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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 264 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 5261

Topic: 3. Adult Reconstruction (Hip & Knee)

An asymptomatic 58-year-old female with a large-head metal-on-metal THA placed 8 years ago presents for a routine follow-up. Her serum cobalt level is 8.5 ppb and chromium is 7.2 ppb. According to consensus regulatory guidelines, what is the most appropriate next step in management?

. Immediate revision to a metal-on-polyethylene bearing
. Perform an MRI with metal artifact reduction sequence (MARS) to evaluate for pseudotumor
. Reassure the patient and schedule routine clinical follow-up in 5 years
. Initiate systemic chelation therapy to lower heavy metal burden
. Perform a diagnostic intra-articular steroid injection

Correct Answer & Explanation

. Immediate revision to a metal-on-polyethylene bearing

Explanation

Consensus guidelines (such as MHRA and FDA) recommend cross-sectional imaging (MARS MRI or specialized ultrasound) for any patient with a metal-on-metal hip and elevated metal ions (typically > 7 ppb for Co or Cr), even if asymptomatic. This is to rule out silent adverse local tissue reactions (ALTR) or pseudotumors, which can cause severe, irreversible muscle and tissue destruction.

Question 5262

Topic: Total Knee Arthroplasty (TKA)

A patient presents with a feeling of the knee 'giving way' when descending stairs one year following a primary TKA. Varus/valgus stress testing is stable in full extension and at 90 degrees of flexion, but there is marked laxity at 30-45 degrees of flexion. Which of the following technical errors is the most likely cause of this mid-flexion instability?

. Use of an undersized femoral component in the anteroposterior plane
. Excessive resection of the distal femur with compensatory thicker polyethylene insert
. Inadvertent release of the posterior cruciate ligament in a cruciate-retaining knee
. Unrecognized rupture of the superficial medial collateral ligament
. Over-resection of the posterior tibial slope during the initial tibial cut

Correct Answer & Explanation

. Use of an undersized femoral component in the anteroposterior plane

Explanation

Elevation of the joint line (commonly caused by excessive distal femoral resection combined with a thicker tibial insert to restore extension stability) alters the isometry of the collateral ligaments. While the knee may be stable in full extension and 90 degrees of flexion, the elevated joint line creates relative laxity of the collateral ligaments in mid-flexion (30-60 degrees), leading to mid-flexion instability.

Question 5263

Topic: 3. Adult Reconstruction (Hip & Knee)

Tantalum and highly porous titanium constructs are extensively used in revision arthroplasty to manage bone loss due to their excellent biologic fixation properties. What is the approximate porosity of these advanced trabecular metals compared to traditional sintered bead porous coatings?

. 20-30% compared to 10%
. 50-60% compared to 15-20%
. 70-80% compared to 30-50%
. 95-99% compared to 60-70%
. 10-15% compared to 5%

Correct Answer & Explanation

. 20-30% compared to 10%

Explanation

Highly porous metals (like trabecular metal/tantalum) have a porosity of approximately 75-80%, which closely mimics native cancellous bone. Traditional porous coatings (like sintered beads or plasma spray) generally have a lower porosity, ranging from 30% to 50%. The higher porosity allows for greater initial friction and superior biologic bone ingrowth.

Question 5264

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old male presents with medial compartment knee osteoarthritis. He is being evaluated for a unicompartmental knee arthroplasty (UKA). Which of the following findings is widely considered an absolute contraindication to proceeding with a UKA?

. Age less than 60 years
. Presence of asymptomatic patellofemoral chondrocalcinosis
. Rheumatoid arthritis
. Body mass index greater than 35 kg/m2
. Previous arthroscopic partial medial meniscectomy

Correct Answer & Explanation

. Age less than 60 years

Explanation

Inflammatory arthropathies, such as rheumatoid arthritis, are considered absolute contraindications to unicompartmental knee arthroplasty (UKA) because the systemic and progressive nature of the disease will inevitably involve the preserved compartments. Age, obesity, asymptomatic chondrocalcinosis, and prior meniscectomy are relative or non-contraindications depending on surgeon preference and implant design.

