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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 148 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 2941

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old man sustains a periprosthetic femur fracture around his cementless total hip arthroplasty stem following a fall. Radiographs show a fracture around the stem with evidence of subsidence and a loose implant. The remaining femoral bone stock is adequate. What is the appropriate treatment?

. Open reduction and internal fixation with cerclage wires alone
. Open reduction and internal fixation with a locking plate
. Revision to a long uncemented diaphyseal-fitting stem
. Revision to a cemented stem
. Skeletal traction for 6 weeks

Correct Answer & Explanation

. Revision to a long uncemented diaphyseal-fitting stem

Explanation

This is a Vancouver B2 periprosthetic fracture (fracture around the stem, loose implant, good bone stock). The standard treatment is revision to a longer, uncemented, extensively porous-coated stem that bypasses the fracture by at least 2 cortical diameters.

Question 2942

Topic: 3. Adult Reconstruction (Hip & Knee)

In a posterior-stabilized total knee arthroplasty, the cam-post mechanism is designed to substitute for the posterior cruciate ligament (PCL). At approximately what degree of knee flexion does the femoral cam typically engage the tibial post to initiate femoral rollback?

. 0 to 15 degrees
. 20 to 40 degrees
. 50 to 75 degrees
. 90 to 110 degrees
. 120 to 135 degrees

Correct Answer & Explanation

. 50 to 75 degrees

Explanation

In most posterior-stabilized TKA designs, the cam engages the post at approximately 50 to 75 degrees of flexion to initiate posterior femoral rollback and prevent anterior translation of the femur.

Question 2943

Topic: 3. Adult Reconstruction (Hip & Knee)

Recurrent posterior instability in a total hip arthroplasty can be managed by several strategies. Increasing the femoral head size improves stability primarily through which mechanism?

. Increasing the head-to-neck ratio and jump distance
. Medializing the center of rotation
. Increasing soft tissue tension
. Restoring native femoral offset
. Changing the pelvic tilt

Correct Answer & Explanation

. Increasing the head-to-neck ratio and jump distance

Explanation

A larger femoral head increases the jump distance (the distance the head must travel to dislocate) and improves the head-to-neck ratio, maximizing impingement-free range of motion.

Question 2944

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman with a severe 20-degree valgus deformity undergoes a primary total knee arthroplasty. In the recovery room, she is found to have a complete foot drop. What is the immediate first step in management?

. Immediate surgical exploration of the peroneal nerve
. Remove all compressive dressings and flex the knee
. Obtain an EMG and nerve conduction study
. Order an urgent MRI of the lumbar spine
. Administer high-dose intravenous corticosteroids

Correct Answer & Explanation

. Remove all compressive dressings and flex the knee

Explanation

Common peroneal nerve palsy can occur after correction of severe valgus deformities. The immediate treatment is removing all constrictive dressings and flexing the knee to relieve tension on the nerve.

Question 2945

Topic: 3. Adult Reconstruction (Hip & Knee)

Which cell type is considered the primary effector in the biological pathway leading to aseptic loosening and osteolysis around a total hip arthroplasty?

. Osteoblasts
. Chondrocytes
. T-lymphocytes
. Macrophages
. Neutrophils

Correct Answer & Explanation

. Macrophages

Explanation

Macrophages phagocytose particulate wear debris (like polyethylene particles), which triggers the release of pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6). This cascade ultimately activates osteoclasts, leading to osteolysis.

Question 2946

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old man presents with an inability to perform a straight leg raise 3 years after a total knee arthroplasty. Ultrasound confirms a complete, chronic patellar tendon rupture. He has significant difficulty ambulating. What is the most reliable surgical treatment?

. Primary end-to-end repair with heavy nonabsorbable sutures
. Reconstruction with a synthetic mesh tape
. Reconstruction with an extensor mechanism allograft
. Hamstring autograft reconstruction
. Tibial tubercle advancement

Correct Answer & Explanation

. Reconstruction with an extensor mechanism allograft

Explanation

Chronic extensor mechanism disruptions after TKA have poor outcomes with direct repair. Reconstruction with a full extensor mechanism allograft (including tibial tubercle, patellar tendon, patella, and quadriceps tendon) provides the most reliable long-term result.

Question 2947

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old woman has a persistent Trendelenburg gait 1 year after a total hip arthroplasty performed via a direct lateral (Hardinge) approach. Assuming equal leg lengths and proper component offset, what is the most likely cause?

