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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 145 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 2881

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old woman sustains a periprosthetic femur fracture 10 years after a cemented THA. Radiographs show a fracture around the tip of the stem. The stem is loose, but the proximal femoral bone stock is well preserved. According to the Vancouver classification, what is the most appropriate management?

. ORIF with a locking plate and cerclage cables
. Revision to a standard length cemented stem
. Revision to a long fully porous-coated uncemented stem
. Impaction bone grafting alone
. Cortical strut allografting alone

Correct Answer & Explanation

. Revision to a long fully porous-coated uncemented stem

Explanation

This is a Vancouver B2 fracture (fracture around the stem, loose implant, good bone stock). The standard of care is revision arthroplasty bypassing the fracture site with a long, diaphyseal-engaging uncemented stem.

Question 2882

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary cellular mechanism of osteolysis induced by polyethylene wear debris in total joint arthroplasty?

. Direct toxicity of polyethylene particles to osteoblasts
. Macrophage phagocytosis leading to IL-1, IL-6, and TNF-alpha release
. T-cell mediated delayed hypersensitivity reaction
. Complement activation by wear particles
. Neutrophil degranulation and release of reactive oxygen species

Correct Answer & Explanation

. Macrophage phagocytosis leading to IL-1, IL-6, and TNF-alpha release

Explanation

Wear debris osteolysis is primarily a macrophage-mediated response. Macrophages phagocytose particulate debris and release cytokines (TNF-alpha, IL-1, IL-6), which stimulate osteoclastic bone resorption via the RANK/RANKL pathway.

Question 2883

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man who underwent a metal-on-metal THA 6 years ago presents with new-onset groin pain and a palpable anterior mass. Joint aspiration yields sterile fluid with elevated cobalt levels. What is the most likely histological finding of the periprosthetic tissue?

. Intense neutrophilic infiltrate
. Perivascular lymphocytic infiltrate with macrophages
. Extensive caseating granulomas
. Multinucleated giant cells with birefringent polyethylene debris
. Malignant spindle cells

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate with macrophages

Explanation

The clinical picture describes an adverse local tissue reaction (ALTR) or ALVAL, common in metal-on-metal implants. Histology typically shows a perivascular infiltrate of T-lymphocytes and macrophages.

Question 2884

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA, after making the initial bony cuts, the surgeon notices that the knee is tight in flexion but well-balanced in extension. Which of the following maneuvers is most appropriate to balance the knee?

. Resect more distal femur
. Upsize the femoral component
. Release the medial collateral ligament
. Increase the posterior slope of the tibial cut
. Recess the popliteus tendon

Correct Answer & Explanation

. Increase the posterior slope of the tibial cut

Explanation

A knee that is tight in flexion but balanced in extension requires an increase in the flexion gap without altering the extension gap. Increasing the posterior tibial slope, resecting more posterior femoral condyle, or releasing the PCL will achieve this.

Question 2885

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient presents with a painful total knee arthroplasty 8 weeks postoperatively. The ESR is 45 mm/hr and CRP is 35 mg/L. Knee aspiration yields 45,000 WBC/uL with 92% neutrophils. What is the most appropriate next step in management?

. Oral antibiotic suppression
. Arthroscopic irrigation and debridement
. Open debridement with polyethylene exchange (DAIR)
. Two-stage exchange arthroplasty
. One-stage exchange arthroplasty

Correct Answer & Explanation

. Two-stage exchange arthroplasty

Explanation

This patient has a chronic periprosthetic joint infection, as the symptom onset is >4 weeks postoperatively. The gold standard treatment for chronic PJI in North America is a two-stage exchange arthroplasty.

Question 2886

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. Age greater than 60 years
. Inflammatory arthropathy
. Mild patellofemoral osteoarthritis
. Body Mass Index greater than 30
. Flexion contracture of 5 degrees

Correct Answer & Explanation

. Inflammatory arthropathy

Explanation

Inflammatory arthropathy (e.g., rheumatoid arthritis) is considered an absolute contraindication for UKA due to global joint involvement. Age and BMI are controversial but not absolute contraindications.

Question 2887

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a total hip arthroplasty is experiencing recurrent posterior dislocations. Radiographs reveal appropriate cup abduction and anteversion, but the femoral component has inadequate offset. What is the most likely clinical finding on physical examination?

. Positive Trendelenburg sign
. Severe thigh pain with weight-bearing
. Fixed external rotation deformity
. Leg length discrepancy with the operative leg longer
. Absent patellar reflex

Correct Answer & Explanation

. Positive Trendelenburg sign

Explanation

Inadequate femoral offset reduces the moment arm of the hip abductors, leading to mechanical disadvantage and abductor weakness. This clinically manifests as a positive Trendelenburg sign and limp.

