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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 170 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 3381

Topic: Total Hip Arthroplasty (THA)

To protect the deep branch of the medial femoral circumflex artery (MFCA) during a posterior approach to the hip, the surgeon should carefully avoid aggressive dissection and electrocautery at the upper border of which of the following muscles?

. Obturator internus
. Piriformis
. Quadratus femoris
. Gluteus minimus
. Superior gemellus

Correct Answer & Explanation

. Obturator internus

Explanation

The deep branch of the MFCA courses posteriorly between the lower border of the inferior gemellus and the upper border of the quadratus femoris. Protecting the superior aspect of the quadratus femoris prevents iatrogenic injury to the primary blood supply of the femoral head.

Question 3382

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old man presents with groin pain three years after a primary metal-on-polyethylene total hip arthroplasty. Aspiration yields fluid with elevated cobalt levels but normal chromium levels. MARS MRI demonstrates a solid pseudotumor. Which of the following implant design factors most significantly increases the risk of this specific complication?

. Small femoral head size (28 mm)
. Large trunnion diameter (14/16 mm)
. Decreased modular neck offset
. Large metal femoral head (36 mm or larger) on a small trunnion
. Use of a ceramic femoral head

Correct Answer & Explanation

. Small femoral head size (28 mm)

Explanation

Mechanically assisted crevice corrosion (trunnionosis) at the head-neck junction is characterized by elevated cobalt relative to chromium. Risk factors include larger metal femoral heads, small trunnion tapers, and high off-set necks, which increase the mechanical lever arm and micromotion at the taper interface.

Question 3383

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old osteoporotic woman is undergoing cemented total hip arthroplasty. The surgeon utilizes a highly polished, collarless, double-tapered (taper-slip) stem. Which of the following biomechanical principles is essential for the long-term success of this specific stem design?

. Macrolocking to the cement mantle to prevent subsidence
. Creating predominantly tensile stresses within the proximal cement mantle
. Controlled stem subsidence to generate compressive hoop stresses in the cement
. Proximal off-loading to encourage distal diaphyseal stress transfer
. Integrating directly with endosteal bone via an osteoconductive coating

Correct Answer & Explanation

. Macrolocking to the cement mantle to prevent subsidence

Explanation

Force-closed or taper-slip cemented stems (e.g., Exeter) are highly polished and lack macroscopic locking features. They are explicitly designed to subside slightly within the cement mantle, functioning as a wedge that generates compressive hoop stresses, which bone cement is highly capable of tolerating.

Question 3384

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total hip arthroplasty via a posterior approach, the surgeon utilizes the transverse acetabular ligament (TAL) as a soft-tissue landmark. Positioning the acetabular component parallel to the native TAL helps primarily determine which aspect of component orientation?

. Abduction angle
. Anteversion
. Center of rotation
. Leg length
. Offset

Correct Answer & Explanation

. Abduction angle

Explanation

The transverse acetabular ligament (TAL) spans the acetabular notch and serves as a reliable intraoperative landmark. Studies have shown that orienting the acetabular component parallel to the TAL establishes patient-specific anteversion, thereby minimizing the risk of postoperative dislocation.

Question 3385

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old woman with a cemented total hip arthroplasty sustains a fall. Radiographs show a periprosthetic fracture around the stem tip. The stem appears loose within the cement mantle, but there is adequate distal bone stock. According to the Vancouver classification, what is the appropriate treatment?

. Open reduction and internal fixation with a lateral locking plate
. Revision to a long-stemmed prosthesis bypassing the fracture
. Cortical strut allograft only
. Traction and prolonged bed rest
. Revision of the acetabular component only

Correct Answer & Explanation

. Open reduction and internal fixation with a lateral locking plate

Explanation

A Vancouver B2 periprosthetic femur fracture is characterized by a fracture around a loose stem in the presence of adequate bone stock. The definitive treatment is revision arthroplasty with a long stem that bypasses the fracture site.

Question 3386

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old patient sustains a Vancouver type B2 periprosthetic femur fracture around a cemented, polished taper-slip stem. Radiographs demonstrate a loose femoral component but adequate proximal bone stock. What is the gold standard surgical treatment?

. Open reduction and internal fixation with a locking plate and cerclage wires
. Revision arthroplasty using a long cementless diaphyseal-engaging stem
. Cable-only fixation of the fracture fragments
. Revision arthroplasty using a standard-length cemented stem
. Impaction bone grafting alone without stem revision

Correct Answer & Explanation

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

Explanation

A Vancouver B2 periprosthetic fracture is characterized by a fracture around a loose stem in the presence of good proximal bone stock. The standard of care is revision to a long, cementless, extensively porous-coated or fluted tapered stem that bypasses the fracture site.

