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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 243 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 4841

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old woman presents with an inability to actively extend her knee 3 years after a primary total knee arthroplasty. Radiographs show a high-riding patella indicating a complete patellar tendon rupture. Given the chronicity and setting of TKA, what is the most reliable surgical reconstruction option yielding the best long-term outcomes?

. Primary end-to-end repair with heavy nonabsorbable sutures
. Hamstring autograft reconstruction
. Extensor mechanism allograft or synthetic mesh reconstruction
. Gastrocnemius rotational flap alone
. Revision to a hinged knee prosthesis

Correct Answer & Explanation

. Primary end-to-end repair with heavy nonabsorbable sutures

Explanation

Patellar tendon rupture following TKA is a devastating complication. Direct primary repair in the chronic setting or over a TKA is associated with unacceptably high failure rates due to poor tissue quality and a compromised vascular envelope. The gold standard treatments for chronic extensor mechanism disruption in the setting of a TKA are an extensor mechanism allograft (tibial tubercle, patellar tendon, patella, and quadriceps tendon) or synthetic mesh (e.g., Marlex mesh) reconstruction. These provide the necessary structural integrity.

Question 4842

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male presents with a painful total knee arthroplasty 4 years postoperatively. Erythrocyte sedimentation rate (ESR) is 45 mm/hr and C-reactive protein (CRP) is 22 mg/L. Joint aspiration yields a synovial white blood cell count of 4,500 cells/µL with 85% polymorphonuclear (PMN) leukocytes. What is the next best step in management?

. Proceed with isolated polyethylene exchange
. Proceed with two-stage exchange arthroplasty
. Perform a synovial biopsy for crystals
. Administer 6 weeks of intravenous antibiotics without surgery
. Prescribe oral NSAIDs and physical therapy

Correct Answer & Explanation

. Proceed with isolated polyethylene exchange

Explanation

Based on the 2018 Musculoskeletal Infection Society (MSIS) / International Consensus Meeting (ICM) criteria, a synovial fluid WBC count > 3,000 cells/µL and > 80% PMNs in a chronic setting (>90 days post-op) is diagnostic for a periprosthetic joint infection (PJI). The gold standard treatment for chronic PJI in North America is a two-stage exchange arthroplasty, which involves explantation, placement of an antibiotic spacer, a course of IV antibiotics, and subsequent reimplantation.

Question 4843

Topic: Total Knee Arthroplasty (TKA)

In conventional mechanical alignment for total knee arthroplasty, the goal is to create a neutral mechanical axis. How are the femoral and tibial component bone cuts classically oriented relative to their respective mechanical axes?

. Femur at 5 degrees valgus, Tibia at 3 degrees varus
. Femur perpendicular (0 degrees), Tibia perpendicular (0 degrees)
. Femur at 5 degrees valgus, Tibia perpendicular (0 degrees)
. Femur at 3 degrees internal rotation, Tibia perpendicular (0 degrees)
. Femur at 3 degrees varus, Tibia at 3 degrees varus

Correct Answer & Explanation

. Femur at 5 degrees valgus, Tibia at 3 degrees varus

Explanation

In classic mechanical alignment for TKA, both the distal femoral cut and the proximal tibial cut are made strictly perpendicular (90 degrees, or 0 degrees of deviation) to their respective mechanical axes. This results in an overall mechanical axis that is neutral (0 degrees). It is important not to confuse the anatomic axis with the mechanical axis; the femoral mechanical axis is generally 5-7 degrees valgus to the femoral anatomic axis.

Question 4844

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman experiences recurrent posterior dislocations of her total hip arthroplasty. Radiographic evaluation demonstrates the acetabular component is placed in 5 degrees of retroversion and 45 degrees of inclination. The femoral stem is in neutral version. What is the most appropriate surgical intervention?

. Revision of the femoral stem to increase anteversion
. Revision of the acetabular component to increase anteversion
. Application of a constrained acetabular liner
. Trochanteric advancement
. Placement of a larger femoral head retaining the existing cup

Correct Answer & Explanation

. Revision of the femoral stem to increase anteversion

Explanation

The patient has recurrent posterior dislocations driven by a malpositioned (retroverted) acetabular component. The "safe zone" described by Lewinnek suggests an acetabular anteversion of 15 ± 10 degrees. A cup placed in 5 degrees of retroversion will cause posterior impingement and instability. The most anatomic and reliable solution is to revise the acetabular component to the correct anteversion. Constrained liners should be reserved for cases of abductor deficiency or cognitive issues where anatomic alignment cannot restore stability.

Question 4845

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old male with a metal-on-metal total hip arthroplasty presents with new-onset groin pain and a palpable mass. Serum cobalt levels are elevated at 15 ppb. MRI demonstrates a large cystic fluid collection around the hip joint.

