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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 93 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 1841

Topic: 3. Adult Reconstruction (Hip & Knee)

Based on the 2018 International Consensus Meeting (ICM) criteria for periprosthetic joint infection (PJI), which of the following synovial fluid analysis results in a patient 2 years status-post total hip arthroplasty provides the strongest evidence for a definitive diagnosis of chronic PJI?

. Synovial WBC count of 1,500 cells/µL with 60% PMNs
. Synovial WBC count of 3,500 cells/µL with 85% PMNs
. Synovial WBC count of 2,000 cells/µL with 75% PMNs
. Synovial fluid alpha-defensin test with an inconclusive result
. Positive leukocyte esterase (+) on a single test strip

Correct Answer & Explanation

. Synovial WBC count of 1,500 cells/µL with 60% PMNs

Explanation

According to the 2018 ICM criteria for chronic PJI (>90 days post-op), a synovial fluid white blood cell (WBC) count > 3,000 cells/µL or a polymorphonuclear (PMN) percentage > 80% yields major points toward diagnosing a PJI. Therefore, a WBC count of 3,500 with 85% PMNs strongly points to infection, well above the diagnostic threshold. Note that thresholds are lower for acute PJI or within the first 6 weeks post-op.

Question 1842

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents 14 months after a primary posterior-stabilized (PS) total knee arthroplasty complaining of a painful catching sensation in her anterior knee when extending from a flexed position. What is the most likely pathophysiologic mechanism responsible for this complication?

. Impingement of a retained posterior osteophyte on the tibial post
. Hypertrophy of the infrapatellar fat pad catching on the anterior tibial tray
. A fibrous nodule at the superior pole of the patella catching in the femoral intercondylar box
. Asymmetric wear of the polyethylene bearing due to varus malalignment
. Subluxation of the popliteus tendon over the lateral femoral condyle

Correct Answer & Explanation

. Impingement of a retained posterior osteophyte on the tibial post

Explanation

Patellar clunk syndrome is classically associated with posterior-stabilized (PS) total knee arthroplasty designs. It is caused by the formation of a fibrosynovial nodule on the undersurface of the quadriceps tendon just proximal to the superior pole of the patella. As the knee extends from a flexed position (usually around 30-45 degrees of flexion), this nodule catches in the intercondylar box of the femoral component, then abruptly pops out, creating a painful 'clunk'.

Question 1843

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male presents with a periprosthetic femur fracture around his total hip arthroplasty. Radiographs demonstrate a fracture propagating around the tip of the femoral stem. The stem is radiographically loose, but there is adequate circumferential femoral bone stock. According to the Vancouver classification, what is the most appropriate surgical treatment?

. Open reduction and internal fixation with a lateral locking plate alone
. Open reduction and internal fixation with cortical strut allografts alone
. Revision to a long extensively porous-coated or fluted tapered modular stem bypassing the fracture
. Revision to a standard-length cemented femoral stem
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. Revision to a long extensively porous-coated or fluted tapered modular stem bypassing the fracture

Explanation

This is a Vancouver type B2 fracture (fracture around or just below the stem, the stem is loose, but bone stock is good). The standard of care for a B2 fracture is revision arthroplasty using a long extensively porous-coated or fluted tapered modular diaphyseal-engaging stem. The new stem must bypass the fracture site by at least two cortical diameters to ensure adequate distal fixation.

Question 1844

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male presents with new-onset groin pain and a palpable mass 6 years after an uncomplicated metal-on-polyethylene total hip arthroplasty. Radiographs show a well-fixed construct with no osteolysis. A aspiration yields sterile, turbid fluid. Blood tests reveal elevated serum cobalt levels. What is the most likely etiology of this condition?

. Polyethylene wear debris causing a massive granulomatous response
. Unrecognized low-grade Cutibacterium acnes infection
. Mechanically assisted crevice corrosion at the modular head-neck junction
. Aseptic loosening of the femoral stem at the bone-cement interface
. Galvanic corrosion between the acetabular shell and the titanium screws

Correct Answer & Explanation

. Mechanically assisted crevice corrosion at the modular head-neck junction

Explanation

This patient is presenting with an adverse local tissue reaction (ALTR) secondary to mechanically assisted crevice corrosion (MACC), commonly referred to as 'trunnionosis'. Even in metal-on-polyethylene implants, fretting and corrosion can occur at the modular junction between the femoral head and the stem trunnion. This releases cobalt and chromium ions, leading to a local inflammatory response, pseudotumor formation, and elevated serum metal ions.

