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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 283 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 5641

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Musculoskeletal Infection Society (MSIS) criteria, which of the following is considered a major criterion for diagnosing a periprosthetic joint infection?

. Elevated serum CRP > 10 mg/L
. Purulence in the affected joint
. Sinus tract communicating with the prosthesis
. Elevated synovial fluid WBC count
. Positive histological analysis of periprosthetic tissue

Correct Answer & Explanation

. Elevated serum CRP > 10 mg/L

Explanation

A sinus tract communicating with the prosthesis or a pathogen isolated by culture from at least two separate tissue/fluid samples are the major criteria. Purulence is a minor criterion, as are elevated CRP and synovial WBC.

Question 5642

Topic: 3. Adult Reconstruction (Hip & Knee)

The primary blood supply to the proximal pole of the scaphoid is derived from vessels entering at which anatomical location?

. Volar tubercle
. Scapholunate ligament
. Dorsal ridge
. Proximal articular surface
. Volar radiocarpal ligament

Correct Answer & Explanation

. Volar tubercle

Explanation

The scaphoid receives 70-80% of its blood supply via branches of the radial artery that enter the dorsal ridge in a retrograde fashion. This retrograde flow makes proximal pole fractures highly susceptible to avascular necrosis.

Question 5643

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior approach to the hip for a total hip arthroplasty, the short external rotators are divided. Which of the following nerves exits the pelvis through the greater sciatic foramen superior to the piriformis muscle?

. Sciatic nerve
. Inferior gluteal nerve
. Superior gluteal nerve
. Pudendal nerve
. Posterior femoral cutaneous nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

The superior gluteal nerve is the only structure that exits the greater sciatic foramen superior to the piriformis muscle. All other nerves, including the sciatic and inferior gluteal nerves, exit inferior to the piriformis.

Question 5644

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, the use of highly cross-linked polyethylene has significantly reduced wear rates. However, the cross-linking process generates free radicals. How are these free radicals typically eliminated to prevent in vivo oxidative degradation?

. Vitamin E doping or post-irradiation remelting/annealing
. Ethylene oxide sterilization
. Addition of barium sulfate
. Gamma irradiation in air
. Cold sterilization with hydrogen peroxide

Correct Answer & Explanation

. Vitamin E doping or post-irradiation remelting/annealing

Explanation

Gamma irradiation creates cross-links but also leaves behind free radicals that cause oxidative wear over time. These are eliminated by thermal treatments (remelting or annealing) or by adding an antioxidant like Vitamin E (alpha-tocopherol).

Question 5645

Topic: 3. Adult Reconstruction (Hip & Knee)

In a 6-year-old child with spastic quadriplegic cerebral palsy, the Reimers migration percentage of the right hip is measured at 55%. What is the most appropriate surgical management?

. Adductor tenotomy alone
. Bilateral varus derotational osteotomy (VDRO) with pelvic osteotomies
. Total hip arthroplasty
. Proximal femoral resection (Castle procedure)
. Observation

Correct Answer & Explanation

. Adductor tenotomy alone

Explanation

A Reimers Migration Percentage greater than 50% in a spastic CP patient indicates severe subluxation progressing to dislocation. Concurrent varus derotational osteotomy (VDRO) and pelvic osteotomy are required to restore joint congruency and stability.

Question 5646

Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old patient undergoes a total knee arthroplasty and is placed on unfractionated heparin for DVT prophylaxis. On postoperative day 6, his platelet count drops by 60% and he develops a deep venous thrombosis. The pathophysiology of this complication involves autoantibodies directed against which specific molecular complex?
. Heparin and Antithrombin III
. Heparin and Platelet Factor 4 (PF4)
. Heparin and Factor Xa
. Heparin and Fibrinogen
. Heparin and von Willebrand Factor

Correct Answer & Explanation

. Heparin and Platelet Factor 4 (PF4)

Explanation

The patient is experiencing Heparin-Induced Thrombocytopenia (HIT), a prothrombotic, immune-mediated adverse drug reaction. HIT is caused by the formation of IgG autoantibodies against the complex of heparin and Platelet Factor 4 (PF4). This antibody-complex binds to Fc receptors on platelets, causing massive platelet activation, consumption (thrombocytopenia), and paradoxical thrombosis.