Question 5265

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female experiences her third posterior dislocation following a primary total hip arthroplasty. CT scan evaluation of her component positioning reveals an acetabular cup anteversion of 10 degrees and a femoral stem retroversion of 5 degrees. According to the combined anteversion theory (Ranawat/McKee), what is her combined anteversion, and what is its clinical implication?

. 5 degrees; places her at high risk for posterior dislocation.
. 15 degrees; within the safe zone, suggesting a soft tissue etiology.
. 5 degrees; places her at high risk for anterior dislocation.
. 15 degrees; places her at high risk for posterior dislocation.
. 25 degrees; within the safe zone, suggesting component malposition is not the cause.

Correct Answer & Explanation

. 5 degrees; places her at high risk for posterior dislocation.

Explanation

Combined anteversion is the sum of acetabular anteversion and femoral anteversion. In this case, 10 degrees (cup) + (-5 degrees) (stem) = 5 degrees. The normal 'safe zone' for combined anteversion to prevent impingement and dislocation is typically between 25 and 45 degrees. A combined anteversion of 5 degrees is severely deficient and places the patient at a high risk for posterior dislocation due to early anterior bony or component impingement during internal rotation.

Question 5266

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting on Periprosthetic Joint Infection (PJI), which of the following serves as a major criterion (providing definitive evidence) for the diagnosis of PJI?

. Elevated serum C-reactive protein (>10 mg/L) and D-dimer (>860 ng/mL)
. Synovial fluid leukocyte count > 3,000 cells/ยตL
. A single positive tissue culture with a highly virulent organism (e.g., S. aureus)
. A sinus tract communicating with the joint
. Positive synovial alpha-defensin immunoassay

Correct Answer & Explanation

. Elevated serum C-reactive protein (>10 mg/L) and D-dimer (>860 ng/mL)

Explanation

According to the 2018 MSIS/ICM criteria, definitive evidence (major criteria) for PJI includes either: (1) a sinus tract communicating with the joint, or (2) two positive periprosthetic cultures with phenotypically identical organisms. The other options represent minor criteria or components of the scoring algorithm.

Question 5267

Topic: 3. Adult Reconstruction (Hip & Knee)

A 74-year-old female sustains a catastrophic rupture of the patellar tendon 4 years after a primary posterior-stabilized total knee arthroplasty. Physical examination reveals a palpable 5 cm gap, and she is unable to actively extend the knee. Which of the following is the most reliable surgical management for this chronic, massive defect?

. Primary end-to-end repair with nonabsorbable sutures and cerclage wire
. Extensor mechanism allograft reconstruction
. Autologous hamstring tendon reconstruction
. Gastrocnemius rotational flap
. Immobilization in a cylinder cast for 8 weeks

Correct Answer & Explanation

. Primary end-to-end repair with nonabsorbable sutures and cerclage wire

Explanation

Chronic extensor mechanism disruptions in the setting of a TKA, especially with a large gap (>3-4 cm) and poor tissue quality, cannot be reliably treated with primary repair. Extensor mechanism allograft (incorporating the tibial tubercle, patellar tendon, patella, and quadriceps tendon) or synthetic mesh reconstructions are the standard of care for restoring active extension.

Question 5268

Topic: 3. Adult Reconstruction (Hip & Knee)
During preoperative planning for a revision total hip arthroplasty, you classify the acetabular defect as a Paprosky Type IIIB. Which of the following radiographic findings characterizes this specific defect?
. Superior component migration < 3 cm with intact teardrop and Kohler's line.
. Superior component migration > 3 cm, intact Kohler's line, and supportive lower ischium.
. Superior component migration > 3 cm, medial migration past Kohler's line, and severe ischial bone loss.
. Massive pelvic dissociation with discontinuity of the anterior and posterior columns.
. Intact acetabular rim with central cavitary bone loss only.

Correct Answer & Explanation

. Superior component migration > 3 cm, medial migration past Kohler's line, and severe ischial bone loss.