Histological analysis of the periprosthetic tissue during revision surgery is most likely to show which of the following?

. Abundant polymorphonuclear leukocytes and intracellular bacteria
. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Sheets of lipid-laden macrophages with birefringent particles
. Extensive woven bone formation and osteoblastic rimming
. Fungal hyphae with multinucleated giant cells

Correct Answer & Explanation

. Abundant polymorphonuclear leukocytes and intracellular bacteria

Explanation

The patient is presenting with an adverse local tissue reaction (ALTR) or pseudotumor secondary to metal-on-metal bearing wear. The hallmark histological finding in this condition is ALVAL (aseptic lymphocyte-dominated vasculitis-associated lesion), which is a Type IV delayed hypersensitivity reaction characterized by perivascular lymphocytic infiltrates, tissue necrosis, and macrophages containing fine metallic debris. Birefringent particles (Option C) are characteristic of polyethylene wear.

Question 4846

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, trial reduction reveals that the knee is symmetric and stable in full extension but excessively tight in 90 degrees of flexion, causing lift-off. Which of the following adjustments is the most appropriate next step to balance the knee?

. Recess the posterior cruciate ligament
. Downsize the femoral component
. Resect 2 mm more of the distal femur
. Increase the size of the tibial polyethylene insert
. Release the posterior capsule

Correct Answer & Explanation

. Recess the posterior cruciate ligament

Explanation

A knee that is balanced in extension but tight in flexion has an isolated tight flexion gap. Since it is a posterior-stabilized knee, the PCL has already been sacrificed. Downsizing the femoral component (using a smaller AP size) translates the posterior condyles anteriorly, which increases the flexion gap without affecting the distal femoral surface, thus leaving the extension gap unchanged. Resecting more distal femur would increase the extension gap. Releasing the posterior capsule increases the extension gap.

Question 4847

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female sustains a fall and presents with thigh pain. Radiographs reveal a spiral fracture around the tip of her cementless femoral stem. The stem is visibly subsided and loose, but the proximal femoral bone stock remains adequate.

According to the Vancouver classification, what is the recommended treatment?

. Open reduction and internal fixation with cerclage wires and a locking plate
. Revision to a long uncemented diaphyseal-engaging stem
. Revision with a proximal femoral replacement (tumor prosthesis)
. Strut allografting alone
. Nonoperative management with a hinged fracture brace

Correct Answer & Explanation

. Open reduction and internal fixation with cerclage wires and a locking plate

Explanation

This is a Vancouver B2 periprosthetic femur fracture. The fracture occurs around the stem or just distal to it (Type B), the stem is loose (2), but the proximal bone stock is adequate. The standard of care for a Vancouver B2 fracture is revision arthroplasty using a long, diaphyseal-engaging stem to bypass the fracture by at least 2 cortical diameters. ORIF alone (Option A) is reserved for Vancouver B1 fractures (well-fixed stem). Proximal femoral replacement is indicated for Vancouver B3 fractures (loose stem, poor proximal bone stock).

Question 4848

Topic: 3. Adult Reconstruction (Hip & Knee)
In the pathogenesis of aseptic loosening secondary to polyethylene wear debris in total joint arthroplasty, which of the following cell types is primarily responsible for the initial phagocytosis of the submicron wear particles and subsequent release of pro-inflammatory cytokines such as TNF-α and IL-1?
. Osteoblasts
. Osteoclasts
. Macrophages
. T-lymphocytes
. Fibroblasts

Correct Answer & Explanation

. Macrophages

Explanation

The biological cascade of particle disease (osteolysis) begins when submicron polyethylene wear debris is generated. These particles are phagocytosed by macrophages. The macrophages cannot digest the polyethylene and subsequently release a cascade of pro-inflammatory cytokines, including TNF-α, IL-1, and IL-6. This leads to the upregulation of RANKL, which activates osteoclasts, culminating in periprosthetic bone resorption (osteolysis) and eventual aseptic loosening.

Question 4849

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with persistent anterior knee pain and lateral patellar subluxation 6 months following a primary total knee arthroplasty. A CT scan protocol is obtained to evaluate component rotation. Which of the following errors in component positioning is the most likely cause of lateral patellar maltracking?

. External rotation of the femoral component
. Internal rotation of the tibial component
. External rotation of the tibial component
. Medialization of the patellar button
. Excessive varus alignment of the tibial component

Correct Answer & Explanation

. External rotation of the femoral component

Explanation

Lateral patellar maltracking is frequently caused by component malrotation. Internal rotation of the tibial component effectively lateralizes the tibial tubercle relative to the trochlear groove, increasing the Q-angle and causing a lateral pull on the patella. Similarly, internal rotation of the femoral component medializes the trochlear groove, also increasing the Q-angle. External rotation of the tibial or femoral components tends to improve patellar tracking. Medialization of the patellar button improves tracking by lateralizing the patellar bone.

