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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 19 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 361

Topic: 3. Adult Reconstruction (Hip & Knee)

A 35-year-old highly active male receives a ceramic-on-ceramic total hip arthroplasty. Postoperatively, he complains of an audible squeaking sound from his hip when walking. Which of the following component malpositions is most highly correlated with the development of squeaking in ceramic-on-ceramic articulations?

. Decreased femoral anteversion.
. Increased acetabular anteversion and high inclination angle leading to edge loading.
. Decreased acetabular inclination angle (<30 degrees).
. Varus positioning of the femoral stem.
. Use of a 36-mm femoral head instead of a 28-mm femoral head.

Correct Answer & Explanation

. Increased acetabular anteversion and high inclination angle leading to edge loading.

Explanation

Squeaking in ceramic-on-ceramic THA is most commonly associated with edge loading of the bearing surfaces. Edge loading typically occurs due to cup malposition, specifically excessive acetabular inclination and anteversion, which disrupts fluid film lubrication.

Question 362

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Musculoskeletal Infection Society (MSIS) / International Consensus Meeting (ICM) criteria, which of the following synovial fluid profiles is most consistent with a chronic periprosthetic joint infection in a total hip arthroplasty?

. WBC count of 1,500 cells/µL and 45% polymorphonuclear leukocytes (PMNs).
. WBC count of 2,500 cells/µL and 55% PMNs.
. WBC count of 4,000 cells/µL and 85% PMNs.
. WBC count of 500 cells/µL and 90% PMNs.
. RBC count of 50,000 cells/µL and 10% PMNs.

Correct Answer & Explanation

. WBC count of 4,000 cells/µL and 85% PMNs.

Explanation

For chronic periprosthetic joint infection of the hip or knee, the 2018 ICM diagnostic thresholds are a synovial fluid WBC count greater than 3,000 cells/µL or a PMN percentage greater than 80%. Acute infections (within 6 weeks of surgery) have higher thresholds, typically >10,000 cells/µL.

Question 363

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male with a history of severe heterotopic ossification (HO) following an acetabular fracture is scheduled for a total hip arthroplasty. To prevent the recurrence of HO, which of the following prophylactic regimens is most appropriate and supported by evidence?

. A single dose of 700 cGy radiation administered within 24 to 48 hours preoperatively or postoperatively.
. Oral bisphosphonates starting 1 week prior to surgery and continuing for 6 months.
. Intravenous corticosteroids immediately postoperatively for 3 days.
. Prolonged immobilization in an abduction brace for 6 weeks.
. High-dose oral vitamin C for 50 days postoperatively.

Correct Answer & Explanation

. A single dose of 700 cGy radiation administered within 24 to 48 hours preoperatively or postoperatively.

Explanation

Patients at high risk for heterotopic ossification (e.g., prior HO, ankylosing spondylitis, hypertrophic osteoarthritis) should receive prophylaxis. Evidence supports either NSAIDs (such as indomethacin for 3-6 weeks) or a single fraction of 700-800 cGy radiation given within 24-48 hours before or after surgery.

Question 364

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty via the posterior approach, aggressive retraction or careless division of the short external rotators can lead to profuse bleeding. The inferior gluteal artery and the medial circumflex femoral artery are both at risk. Which specific vascular structure typically provides the main blood supply to the native femoral head and is frequently encountered and coagulated near the quadratus femoris?

. Ascending branch of the lateral circumflex femoral artery.
. Descending branch of the lateral circumflex femoral artery.
. First perforating branch of the profunda femoris.
. Ascending branch of the medial circumflex femoral artery.
. Obturator artery.

Correct Answer & Explanation

. Ascending branch of the medial circumflex femoral artery.

Explanation

The medial circumflex femoral artery (MCFA) provides the primary blood supply to the native femoral head. Its ascending branch lies adjacent to the superior border of the quadratus femoris muscle and must be carefully identified and coagulated during a posterior THA approach to prevent significant postoperative hematoma.

Question 365

Topic: 3. Adult Reconstruction (Hip & Knee)

A dual-mobility acetabular cup is utilized in a primary total hip arthroplasty for a patient with Parkinson's disease. By what specific tribological and geometric mechanism does a dual-mobility construct primarily reduce the risk of dislocation?

