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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 275 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 5481

Topic: Total Hip Arthroplasty (THA)

C orrection of the congenital gibbus in spina bifida must follow which of these surgical principles:

. Long instrumentation
. Short instrumentation
. Avoidance of instrumentation
. Avoidance of bony resection
. Anterior approach to deformity

Correct Answer & Explanation

. Long instrumentation

Explanation

The leverage provided by long instrumentation prevents loss of correction and junctional deformity.Short instrumentation poses a risk of junctional kyphosis or loss of fixation.Because of the severe angular deformity, fusion in situ without correction will be followed by increasing deformity. Resection of one to three of the vertebrae on the lower limb of the kyphosis is essential to allow safe correction without excessive tension on vessels and viscera.The anterior approach to the gibbus is deep and impractical. This approach does not allow mechanically efficient instrumentation.

Question 5482

Topic: 3. Adult Reconstruction (Hip & Knee)
Figure 64 shows the radiograph of a 61-year-old man with ankylosing spondylitis. He is scheduled to undergo left total hip arthroplasty. Which of the following perioperative interventions should be considered?
. Intraoperative sciatic nerve monitoring
. Preoperative radiation therapy with 700 centigray
. Postoperative radiation therapy with 1,500 centigray
. Postoperative continuous passive motion
. Soft cervical collar during postoperative physical therapy

Correct Answer & Explanation

. Preoperative radiation therapy with 700 centigray

Explanation

Patients with ankylosing spondylitis are at high risk for heterotopic ossification after total hip arthroplasty, and perioperative prophylaxis with nonsteroidal anti-inflammatory drugs or radiation therapy has been effective at reducing the risk. Radiation prophylaxis given within 24 hours preoperatively has been shown to be as effective as radiation given postoperatively. Doses of 700 to 800 centigray have been shown to be as effective as higher doses with less potential risk.

Question 5483

Topic: Total Hip Arthroplasty (THA)

During a primary total hip arthroplasty (THA) using a posterior approach, the surgeon inadvertently places the acetabular component in excessive retroversion. Which of the following complications is this patient at greatest risk for developing postoperatively?

. Posterior dislocation
. Anterior dislocation
. Sciatic nerve palsy
. Iliopsoas impingement
. Superior gluteal nerve injury

Correct Answer & Explanation

. Posterior dislocation

Explanation

Acetabular component version is critical to THA stability. The 'safe zone' described by Lewinnek suggests an optimal anteversion of 15 ± 10 degrees. Excessive retroversion of the acetabular component predisposes the hip to posterior impingement and subsequent posterior dislocation, particularly when the hip is placed in a position of flexion, adduction, and internal rotation. Conversely, excessive anteversion risks anterior dislocation.

Question 5484

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with severe tricompartmental knee osteoarthritis undergoes total knee arthroplasty (TKA). During the trialing phase with the trial components in place, the knee is completely stable symmetrically in full extension, but demonstrates 5 mm of laxity to both varus and valgus stress when placed in 90 degrees of flexion. Which of the following intraoperative adjustments is the most appropriate to achieve a balanced knee?

. Increase the size of the femoral component
. Decrease the size of the femoral component
. Increase the thickness of the polyethylene insert
. Recut the distal femur, taking more bone
. Perform a pie-crusting release of the medial collateral ligament

Correct Answer & Explanation

. Increase the size of the femoral component

Explanation

This scenario describes a 'loose flexion gap' and a 'stable extension gap'. If you simply increase the polyethylene thickness, the flexion gap will balance, but the extension gap will become too tight (leading to a flexion contracture). To specifically tighten the flexion gap without altering the extension gap, the surgeon must increase the posterior condylar offset. This is most effectively accomplished by upsizing the femoral component (which increases the anteroposterior dimension of the femur) and potentially using posterior augments if needed, thereby tensioning the collateral ligaments in flexion.