Question 5647

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon prepares to deflate the pneumatic tourniquet after a 90-minute total knee arthroplasty. Immediately following deflation, the anesthesiologist should anticipate which of the following systemic physiological changes?

. Decreased end-tidal CO2 (ETCO2) and increased core temperature
. Increased end-tidal CO2 (ETCO2) and decreased central venous pressure
. Decreased heart rate and increased systemic vascular resistance
. Increased mean arterial pressure and decreased PaCO2
. Increased core temperature and increased blood pH

Correct Answer & Explanation

. Increased end-tidal CO2 (ETCO2) and decreased central venous pressure

Explanation

Deflation of a tourniquet releases acidic, hypercarbic, and hypoxic blood back into systemic circulation. This transiently increases ETCO2, decreases systemic blood pressure, and lowers core body temperature.

Question 5648

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, utilizing a ceramic-on-ceramic bearing surface offers the lowest wear rate of all bearing couples. However, it carries a unique risk not seen with metal-on-polyethylene. What is this distinct disadvantage?

. Trunnionosis and cold welding
. Adverse local tissue reaction (ALTR) from heavy metal ions
. Squeaking and catastrophic brittle fracture
. Accelerated osteolysis from volumetric particulate debris
. Galvanic corrosion at the modular junction

Correct Answer & Explanation

. Squeaking and catastrophic brittle fracture

Explanation

Ceramic-on-ceramic bearings provide extremely low wear and excellent biocompatibility. However, they are uniquely susceptible to audible squeaking during ambulation and catastrophic, brittle fracture of the ceramic components.

Question 5649

Topic: 3. Adult Reconstruction (Hip & Knee)

Metal-on-metal hip replacements can fail due to an Adverse Local Tissue Reaction (ALTR). Histologically, this specific response is predominantly characterized by which type of cellular infiltrate?

. Neutrophilic infiltration with micro-abscess formation
. Eosinophilic granulomas
. Perivascular lymphocytic infiltrate (ALVAL)
. Multinucleated giant cells responding to polyethylene
. Monocyte-macrophage dominant granuloma without lymphocytes

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate (ALVAL)

Explanation

ALTR in metal-on-metal arthroplasty is considered a delayed-type hypersensitivity reaction (Type IV) to metal ions. Histologically, it is classically characterized by Aseptic Lymphocyte-dominated Vasculitis-Associated Lesions (ALVAL) featuring dense perivascular T-cell infiltrates.

Question 5650

Topic: 3. Adult Reconstruction (Hip & Knee)
A patient with rheumatoid arthritis undergoes a total hip arthroplasty using a highly cross-linked ultra-high molecular weight polyethylene (UHMWPE) liner. Which of the following mechanical trade-offs is most associated with the cross-linking process?
. Increased volumetric wear rate
. Decreased fatigue crack propagation resistance
. Increased surface friction coefficient
. Decreased resistance to oxidation in vivo
. Increased risk of backside wear

Correct Answer & Explanation

. Decreased fatigue crack propagation resistance

Explanation

Highly cross-linked UHMWPE significantly reduces volumetric wear, thereby lowering the risk of osteolysis. However, the cross-linking and thermal processes reduce the material's mechanical properties, decreasing its yield strength and fatigue crack propagation resistance.

Question 5651

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active male undergoes a total hip arthroplasty (THA) with a ceramic-on-ceramic bearing. At 2 years postoperatively, he complains of a reproducible squeaking noise when bending down. What is the most common biomechanical cause associated with this phenomenon?

