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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 157 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 3121

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary advantage of highly cross-linked polyethylene (HXLPE) compared to conventional polyethylene in total hip arthroplasty?

. Decreased risk of catastrophic liner fracture
. Reduced volumetric wear
. Increased oxidative resistance without remelting
. Elimination of impingement
. Increased material toughness

Correct Answer & Explanation

. Decreased risk of catastrophic liner fracture

Explanation

Highly cross-linked polyethylene significantly reduces volumetric wear compared to conventional polyethylene, thus decreasing the incidence of wear debris osteolysis. However, the cross-linking and subsequent thermal treatments can decrease the mechanical toughness of the material.

Question 3122

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoes a primary total hip arthroplasty via a direct anterior approach. If this patient experiences a postoperative dislocation, in which position is the hip most likely to be unstable?

. Flexion, adduction, and internal rotation
. Extension, adduction, and external rotation
. Flexion, abduction, and external rotation
. Extension, abduction, and internal rotation
. Hyperflexion and internal rotation

Correct Answer & Explanation

. Flexion, adduction, and internal rotation

Explanation

Dislocation following a direct anterior approach typically occurs with the hip in extension, adduction, and external rotation due to the anterior capsular defect. This contrasts with the posterior approach, which generally dislocates in flexion, adduction, and internal rotation.

Question 3123

Topic: 3. Adult Reconstruction (Hip & Knee)

During preoperative templating for a total hip arthroplasty, increasing the femoral neck offset without changing the neck resection level or stem length will result in which of the following?

. Increased leg length and increased abductor tension
. Unchanged leg length and increased abductor tension
. Decreased leg length and decreased abductor tension
. Increased leg length and decreased joint reaction force
. Unchanged leg length and increased joint reaction force

Correct Answer & Explanation

. Increased leg length and increased abductor tension

Explanation

Increasing the femoral neck offset lateralizes the femur, which increases abductor tension and mechanical advantage without altering the vertical leg length. This enhanced abductor lever arm effectively decreases the overall joint reaction force on the hip.

Question 3124

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman presents with persistent groin pain 2 years after a primary total hip arthroplasty. Aspiration of the hip joint yields synovial fluid with a white blood cell (WBC) count of 4,500 cells/mcL and 85% polymorphonuclear neutrophils (PMNs). What is the most appropriate next step in management?

. Observation and oral NSAIDs
. Oral suppressive antibiotics
. Two-stage revision arthroplasty
. Single-stage exchange arthroplasty
. Irrigation and debridement with modular component exchange

Correct Answer & Explanation

. Observation and oral NSAIDs

Explanation

The synovial fluid analysis (WBC > 3,000 cells/mcL and >80% PMNs) is highly diagnostic for a chronic periprosthetic joint infection in a hip. The standard of care for a chronic PJI in the United States remains a two-stage revision arthroplasty.

Question 3125

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man presents with progressive groin pain 5 years after receiving a total hip arthroplasty utilizing a 40-mm cobalt-chromium femoral head on a titanium stem. MRI with metal artifact reduction sequence (MARS) shows a solid cystic mass in the abductor musculature. Blood metal ion testing shows significantly elevated serum cobalt with normal chromium. What is the most likely diagnosis?

. Polyethylene wear debris osteolysis
. Taper corrosion (trunnionosis)
. Unrecognized periprosthetic joint infection
. Metal-on-metal articular wear
. Ceramic component fracture

Correct Answer & Explanation

. Polyethylene wear debris osteolysis

Explanation

Trunnionosis (mechanically assisted crevice corrosion) occurs at the head-neck junction, classically presenting with an elevated cobalt-to-chromium ratio and adverse local tissue reactions. The use of large-diameter, heavy CoCr heads on titanium tapers significantly increases this risk.

Question 3126

Topic: 3. Adult Reconstruction (Hip & Knee)

During acetabular component fixation in total hip arthroplasty, screw placement in the anterosuperior quadrant places which of the following structures at greatest risk of injury?

. External iliac artery
. Sciatic nerve
. Obturator nerve
. Superior gluteal nerve
. Pudendal nerve

Correct Answer & Explanation

. External iliac artery

Explanation

The anterosuperior quadrant is considered the "danger zone" because aberrant screw placement places the external iliac artery and vein at high risk. The safest region for screw placement is the posterosuperior quadrant, which has excellent bone stock and the lowest risk to neurovascular structures.

Question 3127

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient experiences recurrent posterior dislocations after a total hip arthroplasty. Radiographs and CT scans reveal the acetabular component is placed in 10 degrees of anteversion and 35 degrees of inclination. The femoral stem is in 15 degrees of anteversion. What is the most appropriate definitive management?