. Injury to the superior gluteal nerve or avulsion of the gluteus medius repair
. Intraoperative injury to the sciatic nerve
. Leg length discrepancy of 5 mm
. Excessive offset of the femoral component
. Iliopsoas impingement on the anterior acetabular rim

Correct Answer & Explanation

. Injury to the superior gluteal nerve or avulsion of the gluteus medius repair

Explanation

The direct lateral approach splits the gluteus medius and minimus, placing the superior gluteal nerve at risk if the split is extended >5 cm proximal to the greater trochanter. Failure of the abductor repair also leads to a prominent Trendelenburg gait.

Question 2948

Topic: Total Knee Arthroplasty (TKA)

When converting a failed medial unicompartmental knee arthroplasty (UKA) to a total knee arthroplasty (TKA), what is the most common intraoperative challenge compared to a primary TKA?

. Need for lateral collateral ligament reconstruction
. Use of a highly constrained hinged prosthesis
. Management of a medial tibial bone defect often requiring augments
. Difficulty correcting a residual valgus deformity
. Severe patella baja requiring tubercle osteotomy

Correct Answer & Explanation

. Management of a medial tibial bone defect often requiring augments

Explanation

Revision of a UKA to a TKA frequently reveals substantial bone loss on the involved side (usually medial tibial plateau), necessitating the use of metal augments, bone grafting, or tibial stems to achieve stable fixation.

Question 2949

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient with a metal-on-metal total hip arthroplasty, elevated serum levels of which two ions are most indicative of excessive bearing wear?

. Titanium and Vanadium
. Cobalt and Chromium
. Aluminum and Titanium
. Iron and Zinc
. Molybdenum and Manganese

Correct Answer & Explanation

. Cobalt and Chromium

Explanation

Metal-on-metal bearings are composed primarily of a Cobalt-Chromium-Molybdenum alloy. Elevated serum cobalt and chromium levels (>7 ppb) are biomarkers for excessive wear and potential adverse local tissue reactions.

Question 2950

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old woman presents with only 70 degrees of maximal knee flexion 8 weeks after a primary total knee arthroplasty. She has been fully compliant with physical therapy, and radiographs show well-positioned components. What is the most appropriate next step in management?

. Continued physical therapy for 3 more months
. Manipulation under anesthesia (MUA)
. Arthroscopic lysis of adhesions
. Open lysis of adhesions and polyethylene exchange
. One-stage revision total knee arthroplasty

Correct Answer & Explanation

. Manipulation under anesthesia (MUA)

Explanation

For severe stiffness following TKA despite adequate physical therapy, Manipulation Under Anesthesia (MUA) is most effective when performed between 6 and 12 weeks postoperatively.

Question 2951

Topic: 3. Adult Reconstruction (Hip & Knee)

According to Lewinnek, the 'safe zone' for acetabular component positioning in total hip arthroplasty to minimize dislocation risk is characterized by which of the following parameters?

. 40 degrees of abduction and 15 degrees of anteversion
. 50 degrees of abduction and 30 degrees of anteversion
. 30 degrees of abduction and 0 degrees of anteversion
. 45 degrees of abduction and 45 degrees of anteversion
. 20 degrees of abduction and 10 degrees of retroversion

Correct Answer & Explanation

. 40 degrees of abduction and 15 degrees of anteversion

Explanation

The classic Lewinnek safe zone is defined as 40 degrees (+/- 10 degrees) of inclination/abduction and 15 degrees (+/- 10 degrees) of anteversion. Implants outside this zone have a historically higher rate of dislocation.

Question 2952

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old woman is 2 years status-post a posterior stabilized total knee arthroplasty. She complains of a painful catching sensation in her knee when extending from a flexed position. What is the most appropriate management?

. Revision of the patellar component
. Arthroscopic debridement
. Open synovectomy
. Femoral component revision
. Manipulation under anesthesia

Correct Answer & Explanation

. Arthroscopic debridement

Explanation

This patient is presenting with patellar clunk syndrome, which occurs in posterior stabilized TKAs due to a fibrous nodule catching in the intercondylar box. Arthroscopic debridement of the nodule is highly successful and the treatment of choice.

Question 2953

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active male undergoes a total hip arthroplasty. A ceramic-on-ceramic bearing is chosen to minimize volumetric wear. What is a unique complication associated with this bearing surface compared to metal-on-polyethylene?

. Trunnionosis
. Audible squeaking
. Adverse local tissue reaction (ALVAL)
. Creep
. Galvanic corrosion

Correct Answer & Explanation

. Audible squeaking

Explanation

Ceramic-on-ceramic bearings offer the lowest wear rates but are uniquely associated with audible squeaking (up to 10% in some series) and catastrophic ceramic fracture. ALVAL is characteristic of metal-on-metal bearings.

