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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 281 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 5601

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Musculoskeletal Infection Society (MSIS) / International Consensus Meeting (ICM) criteria, which of the following constitutes an absolute major criterion for the definitive diagnosis of a periprosthetic joint infection (PJI)?

. Elevated serum ESR > 30 mm/hr and CRP > 10 mg/L
. A single positive intraoperative tissue culture
. Elevated synovial fluid leukocyte count > 3,000 cells/ยตL
. A sinus tract communicating directly with the prosthesis
. Positive synovial fluid alpha-defensin immunoassay

Correct Answer & Explanation

. Elevated serum ESR > 30 mm/hr and CRP > 10 mg/L

Explanation

According to the MSIS/ICM criteria, the two major criteria (either of which definitively diagnoses a PJI on its own) are: 1) A sinus tract communicating directly with the prosthesis, and 2) Two positive periprosthetic cultures with phenotypically identical organisms. The other options are considered minor criteria, a combination of which is required to meet the definition of PJI if a major criterion is absent.

Question 5602

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman presents with worsening right groin pain 4 years after a primary total hip arthroplasty. Her implant is a conventional metal-on-polyethylene bearing. Radiographs demonstrate a well-fixed stem and cup with no evidence of osteolysis. Serum inflammatory markers (ESR, CRP) are normal. Aspiration of the hip yields clear fluid with a low cell count. MRI with Metal Artifact Reduction Sequence (MARS) reveals a large, complex cystic pseudotumor adjacent to the femoral neck. Which of the following is the most likely etiology of her symptoms?

. Conventional polyethylene wear debris causing macroscopic osteolysis
. Indolent periprosthetic joint infection by Cutibacterium acnes
. Mechanically assisted crevice corrosion at the modular head-neck junction
. Iliopsoas tendon impingement against the anterior acetabular rim
. Unrecognized intraoperative periprosthetic fracture

Correct Answer & Explanation

. Conventional polyethylene wear debris causing macroscopic osteolysis

Explanation

The presence of an Adverse Local Tissue Reaction (ALTR) or pseudotumor in a metal-on-polyethylene total hip arthroplasty, combined with a normal infection workup and well-fixed components without massive osteolysis, points toward mechanically assisted crevice corrosion (MACC) at the modular head-neck junction (also known as trunnionosis). This corrosion releases metal ions that incite a lymphocytic inflammatory response.

Question 5603

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with a painful right total knee arthroplasty, 3 years post-operatively. According to the 2018 International Consensus Meeting (ICM) criteria for Periprosthetic Joint Infection (PJI), which of the following is considered a 'Major Criterion' definitively diagnostic of a PJI?

. Positive leukocyte esterase (++ or greater) on synovial fluid dipstick
. Synovial fluid white blood cell count greater than 3,000 cells/uL
. Elevated synovial fluid Alpha-defensin levels
. Elevated serum C-reactive protein (>10 mg/L) and D-dimer (>860 ng/mL)
. Two positive periprosthetic tissue cultures yielding phenotypically identical organisms

Correct Answer & Explanation

. Positive leukocyte esterase (++ or greater) on synovial fluid dipstick

Explanation

According to the 2018 ICM criteria, the Major Criteria for diagnosing PJI (either one is definitively diagnostic) are: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. All other options (leukocyte esterase, synovial WBC count, alpha-defensin, serum CRP/D-dimer) are minor criteria used in the scoring system.

Question 5604

Topic: 3. Adult Reconstruction (Hip & Knee)
In the evolution of bearing surfaces for total hip arthroplasty, ultra-high-molecular-weight polyethylene (UHMWPE) is often subjected to gamma irradiation to induce high degrees of cross-linking, followed by a thermal treatment (remelting or annealing). Highly cross-linking the polyethylene results in which of the following mechanical trade-offs?
. Increased ultimate tensile strength
. Decreased volumetric wear but decreased fracture toughness
. Increased fatigue resistance
. Increased elongation to failure (ductility)
. Elimination of the need to sterilize the implant

Correct Answer & Explanation

. Decreased volumetric wear but decreased fracture toughness

Explanation

Highly cross-linked polyethylene (HXLPE) was developed to significantly decrease the volumetric wear rate, thereby reducing osteolysis and aseptic loosening. However, the cross-linking process alters the mechanical properties of the material, leading to a decrease in ultimate tensile strength, fatigue resistance, and fracture toughness. This makes HXLPE more susceptible to fatigue-related mechanical failure, such as rim fracture, though its wear properties are vastly superior to conventional UHMWPE.