. Prescribe a hip abduction brace for 3 months
. Revision of the acetabular component to increase anteversion
. Revision of the femoral component to increase anteversion
. Exchange to a larger femoral head size
. Conversion to a constrained acetabular liner

Correct Answer & Explanation

. Prescribe a hip abduction brace for 3 months

Explanation

Recurrent posterior instability is commonly caused by inadequate combined anteversion. Normal acetabular anteversion is 15-20 degrees; revising the under-anteverted cup will correct the underlying mechanical cause of the posterior dislocations.

Question 3128

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the trial components are evaluated. The knee is tight in both flexion and extension. What is the most appropriate next step to balance the gaps?

. Recut the distal femur to remove more bone
. Release the posterior cruciate ligament (PCL)
. Downsize the femoral component
. Decrease the thickness of the tibial polyethylene insert
. Recut the proximal tibia with an increased posterior slope

Correct Answer & Explanation

. Recut the distal femur to remove more bone

Explanation

When the knee is symmetrically tight in both flexion and extension, the tibial component (or polyethylene insert) is the common denominator. Decreasing the thickness of the polyethylene insert will equally increase both the flexion and extension gaps.

Question 3129

Topic: 3. Adult Reconstruction (Hip & Knee)

In an active, community-dwelling 70-year-old patient with a displaced femoral neck fracture, what is the primary advantage of total hip arthroplasty (THA) over bipolar hemiarthroplasty?

. Lower risk of postoperative dislocation
. Shorter surgical time and reduced blood loss
. Decreased risk of acetabular erosion and groin pain
. Lower early mortality rates
. Less technically demanding procedure

Correct Answer & Explanation

. Lower risk of postoperative dislocation

Explanation

THA provides superior long-term functional outcomes and eliminates the risk of acetabular cartilage wear (erosion) and subsequent groin pain compared to hemiarthroplasty in active, older patients. However, THA does carry a higher risk of postoperative dislocation.

Question 3130

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the predominant blood supply to the adult femoral head?

. Artery of the ligamentum teres
. Inferior gluteal artery
. Lateral epiphyseal artery
. Medial femoral circumflex artery
. Lateral femoral circumflex artery

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 adult femoral head. Injury to this vessel during trauma or surgery significantly increases the risk of avascular necrosis.

Question 3131

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old woman sustains a fall. Radiographs reveal a displaced femoral neck fracture.

She is an active community ambulator and cognitively intact. Which of the following treatments provides the lowest rate of reoperation?

. Cannulated screw fixation
. Sliding hip screw
. Unipolar hemiarthroplasty
. Bipolar hemiarthroplasty
. Total hip arthroplasty

Correct Answer & Explanation

. Cannulated screw fixation

Explanation

In an active, cognitively intact elderly patient with a displaced femoral neck fracture, total hip arthroplasty provides better functional outcomes and lower reoperation rates compared to internal fixation or hemiarthroplasty. Hemiarthroplasty carries a higher risk of acetabular wear and subsequent revision.

Question 3132

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old woman presents with persistent anterior groin pain one year after a primary total hip arthroplasty. The pain is exacerbated by rising from a seated position and active straight leg raising. Radiographs demonstrate the acetabular component is placed in 15 degrees of anteversion, but the anterior edge extends 8 mm beyond the native anterior acetabular rim. What is the most likely diagnosis?

. Aseptic loosening
. Iliopsoas impingement
. Periprosthetic joint infection
. Heterotopic ossification
. Gluteus medius tear

Correct Answer & Explanation

. Aseptic loosening

Explanation

Iliopsoas impingement commonly presents as anterior groin pain exacerbated by active straight leg raise or resisted hip flexion. An oversized or malpositioned acetabular component overhanging the anterior rim mechanically irritates the psoas tendon.

Question 3133

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old patient falls and sustains a periprosthetic femur fracture around a fully porous-coated cementless stem.

Radiographs show a fracture at the tip of the stem. The stem is definitively loose, but there is excellent proximal bone stock. According to the Vancouver classification, what is the fracture subtype and optimal treatment?

. Vancouver A; nonoperative management
. Vancouver B1; open reduction internal fixation with cables and plate
. Vancouver B2; revision to a long cementless stem
. Vancouver B3; proximal femoral replacement
. Vancouver C; open reduction internal fixation

Correct Answer & Explanation

. Vancouver A; nonoperative management

Explanation

A Vancouver B2 fracture occurs around or just below the stem tip with a loose implant but adequate bone stock. The standard treatment is bypass of the fracture by at least two cortical diameters using a longer fully porous-coated or fluted tapered cementless stem.

Question 3134

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a metal-on-metal total hip arthroplasty presents with increasing pain and a large, sterile fluid collection around the hip. MRI with metal artifact reduction shows a solid and cystic mass. A biopsy is obtained. What is the most likely histologic finding of the periprosthetic tissue?

