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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 239 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 4761

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a ceramic-on-ceramic total hip arthroplasty complains of a new-onset "squeaking" noise from the hip with every step. Which of the following biomechanical issues is the most highly associated cause of this phenomenon?

. Edge loading due to component malposition
. Trunnionosis at the head-neck junction
. Galvanic corrosion
. Polyethylene wear debris
. Femoral stem subsidence

Correct Answer & Explanation

. Edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic hips is heavily correlated with edge loading. This occurs when the cup is malpositioned (typically excessive inclination or anteversion), causing the femoral head to articulate against the hard edge of the ceramic liner, disrupting fluid film lubrication.

Question 4762

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with severe rheumatoid arthritis is undergoing THA for protrusio acetabuli. During acetabular preparation, the medial wall is found to be extremely thin and functionally incompetent. What is the most appropriate method to manage this defect and restore the hip center?

. Ream deeply until bleeding subchondral bone is reached
. Use a cemented cup without bone graft
. Use a jumbo cementless cup that relies on the medial wall
. Impaction bone grafting of the medial wall defect with a cementless cup achieving peripheral rim fit
. Structural distal femoral allograft

Correct Answer & Explanation

. Impaction bone grafting of the medial wall defect with a cementless cup achieving peripheral rim fit

Explanation

In protrusio acetabuli, the goal is to lateralize the hip center back to its anatomic position. This is best achieved by placing morselized cancellous bone graft (impaction grafting) into the medial defect and gaining secure initial fixation on the peripheral rim of the acetabulum with a cementless hemispherical shell.

Question 4763

Topic: 3. Adult Reconstruction (Hip & Knee)

In modern total hip arthroplasty, highly cross-linked polyethylene (HXLPE) is used to drastically reduce volumetric wear. Which process is essential after irradiation to prevent the polyethylene from undergoing in vivo oxidation and subsequent failure?

. Sterilization in ethylene oxide gas
. Remelting or annealing to eliminate free radicals
. Cold sterilization in an argon environment
. Adding calcium phosphate to the matrix
. Submerging the polyethylene in saline

Correct Answer & Explanation

. Remelting or annealing to eliminate free radicals

Explanation

While irradiation creates the cross-links that improve wear resistance, it also leaves behind free radicals. If left untreated, these react with oxygen in vivo, embrittling the plastic. Heating the material above its melting point (remelting) or close to it (annealing) mobilizes and eliminates these free radicals. Vitamin E doping is another modern alternative.

Question 4764

Topic: 3. Adult Reconstruction (Hip & Knee)

Which diagnostic test provides the highest specificity for ruling in a periprosthetic joint infection (PJI) by measuring a synovial biomarker produced directly by activated neutrophils?

. Serum Erythrocyte Sedimentation Rate (ESR)
. Serum C-Reactive Protein (CRP)
. Synovial Alpha-defensin
. Serum Interleukin-6 (IL-6)
. White Blood Cell (WBC) count

Correct Answer & Explanation

. Synovial Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. A positive synovial alpha-defensin test has an exceptionally high sensitivity and specificity for periprosthetic joint infection and is not artificially elevated by recent antibiotics or systemic inflammatory conditions.

Question 4765

Topic: 3. Adult Reconstruction (Hip & Knee)

The gold standard treatment for a chronic periprosthetic joint infection of the hip is a two-stage revision. Which of the following accurately describes the key components of the first stage?

. Removal of all implants and cement, radical debridement, and placement of an antibiotic-loaded PMMA spacer
. Exchange of the modular polyethylene liner and head, leaving the well-fixed stem and cup
. Immediate reimplantation of new permanent components soaked in antibiotics
. Suppressive intravenous antibiotics alone for 6 weeks prior to surgery
. Arthroscopic irrigation and debridement

Correct Answer & Explanation

. Removal of all implants and cement, radical debridement, and placement of an antibiotic-loaded PMMA spacer

Explanation

The first step of a two-stage exchange for chronic PJI involves removing all foreign materials (implants, cement, necrotic bone), radically debriding the joint, and placing a high-dose antibiotic-loaded spacer to deliver local therapy while keeping the tissues under tension.