Question 2954

Topic: Total Hip Arthroplasty (THA)

A patient has recurrent posterior dislocations post-THA. Radiographs demonstrate that the acetabular component is retroverted, while the femoral stem is well-fixed with normal anteversion. What is the best definitive treatment?

. Placement of a constrained liner
. Exchange to an elevated rim liner
. Acetabular component revision
. Femoral component revision
. Trochanteric advancement

Correct Answer & Explanation

. Acetabular component revision

Explanation

When recurrent dislocation is caused by component malposition (such as a retroverted cup), the primary treatment is revision of the malpositioned component to restore proper biomechanics. Constrained liners should be reserved for cases of abductor deficiency or cognitive dysfunction.

Question 2955

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male is 3 weeks status-post TKA. He reports a 2-day history of acute knee pain, swelling, and erythema. Aspiration yields 65,000 WBCs/uL with 95% polymorphonuclear cells. What is the most appropriate management?

. Intravenous antibiotics for 6 weeks without surgery
. Arthroscopic irrigation and drainage
. Open debridement, modular component exchange, and retention of implants
. Two-stage exchange arthroplasty
. Single-stage exchange arthroplasty

Correct Answer & Explanation

. Open debridement, modular component exchange, and retention of implants

Explanation

For acute periprosthetic joint infections (within 4 weeks of surgery or acute hematogenous spread), DAIR (debridement, antibiotics, and implant retention) with modular polyethylene exchange is indicated. Arthroscopic irrigation has an unacceptably high failure rate.

Question 2956

Topic: 3. Adult Reconstruction (Hip & Knee)

A post-TKA patient complains of a sense of instability when descending stairs. Physical examination reveals the knee is stable in extension but opens 10 mm to varus and valgus stress at 90 degrees of flexion. How could this have been prevented intraoperatively?

. Downsizing the femoral component
. Increasing the posterior femoral offset
. Using a thicker polyethylene insert
. Releasing the posterior cruciate ligament
. Recutting the proximal tibia

Correct Answer & Explanation

. Increasing the posterior femoral offset

Explanation

Flexion instability results from a loose flexion gap relative to a balanced extension gap. Increasing the posterior femoral offset or using a larger femoral component helps tighten and balance the flexion gap without affecting extension.

Question 2957

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, internal rotation of the tibial or femoral component leads to which of the following complications?

. Medial patellar subluxation
. Lateral patellar subluxation
. Patellar clunk syndrome
. Flexion instability
. Extension stiffness

Correct Answer & Explanation

. Lateral patellar subluxation

Explanation

Internal rotation of either the femoral or tibial component increases the Q-angle dynamically, leading to lateral patellar tracking and potential subluxation. External rotation of the components is often used to optimize patellar tracking.

Question 2958

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a metal-on-metal THA presents with groin pain and a palpable mass. Blood cobalt and chromium levels are elevated. Histologic examination of the periarticular tissue is most likely to show:

. Abundant polymorphonuclear leukocytes
. Birefringent particles under polarized light
. Perivascular lymphocytic infiltrates
. Sheets of lipid-laden macrophages
. Granulation tissue with eosinophils

Correct Answer & Explanation

. Perivascular lymphocytic infiltrates

Explanation

Adverse local tissue reaction (ALTR/ALVAL) to metal-on-metal bearings is characterized histologically by an aseptic, lymphocyte-dominated vasculitis. This perivascular lymphocytic infiltrate indicates a delayed-type hypersensitivity reaction.

Question 2959

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient is considering total knee arthroplasty for severe osteoarthritis. Which of the following preoperative factors is the strongest predictor of postoperative range of motion?

. Preoperative range of motion
. Patient age
. Body mass index
. Preoperative pain severity
. Radiographic Kellgren-Lawrence grade

Correct Answer & Explanation

. Preoperative range of motion

Explanation

The strongest and most consistent predictor of postoperative range of motion following a total knee arthroplasty is the patient's preoperative range of motion. Age, BMI, and pain scores have significantly less predictive value for final ROM.

Question 2960

Topic: Total Knee Arthroplasty (TKA)

A patient requires revision TKA for severe valgus deformity combined with medial collateral ligament (MCL) incompetency. Which level of implant constraint is most appropriate?

. Posterior stabilized
. Cruciate retaining
. Unconstrained varus-valgus plus
. Rotating hinge
. Condylar constrained knee (CCK)

Correct Answer & Explanation

. Rotating hinge

Explanation

In the setting of severe collateral ligament incompetency (such as a completely deficient MCL), a rotating hinge knee is indicated to provide the necessary coronal stability. A CCK device relies on intact, functional collateral ligaments.

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