Question 1845

Topic: Total Hip Arthroplasty (THA)

A 45-year-old male with a ceramic-on-ceramic total hip arthroplasty presents 3 years postoperatively complaining of a loud squeaking noise with walking. Radiographs demonstrate well-fixed components. Which of the following factors is most strongly associated with the etiology of this phenomenon?

. Acetabular component retroversion
. Increased femoral offset
. Body mass index > 35 kg/m^2
. Stripe wear from edge loading due to component malposition
. Use of a titanium femoral stem

Correct Answer & Explanation

. Stripe wear from edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic THA is a well-documented complication occurring in approximately 1-10% of patients. It is most strongly associated with edge loading of the ceramic bearings, which disrupts the fluid film lubrication. Edge loading typically occurs due to component malposition (e.g., excessive acetabular anteversion, high abduction angle), which leads to 'stripe wear' on the ceramic head and subsequent squeaking. While a titanium stem might be present, the edge loading mechanism is the primary cause.

Question 1846

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female develops a painful 'clunk' at approximately 40 degrees of flexion as she actively extends her knee, 1 year following a posterior-stabilized total knee arthroplasty. What is the primary anatomic etiology of this condition?

. Oversized femoral component causing retinacular tightness
. A fibrous nodule at the superior pole of the patella catching in the intercondylar box
. An undersized patellar button causing patellar tracking abnormalities
. Internal rotation of the tibial component causing lateral patellar subluxation
. Over-resection of the distal femur leading to a loose extension gap

Correct Answer & Explanation

. A fibrous nodule at the superior pole of the patella catching in the intercondylar box

Explanation

Patellar clunk syndrome is a complication classically seen with posterior-stabilized TKA designs. It is caused by the formation of a fibrosynovial nodule at the superior pole of the patella. As the knee extends from a flexed position, this nodule catches in the intercondylar box of the femoral component and then pops out with a painful 'clunk' at around 30 to 45 degrees of flexion. Treatment is typically arthroscopic excision of the nodule.

Question 1847

Topic: Total Hip Arthroplasty (THA)

A patient undergoes a primary total hip arthroplasty (THA) via a posterior approach. Six weeks postoperatively, the patient sustains a posterior dislocation while sitting in a low chair. Which combination of component malpositioning most commonly predisposes to this specific pattern of instability?

. Acetabular excessive anteversion and femoral retroversion
. Acetabular retroversion and femoral retroversion
. Acetabular excessive abduction and femoral excessive anteversion
. Acetabular retroversion and femoral excessive anteversion
. Acetabular excessive anteversion and femoral excessive anteversion

Correct Answer & Explanation

. Acetabular retroversion and femoral retroversion

Explanation

Posterior dislocation of a THA typically occurs with a combination of hip flexion, internal rotation, and adduction. Component malposition that decreases the anterior coverage or opens the hip up posteriorly predisposes to this. Specifically, retroversion of the acetabular component and/or retroversion of the femoral stem significantly increases the risk of posterior dislocation.

Question 1848

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty for a patient with a severe, fixed 15-degree varus deformity, the surgeon performs a sequential medial release to balance the knee. After resecting deep MCL osteophytes, the knee remains tight medially in extension, but is perfectly balanced in 90 degrees of flexion. Which structure should be selectively released next to correct this specific mismatch?

. Anterior portion of the superficial medial collateral ligament
. Posterior medial capsule and posteromedial corner
. Pes anserinus tendons
. Lateral collateral ligament
. Popliteus tendon

Correct Answer & Explanation

. Posterior medial capsule and posteromedial corner

Explanation

In TKA, a knee that is tight medially in extension but balanced in flexion requires release of structures that are under tension primarily in extension. The posterior medial capsule and the posteromedial corner are the primary stabilizers against medial opening in extension, while the superficial MCL is the primary stabilizer in flexion. Releasing the posteromedial capsule will correct the extension gap without significantly altering the flexion gap.

