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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 152 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 3021

Topic: 3. Adult Reconstruction (Hip & Knee)

The generation of polyethylene wear debris in a standard metal-on-polyethylene total joint arthroplasty most commonly occurs through which mode of wear?

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

Correct Answer & Explanation

. Adhesive wear

Explanation

Adhesive wear is the most common mode in standard metal-on-polyethylene joints, occurring when microscopic asperities on the metal head bond to the softer polyethylene, tearing off small particles during motion.

Question 3022

Topic: 3. Adult Reconstruction (Hip & Knee)

The main blood supply to the adult femoral head is primarily derived from which of the following vessels?

. Lateral femoral circumflex artery
. Medial femoral circumflex artery
. Obturator artery
. Inferior gluteal artery
. Superior gluteal artery

Correct Answer & Explanation

. Medial femoral circumflex artery

Explanation

The medial femoral circumflex artery (MFCA), specifically its deep branch, provides the predominant blood supply to the adult femoral head via the lateral epiphyseal arteries. Injury to this vessel increases the risk of avascular necrosis.

Question 3023

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following factors is most directly proportional to the volumetric wear of ultra-high molecular weight polyethylene (UHMWPE) in total hip arthroplasty?
. Femoral head roughness
. Femoral neck length
. Acetabular cup thickness
. Femoral head diameter
. Acetabular inclination angle

Correct Answer & Explanation

. Femoral head diameter

Explanation

Volumetric wear of polyethylene is directly proportional to the sliding distance per cycle, which is a function of the femoral head diameter. Larger heads increase the sliding distance per articulation, thereby increasing overall volumetric wear.

Question 3024

Topic: 3. Adult Reconstruction (Hip & Knee)

In a posterior-stabilized total knee arthroplasty (TKA), the cam and post mechanism is primarily designed to replicate the function of the resected posterior cruciate ligament (PCL). What specific kinematic function does this substitution promote?

. Femoral rollback during flexion
. Anterior tibial translation during extension
. Internal rotation of the femur on the tibia during extension
. Varus/valgus stability in terminal extension
. Prevention of hyperextension

Correct Answer & Explanation

. Femoral rollback during flexion

Explanation

The PCL normally functions to roll the femur posteriorly on the tibia during deep flexion, maximizing the range of motion and improving the quadriceps moment arm. In a posterior-stabilized TKA, the interaction of the femoral cam and tibial post forces this femoral rollback.

Question 3025

Topic: 3. Adult Reconstruction (Hip & Knee)

The introduction of highly cross-linked polyethylene (HXLPE) in total hip arthroplasty has significantly reduced volumetric wear. However, the process of cross-linking using irradiation alters its mechanical properties. Which property is significantly decreased in HXLPE compared to conventional ultra-high molecular weight polyethylene?

. Ultimate tensile strength
. Elastic modulus
. Fatigue strength
. Hardness
. Yield strength

Correct Answer & Explanation

. Fatigue strength

Explanation

While irradiation and cross-linking dramatically improve wear resistance, they significantly decrease fatigue strength, ultimate tensile strength, and fracture toughness. This makes HXLPE theoretically more susceptible to catastrophic failure under high cyclic stresses.

Question 3026

Topic: 3. Adult Reconstruction (Hip & Knee)

Ceramic-on-ceramic bearings in total hip arthroplasty offer excellent wear characteristics but are associated with squeaking and catastrophic failure. Which of the following mechanical characteristics best describes ceramics compared to cobalt-chromium alloys?

. Higher ductility and lower elastic modulus
. Lower wettability and lower hardness
. Higher compressive strength and lower fracture toughness
. Higher fracture toughness and higher yield strength
. Lower hardness and higher fatigue resistance

Correct Answer & Explanation

. Higher compressive strength and lower fracture toughness

Explanation

Ceramics (such as alumina and zirconia) possess extreme hardness and high compressive strength, contributing to their low wear rates. However, they are highly brittle materials with very low fracture toughness, making them vulnerable to catastrophic shattering under impact or tensile loads.

Question 3027

Topic: 3. Adult Reconstruction (Hip & Knee)

Polyethylene wear in total joint arthroplasty can lead to particulate debris and subsequent osteolysis. The specific mechanism of wear resulting from hard particles (like bone cement fragments) becoming trapped between the articular surfaces is:

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

Correct Answer & Explanation

. Third-body wear

Explanation

Third-body wear occurs when independent, hard particles (such as cement debris or bone fragments) become embedded in the polyethylene and abrade the opposing metal or ceramic articular surface.

Question 3028

Topic: 3. Adult Reconstruction (Hip & Knee)

In a well-functioning metal-on-polyethylene total hip arthroplasty, which specific mechanism of wear generates the majority of the biologically active submicron particles that lead to periprosthetic osteolysis?

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

Correct Answer & Explanation

. Adhesive wear

Explanation

Adhesive wear occurs when microscopic asperities between the metal head and polyethylene liner temporarily bond and shear off. This process generates millions of submicron polyethylene particles, which are the primary drivers of macrophage-mediated osteolysis.