Question 2888

Topic: 3. Adult Reconstruction (Hip & Knee)
During a revision total hip arthroplasty, severe acetabular bone loss is encountered. Radiographs and intraoperative findings demonstrate a complete separation of the superior and inferior halves of the hemipelvis. What is the diagnosis and best reconstruction option?
. Paprosky Type IIIA defect; Jumbo cup
. Paprosky Type IIIB defect; Standard hemispherical cup with screws
. Pelvic discontinuity; Cup-cage construct or custom triflange
. Pelvic discontinuity; Cemented cup alone
. Protrusio acetabuli; Impaction bone grafting

Correct Answer & Explanation

. Pelvic discontinuity; Cup-cage construct or custom triflange

Explanation

Separation of the superior and inferior hemipelvis defines a pelvic discontinuity. Stable reconstruction typically requires bridging the discontinuity with a cup-cage construct, custom triflange, or a distraction technique.

Question 2889

Topic: 3. Adult Reconstruction (Hip & Knee)

In total knee arthroplasty, the posterior stabilized (PS) design utilizes a cam and post mechanism. Which of the following normal knee kinematics does this mechanism primarily replicate?

. Anterior translation of the tibia during flexion
. Posterior femoral rollback during flexion
. Internal rotation of the femur during extension
. Valgus alignment during deep flexion
. Prevention of hyperextension in the stance phase

Correct Answer & Explanation

. Posterior femoral rollback during flexion

Explanation

The cam and post mechanism in a PS knee substitutes for the posterior cruciate ligament (PCL). As the knee flexes, the femoral cam engages the tibial post to drive the femur posteriorly, replicating physiologic femoral rollback.

Question 2890

Topic: 3. Adult Reconstruction (Hip & Knee)

Highly cross-linked polyethylene (HXLPE) was developed to reduce wear in total hip arthroplasty. What is the primary purpose of the post-irradiation remelting or annealing step in the manufacturing process?

. Increase the ultimate tensile strength of the polyethylene
. Eliminate free radicals to prevent oxidative degradation
. Enhance the biological integration of the liner
. Reduce the elasticity of the polyethylene
. Promote cross-linking of surface molecules

Correct Answer & Explanation

. Eliminate free radicals to prevent oxidative degradation

Explanation

Irradiation is used to cross-link the polyethylene, but it generates free radicals that can cause oxidative degradation over time. Remelting or annealing the material extinguishes these free radicals, improving oxidation resistance.

Question 2891

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male undergoes a ceramic-on-ceramic total hip arthroplasty. Two years postoperatively, he complains of a loud audible squeaking during normal ambulation. What factor is most strongly associated with this complication?

. Component malposition leading to edge loading
. Use of a 28 mm femoral head
. Body mass index less than 25
. Bilateral total hip arthroplasty
. Excessive femoral offset

Correct Answer & Explanation

. Component malposition leading to edge loading

Explanation

Squeaking in ceramic-on-ceramic hips is most commonly associated with component malposition (e.g., vertical cup placement), which leads to stripe wear and edge loading. Loss of fluid film lubrication follows.

Question 2892

Topic: Total Knee Arthroplasty (TKA)

A 48-year-old female presents with complete disruption of her extensor mechanism 3 months following a primary TKA. Examination shows a palpable gap at the patellar tendon and an inability to actively extend the knee. What is the most reliable surgical treatment?

. Primary end-to-end repair with nonabsorbable suture
. Reconstruction with an extensor mechanism allograft or synthetic mesh
. Medial gastrocnemius rotational flap
. Patellar tendon tenodesis to the tibial tubercle
. Revision of the tibial component

Correct Answer & Explanation

. Reconstruction with an extensor mechanism allograft or synthetic mesh

Explanation

Primary repair of late extensor mechanism ruptures post-TKA has an extremely high failure rate. Reconstruction utilizing a whole extensor mechanism allograft or synthetic mesh (e.g., Marlex) offers the most reliable results.

Question 2893

Topic: Total Hip Arthroplasty (THA)

During preoperative templating for a primary THA, the surgeon identifies a significant leg length discrepancy, with the operative side being 2 cm shorter. To lengthen the leg without excessively increasing the femoral offset, which intraoperative adjustment should be made?

. Use a femoral head with a longer neck
. Use a stem with a higher neck-shaft angle (more valgus)
. Use a stem with a lower neck-shaft angle (more varus)
. Deepen the acetabular component medially
. Increase the anteversion of the acetabular cup

Correct Answer & Explanation

. Use a stem with a lower neck-shaft angle (more varus)

Explanation

A high offset stem (lower neck-shaft angle/more varus) increases offset with minimal effect on leg length. Conversely, a standard offset stem (higher neck-shaft angle/more valgus) gains more vertical length for every unit of offset added.

Question 2894

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon is performing a posterior-stabilized total knee arthroplasty. During trialing, the knee is tight in flexion and symmetrically balanced in extension. Which of the following is the most appropriate next step?