Question 1849

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old female presents with a periprosthetic femur fracture around a cemented total hip arthroplasty stem. Radiographs show a fracture at the tip of the stem. The stem has subsided 5 mm with a varus tilt, indicating macroscopic loosening. The cortical bone stock of the proximal femur is thick and of good quality. What is the most appropriate surgical treatment according to the Vancouver classification?

. Open reduction internal fixation with a lateral locking plate and cerclage wires
. Revision to a standard length, fully coated cylindrical uncemented stem
. Revision to a long, modular fluted tapered uncemented stem bypassing the fracture
. Proximal femoral replacement (megaprosthesis)
. Nonoperative management with skeletal traction

Correct Answer & Explanation

. Revision to a long, modular fluted tapered uncemented stem bypassing the fracture

Explanation

This is a Vancouver Type B2 periprosthetic fracture (fracture around or just below the stem, the stem is loose, but there is good proximal bone stock). The standard of care for a Vancouver B2 fracture is revision of the loose component using a long stem that bypasses the fracture by at least 2 cortical diameters, typically achieved with a modular fluted tapered uncemented stem. ORIF alone (Option A) is contraindicated for a loose stem. Proximal femoral replacement (Option D) is reserved for Vancouver B3 (loose stem with poor bone stock).

Question 1850

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 Evidence-Based International Consensus Meeting (ICM) criteria, which of the following is considered a major criterion, sufficient on its own, to definitively diagnose a periprosthetic joint infection (PJI)?

. Elevated serum CRP > 10 mg/L and ESR > 30 mm/hr
. Synovial fluid leukocyte count > 3,000 cells/µL
. Two positive periprosthetic tissue cultures with identical organisms
. Positive leukocyte esterase on a synovial fluid test strip
. A single positive tissue culture for Staphylococcus epidermidis

Correct Answer & Explanation

. Two positive periprosthetic tissue cultures with identical organisms

Explanation

According to the 2018 ICM criteria (and the MSIS criteria), there are two major criteria for diagnosing PJI, either of which is definitive: 1) A sinus tract communicating with the joint, or 2) Two positive periprosthetic cultures with phenotypically identical organisms. The other options (elevated CRP/ESR, elevated synovial fluid WBC, positive LE strip) are minor criteria, requiring a combination of points to establish the diagnosis.

Question 1851

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old male with a ceramic-on-ceramic total hip arthroplasty presents with a new-onset high-pitched 'squeaking' sound during active hip flexion. Radiographs demonstrate appropriate cup positioning but reveal signs of edge loading. Which of the following factors is most strongly associated with the development of squeaking in a ceramic-on-ceramic bearing surface?

. Increased femoral head size (>36mm)
. Use of a cobalt-chromium femoral stem
. Stripe wear from edge loading
. Excessive anteversion of the femoral stem
. Polyethylene liner oxidation

Correct Answer & Explanation

. Stripe wear from edge loading

Explanation

Squeaking is a known complication of ceramic-on-ceramic (CoC) total hip arthroplasty, occurring in 1-10% of patients. It is strongly correlated with edge loading of the ceramic liner, which creates linear tracts of wear known as 'stripe wear'. Factors leading to edge loading include cup malposition (steep abduction, excessive anteversion/retroversion), microseparation during the swing phase, and loss of the fluid film lubrication. Ceramic squeaking is less commonly associated with isolated large head sizes.

Question 1852

Topic: 3. Adult Reconstruction (Hip & Knee)

In a standard measured-resection mechanically aligned total knee arthroplasty, the femoral component is typically externally rotated relative to the posterior condylar axis. What is the primary functional objective of this specific maneuver?

. Create a rectangular flexion gap
. Create a rectangular extension gap
. Replicate the native joint line obliquity
. Increase the Q-angle to improve patellar tracking
. Compensate for internal rotation of the tibial component

Correct Answer & Explanation

. Compensate for internal rotation of the tibial component

Explanation

In mechanically aligned TKA, the proximal tibia is cut perpendicular to its mechanical axis, removing the native 3 degrees of varus. Because the native posterior femoral condyles are naturally offset, cutting the posterior femur parallel to the posterior condylar axis would result in an asymmetric, tight medial flexion gap. By externally rotating the femoral component (typically 3 degrees, parallel to the surgical transepicondylar axis), the surgeon compensates for the neutral tibial cut, equalizing tension on the medial and lateral collateral ligaments in flexion to create a symmetric, rectangular flexion gap.

