Menu

3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 64 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 1261

Topic: 3. Adult Reconstruction (Hip & Knee)

When evaluating a painful total hip arthroplasty for potential periprosthetic joint infection (PJI), a synovial fluid alpha-defensin test is ordered. What is the biological origin and significance of alpha-defensin in this context?

. It is a cytokine secreted by macrophages indicating aseptic loosening
. It is an antimicrobial peptide released by neutrophils in response to pathogens
. It is an acute-phase reactant produced by the liver, similar to CRP
. It is a degradation product of bacterial cell walls, specifically targeting Gram-positive organisms
. It is an enzyme produced by fibroblasts during adverse local tissue reactions

Correct Answer & Explanation

. It is a cytokine secreted by macrophages indicating aseptic loosening

Explanation

Alpha-defensin is an antimicrobial peptide secreted primarily by neutrophils in response to the presence of pathogens. In the setting of periprosthetic joint infection (PJI), it serves as a highly sensitive and specific synovial fluid biomarker. Its levels are not significantly elevated in aseptic failure, ALTR, or inflammatory arthropathies, making it a valuable tool in diagnosing PJI.

Question 1262

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient develops anterior groin pain and posterior hip instability following a primary total hip arthroplasty. Radiographs demonstrate the acetabular component is placed in 5 degrees of retroversion and the femoral stem is in 0 degrees of anteversion. Which of the following biomechanical phenomena is most likely occurring?

. Posterior prosthetic impingement during extension and external rotation, levering the head anteriorly
. Anterior prosthetic impingement during flexion and internal rotation, levering the head posteriorly
. Direct posterior subluxation due to loss of the native iliofemoral ligament
. Anterior prosthetic impingement causing posterior instability during extension and external rotation
. Posterior prosthetic impingement causing anterior instability during flexion and internal rotation

Correct Answer & Explanation

. Posterior prosthetic impingement during extension and external rotation, levering the head anteriorly

Explanation

The components are retroverted (acetabular cup in 5 deg retroversion, femoral stem in 0 deg anteversion). Combined retroversion predisposes the hip to anterior prosthetic impingement (the neck hits the front of the cup) when the hip is placed in flexion and internal rotation. This anterior impingement acts as a fulcrum, levering the femoral head out posteriorly, leading to posterior instability.

Question 1263

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old female undergoes revision THA for aseptic loosening. Intraoperatively, the surgeon notes independent motion between the superior and inferior halves of the acetabulum. Which of the following reconstructive techniques is most appropriate for achieving stable long-term fixation in this setting?

. Cementless hemispherical cup with multiple superior dome screws
. Impaction bone grafting with a cemented polyethylene liner
. Highly porous tantalum cup with an ilioischial cage (cup-cage construct) or custom triflange
. Standard unconstrained dual mobility cup cemented into the remaining bone defect
. Bipolar hemiarthroplasty of the hip

Correct Answer & Explanation

. Cementless hemispherical cup with multiple superior dome screws

Explanation

Independent motion between the superior and inferior halves of the acetabulum is the hallmark of pelvic discontinuity. Standard hemispherical cups (even with screws) will fail because they cannot bridge and stabilize the discontinuity. Reconstructive options must mechanically bridge the defect and provide stability, typically requiring a highly porous metal cup with an ilioischial cage (cup-cage construct), a custom triflange component, or a distraction technique using a highly porous jumbo cup if acute.

Question 1264

Topic: 3. Adult Reconstruction (Hip & Knee)

A 50-year-old male presents with an acutely painful, swollen hip 3 years after a primary THA. Synovial fluid is aspirated. The fluid is cloudy, has low viscosity, and a white blood cell count of 45,000 cells/ยตL with 92% neutrophils. The decrease in synovial fluid viscosity in this scenario is primarily due to the breakdown of which molecule?

. Type II Collagen
. Aggrecan
. Hyaluronic acid
. Chondroitin sulfate
. Fibronectin

Correct Answer & Explanation

. Type II Collagen

Explanation

Synovial fluid viscosity is primarily determined by hyaluronic acid (hyaluronan), a glycosaminoglycan secreted by type B synovial cells. In infectious or highly inflammatory states (such as acute PJI with 45,000 WBCs and high PMN%), bacterial hyaluronidases and inflammatory enzymes degrade hyaluronic acid, resulting in watery, low-viscosity synovial fluid with poor string sign.