Question 5485

Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female who underwent an uncemented total hip arthroplasty 10 years ago presents with new-onset thigh pain. Radiographs reveal massive focal areas of radiolucency (osteolysis) around the proximal femoral stem. At revision surgery, copious hypertrophic membrane is noted. Which of the following particulate debris types is the most potent biological stimulator of the macrophage-induced osteolytic cascade in this conventional bearing surface?
. Titanium alloy particles
. Cobalt-chromium ions
. Polymethylmethacrylate (PMMA) fragments
. Ultra-high-molecular-weight polyethylene (UHMWPE) particles
. Hydroxyapatite debris

Correct Answer & Explanation

. Ultra-high-molecular-weight polyethylene (UHMWPE) particles

Explanation

Aseptic loosening secondary to osteolysis is the most common long-term mode of failure in conventional metal-on-polyethylene total hip arthroplasty. Submicron ultra-high-molecular-weight polyethylene (UHMWPE) wear particles are phagocytosed by macrophages. This triggers an intense foreign-body inflammatory response, causing the release of cytokines such as TNF-alpha, IL-1, IL-6, and PGE2, which subsequently activate osteoclasts.

Question 5486

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty (TKA), after the initial bone cuts are made and trial components are inserted, the surgeon notes that the extension gap is perfectly balanced, but the flexion gap is excessively tight. Which of the following surgical maneuvers is the most appropriate next step to balance the knee?

. Release the posterior capsule
. Recut the distal femur to resect more bone
. Upsize the tibial polyethylene insert
. Downsize the femoral component and use a thicker polyethylene insert
. Downsize the femoral component (anterior referencing) to decrease posterior condylar offset

Correct Answer & Explanation

. Release the posterior capsule

Explanation

A tight flexion gap with a perfectly balanced extension gap requires a maneuver that only affects the flexion space. Downsizing the femoral component (using an anterior referencing system) will decrease the anteroposterior (AP) dimension of the femur, specifically reducing the posterior condylar offset. This selectively opens (increases) the flexion gap without altering the distal femoral cut, thus leaving the extension gap unchanged. Resecting more distal femur would affect only the extension gap. Releasing the posterior capsule affects the extension gap more than the flexion gap.

Question 5487

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female who underwent a primary total hip arthroplasty (THA) 2 years ago presents with a loud "squeaking" noise coming from her hip when she bends down or climbs stairs. She has no pain and radiographs show perfectly fixed, well-positioned components. Her THA most likely utilized which of the following bearing surface combinations?

. Metal-on-highly cross-linked polyethylene
. Ceramic-on-highly cross-linked polyethylene
. Ceramic-on-ceramic
. Metal-on-metal
. Oxidized zirconium (Oxinium)-on-polyethylene

Correct Answer & Explanation

. Metal-on-highly cross-linked polyethylene

Explanation

Squeaking is a well-documented, specific complication associated with ceramic-on-ceramic (CoC) bearing surfaces in total hip arthroplasty. The exact etiology is multifactorial, including stripe wear, edge loading from micro-separation, component malposition (e.g., steep acetabular cup), or third-body wear. It is rarely associated with catastrophic failure if painless, but it can be highly annoying to the patient.

Question 5488

Topic: 3. Adult Reconstruction (Hip & Knee)
Ultra-high molecular weight polyethylene (UHMWPE) undergoes cross-linking via gamma irradiation or electron beam radiation prior to use in modern total joint arthroplasty. While this process achieves the desired goal of decreasing osteolysis, it results in which of the following mechanical trade-offs?
. Decreased wear resistance with increased fracture toughness
. Increased wear resistance with decreased fracture toughness and decreased fatigue strength
. Increased wear resistance with increased ultimate tensile strength
. Decreased wear resistance with decreased fatigue strength
. Increased fatigue strength with increased wear resistance

Correct Answer & Explanation

. Increased wear resistance with decreased fracture toughness and decreased fatigue strength

Explanation

Highly cross-linking UHMWPE significantly increases its wear resistance, thereby drastically reducing the volume of wear debris generated and lowering the risk of periprosthetic osteolysis. However, the radiation process and subsequent thermal treatments (melting or annealing to eliminate free radicals and prevent oxidation) alter the crystalline structure. This mechanical trade-off results in decreased fracture toughness, reduced fatigue strength, and lowered ultimate tensile strength, making the material more susceptible to catastrophic failure in thin inserts or high-stress designs.