Question 5605

Topic: 3. Adult Reconstruction (Hip & Knee)

A 24-year-old male falls onto an outstretched hand and sustains a minimally displaced fracture through the proximal third of the scaphoid. The proximal pole is highly susceptible to avascular necrosis due to its tenuous blood supply. The primary blood supply to the proximal pole of the scaphoid originates from branches of the radial artery that enter the bone at which specific anatomical location?

. The volar scaphoid tubercle
. The proximal articular surface
. The dorsal ridge (distal to the waist)
. The scapholunate interosseous ligament insertion
. The volar radiocarpal ligament insertion

Correct Answer & Explanation

. The volar scaphoid tubercle

Explanation

The blood supply to the scaphoid is retrograde. Branches of the radial artery enter the scaphoid predominantly at the dorsal ridge, which is located on the non-articular dorsal surface at the level of the scaphoid waist/distal pole. From there, the intraosseous vessels travel proximally to supply the proximal pole. Thus, proximal pole fractures interrupt this retrograde supply, leading to a high risk of avascular necrosis.

Question 5606

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized (PS) total knee arthroplasty, trial components are inserted. The surgeon evaluates the gap kinematics and notes that the knee is perfectly balanced in full extension, but the joint is exceptionally tight in 90 degrees of flexion, restricting rollback. Assuming the tibial cut is correct, which of the following is the most appropriate surgical step to achieve a balanced flexion-extension gap?

. Resect an additional 2 mm of the distal femur
. Downsize the femoral component and use anterior referencing
. Perform a complete release of the posterior capsule
. Increase the thickness of the tibial polyethylene insert
. Release the medial collateral ligament (MCL) from its tibial insertion

Correct Answer & Explanation

. Resect an additional 2 mm of the distal femur

Explanation

A knee that is tight in flexion but balanced in extension requires an isolated increase in the flexion gap. Downsizing the femoral component (when referencing anteriorly) decreases the anterior-posterior dimension of the femoral component by resecting more posterior condylar bone, thus selectively opening and loosening the flexion gap without affecting the extension gap. Resecting more distal femur would open the extension gap. Releasing the posterior capsule affects the extension gap.

Question 5607

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon assesses the gaps with trial components. The knee is balanced in extension but is too tight in flexion. Which of the following is the most appropriate surgical step to correct this mismatch?

. Recut the distal femur
. Increase the posterior slope of the tibial cut
. Release the posterior cruciate ligament (PCL)
. Downsize the femoral component and use a thicker tibial insert
. Release the posterior capsule

Correct Answer & Explanation

. Recut the distal femur

Explanation

A tight flexion gap with a balanced extension gap can be addressed by increasing the posterior tibial slope, which opens the flexion gap without affecting the extension gap. Recessing the PCL or downsizing the femoral component are alternative options.

Question 5608

Topic: 3. Adult Reconstruction (Hip & Knee)

A 22-year-old male presents with a scaphoid waist fracture. He is counseled on the risk of avascular necrosis (AVN). The major blood supply to the proximal pole of the scaphoid is derived from vessels entering at which of the following locations?

. Volar distal pole
. Dorsal distal pole
. Volar proximal pole
. Dorsal ridge
. Scaphotrapezial joint capsule

Correct Answer & Explanation

. Volar distal pole

Explanation

The primary blood supply to the scaphoid comes from the dorsal carpal branch of the radial artery. It enters the scaphoid at the dorsal ridge (distal to the waist) and flows retrogradely to the proximal pole.

Question 5609

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male is undergoing total hip arthroplasty. The surgeon opts for a highly cross-linked polyethylene (XLPE) liner. Which of the following best describes the mechanical trade-off associated with the increased radiation dose used to cross-link the polyethylene?

. Decreased wear resistance
. Increased ultimate tensile strength
. Decreased fatigue and fracture resistance
. Increased oxidative potential
. Decreased risk of rim fracture

Correct Answer & Explanation

. Decreased wear resistance

Explanation

While highly cross-linking polyethylene significantly improves wear resistance, it concurrently decreases its mechanical properties, including ultimate tensile strength, fatigue resistance, and fracture toughness. This makes the liner more susceptible to fracture under high loads.