. By increasing the functional anteversion of the acetabulum through constrained geometry.
. By incorporating a locking ring that physically tethers the femoral head to the liner.
. By utilizing a large outer polyethylene diameter that maximizes jump distance, while maintaining a smaller inner head for primary articulation.
. By intentionally causing impingement at the extremes of motion to block dislocation.
. By using cross-linked polyethylene to create higher frictional torque against the metal cup.

Correct Answer & Explanation

. By utilizing a large outer polyethylene diameter that maximizes jump distance, while maintaining a smaller inner head for primary articulation.

Explanation

A dual-mobility component features a small primary metal or ceramic head that articulates within a larger, mobile polyethylene liner, which in turn articulates within the metal acetabular shell. The massive effective diameter of the outer liner significantly increases the 'jump distance' required for dislocation.

Question 366

Topic: Total Hip Arthroplasty (THA)

A 55-year-old male presents with audible squeaking from his right ceramic-on-ceramic total hip arthroplasty two years postoperatively. Radiographs show a well-fixed cup with 55 degrees of inclination. What is the most likely biomechanical cause of this squeaking phenomenon?

. Stripe wear from edge loading due to component malposition
. Third-body wear from retained cement mantle fragments
. Galvanic corrosion at the head-neck junction
. Fatigue failure of the ceramic head
. Impingement of the femoral neck on the anterior capsule

Correct Answer & Explanation

. Stripe wear from edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading caused by component malposition, such as excessive cup inclination or version. Edge loading leads to stripe wear and loss of fluid-film lubrication, producing the audible squeak.

Question 367

Topic: Total Hip Arthroplasty (THA)

During a total hip arthroplasty, the surgeon increases the femoral offset by 5 mm without altering the vertical leg length. What is the primary biomechanical effect of this modification?

. Increases the joint reactive force across the hip
. Decreases the moment arm of the abductor musculature
. Increases the resting tension of the abductor musculature
. Increases the risk of posterior dislocation
. Decreases the varus bending moment on the femoral stem

Correct Answer & Explanation

. Increases the resting tension of the abductor musculature

Explanation

Increasing femoral offset lateralizes the femur, which increases the moment arm and resting tension of the abductor musculature. This improves abductor mechanical advantage, thereby decreasing the overall joint reactive force while increasing the bending moment on the stem.

Question 368

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old female sustains a periprosthetic femur fracture around a cemented total hip arthroplasty. Radiographs show a spiral fracture around a loose femoral stem, but the proximal femoral bone stock is of good quality. What is the optimal surgical management according to the Vancouver classification?

. Open reduction internal fixation with locking plates and cerclage wires
. Revision to a fully porous-coated long cylindrical stem bypassing the fracture
. Revision to a modular fluted tapered stem bypassing the fracture by two cortical diameters
. Impaction bone grafting with a standard length cemented stem
. Proximal femoral replacement

Correct Answer & Explanation

. Revision to a modular fluted tapered stem bypassing the fracture by two cortical diameters

Explanation

This is a Vancouver B2 fracture (fracture around a loose stem with adequate bone stock). The standard of care is revision arthroplasty using a long, uncemented, diaphyseal-engaging stem (such as a fluted tapered stem) that bypasses the fracture by at least two cortical diameters.

Question 369

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male with a Walch B2 glenoid is scheduled for total shoulder arthroplasty. If the posterior glenoid erosion is not adequately corrected during surgery, which of the following is the most likely mechanism of early failure?

. Anterior instability of the humeral component
. Superior migration of the humeral head
. Posterior subluxation causing asymmetric polyethylene wear and glenoid loosening
. Rotator cuff failure due to overtensioning
. Acromial stress fracture

Correct Answer & Explanation

. Posterior subluxation causing asymmetric polyethylene wear and glenoid loosening

Explanation

Failure to correct the excessive retroversion and biconcavity of a Walch B2 glenoid leaves the joint unstable posteriorly. This leads to posterior subluxation of the humeral head, eccentric wear, and early mechanical loosening of the glenoid component.

Question 370

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old female presents with severe pain two years after a primary metal-on-polyethylene total hip arthroplasty. Aspiration is performed to rule out periprosthetic joint infection (PJI). According to the 2018 International Consensus Meeting criteria, which synovial fluid biomarker has the highest specificity for diagnosing PJI?