Question 1265

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon places a constrained acetabular liner in a patient undergoing revision THA for recurrent posterior dislocations. The patient has a well-fixed, horizontally positioned acetabular shell but severely deficient abductor musculature. Three months later, the implant fails. What is the most common mode of failure for a constrained liner in this setting?

. Aseptic loosening of the femoral stem due to increased stress transfer
. Fracture of the polyethylene locking ring leading to head dissociation
. Aseptic loosening of the acetabular cup at the bone-implant interface due to increased torque
. Fatigue fracture of the femoral neck trunnion
. Metallosis from impingement of the femoral neck on the constrained rim

Correct Answer & Explanation

. Aseptic loosening of the femoral stem due to increased stress transfer

Explanation

Constrained liners securely capture the femoral head, effectively linking the femur to the acetabulum. This dramatically decreases the range of motion before impingement occurs and transfers massive torque and shear forces to the acetabular bone-implant interface during extreme motion. Consequently, the most common mode of failure for constrained liners is aseptic loosening of the acetabular shell (pull-out from the bone) or dissociation of the liner from the shell.

Question 1266

Topic: Total Hip Arthroplasty (THA)

During the removal of a well-fixed, fully porous-coated stem in a revision THA, an extended trochanteric osteotomy (ETO) is performed. Which muscle's attachment must be meticulously preserved on the osteotomized fragment to ensure adequate blood supply and subsequent osteotomy healing?

. Gluteus maximus
. Vastus lateralis
. Iliopsoas
. Piriformis
. Rectus femoris

Correct Answer & Explanation

. Gluteus maximus

Explanation

An extended trochanteric osteotomy (ETO) involves elevating the greater trochanter and the lateral diaphyseal cortex. The blood supply to this fragment, which is crucial for union, is predominantly provided by the vastus lateralis (and its muscular branches). Preserving the attachment of the vastus lateralis (as well as the gluteus medius/minimus proximally) ensures the fragment remains vascularized and stabilizes it against proximal migration.

Question 1267

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with acute onset of intense right hip pain, fever, and chills. She underwent an uncomplicated primary THA 4 years ago. Hip aspiration yields purulent fluid growing Methicillin-sensitive Staphylococcus aureus (MSSA). Her symptoms began 48 hours prior to presentation. Radiographs show well-fixed components. What is the most appropriate surgical management?

. One-stage exchange arthroplasty
. Two-stage exchange arthroplasty with an antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with modular head and liner exchange
. Suppressive intravenous antibiotics alone for 6 weeks
. Removal of implants and placement of a definitive cement spacer without reimplantation

Correct Answer & Explanation

. One-stage exchange arthroplasty

Explanation

The patient has an acute hematogenous periprosthetic joint infection (symptoms <3 weeks, well-fixed implants, mature prior THA). The standard of care for acute hematogenous infections (or acute postoperative infections <4 weeks) with well-fixed components is DAIR (Debridement, Antibiotics, and Implant Retention), which must include the exchange of modular components (polyethylene liner and femoral head) to optimally reduce biofilm load.

Question 1268

Topic: 3. Adult Reconstruction (Hip & Knee)

One year following a primary total hip arthroplasty using a proximally porous-coated, tapered titanium stem, AP and lateral radiographs demonstrate radiodense lines bridging the endosteum to the distal extent of the porous coating. The patient is asymptomatic. What do these radiographic findings represent?

. Aseptic loosening with subsidence
. Reactive bone formation secondary to a low-grade infection
. Stress shielding of the proximal femur
. 'Spot welds' indicative of bone ingrowth and stable fixation
. Pedestal formation indicating distal point loading and impending failure

Correct Answer & Explanation

. Aseptic loosening with subsidence

Explanation

Endosteal bone bridges joining the cortex to the distal aspect of the porous coating are commonly referred to as 'spot welds.' Their presence is a classic radiographic sign of secondary biological fixation (bone ingrowth or ongrowth) indicating a stable, functioning cementless implant. A pedestal at the distal tip without proximal ingrowth would suggest distal toggle and instability.