Explanation

In the Paprosky classification for acetabular defects, a Type IIIB defect ('up and in') involves superior migration > 3 cm, medial migration past Kohler's line (broken Kohler's), teardrop lysis, and severe ischial bone loss. This contrasts with Type IIIA ('up and out'), where Kohler's line is intact and there is moderate supportive ischial bone remaining.

Question 5269

Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old male with a metal-on-metal total hip arthroplasty presents with progressive groin pain 6 years postoperatively. Radiographs show well-fixed components with a cup abduction angle of 55 degrees. Laboratory testing reveals a serum cobalt level of 14 ppb (normal < 1 ppb). A Metal Artifact Reduction Sequence (MARS) MRI demonstrates a 6 cm thick-walled cystic mass communicating with the joint. What is the most appropriate definitive management?
. Ultrasound-guided aspiration of the cystic mass and intra-articular corticosteroid injection.
. Revision of the acetabular and femoral components to a ceramic-on-polyethylene bearing surface.
. Addition of oral bisphosphonates and repeat metal ion testing in 6 months.
. Isolated revision of the femoral head to a ceramic head with a titanium sleeve, retaining the metal liner.
. Six-week course of intravenous antibiotics followed by single-stage revision.

Correct Answer & Explanation

. Revision of the acetabular and femoral components to a ceramic-on-polyethylene bearing surface.

Explanation

This patient has an Adverse Local Tissue Reaction (ALTR/ALVAL) or pseudotumor due to metal wear debris, exacerbated by the steep cup angle (edge loading). The definitive treatment for a symptomatic pseudotumor with elevated metal ions and malpositioned components is revision surgery to remove the metal-on-metal bearing surfaces, commonly changing to a ceramic-on-polyethylene bearing.

Question 5270

Topic: 3. Adult Reconstruction (Hip & Knee)

To optimize patellofemoral tracking and minimize the risk of patellar subluxation during a total knee arthroplasty, the patellar component should ideally be placed in which position on the resected patellar surface?

. Medial and superior
. Medial and inferior
. Central and inferior
. Lateral and superior
. Lateral and inferior

Correct Answer & Explanation

. Medial and superior

Explanation

The native median ridge of the patella is slightly medial to the geometric center. Placing the patellar button slightly medial and superior on the resected bone surface best reproduces the native anatomy, optimizes patellar tracking by lateralizing the remaining bony patella relative to the button, and reduces the risk of patellar clunk or subluxation.

Question 5271

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, hard-on-hard bearing surfaces (such as ceramic-on-ceramic) demonstrate exceptionally low wear rates. This is primarily attributed to which of the following lubrication regimes occurring during normal walking?

. Boundary lubrication
. Mixed lubrication
. Fluid-film lubrication
. Solid-state lubrication
. Elastohydrodynamic lubrication

Correct Answer & Explanation

. Boundary lubrication

Explanation

Hard-on-hard bearings (ceramic-on-ceramic, metal-on-metal) rely heavily on fluid-film lubrication. In this regime, the articulating surfaces are completely separated by a thin, continuous layer of synovial fluid, minimizing direct surface asperity contact and resulting in dramatically lower wear rates compared to boundary lubrication (seen more in metal-on-polyethylene).

Question 5272

Topic: 3. Adult Reconstruction (Hip & Knee)

In a posterior-stabilized (PS) total knee arthroplasty design, what is the primary biomechanical function of the femoral cam and tibial post mechanism during knee flexion?

. It prevents anterior translation of the tibia relative to the femur.
. It provides varus-valgus stability in the absence of the collateral ligaments.
. It induces compulsory posterior femoral rollback to optimize clearance and flexion.
. It restricts internal and external rotation of the tibia.
. It substitutes for the function of the anterior cruciate ligament.

Correct Answer & Explanation

. It prevents anterior translation of the tibia relative to the femur.