. Component impingement leading to stripe wear
. Excessive femoral anteversion
. Head-neck taper corrosion
. Third-body wear from acrylic cement debris
. Pseudotumor formation

Correct Answer & Explanation

. Component impingement leading to stripe wear

Explanation

Squeaking in ceramic-on-ceramic THA is uniquely associated with component impingement, edge loading, and resulting stripe wear on the ceramic head, which permanently alters the fluid-film lubrication dynamics.

Question 5652

Topic: Total Knee Arthroplasty (TKA)

During a posterior-stabilized TKA, trial components are inserted. The knee is perfectly balanced and stable in full extension, but it is significantly tight in 90 degrees of flexion. What is the most appropriate intraoperative step to achieve a balanced gap?

. Resect more distal femur
. Downsize the femoral component and use a thicker polyethylene insert
. Downsize the femoral component using an anterior referencing guide
. Release the posterior capsule
. Resect more proximal tibia

Correct Answer & Explanation

. Downsize the femoral component using an anterior referencing guide

Explanation

If the knee is balanced in extension but tight in flexion, the flexion gap must be increased selectively. Downsizing the femoral component using an anterior referencing system keeps the anterior flange flush but resects more posterior condylar bone, selectively opening the flexion gap without affecting the balanced extension gap.

Question 5653

Topic: 3. Adult Reconstruction (Hip & Knee)

An 80-year-old female presents with a periprosthetic femur fracture around her cemented THA stem following a mechanical fall. Radiographs demonstrate a fracture at the tip of the stem. The stem appears radiographically loose, but there is adequate remaining proximal femoral bone stock. What is the correct Vancouver classification and most appropriate treatment?

. Vancouver B1; Open reduction internal fixation with cables and plates
. Vancouver B2; Revision to a long uncemented diaphyseal-engaging stem
. Vancouver B2; Revision to a tumor prosthesis
. Vancouver B3; Revision to a long uncemented diaphyseal-engaging stem
. Vancouver B3; Proximal femoral replacement

Correct Answer & Explanation

. Vancouver B2; Revision to a long uncemented diaphyseal-engaging stem

Explanation

Vancouver B2 fractures occur around or just distal to the stem tip with a loose prosthesis but adequate bone stock. The standard of care is revision arthroplasty using a long, diaphyseal-engaging uncemented stem to bypass the fracture by at least two cortical diameters.

Question 5654

Topic: 3. Adult Reconstruction (Hip & Knee)

Following a total knee arthroplasty, the surgeon notices lateral patellar maltracking during trial reduction. Which of the following component adjustments would most effectively improve patellar tracking?

. Internal rotation of the tibial component
. Internal rotation of the femoral component
. Lateral translation of the femoral component
. Medial translation of the femoral component
. Medialization of the patellar button

Correct Answer & Explanation

. Medialization of the patellar button

Explanation

Medializing the patellar component decreases the Q-angle, effectively improving patellar tracking. Internal rotation of the femur or tibia, or medializing the femoral component, would increase the Q-angle and exacerbate lateral tracking.

Question 5655

Topic: Total Hip Arthroplasty (THA)

A surgeon is performing a primary THA using a direct lateral (Hardinge) approach. Which of the following structures is at greatest risk of denervation if the proximal split in the gluteus medius exceeds 5 cm from the greater trochanter?

. Sciatic nerve
. Femoral nerve
. Superior gluteal nerve
. Inferior gluteal nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Superior gluteal nerve

Explanation

The superior gluteal nerve supplies the gluteus medius, minimus, and tensor fasciae latae. It courses approximately 3 to 5 cm proximal to the tip of the greater trochanter. Extending the abductor split beyond 5 cm puts the nerve at high risk, leading to abductor weakness and a postoperative Trendelenburg gait.

Question 5656

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male presents with deep groin pain and a palpable anterior thigh mass 6 years after a metal-on-metal THA. Serum cobalt and chromium levels are highly elevated. MRI reveals a complex cystic mass communicating with the joint space. What histological finding is most characteristic of this condition?