Question 4850

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old diabetic male is evaluated in the clinic prior to an elective total hip arthroplasty. Which of the following preoperative hemoglobin A1c (HbA1c) levels is the generally accepted strict upper threshold above which the risk of periprosthetic joint infection (PJI) is significantly elevated, typically prompting delay of elective arthroplasty?

. 6.0%
. 6.5%
. 7.0%
. 8.0%
. 10.0%

Correct Answer & Explanation

. 8.0%

Explanation

Tight glycemic control is paramount in preventing surgical site infections and PJI. Extensive orthopedic literature and consensus guidelines generally cite an HbA1c threshold of > 7.5% to 8.0% as a significant inflection point where the risk of postoperative complications, including infection, dramatically increases. Most institutional protocols delay elective joint arthroplasty if the HbA1c is 8.0% or higher, optimizing the patient prior to surgery.

Question 4851

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon is performing the proximal tibial resection. Injury to the popliteal artery is a rare but catastrophic complication. Anatomically, at what level is the popliteal artery most tethered and vulnerable during the standard tibial cut?

. At the level of the adductor hiatus
. Just posterior to the posterior cruciate ligament tibial attachment
. Distal to the trifurcation of the tibial vessels
. Posterior to the medial femoral condyle
. At the fibular neck

Correct Answer & Explanation

. Just posterior to the posterior cruciate ligament tibial attachment

Explanation

The popliteal artery is located directly posterior to the posterior joint capsule. It is most vulnerable to injury during the proximal tibial bone cut because it runs in close proximity to the posterior capsule just behind the tibial attachment of the posterior cruciate ligament (PCL). Careful retractor placement and awareness of saw blade depth in this exact region are critical to avoid vascular injury.

Question 4852

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following procedural steps is a defining characteristic of a "third-generation" cementing technique in total hip arthroplasty, aimed at maximizing the mechanical interlock and longevity of the cemented stem?

. Hand-mixing of cement in an open bowl at room temperature
. Antegrade filling of the femoral canal with a digital packing technique
. Use of a distal medullary restrictor, vacuum mixing, and retrograde filling
. Application of cement directly to the prosthesis before insertion
. Elimination of pulsatile canal lavage to preserve the endosteal blood supply

Correct Answer & Explanation

. Use of a distal medullary restrictor, vacuum mixing, and retrograde filling

Explanation

Third-generation cementing techniques significantly improve the survivorship of cemented femoral stems. Key components include: thorough pulsatile lavage of the cancellous bone to remove fat and marrow, insertion of a distal medullary restrictor (plug), vacuum mixing or centrifugation of the cement to reduce porosity, retrograde filling of the canal using a cement gun, and pressurization of the cement prior to stem insertion to ensure micro-interlock with the cancellous bone bed.

Question 4853

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female is scheduled for a primary total knee arthroplasty. She reports a history of severe localized blistering rash when wearing cheap jewelry or metal watch bands. Dermatological patch testing confirms a severe Nickel allergy. Which of the following femoral component materials is most appropriate for this patient?

. Cobalt-Chromium-Molybdenum alloy
. Medical grade Stainless steel
. Oxidized Zirconium
. Porous Tantalum
. Highly cross-linked polyethylene

Correct Answer & Explanation

. Oxidized Zirconium

Explanation

Nickel is a common sensitizing agent in metal allergies. Standard Cobalt-Chromium-Molybdenum (CoCr) alloys and stainless steel both contain small but significant amounts of nickel, which can elicit an allergic response in highly sensitized individuals leading to aseptic failure. Oxidized Zirconium (Oxinium) and pure Titanium alloys do not contain nickel and are the preferred bearing surfaces for the femoral component in patients with severe, confirmed metal hypersensitivities. Tantalum is used for ingrowth surfaces, not articular surfaces. Polyethylene is a plastic bearing insert, not a femoral component.

Question 4854

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty for a severe fixed varus deformity, the surgeon performs sequential medial soft tissue releases to balance the extension gap. After removing medial osteophytes and releasing the deep medial collateral ligament (MCL) and the posteromedial corner, the knee remains tight medially in full extension. What is the next most appropriate structure to release?

. Superficial medial collateral ligament
. Lateral collateral ligament
. Popliteus tendon
. Iliotibial band
. Anterior cruciate ligament

Correct Answer & Explanation

. Superficial medial collateral ligament

Explanation

The standard step-wise medial release for a varus knee deformity begins with the removal of medial and posterior tibial osteophytes. If the medial side remains tight, the deep MCL is released, followed by the posteromedial capsule. If further release is necessary, the superficial MCL is progressively released (often subperiosteally elevated off the proximal tibia). If profound deformity exists, a final step may involve releasing the pes anserinus. Releasing lateral structures (LCL, IT band, popliteus) is indicated for valgus knees, not varus knees.