Question 5489

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, the choice of bearing surface impacts longevity. Which of the following bearing surface combinations exhibits the lowest volumetric wear rate in laboratory simulator testing?

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

Correct Answer & Explanation

. Cobalt-chrome on highly cross-linked polyethylene

Explanation

Ceramic-on-ceramic bearing surfaces demonstrate the lowest volumetric wear rates in simulator studies, typically measuring less than 1 cubic millimeter per million cycles. However, they carry unique risks, including component fracture and squeaking.

Question 5490

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary posterior-stabilized total knee arthroplasty, trial reduction reveals that the knee is completely balanced in full extension but excessively tight in 90 degrees of flexion, limiting range of motion. Which of the following technical adjustments is most appropriate to balance this knee?

. Increase the distal femoral resection
. Decrease the distal femoral resection
. Increase the posterior tibial slope
. Upsize the femoral component
. Release the posterior capsule

Correct Answer & Explanation

. Increase the distal femoral resection

Explanation

A knee that is balanced in extension but tight in flexion represents an isolated tight flexion gap. Appropriate adjustments to increase the flexion gap without affecting the extension gap include increasing the posterior tibial slope, downsizing the femoral component, or anteriorly translating the femoral component.

Question 5491

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary posterior-stabilized total knee arthroplasty (TKA), the surgeon finds the knee to be symmetrically balanced in extension but significantly tight in flexion. Which of the following intraoperative adjustments is most appropriate to resolve this specific mismatch?

. Release the posterior capsule
. Increase the thickness of the tibial polyethylene insert
. Downsize the femoral component with anterior referencing
. Upsize the femoral component with posterior referencing
. Distalize the femoral component

Correct Answer & Explanation

. Release the posterior capsule

Explanation

A knee that is tight in flexion but balanced in extension requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component using anterior referencing reduces the posterior condylar offset, effectively increasing the flexion gap.

Question 5492

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old active male underwent a total hip arthroplasty (THA) using a ceramic-on-ceramic bearing surface. Two years postoperatively, he complains of an audible squeaking sound from his hip during walking, but denies any pain. Radiographs show no loosening. What is the most likely biomechanical cause of the squeaking?

. Subclinical infection
. Femoral stem subsidence
. Edge loading due to component malposition
. Accelerated polyethylene wear
. Adverse local tissue reaction to metal debris

Correct Answer & Explanation

. Subclinical infection

Explanation

Squeaking in ceramic-on-ceramic total hips is primarily associated with edge loading, often resulting from a malpositioned acetabular cup (e.g., vertical inclination). While often painless, it can increase the risk of component wear or catastrophic fracture.

Question 5493

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male presents with aseptic loosening 15 years after a total knee arthroplasty. Radiographs show extensive scalloping and periprosthetic osteolysis. The primary biological mediator of this osteolysis is the activation of which specific cell type by submicron particulate debris?

. Osteoblasts
. Neutrophils
. Macrophages
. T-lymphocytes
. Mast cells

Correct Answer & Explanation

. Osteoblasts

Explanation

Aseptic loosening secondary to osteolysis is driven by macrophages that phagocytose submicron wear debris (especially polyethylene). The activated macrophages release pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6), stimulating aggressive osteoclastic bone resorption.

Question 5494

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with recurrent posterior dislocations following primary total hip arthroplasty. Surgical exploration reveals an irreparably deficient abductor mechanism. The acetabular component is well-fixed and correctly positioned. What is the most appropriate management?

. Revision to a larger femoral head
. Revision to a dual mobility bearing
. Revision to a constrained acetabular liner
. Revision to a hemiarthroplasty
. Application of a prolonged hip spica cast

Correct Answer & Explanation

. Revision to a larger femoral head

Explanation

Constrained liners are specifically indicated for recurrent instability in the setting of severe abductor deficiency or severe cognitive impairment. Dual mobility is preferred for patients with intact abductors to prevent impingement.

Question 5495

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male develops a culture-positive periprosthetic joint infection (Staphylococcus aureus) 3 weeks after an uncomplicated primary total knee arthroplasty. The implants are well-fixed on radiographs. What is the most appropriate surgical intervention?