Question 3029

Topic: 3. Adult Reconstruction (Hip & Knee)

A 35-year-old man sustains a posterior wall acetabular fracture with severe marginal impaction of the articular cartilage after a motor vehicle collision. He is planned for open reduction and internal fixation via a Kocher-Langenbeck approach. What is the most critical intraoperative step for managing the marginal impaction to prevent early osteoarthritis?

. Elevation of the articular surface and packing the defect with cancellous bone graft
. Complete excision of the impacted fragment and fixation of the posterior wall
. Primary total hip arthroplasty using a dual-mobility construct
. Reduction of the posterior wall over the impacted segment to act as a buttress

Correct Answer & Explanation

. Elevation of the articular surface and packing the defect with cancellous bone graft

Explanation

Marginal impaction in posterior wall acetabular fractures represents osteochondral fragments driven into the underlying cancellous bone. These must be carefully elevated to restore joint congruity, and the resulting void must be filled with bone graft prior to definitive wall fixation.

Question 3030

Topic: 3. Adult Reconstruction (Hip & Knee)
A 28-year-old man sustains a completely displaced, highly vertical (Pauwels type III) femoral neck fracture. Which of the following fixation constructs provides the highest biomechanical stability for this specific fracture pattern?
. Three parallel cannulated cancellous screws
. Dynamic hip screw (sliding hip screw) with a derotational screw
. Cephalomedullary nail
. Hemiarthroplasty
. Total hip arthroplasty

Correct Answer & Explanation

. Dynamic hip screw (sliding hip screw) with a derotational screw

Explanation

Pauwels type III femoral neck fractures in young adults experience high shear forces. A fixed-angle device, such as a sliding hip screw with a derotational screw, provides superior biomechanical stability compared to multiple cancellous screws.

Question 3031

Topic: 3. Adult Reconstruction (Hip & Knee)

A 32-year-old man sustains a posterior hip dislocation and an associated posterior wall acetabular fracture. Following closed reduction, a CT scan of the pelvis is obtained, which demonstrates a 15-mm area of marginal impaction of the articular cartilage. What is the most critical step during the operative management of this fracture?

. Excision of the impacted articular fragment
. Elevation of the impacted fragment and bone grafting of the resultant metaphyseal void
. Placement of a spanning external fixator
. Fixation of the posterior wall without altering the impacted fragment
. Total hip arthroplasty

Correct Answer & Explanation

. Elevation of the impacted fragment and bone grafting of the resultant metaphyseal void

Explanation

Marginal impaction involves osteochondral fragments pushed into the underlying cancellous bone. Successful ORIF requires elevation of these fragments to restore joint congruity, followed by bone grafting of the underlying void.

Question 3032

Topic: 3. Adult Reconstruction (Hip & Knee)
A 28-year-old female presents with a closed Hawkins type III fracture of the talar neck (associated with tibiotalar and subtalar dislocations). Despite prompt and anatomic open reduction and internal fixation, the surgeon counsels her regarding the high risk of a specific complication. What is the approximate risk of avascular necrosis (AVN) of the talar body in this injury pattern?
. Less than 10%
. 15% to 25%
. 30% to 50%
. 75% to 100%
. Avascular necrosis does not occur in Hawkins type III fractures

Correct Answer & Explanation

. 75% to 100%

Explanation

Hawkins type III fractures involve disruption of the three major blood supplies to the talar body (artery of the tarsal canal, deltoid branch, and branches from the dorsalis pedis). Consequently, the incidence of avascular necrosis in these high-energy injuries approaches 75% to 100%.

Question 3033

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman with a history of total knee arthroplasty sustains a periprosthetic distal femur fracture

. Radiographs demonstrate a displaced Su/Mody Type II fracture above a well-fixed femoral component. Which of the following treatments provides the most biomechanically stable construct for early mobilization?

. Application of a hinged fracture brace and touch-down weight bearing
. Open reduction and internal fixation with a lateral locking plate
. Revision arthroplasty with a distal femoral replacement
. Retrograde intramedullary nailing
. Skeletal traction for 6 weeks

Correct Answer & Explanation

. Open reduction and internal fixation with a lateral locking plate

Explanation

For a periprosthetic distal femur fracture with a well-fixed TKA component, lateral locking plate osteosynthesis offers robust fixed-angle stability. This construct effectively preserves the functioning arthroplasty while allowing early range of motion.

Question 3034

Topic: 3. Adult Reconstruction (Hip & Knee)
A 24-year-old male sustains a displaced, vertically oriented (Pauwels type III) femoral neck fracture. What is the most appropriate definitive management?
. Hemiarthroplasty
. Total hip arthroplasty
. Closed reduction and percutaneous pinning with 3 parallel screws
. Open reduction and internal fixation with a fixed-angle device
. Nonoperative management with strict bed rest

Correct Answer & Explanation

. Open reduction and internal fixation with a fixed-angle device

Explanation

In young patients with displaced, vertically oriented femoral neck fractures (Pauwels III), there are high shear forces. Open reduction and internal fixation using a fixed-angle construct (like a dynamic hip screw with a derotational screw) provides better biomechanical stability than parallel cannulated screws.