Question 1269

Topic: 3. Adult Reconstruction (Hip & Knee)

In patients with metal-on-metal total hip arthroplasty, the generation of systemic wear debris is a concern. Systemic accumulation of chromium ions is most heavily dependent on which primary route of elimination?

. Hepatic metabolism and biliary excretion
. Pulmonary exhalation
. Renal filtration and excretion
. Sequestration in the reticuloendothelial system of the spleen
. Deposition into the skeletal hydroxyapatite matrix

Correct Answer & Explanation

. Hepatic metabolism and biliary excretion

Explanation

Chromium and cobalt ions generated from the wear and corrosion of metal-on-metal implants or from trunnionosis are systemically absorbed. They are primarily cleared from the body via renal filtration and excretion in the urine. Therefore, patients with impaired renal function are at significantly higher risk for systemic metal ion toxicity (metallosis) and elevated serum levels.

Question 1270

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old female presents with a periprosthetic femur fracture around a cemented total hip arthroplasty. Radiographs show a transverse fracture at the tip of the stem, gross loosening of the femoral component, and severe comminution and osteolysis of the proximal femur extending to the mid-diaphysis. Which of the following is the most appropriate surgical management?

. Open reduction and internal fixation with a lateral locking plate and cerclage wires
. Revision to a fully porous-coated cylindrical stem
. Revision to a long cemented stem with impaction bone grafting
. Proximal femoral replacement (tumor prosthesis)
. Revision to a standard length cementless proximally coated stem

Correct Answer & Explanation

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

Explanation

This is a Vancouver B3 fracture (loose stem with poor proximal bone stock). In an elderly, low-demand patient, proximal femoral replacement (PFR) is the most reliable option. It allows for immediate weight-bearing and avoids the high complication and nonunion rates associated with complex reconstructions like impaction allografting in this age group.

Question 1271

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female with a metal-on-metal total hip arthroplasty presents with worsening groin pain. Advanced imaging demonstrates a solid and cystic soft tissue mass adjacent to the joint. If tissue from this pseudotumor were examined histologically, which of the following findings would be most characteristic of ALVAL (Aseptic Lymphocytic Vasculitis-Associated Lesion)?

. Predominance of polymorphonuclear leukocytes (neutrophils) with fibrin exudation
. Extensive perivascular infiltrate composed predominantly of T-lymphocytes
. Abundant birefringent polyethylene particles surrounded by multinucleated giant cells
. Granulomas with central caseating necrosis
. Malignant spindle cells with high mitotic figures and anaplastic nuclei

Correct Answer & Explanation

. Predominance of polymorphonuclear leukocytes (neutrophils) with fibrin exudation

Explanation

ALVAL represents a Type IV (delayed) hypersensitivity reaction to metal ions (cobalt and chromium). The classic histological feature is a dense, perivascular infiltrate of predominantly CD4+ T-lymphocytes, distinct from the macrophage-dominated response seen in standard polyethylene wear or the neutrophil-dominated response in acute infection.

Question 1272

Topic: 3. Adult Reconstruction (Hip & Knee)

In evaluating a patient with a painful total hip arthroplasty 4 years post-operatively, a joint aspiration is performed. According to the Musculoskeletal Infection Society (MSIS) criteria, which of the following synovial fluid profiles is the threshold most indicative of a chronic periprosthetic joint infection?

. WBC > 1,100 cells/ยตL and > 64% PMNs
. WBC > 3,000 cells/ยตL and > 80% PMNs
. WBC > 10,000 cells/ยตL and > 90% PMNs
. WBC > 25,000 cells/ยตL and > 95% PMNs
. WBC > 50,000 cells/ยตL and > 98% PMNs

Correct Answer & Explanation

. WBC > 1,100 cells/ยตL and > 64% PMNs

Explanation

For chronic periprosthetic joint infections (PJI) occurring >90 days after surgery, the accepted MSIS threshold for synovial fluid is WBC > 3,000 cells/ยตL and > 80% PMNs. Acute PJIs (within 90 days) have a higher threshold of WBC > 10,000 cells/ยตL and > 90% PMNs.