. Intravenous antibiotics alone for 6 weeks
. One-stage exchange arthroplasty
. Two-stage exchange arthroplasty with an antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with modular component exchange
. Arthrodesis of the knee joint

Correct Answer & Explanation

. Intravenous antibiotics alone for 6 weeks

Explanation

For acute postoperative periprosthetic joint infections (typically within 4 weeks of the index surgery) with well-fixed components, DAIR (Debridement, Antibiotics, and Implant Retention) is the standard of care. This procedure must include the exchange of modular components, such as the polyethylene insert.

Question 5496

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male is 2 weeks post-Total Hip Arthroplasty (THA) via a posterior approach and experiences recurrent posterior dislocations. Radiographs show the acetabular component in 40 degrees of abduction and 0 degrees of version. What is the most appropriate surgical intervention?

. Application of a hip spica cast
. Revision of the acetabular component to increase anteversion
. Revision of the femoral component to increase offset
. Placement of a constrained liner
. Conversion to bipolar hemiarthroplasty

Correct Answer & Explanation

. Application of a hip spica cast

Explanation

The acetabular component is neutral/retroverted (normal target is 15-20 degrees of anteversion). Revision of the cup to increase anteversion is required to correct the underlying mechanical cause of the recurrent posterior instability.

Question 5497

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary Total Knee Arthroplasty (TKA), trial components are inserted. The surgeon notes a tight flexion gap and a perfectly balanced extension gap. Which surgical maneuver correctly addresses this mismatch?

. Resecting more distal femur
. Decreasing the posterior slope of the tibial cut
. Increasing the thickness of the tibial polyethylene insert
. Performing a posterior capsular release
. Downsizing the femoral component using an anterior referencing system

Correct Answer & Explanation

. Resecting more distal femur

Explanation

A tight flexion gap with a balanced extension gap requires increasing only the flexion space. This can be achieved by downsizing the femoral component (which removes more posterior condylar bone) or increasing the posterior tibial slope.

Question 5498

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man who underwent a total hip arthroplasty 3 years ago presents with a loud, audible squeaking noise from his hip with movement. Radiographs show well-fixed components. Which bearing surface combination is most classically associated with this phenomenon?

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

Correct Answer & Explanation

. Metal-on-polyethylene

Explanation

Squeaking is a specific and well-documented complication of ceramic-on-ceramic total hip arthroplasty. It is often related to component malposition, microseparation, or stripe wear.

Question 5499

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male is undergoing a total hip arthroplasty and asks about the specific risks of using a ceramic-on-ceramic bearing surface. Which of the following is a well-documented complication unique to this bearing combination?

. Metallosis and pseudotumor formation
. Trunnionosis
. Audible squeaking during gait
. Accelerated polyethylene wear
. Increased risk of early deep infection

Correct Answer & Explanation

. Metallosis and pseudotumor formation

Explanation

Ceramic-on-ceramic bearings offer ultra-low wear rates and no risk of metallosis. However, they are uniquely associated with audible squeaking during motion in a small percentage of patients, which can cause significant dissatisfaction.

Question 5500

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient presents with thigh pain 12 years after a cementless total hip arthroplasty. Radiographs show eccentric polyethylene wear and significant periprosthetic radiolucent lines. What is the primary biological mediator initiating this osteolysis?

. Macrophage release of Interleukin-1 (IL-1) and TNF-alpha
. Osteoblast release of Bone morphogenetic protein 2 (BMP-2)
. Chondrocyte release of Transforming growth factor beta (TGF-beta)
. Fibroblast release of Insulin-like growth factor 1 (IGF-1)
. Platelet release of Platelet-derived growth factor (PDGF)

Correct Answer & Explanation

. Macrophage release of Interleukin-1 (IL-1) and TNF-alpha

Explanation

Polyethylene wear debris undergoes phagocytosis by macrophages, leading to the release of inflammatory cytokines such as IL-1, IL-6, and TNF-alpha. These cytokines stimulate osteoclast-mediated bone resorption, resulting in aseptic loosening.

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