Explanation

The cam and post mechanism in a PS TKA is designed to substitute for the resected posterior cruciate ligament (PCL). Its primary function is to engage during flexion and compel the femur to roll back posteriorly on the tibia. This posterior rollback prevents impingement of the posterior femoral cortex on the tibia and maximizes the range of flexion.

Question 5273

Topic: 3. Adult Reconstruction (Hip & Knee)
A 45-year-old male is undergoing revision total hip arthroplasty for aseptic loosening. He has a history of severe Brooker class III heterotopic ossification following his index procedure. What is the most effective prophylactic regimen to prevent recurrence of heterotopic ossification in this high-risk patient?
. Oral diclofenac 50 mg twice daily for 7 days
. Single fraction of radiation therapy (700-800 cGy) within 24-48 hours postoperatively
. Intravenous tranexamic acid administration intraoperatively
. Oral rivaroxaban 10 mg daily for 35 days
. Oral alendronate 70 mg weekly for 6 months

Correct Answer & Explanation

. Single fraction of radiation therapy (700-800 cGy) within 24-48 hours postoperatively

Explanation

For high-risk patients (e.g., history of severe HO, ankylosing spondylitis, hypertrophic osteoarthritis), prophylaxis is indicated. The most reliable regimens are either a single dose of localized radiation (700-800 cGy) given within 24-48 hours pre- or postoperatively, or a 3-6 week course of NSAIDs like indomethacin. Radiation is often preferred due to compliance and GI side effects of prolonged NSAIDs.

Question 5274

Topic: Total Hip Arthroplasty (THA)

The Exeter femoral stem is a classic example of a collarless, polished, double-tapered cemented implant. By which biomechanical principle does this specific stem design achieve long-term stability?

. Shape-closed fixation, relying on rigid bonding between the stem and cement mantle.
. Force-closed fixation, allowing controlled subsidence of the stem within the cement mantle.
. Proximal load transfer, utilizing a collar to offload the distal cement mantle.
. Distal point loading, wedging the tip of the stem into the diaphyseal bone.
. Osseointegration, achieved through ongrowth onto the polished metallic surface.

Correct Answer & Explanation

. Shape-closed fixation, relying on rigid bonding between the stem and cement mantle.

Explanation

Collarless, polished, double-tapered stems (like the Exeter) are designed to function as 'force-closed' devices. Because they are highly polished, they do not bond to the cement. Instead, the double-taper design allows the stem to subside slightly within the intact cement mantle under axial load, effectively acting as a wedge that increases radial compressive forces and stabilizes the implant.

Question 5275

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female requires a revision total knee arthroplasty. Preoperative radiographs and intraoperative assessment reveal substantial metaphyseal bone loss involving both the medial and lateral femoral condyles, while the collateral ligament attachments and joint line remain reasonably identifiable. An intraoperative scenario resembling

is encountered. According to the Anderson Orthopaedic Research Institute (AORI) classification, what is her femoral bone defect type?

. Type F1
. Type F2A
. Type F2B
. Type F3
. Type T2B

Correct Answer & Explanation

. Type F1

Explanation

In the AORI classification for revision TKA bone defects, Type 1 denotes intact metaphyseal bone. Type 2 denotes damaged metaphyseal bone necessitating reconstruction (such as augments, cones, or cement): Type 2A involves one condyle (medial or lateral), while Type 2B involves both condyles. Type 3 indicates severe bone loss compromising the collateral ligaments or patellar tendon attachment.

Question 5276

Topic: 3. Adult Reconstruction (Hip & Knee)

An anterior dislocation of a total hip arthroplasty is most likely to occur when the operative limb is placed in which combination of positions?

. Flexion, adduction, and internal rotation
. Extension, external rotation, and adduction
. Flexion, abduction, and external rotation
. Extension, internal rotation, and abduction
. Flexion, adduction, and external rotation

Correct Answer & Explanation

. Flexion, adduction, and internal rotation

Explanation

Anterior dislocations typically occur when the hip is subjected to extension and external rotation, often coupled with adduction (which levers the head out of the acetabulum anteriorly). Posterior dislocations typically occur with flexion, adduction, and internal rotation.