Question 1273

Topic: Total Hip Arthroplasty (THA)

A surgeon is performing an extended trochanteric osteotomy (ETO) via a posterior approach to facilitate femoral component extraction during a revision THA. To maintain the blood supply to the osteotomized fragment and prevent superior migration, which muscle attachments must be preserved?

. Gluteus maximus and vastus intermedius
. Gluteus medius and vastus lateralis
. Gluteus minimus and rectus femoris
. Piriformis and vastus medialis
. Iliopsoas and tensor fasciae latae

Correct Answer & Explanation

. Gluteus maximus and vastus intermedius

Explanation

An extended trochanteric osteotomy (ETO) involves elevating the lateral third of the proximal femur. The gluteus medius and vastus lateralis must be left attached to the fragment. They provide an uninterrupted vascular supply to the bone flap and act as an antagonist muscle pair, maintaining the fragment's longitudinal position during healing.

Question 1274

Topic: 3. Adult Reconstruction (Hip & Knee)
A 35-year-old male presents with severe groin pain. Radiographs reveal Ficat Stage III osteonecrosis of the left femoral head, characterized by a subchondral crescent sign but preservation of the articular joint space. Given the patient's age and stage, what is the most reliable surgical treatment to optimize pain relief and long-term functional outcomes?
. Core decompression with mesenchymal stem cell injection
. Free vascularized fibular grafting
. Proximal femoral rotational osteotomy
. Total hip arthroplasty
. Bipolar hemiarthroplasty

Correct Answer & Explanation

. Total hip arthroplasty

Explanation

Once subchondral collapse has occurred (Ficat Stage III/crescent sign), head-preserving procedures like core decompression or osteotomies have high failure rates. Despite the patient's young age, Total Hip Arthroplasty (THA) provides the most reliable pain relief and functional improvement, and modern bearing surfaces have excellent long-term survivorship.

Question 1275

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon opts to use a high-offset femoral stem during a primary total hip arthroplasty. Compared to a standard offset stem, what is the expected biomechanical effect of this implant choice on the abductor force required to maintain a level pelvis, and on the joint reactive force?

. Increased abductor force required; increased joint reactive force
. Increased abductor force required; decreased joint reactive force
. Decreased abductor force required; increased joint reactive force
. Decreased abductor force required; decreased joint reactive force
. No change in abductor force required; decreased joint reactive force

Correct Answer & Explanation

. Increased abductor force required; increased joint reactive force

Explanation

Increasing femoral offset moves the greater trochanter laterally, which increases the lever arm (moment arm) of the abductor muscles. A longer moment arm means less abductor muscle force is required to balance the pelvis. Because joint reactive force is largely determined by the muscle force acting across the joint, decreasing the required abductor force proportionally decreases the joint reactive force.

Question 1276

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female is undergoing a complex revision total hip arthroplasty for aseptic loosening. Radiographs demonstrate severe acetabular bone loss. Which of the following radiographic findings is most definitive for the diagnosis of an acetabular pelvic discontinuity?

. Superior migration of the acetabular cup greater than 2 cm
. Osteolysis restricted to DeLee and Charnley zones 1 and 2
. Medial translation of the cup beyond the ilioischial line (Kohler's line)
. A visible fracture line separating the superior and inferior hemipelvis with independent movement
. Ectopic bone formation extending from the greater trochanter to the ilium

Correct Answer & Explanation

. Superior migration of the acetabular cup greater than 2 cm

Explanation

Pelvic discontinuity is defined as a separation of the superior hemipelvis (ilium) from the inferior hemipelvis (ischium and pubis). The most definitive radiographic sign is a transverse fracture line through the acetabulum, often accompanied by medial translation of the inferior hemipelvis relative to the superior hemipelvis, indicating independent movement of the two segments.

Question 1277

Topic: 3. Adult Reconstruction (Hip & Knee)

A total hip arthroplasty is performed using an uncemented acetabular component. If the cup is inadvertently placed in 60 degrees of abduction and 25 degrees of anteversion, which of the following complications is most likely to occur rapidly?