. Neutrophilic infiltration with gram-positive cocci
. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Massive polyethylene wear debris with giant cells
. Malignant spindle cells with high mitotic rate
. Granulation tissue with extensive eosinophils

Correct Answer & Explanation

. Neutrophilic infiltration with gram-positive cocci

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-metal hips are histologically characterized by an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). This represents a delayed type IV hypersensitivity response to metal ions.

Question 3135

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior approach to the hip for total hip arthroplasty, the short external rotators are detached. The primary blood supply to the native adult femoral head, which is sacrificed during the femoral neck osteotomy, arises from which of the following vessels?

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

Correct Answer & Explanation

. Obturator artery

Explanation

The medial femoral circumflex artery (MFCA) provides the predominant blood supply to the adult femoral head via the lateral epiphyseal vessels. It courses posterior to the obturator externus and is at risk during the posterior approach.

Question 3136

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man sustains recurrent posterior dislocations following a primary total hip arthroplasty. Radiographs demonstrate an acetabular component in 10 degrees of retroversion and 40 degrees of abduction. Which of the following is the most appropriate definitive management?

. Application of an abduction brace for 6 weeks
. Revision of the femoral head to a larger diameter
. Revision of the acetabular component to increase anteversion
. Conversion to a constrained acetabular liner
. Trochanteric advancement

Correct Answer & Explanation

. Application of an abduction brace for 6 weeks

Explanation

Posterior instability due to a retroverted acetabular cup requires revision to correct the malposition. A constrained liner or larger head does not correct the underlying mechanical malalignment and will likely fail.

Question 3137

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old man presents with a Vancouver B2 periprosthetic femur fracture 10 years after a cemented total hip arthroplasty. The fracture is located around the tip of the stem, and the stem is demonstrably loose. What is the recommended treatment?

. Open reduction and internal fixation with a locking plate leaving the stem in situ
. Revision to a fully porous-coated long cementless diaphyseal-engaging stem
. Revision to a standard length cemented stem
. Cortical strut allografts alone
. Impaction bone grafting with a short stem

Correct Answer & Explanation

. Open reduction and internal fixation with a locking plate leaving the stem in situ

Explanation

Vancouver B2 fractures involve a loose stem with adequate distal bone stock. The standard of care is revision arthroplasty utilizing a long cementless stem that bypasses the fracture by at least two cortical diameters, often supplemented with cerclage wiring.

Question 3138

Topic: 3. Adult Reconstruction (Hip & Knee)



A 72-year-old woman sustains the fracture shown in the radiograph, characterized as a reverse obliquity intertrochanteric fracture. What is the most appropriate definitive management?

. Sliding hip screw (DHS)
. Long cephalomedullary nail
. Multiple cancellous screws
. Total hip arthroplasty
. Nonoperative management with skeletal traction

Correct Answer & Explanation

. Sliding hip screw (DHS)

Explanation

Reverse obliquity intertrochanteric fractures are mechanically unstable due to the tendency of the shaft to displace medially. A cephalomedullary nail is biomechanically superior to a sliding hip screw, which has an unacceptably high failure rate for this pattern.

Question 3139

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old man presents with a painful THA 4 years postoperatively. Synovial fluid analysis reveals a WBC count of 4,500 cells/uL with 85% neutrophils. What is the next most appropriate step in management if a chronic periprosthetic joint infection is confirmed?

. Single-stage exchange arthroplasty with cementless components
. Two-stage exchange arthroplasty with an antibiotic spacer
. Suppressive oral antibiotics indefinitely
. Polyethylene liner exchange and component retention (DAIR)
. Intravenous antibiotics for 6 weeks without surgical intervention

Correct Answer & Explanation

. Single-stage exchange arthroplasty with cementless components

Explanation

For chronic periprosthetic joint infections in North America, the gold standard treatment remains a two-stage exchange arthroplasty. Debridement, antibiotics, and implant retention (DAIR) is generally reserved for acute infections (within 4 weeks of surgery or acute hematogenous spread).

Question 3140

Topic: 3. Adult Reconstruction (Hip & Knee)



An 81-year-old woman sustains a periprosthetic fracture around her cementless THA stem. Radiographs show a fracture extending just distal to the stem tip with evidence of stem subsidence and loosening. Based on the Vancouver classification, what is the most appropriate treatment?

. Open reduction internal fixation (ORIF) with locking plates and cables
. Isolated cerclage wiring around the fracture site
. Revision to an extensively porous-coated long stem with ORIF
. Distal femoral replacement
. Nonoperative management in a long leg cast

Correct Answer & Explanation

. Open reduction internal fixation (ORIF) with locking plates and cables

Explanation

This is a Vancouver B2 fracture (loose stem with adequate surrounding bone stock). The standard of care is revision arthroplasty using a long, diaphyseal-fitting stem bypassing the fracture by at least two cortical diameters, combined with ORIF.

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