Question 4766

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with massive acetabular bone loss and pelvic discontinuity (complete separation of the superior and inferior halves of the hemipelvis). During revision THA, what is the most mechanically sound construct to achieve rigid fixation?

. A standard hemispherical cementless cup with multiple screws
. A cemented all-polyethylene cup
. A cup-cage construct or custom triflange component
. Impaction bone grafting alone
. An anti-protrusio cage without ischial fixation

Correct Answer & Explanation

. A cup-cage construct or custom triflange component

Explanation

Pelvic discontinuity represents a complete fracture through the acetabulum. The repair requires spanning the defect and providing mechanical rigidity between the ilium and ischium. This is reliably achieved using a highly porous metal cup-cage construct or a custom patient-specific triflange component.

Question 4767

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary biologic mechanism leading to osteolysis and aseptic loosening in total joint arthroplasty?

. Macrophage phagocytosis of submicron polyethylene wear debris leading to cytokine release
. Direct mechanical abrasion of the bone by the metal implant
. Type IV hypersensitivity reaction to titanium alloy
. Osteoblast apoptosis induced by PMMA cement monomer
. Bacterial biofilm formation on the articular surface

Correct Answer & Explanation

. Macrophage phagocytosis of submicron polyethylene wear debris leading to cytokine release

Explanation

Particulate disease (osteolysis) is driven by the generation of submicron polyethylene wear particles. These are phagocytosed by macrophages, which then release pro-inflammatory cytokines (TNF-a, IL-1, IL-6), ultimately stimulating osteoclast-mediated bone resorption.

Question 4768

Topic: Total Hip Arthroplasty (THA)

When cementing a femoral stem during THA, what is the optimal thickness of the cement mantle to ensure long-term survivorship and limit the risk of cement fracture?

. 2 to 3 mm
. Less than 1 mm
. 5 to 7 mm
. 10 mm
. Line-to-line fit with no gap

Correct Answer & Explanation

. 2 to 3 mm

Explanation

Biomechanical studies show that an optimal PMMA cement mantle thickness is between 2 to 3 mm. Mantles thinner than this are prone to brittle fracture under load, while thicker mantles can undergo excessive shrinkage and thermal necrosis of bone.

Question 4769

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient with standard risk for deep vein thrombosis undergoing primary elective total knee arthroplasty, what agent is strongly supported by recent guidelines for chemical VTE prophylaxis?

. Aspirin
. Intravenous Heparin
. Therapeutic Warfarin (INR 3.0)
. Clopidogrel
. Streptokinase

Correct Answer & Explanation

. Aspirin

Explanation

Recent AAOS and ACCP guidelines support the use of Aspirin for VTE prophylaxis in standard-risk patients undergoing total joint arthroplasty. It provides a good balance between preventing clots and minimizing the risk of postoperative hematoma and wound complications compared to aggressive anticoagulants.

Question 4770

Topic: Total Knee Arthroplasty (TKA)

A constrained condylar knee (CCK) prosthesis utilizes a large, tall tibial post fitting into a deep femoral box. Which of the following is the primary indication to upgrade to a CCK design during revision TKA?

. Absent Posterior Cruciate Ligament (PCL) with intact collaterals
. Complete absence of both the Medial Collateral Ligament (MCL) and Lateral Collateral Ligament (LCL)
. Massive uncontained tibial bone defects
. Deficiency or attenuation of the Lateral Collateral Ligament (LCL) or MCL
. Extensor mechanism rupture

Correct Answer & Explanation

. Deficiency or attenuation of the Lateral Collateral Ligament (LCL) or MCL

Explanation

CCK implants provide varus/valgus constraint. They are indicated when the collateral ligaments (MCL or LCL) are attenuated or deficient, but the soft-tissue sleeve is still somewhat intact. Ifbothcollateral ligaments are completely incompetent, a rotating hinge knee (RHK) is required.

Question 4771

Topic: Total Knee Arthroplasty (TKA)

A surgeon performing a TKA internally rotates the femoral component excessively in relation to the epicondylar axis. What is the most likely clinical consequence of this technical error?