Question 1853

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with a painful total hip arthroplasty. Synovial fluid analysis reveals an elevated alpha-defensin level, prompting a diagnosis of periprosthetic joint infection. What is the primary biological mechanism responsible for the production of alpha-defensin in this setting?

. Secretion by synovial fibroblasts in response to cytokines
. Release by activated neutrophils as an antimicrobial peptide
. Production by osteoclasts during periprosthetic osteolysis
. Release by planktonic bacteria during biofilm formation
. Secretion by macrophages during phagocytosis of polyethylene debris

Correct Answer & Explanation

. Release by activated neutrophils as an antimicrobial peptide

Explanation

Alpha-defensin is a naturally occurring antimicrobial peptide that is rapidly released by activated neutrophils in response to the presence of pathogens. It intercalates into and disrupts the cell membranes of bacteria. The alpha-defensin immunoassay is a highly sensitive and specific biomarker used in synovial fluid to differentiate periprosthetic joint infection (PJI) from aseptic failure, as it is elevated when an infectious stimulus triggers neutrophil activation.

Question 1854

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old male with a metal-on-metal total hip arthroplasty presents with a painful groin mass 7 years postoperatively. Serum cobalt and chromium levels are significantly elevated. MRI demonstrates a large cystic fluid collection (pseudotumor) communicating with the joint. Tissue biopsy of the periarticular tissue is most likely to demonstrate which of the following histological findings?

. Massive infiltration of polymorphonuclear leukocytes
. Aseptic lymphocytic vasculitis-associated lesions (ALVAL)
. Birefringent monosodium urate crystals
. Granulomatous inflammation with caseating necrosis
. Abundant sheet-like uniform small round blue cells

Correct Answer & Explanation

. Aseptic lymphocytic vasculitis-associated lesions (ALVAL)

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-metal hips are characterized histologically by Aseptic Lymphocytic Vasculitis-Associated Lesions (ALVAL). This represents a Type IV delayed hypersensitivity reaction to metal wear debris (cobalt and chromium ions). The histology reveals perivascular lymphocytic cuffing, tissue necrosis, and a distinct lack of acute inflammatory cells like polymorphonuclear leukocytes (which would indicate acute infection).

Question 1855

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female with a primary cementless total hip arthroplasty sustains a fall. Radiographs demonstrate a displaced spiral fracture traversing the area surrounding the femoral stem. The stem has subsided by 2 cm and the proximal femoral bone stock is severely comminuted and osteopenic. According to the Vancouver classification system, what is the injury type and most appropriate surgical management?

. Vancouver B1; Open reduction and internal fixation with a lateral locking plate and cerclage cables
. Vancouver B2; Revision to a standard-length cemented femoral stem with plate fixation
. Vancouver B3; Revision to a long cementless fluted tapered stem or proximal femoral replacement
. Vancouver C; Closed reduction and spica casting for 6 weeks
. Vancouver B3; Isolated exchange of the femoral head and polyethylene liner

Correct Answer & Explanation

. Vancouver B3; Revision to a long cementless fluted tapered stem or proximal femoral replacement

Explanation

This is a Vancouver B3 periprosthetic femur fracture. The Vancouver classification is based on fracture location (B = around the stem), stem stability, and bone quality. B1 indicates a stable stem with good bone stock (treat with ORIF). B2 indicates a loose stem with adequate bone stock (treat with revision to a longer bypassing stem). B3 indicates a loose stem with profoundly poor or comminuted proximal bone stock. B3 injuries necessitate bypassing the deficient proximal femur via a long cementless diaphyseal-engaging fluted tapered stem, or utilizing a proximal femoral replacement (megaprosthesis) if the diaphyseal bone is inadequate.

Question 1856

Topic: Total Knee Arthroplasty (TKA)

A patient presents with anterior knee pain and a sensation of instability 1 year after a primary total knee arthroplasty (TKA). Examination reveals lateral subluxation of the patella in early flexion. Radiographic and CT evaluation demonstrates malrotation of the components. Which of the following component alignment errors is most likely responsible for this finding?