. Anterior dislocation of the femoral head
. Impingement of the femoral neck on the posterior acetabular rim
. Edge loading of the polyethylene liner leading to accelerated wear
. Spontaneous fracture of the ceramic femoral head
. Aseptic loosening of the femoral stem

Correct Answer & Explanation

. Anterior dislocation of the femoral head

Explanation

Placing the acetabular cup in excessive abduction (e.g., >50 degrees) moves the contact patch of the femoral head to the superior rim of the liner. This results in edge loading, causing highly localized stress concentrations that lead to rapid, accelerated wear of polyethylene liners or 'stripe wear' and squeaking in ceramic-on-ceramic bearings.

Question 1278

Topic: 3. Adult Reconstruction (Hip & Knee)

In evaluating a patient for recurrent instability following a primary total hip arthroplasty, the surgeon considers using a dual-mobility construct. What is the primary biomechanical mechanism by which a dual-mobility articulation reduces the risk of dislocation compared to a standard single-bearing articulation?

. It limits the total range of motion of the hip joint.
. It relies exclusively on a constrained locking ring to capture the head.
. It increases the jump distance and provides a larger effective head-to-neck ratio.
. It lateralizes the center of rotation to increase abductor tension.
. It automatically corrects for excessive acetabular cup retroversion.

Correct Answer & Explanation

. It limits the total range of motion of the hip joint.

Explanation

A dual-mobility cup features a small inner head articulating within a large, mobile polyethylene liner that itself articulates against the metal acetabular shell. This creates a massive effective head size (the large poly liner), which significantly increases the jump distance (the distance the head center must travel laterally to dislocate) and maximizes the head-to-neck ratio, thereby increasing the impingement-free range of motion.

Question 1279

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient experiences a sciatic nerve palsy immediately following a complex revision total hip arthroplasty. Examination reveals a profound foot drop, weak extensor hallucis longus, and decreased sensation over the dorsal-lateral aspect of the foot, but intact plantar flexion. Which division of the sciatic nerve is injured, and what is its anatomic relationship to the other division within the sciatic sheath?

. Tibial division; it is positioned medial and deep to the peroneal division.
. Peroneal division; it is positioned lateral and superficial to the tibial division.
. Tibial division; it is positioned lateral and superficial to the peroneal division.
. Peroneal division; it is positioned medial and deep to the tibial division.
. Sural division; it runs centrally between the tibial and peroneal divisions.

Correct Answer & Explanation

. Tibial division; it is positioned medial and deep to the peroneal division.

Explanation

The common peroneal division of the sciatic nerve is most frequently injured during THA because it is located more laterally and superficially within the sciatic nerve bundle. Its fibers are also larger and have less supporting connective tissue, making them more susceptible to stretch injuries. The resultant deficit is a foot drop (loss of dorsiflexion/eversion) and dorsal foot numbness.

Question 1280

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with severe rheumatoid arthritis presents for total hip arthroplasty. Radiographs show profound protrusio acetabuli (medial wall defect) with the femoral head migrated medial to Kohler's line. What is the optimal surgical strategy for managing the acetabulum to ensure long-term survivorship?

. Ream deeply and place a jumbo uncemented cup to fill the medial void.
. Use impaction particulate bone grafting in the medial wall defect and place a cementless cup at the anatomic center of rotation.
. Place an anti-protrusio cage without bone grafting.
. Use a bipolar hemiarthroplasty to allow independent movement.
. Fill the entire medial defect with polymethylmethacrylate (PMMA) bone cement and insert a cemented cup.

Correct Answer & Explanation

. Ream deeply and place a jumbo uncemented cup to fill the medial void.

Explanation

In protrusio acetabuli, the center of rotation is displaced medially and superiorly. The goal of reconstruction is to restore the anatomical center of rotation (lateralizing and inferiorizing the cup). This is best achieved by placing morselized (particulate) bone graft in the medial wall defect and securing a cementless hemispherical cup at the anatomic margin with rim fit.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page