. Lateral patellar subluxation/maltracking
. Medial patellar subluxation
. A loose flexion gap laterally
. A tight extension gap medially
. Genu recurvatum

Correct Answer & Explanation

. Lateral patellar subluxation/maltracking

Explanation

Internal rotation of the femoral component translates the trochlear groove medially, which dramatically increases the Q-angle dynamically, leading to lateral patellar maltracking or dislocation.

Question 4772

Topic: Total Knee Arthroplasty (TKA)

When sizing the femoral component in TKA, an anterior referencing system measures from the anterior cortex to establish component size. If the surgeon encounters an "in-between" size and decides to downsize the component using an anterior referencing guide, what happens to the joint gaps?

. The flexion gap becomes looser
. The flexion gap becomes tighter
. The extension gap becomes looser
. The extension gap becomes tighter
. The anterior cortex gets notched

Correct Answer & Explanation

. The flexion gap becomes looser

Explanation

Anterior referencing locks the anterior cut to prevent notching. Therefore, any change in component size alters the posterior condylar resection. Downsizing means more posterior bone is resected, which increases (loosens) the flexion gap.

Question 4773

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old female presents with a severely stiff TKA (ROM 10-60 degrees) two years post-op. Workup for infection is completely negative. She undergoes a revision TKA. Which of the following surgical maneuvers is absolutely critical to successfully expose the joint and avoid catastrophic extensor mechanism avulsion?

. Aggressive manual manipulation and forced flexion before capsulotomy
. Use of an extensile approach (e.g., Tibial Tubercle Osteotomy or Quadriceps Snip)
. Division of the medial collateral ligament (MCL)
. Routine patellectomy
. Z-lengthening of the patellar tendon

Correct Answer & Explanation

. Use of an extensile approach (e.g., Tibial Tubercle Osteotomy or Quadriceps Snip)

Explanation

In stiff knees, the patellar tendon is contracted and at massive risk for avulsion from the tibial tubercle during flexion and eversion. An extensile approach, such as a rectus snip, V-Y turndown, or tibial tubercle osteotomy (TTO), is required to safely evert or laterally sublux the patella.

Question 4774

Topic: 3. Adult Reconstruction (Hip & Knee)

A popliteal artery injury during total knee arthroplasty is a rare but limb-threatening complication. During which specific step of the procedure is this vessel at the greatest anatomic risk of direct transection or injury?

. Making the anterior femoral chamfer cut
. Resecting the patellar articular surface
. Cutting the posterior tibial slope or excising the posterior meniscus/capsule
. Reaming the femoral medullary canal
. Releasing the superficial MCL

Correct Answer & Explanation

. Cutting the posterior tibial slope or excising the posterior meniscus/capsule

Explanation

The popliteal artery runs directly posterior to the knee capsule. It is at maximum risk during the flat posterior tibial bone cut (if the saw blade plunges too deep) and during sharp dissection/release of the posterior capsule and meniscal remnants.

Question 4775

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old female with osteoarthritis of the hip desires a hip resurfacing arthroplasty (HRA) to maintain high-impact activities. Which of the following is considered an absolute contraindication to this procedure?

. Male gender
. Large femoral head diameter
. Renal failure and female of childbearing age
. Bilateral hip osteoarthritis
. Age under 50

Correct Answer & Explanation

. Renal failure and female of childbearing age

Explanation

Hip resurfacing exclusively uses Metal-on-Metal (MoM) bearings, which generate metal ions (cobalt and chromium) cleared by the kidneys. Renal failure prevents clearance, leading to toxicity. Females of childbearing age are also contraindicated due to the unknown teratogenic effects of circulating metal ions crossing the placenta.

Question 4776

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoes a direct lateral (Hardinge) approach for a total hip arthroplasty. Post-operatively, the patient has a severe limp and drops the contralateral pelvis during the stance phase of gait. Which nerve was most likely injured due to excessive superior splitting of the abductor mechanism?

