)

A 32-year-old highly active man undergoes a total hip arthroplasty for osteonecrosis. To minimize long-term wear and eliminate the risk of polyethylene-induced osteolysis, which of the following bearing surface combinations is most appropriate?

. Cobalt-chromium on highly cross-linked polyethylene
. Ceramic on ceramic
. Ceramic on highly cross-linked polyethylene
. Cobalt-chromium on conventional polyethylene
. Oxidized zirconium on highly cross-linked polyethylene

Correct Answer & Explanation

. Ceramic on ceramic

Explanation

Ceramic-on-ceramic bearings offer the lowest wear rates among all bearing surfaces, making them ideal for young, highly active patients. They effectively eliminate the risk of polyethylene-induced osteolysis, though they carry risks of squeaking and catastrophic fracture.

Question 3556

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, trial components are placed. The knee is symmetric and stable in extension but tight in flexion. Which of the following intraoperative modifications will best address this imbalance?

. Decrease the anteroposterior size of the femoral component
. Increase the thickness of the tibial polyethylene insert
. Resect an additional 2 mm of distal femur
. Release the posterior capsule
. Recut the proximal tibia with less posterior slope

Correct Answer & Explanation

. Decrease the anteroposterior size of the femoral component

Explanation

A knee that is tight in flexion and stable in extension has a tight flexion gap and a balanced extension gap. Downsizing the femoral component (when using anterior referencing) increases the posterior condylar resection, effectively opening the flexion gap without affecting the extension gap.

Question 3557

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man returns to the clinic 3 weeks after an uncomplicated primary total knee arthroplasty with acute onset of knee pain, swelling, and a draining sinus tract. Synovial fluid analysis shows a white blood cell count of 45,000/µL with 95% neutrophils. Radiographs show well-fixed components. What is the most appropriate management?

. Intravenous antibiotics alone for 6 weeks
. One-stage revision arthroplasty
. Two-stage revision arthroplasty with an antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. Suppressive oral antibiotics indefinitely

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange

Explanation

Debridement, antibiotics, and implant retention (DAIR) with modular component exchange is indicated for acute periprosthetic joint infections (symptoms < 3 weeks or < 90 days post-op) with well-fixed implants. A draining sinus is not an absolute contraindication to DAIR in the acute postoperative setting.

Question 3558

Topic: Total Hip Arthroplasty (THA)

A 72-year-old woman experiences her third posterior dislocation 2 months after a primary total hip arthroplasty via a posterior approach. Radiographs reveal the acetabular component is placed in 45 degrees of abduction and 5 degrees of retroversion. The femoral stem is anteverted 15 degrees. What is the most appropriate definitive management?

. Revision of the femoral stem to increase anteversion
. Revision of the acetabular component to increase anteversion
. Placement of a constrained polyethylene liner
. Conversion to a dual-mobility construct without changing the shell
. Application of a hip abduction brace for 12 weeks

Correct Answer & Explanation

. Revision of the acetabular component to increase anteversion

Explanation

The patient's acetabular component is retroverted, strongly predisposing her to posterior instability. The most appropriate definitive treatment is isolated revision of the acetabular component to achieve proper anteversion (typically 15 to 20 degrees).

Question 3559

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old woman sustains a fall and presents with a periprosthetic fracture around her total hip arthroplasty stem. Radiographs show a fracture at the tip of the stem. The stem has subsided by 2 cm and the cement mantle is fractured. The acetabular component remains well-fixed. What is the most appropriate surgical treatment?

. Open reduction and internal fixation with a locking plate and cables
. Revision of the femoral component with a long cementless fully porous-coated stem bypassing the fracture
. Revision of both the acetabular and femoral components
. Cortical strut allografting alone
. Traction and non-weight bearing for 6 weeks

Correct Answer & Explanation

. Revision of the femoral component with a long cementless fully porous-coated stem bypassing the fracture

Explanation

This is a Vancouver B2 periprosthetic fracture, characterized by a fracture around a loose femoral stem with adequate proximal bone stock. The standard of care is revision of the femoral component using a long cementless stem that bypasses the fracture by at least two cortical diameters.

Question 3560

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman who underwent a posterior-stabilized total knee arthroplasty 9 months ago presents with a painful catching sensation in her knee. The catching occurs as she actively extends the knee from a flexed position, typically between 30 and 45 degrees of flexion. What is the most likely diagnosis?

. Aseptic loosening of the tibial baseplate
. Patellar clunk syndrome
. Popliteus tendon impingement
. Polyethylene wear and osteolysis
. Pes anserine bursitis

Correct Answer & Explanation

. Patellar clunk syndrome

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA designs when a fibrous nodule forms at the superior pole of the patella. This nodule catches in the intercondylar box of the femoral component during active extension.

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