. Abundant polymorphonuclear leukocytes
. Birefringent polyethylene particles
. Extensive diffuse perivascular lymphocytic infiltrate
. Non-caseating granulomas
. Foamy macrophages with cholesterol clefts

Correct Answer & Explanation

. Extensive diffuse perivascular lymphocytic infiltrate

Explanation

Adverse Local Tissue Reaction (ALTR) or Aseptic Lymphocytic Vasculitis-Associated Lesion (ALVAL) secondary to metal-on-metal implants is a Type IV delayed hypersensitivity reaction. Histologically, it is defined by an extensive diffuse perivascular lymphocytic infiltrate, tissue necrosis, and macrophages containing metallic wear debris.

Question 5657

Topic: Total Hip Arthroplasty (THA)

A patient complains of a severely elongated leg immediately after a primary THA. Radiographs demonstrate an increased vertical distance from the teardrop to the lesser trochanter compared to the native contralateral side, with symmetric femoral offset. Which specific intraoperative error most likely occurred?

. Using a femoral neck with excessive varus
. Using a high hip center for the acetabular cup
. Resecting the femoral neck too far proximally
. Placing the acetabular cup with excessive anteversion
. Over-reaming the acetabulum medially

Correct Answer & Explanation

. Resecting the femoral neck too far proximally

Explanation

An increased teardrop-to-lesser trochanter distance indicates the femoral stem sits too high relative to the pelvis. If the femoral neck is cut too high (proximally), more calcar is left intact, causing the standard stem to sit proud and directly increasing leg length. A high hip center would generally decrease leg length.

Question 5658

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the classic Kozinn and Scott criteria, which of the following is considered an absolute contraindication to a medial unicompartmental knee arthroplasty (UKA)?

. Patient age greater than 60 years
. Fixed varus deformity of 10 degrees
. Flexion contracture of 10 degrees
. Intact ACL with a torn medial meniscus
. Inflammatory arthritis

Correct Answer & Explanation

. Inflammatory arthritis

Explanation

Inflammatory arthritis (e.g., rheumatoid arthritis) is an absolute contraindication to UKA due to global joint involvement. Other classic contraindications include fixed varus >15 degrees, fixed valgus >20 degrees, flexion contracture >15 degrees, and ACL deficiency (though debated in modern mobile-bearing UKA). Age >60 is actually a supportive indication.

Question 5659

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision THA, an Extended Trochanteric Osteotomy (ETO) is performed to remove a well-fixed cementless stem. Which of the following vessels provides the primary critical blood supply to the osteotomized greater trochanteric fragment to ensure union?

. Medial femoral circumflex artery
. Descending branch of the lateral femoral circumflex artery
. Ascending branch of the medial femoral circumflex artery
. Superior gluteal artery
. Inferior gluteal artery

Correct Answer & Explanation

. Descending branch of the lateral femoral circumflex artery

Explanation

The ETO fragment maintains its vascularity through its preserved soft tissue attachments, specifically the vastus lateralis muscle. The vastus lateralis is supplied predominantly by the descending branch of the lateral femoral circumflex artery.

Question 5660

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with a painful catch and an audible pop in her knee when extending from 45 degrees of flexion to full extension. She underwent a posterior-stabilized TKA 1 year ago. What is the most likely etiology of her symptoms?

. Entrapment of the popliteus tendon
. Polyethylene wear of the tibial insert
. Fibrous nodule formation at the superior pole of the patella
. Loosening of the patellar component
. Undersized femoral component causing mid-flexion instability

Correct Answer & Explanation

. Fibrous nodule formation at the superior pole of the patella

Explanation

Patellar clunk syndrome is uniquely associated with posterior-stabilized (PS) TKA designs. A fibrous nodule develops at the superior pole of the patella (deep surface of the quadriceps tendon). During deep flexion, the nodule falls into the intercondylar box and 'clunks' out upon extension (usually between 30 and 45 degrees). Treatment is arthroscopic debridement.

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