. Superior gluteal nerve
. Sciatic nerve
. Femoral nerve
. Inferior gluteal nerve
. Obturator nerve

Correct Answer & Explanation

. Superior gluteal nerve

Explanation

The superior gluteal nerve innervates the gluteus medius and minimus. It enters the deep surface of the muscle approximately 3-5 cm proximal to the greater trochanter. Splitting the gluteus medius too far proximally during a lateral approach will denervate the anterior portion of the muscle, causing a Trendelenburg lurch.

Question 4777

Topic: 3. Adult Reconstruction (Hip & Knee)

A dual-mobility (DM) articulation in total hip arthroplasty provides excellent resistance to dislocation. How does the biomechanics of a DM cup achieve this stability compared to a standard bearing?

. It uses a highly constrained locking ring to hold the head
. It decreases the head-to-neck ratio
. It primarily acts by lengthening the leg
. It utilizes a large-diameter mobile polyethylene liner, which massively increases the jump distance
. It forces scar tissue to form rapidly in the capsule

Correct Answer & Explanation

. It utilizes a large-diameter mobile polyethylene liner, which massively increases the jump distance

Explanation

Dual-mobility cups feature a small metal or ceramic head mobile inside a large polyethylene sphere, which itself moves inside a polished metal shell. This large outer diameter massively increases the "jump distance" (the distance the head must travel to dislocate), dramatically reducing dislocation rates.

Question 4778

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male with end-stage hip osteoarthritis also has a stiff, arthrodesed (fused) ipsilateral knee from childhood trauma. Which of the following complications is he at uniquely high risk for after undergoing a standard primary Total Hip Arthroplasty?

. Deep vein thrombosis
. Periprosthetic femur fracture
. Heterotopic ossification
. Leg length discrepancy
. Sciatic nerve palsy

Correct Answer & Explanation

. Periprosthetic femur fracture

Explanation

Patients with an ipsilateral knee arthrodesis lack the ability to absorb rotational and bending forces at the knee. When getting out of a chair or twisting, the long, rigid lever arm transfers massive torsional stress directly to the femur, creating a very high risk for spiral periprosthetic femur fractures around or below the THA stem.

Question 4779

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old patient who previously sustained an intra-articular tibial plateau fracture treated with ORIF now presents with severe post-traumatic arthritis requiring TKA. The surgeon must carefully plan the incision. What is a cardinal rule regarding parallel incisions around the knee?

. The new incision should be placed as far laterally as possible to preserve the medial flap.
. Parallel incisions should be avoided; if necessary, the most lateral incision should be utilized to maintain the medial vascular supply to the anterior skin.
. A new medial parapatellar incision is always safe regardless of prior incisions.
. The incisions must intersect at a 90-degree angle to maximize blood flow.
. Transverse incisions heal better than longitudinal ones in TKA.

Correct Answer & Explanation

. Parallel incisions should be avoided; if necessary, the most lateral incision should be utilized to maintain the medial vascular supply to the anterior skin.

Explanation

The blood supply to the anterior skin of the knee runs primarily from medial to lateral. A lateral incision cuts off blood supply to the skin medial to it. Therefore, if multiple parallel vertical incisions exist, the surgeon must use themost lateralusable incision to prevent necrosis of the skin bridge.

Question 4780

Topic: Total Knee Arthroplasty (TKA)

During a revision TKA for a stiff knee, the surgeon decides to perform a Tibial Tubercle Osteotomy (TTO) to evert the extensor mechanism safely. What is a critical technical requirement when performing a TTO?

. The bone fragment should be less than 2 cm long
. The lateral muscular hinge (anterior tibial musculature) must be preserved attached to the bone fragment
. The osteotomy must completely sever the patellar tendon
. Fixation is not required because the quadriceps will hold it in place
. The cut should angle sharply anteriorly into the joint

Correct Answer & Explanation

. The bone fragment should be less than 2 cm long

Explanation

A proper TTO leaves the lateral muscular and periosteal attachments (tibialis anterior) intact on the bone block. This provides vascularity to the fragment to ensure healing and acts as a hinge. The block should be long (typically 6-8 cm) to allow secure rigid fixation with screws or wires.

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