Question 3387

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old woman sustains a periprosthetic femur fracture around a cemented total hip arthroplasty. Radiographs demonstrate a fracture around the tip of the stem with evidence of cement mantle disruption and stem subsidence, but the proximal bone stock remains adequate. What is the most appropriate treatment?

. Open reduction and internal fixation with a lateral locking plate
. Cerclage wiring alone
. Revision to a long-stem, fully porous-coated cementless implant
. Removal of the stem and placement of an antibiotic spacer
. Skeletal traction for 6 weeks

Correct Answer & Explanation

. Open reduction and internal fixation with a lateral locking plate

Explanation

This describes a Vancouver B2 periprosthetic fracture (fracture around the stem, loose implant, adequate bone stock). The standard of care is revision arthroplasty using a long-stem implant that bypasses the fracture site, combined with appropriate fixation of the fractured segments.

Question 3388

Topic: 3. Adult Reconstruction (Hip & Knee)

Alumina and zirconia ceramics are utilized in total hip arthroplasty primarily for their excellent wear characteristics. Which of the following best describes the mechanical properties of these materials compared to cobalt-chromium alloys?

. Higher fracture toughness and higher tensile strength
. Lower fracture toughness and higher compressive strength
. Higher modulus of elasticity and higher ductility
. Lower compressive strength and lower modulus of elasticity
. Higher fatigue strength and lower scratch resistance

Correct Answer & Explanation

. Higher fracture toughness and higher tensile strength

Explanation

Ceramics are extremely hard and possess very high compressive strength, making them excellent, low-wear bearing surfaces. However, they are brittle and lack ductility, which results in lower fracture toughness and poor tensile strength compared to metallic alloys.

Question 3389

Topic: 3. Adult Reconstruction (Hip & Knee)

Ceramic-on-ceramic bearings in total hip arthroplasty exhibit which of the following mechanical properties compared to metal-on-polyethylene bearings?

. Higher coefficient of friction
. Greater risk of volumetric wear
. Lower fracture toughness
. Higher ductility
. Increased biological reactivity to wear debris

Correct Answer & Explanation

. Higher coefficient of friction

Explanation

Ceramics are extremely hard and scratch-resistant, producing very low wear, but they are brittle materials. They possess much lower fracture toughness and ductility compared to metals, increasing the risk of catastrophic fracture.

Question 3390

Topic: 3. Adult Reconstruction (Hip & Knee)

In a metal-on-polyethylene total hip arthroplasty, the generation of submicron polyethylene wear debris most commonly initiates an inflammatory osteolysis cascade mediated primarily by which cell type?

. Osteoblasts
. T-lymphocytes
. Macrophages
. Neutrophils
. Eosinophils

Correct Answer & Explanation

. Osteoblasts

Explanation

Submicron polyethylene wear debris is primarily phagocytosed by macrophages. The activated macrophages release pro-inflammatory cytokines such as TNF-alpha and IL-1, which stimulate osteoclastic bone resorption and lead to aseptic loosening.

Question 3391

Topic: 3. Adult Reconstruction (Hip & Knee)

During total hip arthroplasty templating, medializing the acetabular component and increasing the femoral offset will have what effect on the hip joint biomechanics?

. Increase the joint reaction force
. Decrease the abductor muscle moment arm
. Decrease the joint reaction force
. Increase the body weight moment arm
. Increase the required abductor force

Correct Answer & Explanation

. Increase the joint reaction force

Explanation

Medializing the center of rotation decreases the body weight moment arm, while increasing femoral offset increases the abductor moment arm. Both changes mechanically advantage the abductors, thereby decreasing the required abductor force and the overall joint reaction force.

Question 3392

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is the most notable disadvantage of using a ceramic-on-ceramic bearing surface in total hip arthroplasty compared to metal-on-polyethylene?

. Higher volumetric wear rate
. Increased risk of osteolysis
. Risk of catastrophic component fracture
. Increased galvanic corrosion
. Release of toxic systemic metal ions

Correct Answer & Explanation

. Higher volumetric wear rate

Explanation

Ceramic-on-ceramic bearings offer the lowest volumetric wear rates and generate bio-inert debris, nearly eliminating particle-induced osteolysis. However, ceramics are brittle materials with a lower fracture toughness than metals, making them susceptible to catastrophic fracture.

Question 3393

Topic: 3. Adult Reconstruction (Hip & Knee)

Alumina and zirconia are common ceramic materials used in total hip arthroplasty bearings. Yttria-stabilized zirconia has higher fracture toughness than pure alumina due to a microstructural phenomenon known as:

. Phase transformation toughening
. Galvanic protection
. Decreased surface wettability
. Increased grain size
. Work hardening

Correct Answer & Explanation

. Phase transformation toughening

Explanation

Zirconia ceramics utilize phase transformation toughening, where a stress-induced shift from a tetragonal to a monoclinic phase causes a volume expansion. This local expansion generates compressive stresses that help close advancing microcracks.