. Increase the tibial polyethylene thickness
. Recut the proximal tibia to remove more bone
. Downsize the femoral component
. Release the posterior cruciate ligament
. Release the superficial medial collateral ligament

Correct Answer & Explanation

. Downsize the femoral component

Explanation

Downsizing the femoral component translates the posterior femoral condyles anteriorly, which increases the flexion gap. This maneuver successfully addresses a tight flexion gap without altering the extension gap.

Question 2895

Topic: 3. Adult Reconstruction (Hip & Knee)

A 74-year-old woman sustains a fall 6 years after primary total hip arthroplasty. Radiographs reveal a spiral fracture around the tip of the femoral stem. The stem is subsided by 2 cm, but the proximal femoral bone stock remains adequate. According to the Vancouver classification, what is the most appropriate management?

. Open reduction and internal fixation with a locking plate
. Open reduction and internal fixation with strut allografts
. Revision to a standard-length cemented stem
. Revision to a long extensively porous-coated or fluted tapered stem
. Proximal femoral replacement

Correct Answer & Explanation

. Revision to a long extensively porous-coated or fluted tapered stem

Explanation

This is a Vancouver B2 fracture, characterized by a fracture around a loose stem with adequate bone stock. The gold standard treatment is revision to a longer, diaphyseal-engaging cementless stem to bypass the fracture and achieve stability.

Question 2896

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man presents with anterior knee pain and recurrent lateral patellar subluxation 6 months after a primary total knee arthroplasty. Which of the following component malpositions is the most likely cause of his patellar maltracking?

. Internal rotation of the tibial component
. External rotation of the femoral component
. Lateral translation of the femoral component
. Medial translation of the tibial component
. Excessive valgus alignment of the femoral component

Correct Answer & Explanation

. Internal rotation of the tibial component

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle and leads to lateral patellar tracking and potential subluxation. External rotation of the components typically improves patellar tracking.

Question 2897

Topic: 3. Adult Reconstruction (Hip & Knee)
A 58-year-old woman presents with worsening groin pain and swelling 8 years after receiving a metal-on-metal total hip arthroplasty. Laboratory tests show elevated serum cobalt and chromium levels. A MARS MRI demonstrates a large solid and cystic mass communicating with the joint. What is the underlying histologic mechanism of this process?
. Type I IgE-mediated hypersensitivity
. Type II cytotoxic hypersensitivity
. Type III immune complex hypersensitivity
. Type IV delayed-type hypersensitivity
. Foreign body giant cell reaction to polyethylene debris

Correct Answer & Explanation

. Type IV delayed-type hypersensitivity

Explanation

Adverse local tissue reactions (ALTR) or aseptic lymphocytic vasculitis-associated lesions (ALVAL) in metal-on-metal hips are primarily driven by a Type IV delayed hypersensitivity response to metal ions.

Question 2898

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old man develops erythema, swelling, and purulent drainage from his incision 14 days after a primary total knee arthroplasty. He is febrile. Joint aspiration yields 65,000 WBCs/mcL with 95% neutrophils. What is the most appropriate surgical management?

. Prescribe 6 weeks of oral antibiotics
. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. Single-stage revision arthroplasty
. Two-stage revision arthroplasty with an articulating spacer
. Suppressive intravenous antibiotics without surgery

Correct Answer & Explanation

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

Explanation

For acute postoperative periprosthetic joint infections occurring within 4 weeks of the index surgery, DAIR with modular component exchange is the most appropriate and effective initial management strategy.

Question 2899

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision total knee arthroplasty for aseptic loosening, removal of the tibial component reveals an uncontained metaphyseal bone defect measuring 4 cm deep, compromising the cortical rim (AORI Type 3). What is the most reliable method for achieving durable fixation?

. Impaction bone grafting
. Cement filling of the defect
. Structural cortical allograft
. Metaphyseal tantalum cones or sleeves
. Standard primary tibial baseplate with a long cemented stem

Correct Answer & Explanation

. Metaphyseal tantalum cones or sleeves

Explanation

For severe uncontained metaphyseal defects (AORI Type 3) in revision TKA, highly porous metal cones or metaphyseal sleeves provide excellent long-term biologic fixation and construct stability compared to bulk allografts.

Question 2900

Topic: Total Hip Arthroplasty (THA)

A 45-year-old man undergoes total hip arthroplasty using a ceramic-on-ceramic bearing. Three years later, he complains of a reproducible squeaking noise during deep flexion. Which of the following biomechanical factors is most strongly associated with this phenomenon?

. Loss of abductor tension
. Stripe wear from edge loading due to component malposition
. Corrosion at the head-neck junction
. Third-body wear from retained cement debris
. Galvanic corrosion at the modular neck

Correct Answer & Explanation

. Stripe wear from edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic THA is heavily associated with edge loading, often caused by acetabular component malposition. This leads to stripe wear and altered fluid lubrication dynamics.

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