Question 4855

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, trial reduction reveals a joint that is balanced in flexion but excessively tight in extension. Which of the following is the most appropriate intraoperative step to achieve a balanced gap?

. Downsize the femoral component.
. Release the posterior cruciate ligament.
. Recut the proximal tibia to remove more bone.
. Recut the distal femur to remove more bone.
. Upsize the femoral component and use a thinner polyethylene insert.

Correct Answer & Explanation

. Recut the distal femur to remove more bone.

Explanation

An isolated tight extension gap is managed by removing more distal femoral bone, which enlarges the extension gap without affecting the flexion gap. Recutting the proximal tibia would enlarge both the flexion and extension gaps symmetrically.

Question 4856

Topic: 3. Adult Reconstruction (Hip & Knee)

A 76-year-old woman presents with acute thigh pain after a fall. She underwent a total hip arthroplasty 8 years ago. Radiographs demonstrate a fracture around the tip of the femoral stem. The stem appears to be subsided and loose, but there is adequate proximal diaphyseal bone stock.

According to the Vancouver classification, what is the most appropriate surgical management?

. Open reduction and internal fixation with a lateral locking plate and cerclage cables.
. Revision to a fully porous-coated long uncemented stem bypassing the fracture by 2 cortical diameters.
. Revision using an impaction grafting technique with a cemented stem.
. Proximal femoral replacement (tumor prosthesis).
. Traction and non-weight bearing for 6 weeks followed by delayed ORIF.

Correct Answer & Explanation

. Revision to a fully porous-coated long uncemented stem bypassing the fracture by 2 cortical diameters.

Explanation

This represents a Vancouver B2 periprosthetic fracture (loose stem, adequate bone stock). The standard of care is revision of the femoral component using a long uncemented diaphyseal-engaging stem that bypasses the most distal fracture line by at least two cortical diameters.

Question 4857

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female undergoes a primary total hip arthroplasty. The surgeon opts to use a high-offset femoral stem rather than a standard-offset stem, maintaining the identical neck length and seating depth within the medullary canal. What is the expected biomechanical outcome of this modification?

. Increased leg length and increased abductor tension
. Increased leg length and decreased abductor tension
. Unchanged leg length and increased abductor tension
. Unchanged leg length and decreased abductor tension
. Decreased leg length and increased abductor tension

Correct Answer & Explanation

. Increased leg length and increased abductor tension

Explanation

A high-offset stem lateralizes the femoral shaft, which increases the lever arm of the abductor mechanism (increasing tension and efficiency) without altering the vertical height or leg length. Increased offset aids in hip stability and minimizes impingement.

Question 4858

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty using a measured resection technique, trial reduction reveals a symmetric but excessively tight extension gap, while the flexion gap is perfectly balanced. Which of the following is the most appropriate next step to balance the knee?

. Resect additional proximal tibia
. Resect additional distal femur
. Downsize the femoral component
. Release the posterior cruciate ligament
. Upsize the femoral component

Correct Answer & Explanation

. Resect additional distal femur

Explanation

A tight extension gap with a well-balanced flexion gap is managed by resecting additional bone from the distal femur. Resecting more proximal tibia would inappropriately widen both the extension and flexion gaps.

Question 4859

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male presents with chronic pain 2 years following a total hip arthroplasty. Serology reveals an ESR of 45 mm/hr and a CRP of 25 mg/L. Hip aspiration yields synovial fluid with a WBC count of 3,500 cells/uL and 75% neutrophils. Which of the following synovial biomarkers offers the highest specificity for confirming a periprosthetic joint infection (PJI)?

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

Correct Answer & Explanation

. Alpha-defensin

Explanation

Synovial alpha-defensin is an antimicrobial peptide released by neutrophils that has demonstrated extremely high sensitivity and specificity (often >95%) for diagnosing periprosthetic joint infections, making it highly reliable in ambiguous cases.

Question 4860

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old female with advanced knee osteoarthritis is scheduled for a total knee arthroplasty. She has a documented, severe, delayed-type hypersensitivity reaction to nickel. Which of the following femoral component biomaterials is most appropriate to minimize the risk of a hypersensitivity reaction?

. Standard Cobalt-Chromium-Molybdenum alloy
. Stainless steel
. Titanium alloy with an oxidized zirconium surface
. Uncoated titanium alloy
. Tantalum

Correct Answer & Explanation

. Titanium alloy with an oxidized zirconium surface

Explanation

Oxidized zirconium (Oxinium) components have virtually zero nickel content and possess excellent wear characteristics, making them the implant of choice for patients with documented severe nickel or metal hypersensitivity in total knee arthroplasty. Standard CoCr implants contain trace amounts of nickel.

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