Question 5610

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with chronic knee pain 2 years after a primary total knee arthroplasty. Aspiration yields synovial fluid with a WBC count of 4,500 cells/uL and 85% polymorphonuclear leukocytes. Alpha-defensin testing is positive. What is the most appropriate definitive management for a chronic periprosthetic joint infection in a medically optimized patient?

. Arthroscopic irrigation and debridement
. Single-stage revision arthroplasty
. Two-stage revision arthroplasty with an antibiotic spacer
. Long-term suppressive intravenous antibiotics
. Polyethylene exchange and retention of components

Correct Answer & Explanation

. Arthroscopic irrigation and debridement

Explanation

Two-stage revision arthroplasty is the gold standard for chronic periprosthetic joint infection in North America. Debridement, antibiotics, and implant retention (DAIR) is reserved strictly for acute infections.

Question 5611

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female is undergoing a total hip arthroplasty via the posterolateral approach. To prevent sciatic nerve injury, the surgeon must carefully protect it during the exposure. Which of the following external rotators of the hip intimately protects the sciatic nerve deep to it and should be carefully isolated?

. Piriformis
. Obturator externus
. Quadratus femoris
. Obturator internus
. Superior gemellus

Correct Answer & Explanation

. Piriformis

Explanation

The quadratus femoris muscle protects the sciatic nerve deep to it. During the posterior approach, aggressive dissection into the quadratus femoris must be avoided to prevent damage to the underlying sciatic nerve and medial circumflex femoral artery branches.

Question 5612

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old female sustains a periprosthetic femur fracture around a well-fixed cemented total hip arthroplasty stem. Radiographs show a spiral fracture configuration entirely distal to the tip of the stem. How is this classified according to the Vancouver system, and what is the standard treatment?

. Vancouver A - Nonoperative management
. Vancouver B1 - ORIF with cables and a locking plate
. Vancouver B2 - Revision to a long-stem, distally fitting prosthesis
. Vancouver B3 - Proximal femoral replacement
. Vancouver C - ORIF with a standard or locking plate

Correct Answer & Explanation

. Vancouver A - Nonoperative management

Explanation

Vancouver C fractures occur entirely distal to the tip of the prosthesis. The stem remains well-fixed. The treatment is standard Open Reduction and Internal Fixation (ORIF) using a plate, taking care to overlap the tip of the prosthesis appropriately to avoid creating a stress riser. Type B1 involves the fracture around the stem tip but the stem remains well-fixed.

Question 5613

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old female presents with a periprosthetic femur fracture around a cemented total hip arthroplasty. Radiographs demonstrate a fracture at the tip of the stem. The femoral component is grossly loose, and there is severe loss of proximal femoral bone stock. According to the Vancouver classification, what is the type and most appropriate surgical treatment?

. Vancouver A; cerclage wiring alone
. Vancouver B1; ORIF with locked laterally based plating
. Vancouver B2; revision to a long-stem, fully coated cementless prosthesis
. Vancouver B3; revision utilizing a proximal femoral replacement or structural allograft
. Vancouver C; ORIF with an overlapping laterally based plate

Correct Answer & Explanation

. Vancouver A; cerclage wiring alone

Explanation

A Vancouver B3 fracture is characterized by a fracture around a loose stem in the setting of poor proximal bone stock. It requires revision arthroplasty, often utilizing a proximal femoral replacement or structural bone grafting.

Question 5614

Topic: 3. Adult Reconstruction (Hip & Knee)
Aseptic loosening secondary to osteolysis is a leading cause of late failure in total joint arthroplasty. Which fundamental mechanism of wear is primarily responsible for the generation of the millions of submicron-sized ultra-high-molecular-weight polyethylene (UHMWPE) particles that incite this macrophage-mediated osteolysis?
. Two-body abrasive wear
. Three-body abrasive wear
. Adhesive wear
. Fretting wear
. Corrosive wear

Correct Answer & Explanation

. Adhesive wear

Explanation

In metal-on-polyethylene articulations, adhesive wear occurs when localized microscopic bonding/welding happens between the asperities of the metal head and the softer polymer. As the joint moves, these micro-bonds shear off, creating millions of submicron UHMWPE particles. These specific submicron particles (0.1 to 1.0 micrometers) are phagocytosed by macrophages, initiating the inflammatory cascade (TNF-alpha, IL-1, IL-6) leading to osteolysis.