. C-reactive protein (CRP)
. Erythrocyte sedimentation rate (ESR)
. Interleukin-6 (IL-6)
. Alpha-defensin
. Leukocyte esterase

Correct Answer & Explanation

. Alpha-defensin

Explanation

Synovial fluid alpha-defensin is an antimicrobial peptide released by neutrophils. It has extremely high sensitivity and specificity for PJI, and is considered a major diagnostic criterion in the 2018 ICM guidelines.

Question 371

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty using a posterior approach, a patient develops a foot drop immediately postoperatively. Physical examination shows 0/5 ankle dorsiflexion and 5/5 ankle plantar flexion. Sensation is decreased over the first dorsal web space. Which structure was most likely injured during the procedure?

. Tibial division of the sciatic nerve
. Peroneal division of the sciatic nerve
. Femoral nerve
. Obturator nerve
. Superior gluteal nerve

Correct Answer & Explanation

. Peroneal division of the sciatic nerve

Explanation

The peroneal division of the sciatic nerve is lateral and bound more tightly than the tibial division, making it highly susceptible to stretch injury during THA, resulting in a foot drop and sensory loss over the dorsal foot.

Question 372

Topic: 3. Adult Reconstruction (Hip & Knee)

In the evaluation of a painful metal-on-metal total hip arthroplasty, laboratory tests show significantly elevated serum cobalt but normal serum chromium levels. What is the most likely source of the metal debris?

. Bearing surface wear
. Trunnionosis at the head-neck junction
. Impingement of the neck on the acetabular rim
. Corrosion of the acetabular screws
. Femoral stem distal tip fretting

Correct Answer & Explanation

. Trunnionosis at the head-neck junction

Explanation

Elevated cobalt with relatively normal chromium in a hip arthroplasty suggests mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction. Bearing surface wear typically elevates both cobalt and chromium more equally.

Question 373

Topic: Total Hip Arthroplasty (THA)

A 77-year-old female presents with a new dislocation of her dual mobility total hip arthroplasty. Radiographs reveal an 'intra-prosthetic' dislocation. What is the defining mechanical failure in this type of dislocation?

. The outer polyethylene bearing dislocates from the metal acetabular shell
. The entire acetabular shell dislocates from the pelvis
. The inner metal head dislocates out of the larger polyethylene bearing
. The femoral stem dissociates from the inner metal head
. The femoral stem subsides into the femoral canal

Correct Answer & Explanation

. The inner metal head dislocates out of the larger polyethylene bearing

Explanation

An intra-prosthetic dislocation is specific to dual mobility cups. It occurs when the small inner head escapes the captive larger polyethylene liner due to wear or impingement at the retentive rim of the polyethylene.

Question 374

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old female with severe rheumatoid arthritis undergoes a total shoulder arthroplasty. Preoperative imaging showed central glenoid wear and an intact rotator cuff. Ten years later, she presents with severe pain and limited elevation. Radiographs show superior migration of the humeral component and glenoid loosening. What is the most likely initial mode of failure?

. Infection
. Progressive rotator cuff tearing leading to 'rocking horse' glenoid loosening
. Polyethylene wear debris causing osteolysis
. Unrecognized preoperative axillary nerve palsy
. Primary subscapularis failure

Correct Answer & Explanation

. Progressive rotator cuff tearing leading to 'rocking horse' glenoid loosening

Explanation

Patients with inflammatory arthritis frequently develop progressive late rotator cuff tears. Superior migration of the humeral head eccentric loads the upper glenoid (the 'rocking horse' phenomenon), eventually causing catastrophic loosening of the glenoid component.

Question 375

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary mechanism by which highly cross-linked polyethylene (HXLPE) reduces osteolysis in total hip arthroplasty compared to conventional polyethylene?

. It produces larger, more biologically active wear particles that are rapidly cleared
. It drastically reduces the total volume and number of wear particles generated
. It stimulates an anti-inflammatory cytokine profile from macrophages
. It binds to cobalt and chromium ions to prevent third-body wear
. It prevents mechanically assisted crevice corrosion at the head-neck junction

Correct Answer & Explanation

. It drastically reduces the total volume and number of wear particles generated

Explanation

HXLPE improves wear resistance by preventing molecular chain unravelling, which drastically reduces the overall volume and number of wear particles generated. Although individual HXLPE particles are smaller and more biologically active, the massive reduction in total particle load decreases osteolysis risk.