. Internal rotation of the femoral component
. External rotation of the femoral component
. External rotation of the tibial component
. Anterior placement of the tibial component
. Posterior translation of the femoral component

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of either the femoral or the tibial component in a TKA shifts the tibial tubercle laterally relative to the trochlear groove, increasing the Q-angle. This dynamic malalignment leads to lateral patellar maltracking, anterior knee pain, and potential instability. External rotation of the components typically improves patellar tracking.

Question 1857

Topic: 3. Adult Reconstruction (Hip & Knee)

During preoperative planning for a revision total hip arthroplasty, the AP pelvic radiograph shows superior migration of the acetabular component of 4 cm, destruction of the teardrop, and medial migration past Kohler's line indicating pelvic discontinuity. According to the Paprosky classification, what type of defect is present?

. Type 2A
. Type 2C
. Type 3A
. Type 3B
. Type 4

Correct Answer & Explanation

. Type 3B

Explanation

A Paprosky Type 3B defect is characterized by severe acetabular bone loss with >3 cm of superior migration, destruction of the teardrop, and medial migration past Kohler's line. It is highly associated with pelvic discontinuity. Type 3A has >3 cm superior migration but Kohler's line is intact. Type 2 defects have <3 cm of superior migration.

Question 1858

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old woman sustains a periprosthetic femur fracture around her cemented total hip arthroplasty after a fall. Radiographs demonstrate a fracture at the tip of the stem. The stem is loose, but there is excellent proximal femoral bone stock. According to the Vancouver classification, what is the most appropriate surgical management?

. Open reduction internal fixation with a lateral locking plate
. Revision to a long cementless fully porous-coated stem bypassing the fracture
. Impaction bone grafting and revision using a standard length cemented stem
. Revision using a proximal femoral replacement (megaprosthesis)
. Strut allografting alone with cerclage cables

Correct Answer & Explanation

. Revision to a long cementless fully porous-coated stem bypassing the fracture

Explanation

This is a Vancouver B2 fracture (fracture around or just below the stem tip, stem is loose, good bone stock). The gold standard for a Vancouver B2 fracture is revision of the femoral component using a long cementless stem that bypasses the fracture site by at least two cortical diameters. Vancouver B3 (poor bone stock) would warrant proximal femoral replacement.

Question 1859

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon decides to utilize a posterior cruciate retaining (CR) implant. What is the primary biomechanical function of an intact posterior cruciate ligament during active knee flexion in this setting?

. It drives paradoxical anterior translation of the femur on the tibia.
. It causes posterior femoral rollback, improving the lever arm of the quadriceps and increasing maximal flexion.
. It provides primary restraint to valgus stress at 30 degrees of flexion.
. It externally rotates the tibia relative to the femur during deep flexion.
. It limits internal rotation of the femur on the tibia during deep flexion.

Correct Answer & Explanation

. It causes posterior femoral rollback, improving the lever arm of the quadriceps and increasing maximal flexion.

Explanation

The posterior cruciate ligament (PCL) functions to cause posterior rollback of the femoral condyles on the tibial plateau during knee flexion. This rollback creates clearance between the posterior femur and the posterior tibia, allowing for greater maximal knee flexion, and improves the lever arm of the extensor mechanism.

Question 1860

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old woman with severe osteoporosis sustains a heavily comminuted intra-articular distal humerus fracture (AO/OTA 13-C3). She lives independently and performs her own activities of daily living. Compared to open reduction and internal fixation (ORIF), primary total elbow arthroplasty (TEA) in this patient is associated with which of the following?

. Decreased immediate postoperative range of motion
. A lifetime lifting restriction of 10 to 15 pounds
. Higher rate of revision surgery
. Increased risk of hardware prominence and nonunion
. Higher rate of postoperative ulnar neuropathy

Correct Answer & Explanation

. A lifetime lifting restriction of 10 to 15 pounds

Explanation

Total elbow arthroplasty (TEA) is an excellent option for comminuted distal humerus fractures in the elderly with poor bone quality. Compared to ORIF, TEA has lower reoperation rates and allows for immediate range of motion. However, a major limitation of TEA is a strict, lifetime weight-lifting restriction (typically 10-15 lbs single event, 5 lbs repetitive) to prevent aseptic loosening.

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