Question 5277

Topic: 3. Adult Reconstruction (Hip & Knee)

In the setting of revision total knee arthroplasty, a Constrained Condylar Knee (CCK) prosthesis is best indicated for a patient with which of the following clinical scenarios?

. Complete absence of the medial and lateral collateral ligaments.
. Severe uncorrectable recurvatum deformity.
. Profound attenuation of the medial collateral ligament with an intact extensor mechanism.
. Massive metaphyseal bone loss requiring a distal femoral replacement.
. Isolated rupture of the posterior cruciate ligament with intact collaterals.

Correct Answer & Explanation

. Complete absence of the medial and lateral collateral ligaments.

Explanation

A Constrained Condylar Knee (CCK) utilizes a tall, robust tibial post that fits intimately into the femoral box to provide varus-valgus and rotational stability. It is indicated when there is severe attenuation or imbalance of the collateral ligaments (e.g., profound MCL laxity). However, if the collateral ligaments are completely incompetent or absent, a linked rotating hinge prosthesis is required.

Question 5278

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old female presents with a painful 'catching' and an audible pop in her knee when extending from a flexed position, one year after a primary total knee arthroplasty. This complication, known as patellar clunk syndrome, is primarily associated with which of the following arthroplasty designs?

. Cruciate-retaining (CR) TKA
. Posterior-stabilized (PS) TKA
. Medial pivot TKA
. Unicompartmental knee arthroplasty
. Patellofemoral arthroplasty

Correct Answer & Explanation

. Cruciate-retaining (CR) TKA

Explanation

Patellar clunk syndrome is a complication classically seen with posterior-stabilized (PS) TKA designs. It is caused by the formation of a fibrous nodule on the undersurface of the distal quadriceps tendon. During knee extension, this nodule catches in the intercondylar box (cutout for the cam/post mechanism) of the femoral component and then sharply dislodges with a painful 'clunk'.

Question 5279

Topic: 3. Adult Reconstruction (Hip & Knee)

During trial reduction of a primary total hip arthroplasty, the surgeon determines that the hip is stable but the patient's operative leg is 5 mm short and the offset is 5 mm less than the contralateral side. The current trial uses a standard (+0) neck length. If the surgeon changes the modular femoral head to a +5 mm neck length (assuming a standard 135-degree neck angle), what will be the effect on leg length and offset?

. Both leg length and offset will increase.
. Leg length will increase, but offset will remain unchanged.
. Offset will increase, but leg length will remain unchanged.
. Leg length will increase, and offset will decrease.
. Both leg length and offset will decrease.

Correct Answer & Explanation

. Both leg length and offset will increase.

Explanation

Because the femoral neck extends superomedially from the shaft (typically at an angle of 125-135 degrees), increasing the neck length via a modular head change will result in a vector increase that adds to both the vertical distance (leg length) and the horizontal distance (femoral offset).

Question 5280

Topic: 3. Adult Reconstruction (Hip & Knee)

A 52-year-old active male who underwent an uncomplicated primary total hip arthroplasty 4 years ago presents with an audible squeaking noise emanating from his hip during deep flexion and normal gait. He denies any pain, and radiographs show well-fixed components in acceptable alignment. Which of the following bearing surface combinations is most commonly associated with this phenomenon?

. Cobalt-chromium head on a highly cross-linked polyethylene liner
. Ceramic head on a ceramic liner
. Ceramic head on a highly cross-linked polyethylene liner
. Cobalt-chromium head on a cobalt-chromium liner
. Oxinium head on a standard polyethylene liner

Correct Answer & Explanation

. Cobalt-chromium head on a highly cross-linked polyethylene liner

Explanation

Squeaking is a unique, occasionally audible complication most strongly associated with ceramic-on-ceramic hard bearing surfaces. It is thought to occur due to edge loading, micro-separation, or temporary loss of fluid-film lubrication. While benign in the absence of pain, it can be a source of significant patient dissatisfaction.

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