Question 376

Topic: Total Hip Arthroplasty (THA)

A 50-year-old male presents with severe hip pain. Radiographs demonstrate an advanced cam-type femoroacetabular impingement (FAI) leading to end-stage osteoarthritis. If a total hip arthroplasty is performed, which aspect of component positioning is most critical to prevent impingement and dislocation given his history of cam morphology?

. Increasing cup inclination beyond 50 degrees
. Ensuring adequate combined anteversion of the cup and stem
. Placing the femoral stem in relative retroversion
. Using a constrained liner
. Decreasing femoral offset

Correct Answer & Explanation

. Ensuring adequate combined anteversion of the cup and stem

Explanation

Restoring appropriate combined anteversion (typically 25-35 degrees) is critical to preventing component impingement and dislocation in THA. Proper combined version provides clearance during functional ranges of motion, which is crucial in patients with pre-existing impingement anatomy.

Question 377

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old active male presents with a chief complaint of a reproducible "squeaking" noise from his right hip during deep flexion, two years after undergoing a primary cementless total hip arthroplasty. Radiographs reveal a well-fixed implant. Which of the following component factors is most strongly associated with this specific complication?

. Use of a highly cross-linked polyethylene liner
. Acetabular component retroversion
. Acetabular component inclination greater than 50 degrees
. Use of a 28 mm femoral head
. Femoral stem undersizing

Correct Answer & Explanation

. Acetabular component inclination greater than 50 degrees

Explanation

Squeaking is a known complication of ceramic-on-ceramic bearings. It is most commonly associated with edge loading caused by component malposition, specifically acetabular cup inclination greater than 45 to 50 degrees or excessive anteversion.

Question 378

Topic: 3. Adult Reconstruction (Hip & Knee)

A 64-year-old male presents with persistent mild shoulder pain and stiffness 14 months after an anatomic total shoulder arthroplasty. Inflammatory markers are normal, and aspiration yields normal leukocyte counts. At 11 days, the synovial fluid cultures grow Cutibacterium acnes. Which of the following is the most appropriate next step in definitive management?

. Prescribe oral cephalexin for 7 days
. Perform a two-stage revision arthroplasty
. Observe clinically as this is a common contaminant
. Perform arthroscopic debridement and retain the implants
. Perform a one-stage exchange with gentamicin-loaded cement

Correct Answer & Explanation

. Perform a two-stage revision arthroplasty

Explanation

Cutibacterium acnes is an indolent organism that commonly causes shoulder periprosthetic joint infections, often requiring 14 days to grow in culture. Two-stage revision is generally the most reliable treatment for established, late-onset C. acnes periprosthetic joint infections.

Question 379

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male with a history of a Metal-on-Polyethylene total hip arthroplasty utilizing a 36-mm cobalt-chromium head presents with new-onset groin pain and a palpable anterior thigh mass. Serum cobalt levels are markedly elevated, while chromium levels are normal. Which of the following is the most likely source of the elevated metal ions?

. Bearing surface wear
. Impingement of the femoral neck on the acetabular cup
. Corrosion at the head-neck taper junction
. Loosening of the porous-coated acetabular shell
. Galvanic corrosion between the stem and a cerclage wire

Correct Answer & Explanation

. Corrosion at the head-neck taper junction

Explanation

Trunnionosis (taper corrosion) can occur in metal-on-polyethylene THA, particularly with large (e.g., 36 mm) cobalt-chromium heads on titanium stems. It typically presents with significantly higher serum cobalt levels compared to chromium, distinguishing it from metal-on-metal bearing wear.

Question 380

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old female sustains a fall and presents with a periprosthetic fracture around her cemented total hip arthroplasty. Radiographs reveal a spiral fracture extending just distal to the tip of the stem. The stem appears subsided and loose, but there is adequate circumferential bone stock in the proximal femur. According to the Vancouver classification, what is the most appropriate surgical treatment?

. Open reduction and internal fixation with a lateral locking plate
. Revision to a long-stem cementless extensively porous-coated implant
. Revision using a proximal femoral replacement prosthesis
. Cerclage wiring alone
. Non-operative management in a hip spica cast

Correct Answer & Explanation

. Revision to a long-stem cementless extensively porous-coated implant

Explanation

This is a Vancouver B2 fracture, characterized by a loose stem but adequate proximal bone stock. The standard of care is revision arthroplasty using a long stem (often extensively porous-coated or fluted tapered) that bypasses the fracture, combined with fracture fixation.

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