Question 5615

Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old male presents with severe thigh pain 12 years after a cementless total hip arthroplasty. Radiographs reveal extensive endosteal scalloping and proximal femoral osteolysis. What is the primary cellular mediator responsible for this periprosthetic osteolysis?
. Neutrophils responding to metal ions
. Macrophages phagocytosing polyethylene wear debris
. Lymphocytes mediating a delayed hypersensitivity reaction
. Osteoblasts undergoing apoptosis due to stress shielding
. Giant cells reacting to PMMA cement mantle failure

Correct Answer & Explanation

. Macrophages phagocytosing polyethylene wear debris

Explanation

Periprosthetic osteolysis in total joint arthroplasty is primarily driven by a macrophage-mediated foreign body response to ultra-high-molecular-weight polyethylene (UHMWPE) wear debris. Macrophages release inflammatory cytokines like TNF-alpha and IL-1, activating osteoclasts.

Question 5616

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty (TKA), the surgeon places the femoral component in excessive internal rotation relative to the transepicondylar axis. Which of the following complications is most likely to occur postoperatively?

. Medial patellar subluxation
. Lateral patellar subluxation
. Excessive flexion gap laxity
. Excessive extension gap tightness
. Posterior impingement

Correct Answer & Explanation

. Medial patellar subluxation

Explanation

Internal rotation of the femoral component in TKA mediatizes the trochlear groove, which effectively increases the Q-angle and leads to lateral patellar maltracking and potential subluxation.

Question 5617

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male undergoes a total hip arthroplasty using a ceramic-on-ceramic bearing surface. At his 1-year follow-up, he complains of an audible squeaking sound from the hip during certain movements. Which of the following surgical factors is most strongly associated with this complication?

. Use of a larger femoral head diameter (>36mm)
. Inadequate offset restoration
. Malposition of the acetabular component
. Use of an un-cemented femoral stem
. Retention of the posterior capsule

Correct Answer & Explanation

. Use of a larger femoral head diameter (>36mm)

Explanation

Squeaking in ceramic-on-ceramic THA is heavily linked to implant malposition, particularly excessive anteversion or inclination of the acetabular cup. Malposition leads to edge loading, disruption of fluid-film lubrication, and subsequent stripe wear and noise generation.

Question 5618

Topic: 3. Adult Reconstruction (Hip & Knee)

The vascular supply to the adult femoral head is highly precarious, making displaced femoral neck fractures prone to avascular necrosis. Which of the following vessels provides the primary blood supply to the weight-bearing dome of the adult femoral head?

. Artery of the ligamentum teres
. Lateral femoral circumflex artery
. Medial femoral circumflex artery
. Inferior gluteal artery
. First perforating artery of the profunda femoris

Correct Answer & Explanation

. Artery of the ligamentum teres

Explanation

The medial femoral circumflex artery (MFCA), specifically its lateral epiphyseal branches, provides the predominant blood supply to the weight-bearing portion of the adult femoral head. The artery of the ligamentum teres contributes a clinically insignificant amount in adults.

Question 5619

Topic: 3. Adult Reconstruction (Hip & Knee)

Following the deflation of a pneumatic tourniquet that has been inflated for 90 minutes during a total knee arthroplasty, which of the following transient systemic physiological changes is expected?

. Decreased end-tidal CO2
. Increased central venous pressure
. Decreased core body temperature
. Increased systemic vascular resistance
. Decreased serum potassium levels

Correct Answer & Explanation

. Decreased end-tidal CO2

Explanation

Tourniquet deflation releases ischemic, acidotic blood back into the systemic circulation. This typically causes a transient increase in end-tidal CO2, a decrease in core body temperature, and a decrease in blood pressure due to a drop in systemic vascular resistance.

Question 5620

Topic: 3. Adult Reconstruction (Hip & Knee)
A 60-year-old female with advanced Eaton Stage III basal joint arthritis of the thumb undergoes a ligament reconstruction and tendon interposition (LRTI) arthroplasty. Which tendon is most commonly harvested and utilized for the reconstruction phase in this specific procedure?
. Abductor pollicis longus
. Extensor pollicis brevis
. Flexor carpi radialis
. Palmaris longus
. Brachioradialis

Correct Answer & Explanation

. Flexor carpi radialis

Explanation

In the Burton-Pellegrini LRTI procedure, the flexor carpi radialis (FCR) tendon is most commonly harvested (either completely or a distally-based slip) to reconstruct the anterior oblique ligament (beak ligament) and provide a biologic interpositional spacer in the void left by the trapeziectomy.

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