Question 3035

Topic: 3. Adult Reconstruction (Hip & Knee)
A 32-year-old female sustains a displaced, completely off-ended, transcervical femoral neck fracture (Pauwels type III). What is the preferred surgical treatment and timing to minimize the risk of avascular necrosis (AVN)?
. Closed reduction and percutaneous pinning within 48 hours
. Urgent open reduction and internal fixation within 24 hours
. Hemiarthroplasty within 24 hours
. Total hip arthroplasty within 48 hours
. Nonoperative management with bed rest

Correct Answer & Explanation

. Urgent open reduction and internal fixation within 24 hours

Explanation

Displaced femoral neck fractures in young adults are orthopedic emergencies. Urgent open reduction and internal fixation (ORIF) is required to achieve anatomic reduction, provide stable fixation, and minimize the high risks of AVN and nonunion.

Question 3036

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old man with a history of falls presents with a displaced, intracapsular femoral neck fracture. He is previously an independent community ambulator with minimal comorbidities. What is the most appropriate surgical treatment?

. In situ percutaneous pinning
. Sliding hip screw
. Hemiarthroplasty or Total Hip Arthroplasty
. Cephalomedullary nailing
. Proximal femoral replacement

Correct Answer & Explanation

. Hemiarthroplasty or Total Hip Arthroplasty

Explanation

Displaced intracapsular femoral neck fractures in active, community-ambulating elderly patients are best treated with arthroplasty (Hemiarthroplasty or THA). This allows early weight-bearing and avoids the high risk of nonunion and avascular necrosis.

Question 3037

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old woman sustains a Vancouver B2 periprosthetic femur fracture around her cementless total hip arthroplasty stem. Radiographs reveal a loose stem with adequate proximal bone stock. What is the most appropriate surgical treatment?

. Open reduction and internal fixation with cables alone
. Open reduction and internal fixation with a locking plate and cables
. Revision arthroplasty with a long-stem component bypassing the fracture
. Nonoperative management with a hinged fracture brace
. Removal of the prosthesis and placement of an antibiotic spacer

Correct Answer & Explanation

. Revision arthroplasty with a long-stem component bypassing the fracture

Explanation

A Vancouver B2 fracture is located around or just distal to a loose stem with adequate bone stock. The standard treatment is revision to a longer, cementless diaphyseal-engaging stem to achieve stability and bypass the fracture site.

Question 3038

Topic: 3. Adult Reconstruction (Hip & Knee)

A 25-year-old man sustains a displaced, basicervical femoral neck fracture in a motor vehicle collision. What is the most appropriate definitive management to provide biomechanical stability and minimize the risk of nonunion?

. Cannulated screw fixation in an inverted triangle pattern
. Sliding hip screw (SHS) with a derotational screw
. Cementless total hip arthroplasty
. Hemiarthroplasty
. Closed reduction and spica casting

Correct Answer & Explanation

. Sliding hip screw (SHS) with a derotational screw

Explanation

Basicervical femoral neck fractures are biomechanically unstable and behave similarly to intertrochanteric fractures. A sliding hip screw (with or without a derotational screw) or a cephalomedullary nail provides superior biomechanical stability compared to multiple cancellous screws for this specific fracture pattern.

Question 3039

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with end-stage ankle osteoarthritis presents for operative evaluation. He is requesting a total ankle arthroplasty (TAA). Which of the following is considered an absolute contraindication to TAA?

. Age greater than 60 years
. Avascular necrosis involving more than 50% of the talar body
. Concomitant subtalar osteoarthritis
. Mild malalignment of the hindfoot (less than 10 degrees)
. Body Mass Index (BMI) of 28

Correct Answer & Explanation

. Avascular necrosis involving more than 50% of the talar body

Explanation

Avascular necrosis of >50% of the talar body is an absolute contraindication to TAA due to a lack of viable bone for implant support. Neuropathy (e.g., Charcot) and active infection are also absolute contraindications.

Question 3040

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is the most reliable radiographic predictor of humeral head ischemia (avascular necrosis) following a proximal humerus fracture?

. Greater tuberosity displacement of 5 mm
. Varus angulation of 20 degrees
. Disruption of the medial calcar hinge by greater than 2 mm
. Surgical neck translation of 50%
. Age greater than 60 years

Correct Answer & Explanation

. Disruption of the medial calcar hinge by greater than 2 mm

Explanation

Hertel identified specific radiographic risk factors for humeral head ischemia. A disrupted medial hinge (>2 mm displacement) and a short metaphyseal head extension (<8 mm) are the strongest predictors of avascular necrosis due to compromise of the ascending branch of the anterior humeral circumflex artery.

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