Question 3394

Topic: 3. Adult Reconstruction (Hip & Knee)

Fretting corrosion at the modular head-neck junction of a total hip arthroplasty (trunnionosis) is primarily initiated by which of the following mechanisms?

. Galvanic potential differences between identical metals
. Micromotion that disrupts the protective oxide passivation layer
. Crevice corrosion driven by local chloride ion accumulation
. Biologic corrosion mediated by periprosthetic macrophages
. Excessive wear of the polyethylene bearing surface

Correct Answer & Explanation

. Galvanic potential differences between identical metals

Explanation

Fretting corrosion is mechanically assisted crevice corrosion initiated by micromotion between two contacting surfaces. This micromotion continually disrupts the implant's protective oxide layer (passivation layer), leading to metal oxidation and ion release.

Question 3395

Topic: 3. Adult Reconstruction (Hip & Knee)

In aseptic loosening of a total hip arthroplasty, which of the following particle sizes of ultra-high-molecular-weight polyethylene (UHMWPE) wear debris is most biologically reactive and most readily phagocytosed by macrophages?

. 0.1 to 1.0 micrometers
. 5 to 10 micrometers
. 10 to 50 micrometers
. 50 to 100 micrometers
. Greater than 100 micrometers

Correct Answer & Explanation

. 0.1 to 1.0 micrometers

Explanation

Submicron particles, specifically in the 0.1 to 1.0 micrometer range, are the most biologically active. They are easily phagocytosed by macrophages, which then release pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6) driving osteolysis.

Question 3396

Topic: 3. Adult Reconstruction (Hip & Knee)

In a metal-on-polyethylene total hip arthroplasty, which of the following wear mechanisms is primarily responsible for the generation of submicron polyethylene particles that lead to macrophage-mediated osteolysis?

. Abrasive wear
. Adhesive wear
. Third-body wear
. Fretting wear
. Corrosive wear

Correct Answer & Explanation

. Abrasive wear

Explanation

Adhesive wear is the primary mechanism generating submicron ultra-high-molecular-weight polyethylene (UHMWPE) particles in total joint arthroplasty. These submicron particles are phagocytosed by macrophages, initiating an inflammatory cascade that leads to osteolysis.

Question 3397

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, the use of a ceramic-on-ceramic bearing surface is primarily intended to minimize which type of wear?

. Adhesive wear
. Abrasive wear
. Third-body wear
. Corrosive wear
. Fatigue wear

Correct Answer & Explanation

. Adhesive wear

Explanation

Adhesive wear is the primary mode of wear in metal-on-polyethylene bearings, leading to osteolysis. Ceramic-on-ceramic bearings have a highly wettable surface that improves fluid film lubrication, drastically reducing adhesive wear.

Question 3398

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a positive Trendelenburg gait following a total hip arthroplasty via the direct lateral approach. Which nerve was most likely injured during the splitting of the gluteus medius?

. Inferior gluteal nerve
. Superior gluteal nerve
. Sciatic nerve
. Obturator nerve
. Femoral nerve

Correct Answer & Explanation

. Inferior gluteal nerve

Explanation

The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. Injury to this nerve during the direct lateral (Hardinge) approach, especially if splitting more than 5 cm proximal to the greater trochanter, leads to abductor weakness.

Question 3399

Topic: 3. Adult Reconstruction (Hip & Knee)

The primary blood supply to the proximal pole of the scaphoid is delivered via vessels entering the bone at which anatomical location?

. Volarly at the distal pole
. Dorsally at the scaphoid waist
. Volarly at the scaphoid tubercle
. Dorsally at the proximal pole
. Through the scapholunate interosseous ligament

Correct Answer & Explanation

. Volarly at the distal pole

Explanation

The major blood supply to the scaphoid is retrograde, originating from branches of the radial artery that enter the bone dorsally at or distal to the scaphoid waist. This retrograde flow leaves the proximal pole highly susceptible to avascular necrosis following fractures.

Question 3400

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary mode of polyethylene wear in total hip arthroplasty that generates submicron particles leading to osteolysis?

. Abrasive wear
. Adhesive wear
. Third-body wear
. Fretting wear
. Galvanic corrosion

Correct Answer & Explanation

. Abrasive wear

Explanation

Adhesive wear is the primary mode of wear between ultra-high-molecular-weight polyethylene and the metallic femoral head in total hip arthroplasty. This process breaks off tiny fragments of polyethylene, creating submicron debris that triggers macrophage-mediated osteolysis.

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