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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 284 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 5661

Topic: 3. Adult Reconstruction (Hip & Knee)
A 35-year-old male on chronic corticosteroids develops severe left groin pain. Radiographs reveal a subchondral radiolucent line (crescent sign) in the femoral head without flattening or joint space narrowing. MRI confirms osteonecrosis. What is the most definitive and appropriate treatment?
. Core decompression
. Core decompression with non-vascularized fibular graft
. Free vascularized fibular grafting
. Total hip arthroplasty
. Non-weight bearing with intravenous bisphosphonates

Correct Answer & Explanation

. Total hip arthroplasty

Explanation

A crescent sign defines Ficat Stage III (subchondral fracture/collapse). Once structural collapse has occurred, joint-preserving operations such as core decompression are highly ineffective. Total hip arthroplasty (THA) is the definitive standard of care for symptomatic Stage III/IV AVN, even in young patients.

Question 5662

Topic: Total Knee Arthroplasty (TKA)

A 72-year-old male sustains an acute, complete rupture of the patellar tendon 3 weeks following a primary TKA. Radiographs show the implants are perfectly positioned and well-fixed. What is the most reliable surgical management for this devastating complication?

. Direct primary repair with heavy non-absorbable sutures
. Direct primary repair augmented with an unyielding cerclage wire
. Reconstruction using a complete fresh-frozen extensor mechanism allograft
. Arthrodesis of the knee
. Revision to a constrained condylar knee (CCK)

Correct Answer & Explanation

. Reconstruction using a complete fresh-frozen extensor mechanism allograft

Explanation

Complete extensor mechanism disruption after a TKA has notoriously poor outcomes when managed with direct repair, even with wire augmentation. The most reliable and accepted salvage procedure, assuming well-fixed implants, is reconstruction with a complete extensor mechanism allograft (or occasionally synthetic mesh).

Question 5663

Topic: 3. Adult Reconstruction (Hip & Knee)

When evaluating radiographs of a cementless femoral stem at 2 years postoperatively, which of the following findings is the most reliable and specific indicator of successful bone ingrowth (osseointegration) according to Engh's criteria?

. A continuous 1 mm radiolucent line around the entire porous-coated region
. Endosteal spot welds adjacent to the porous coating
. Pedestal formation at the distal tip of the stem
. Proximal calcar resorption
. Stem subsidence of 5 mm over the first year

Correct Answer & Explanation

. Endosteal spot welds adjacent to the porous coating

Explanation

According to Engh's criteria, the presence of endosteal spot welds (new bone bridging the gap from the endosteum to the implant's porous coating) is a primary and highly reliable indicator of biological bone ingrowth. Continuous radiolucencies indicate fibrous stable fixation or loosening.

Question 5664

Topic: Total Knee Arthroplasty (TKA)

In the emerging paradigm of Kinematic Alignment (KA) for Total Knee Arthroplasty, what is the primary overarching goal regarding the final positioning of the components?

. To place both components strictly orthogonal (90 degrees) to the mechanical axis of the lower extremity
. To align the components parallel to the surgical transepicondylar axis to balance collateral ligaments
. To restore the patient's exact pre-arthritic native joint lines and individual physiologic kinematics
. To systematically position the tibial cut in exactly 3 degrees of varus and the femur in 5 degrees of valgus
. To perform step-wise collateral ligament releases to achieve perfectly symmetric rectangular flexion and extension gaps

Correct Answer & Explanation

. To restore the patient's exact pre-arthritic native joint lines and individual physiologic kinematics

Explanation

Kinematic Alignment (KA) aims to co-align the axes of the components with the three native kinematic axes of the knee, effectively restoring the patient's unique pre-arthritic joint line, thereby resurfacing the joint without the need for routine ligament releases. This contrasts with Mechanical Alignment (MA) which dictates orthogonal bone cuts.

Question 5665

Topic: Total Hip Arthroplasty (THA)

During a primary THA, accurate acetabular component positioning is critical to prevent dislocation. According to the classic Lewinnek 'safe zone', what are the optimal target angles for acetabular cup inclination (abduction) and anteversion, respectively?

. 30 degrees +/- 10 degrees inclination, 10 degrees +/- 10 degrees anteversion
. 40 degrees +/- 10 degrees inclination, 15 degrees +/- 10 degrees anteversion
. 45 degrees +/- 10 degrees inclination, 25 degrees +/- 10 degrees anteversion
. 50 degrees +/- 10 degrees inclination, 20 degrees +/- 10 degrees anteversion
. 35 degrees +/- 10 degrees inclination, 30 degrees +/- 10 degrees anteversion

Correct Answer & Explanation

. 40 degrees +/- 10 degrees inclination, 15 degrees +/- 10 degrees anteversion

Explanation

Lewinnek established the widely taught historical 'safe zone' for acetabular cup placement as 40 degrees +/- 10 degrees of inclination (abduction) and 15 degrees +/- 10 degrees of anteversion. Cups placed outside these parameters have historically demonstrated a statistically higher rate of dislocation.

Question 5666

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a painful, swollen knee 2 years post-TKA. According to the 2018 International Consensus Meeting (ICM) criteria, which of the following objective findings serves as a 'major criterion' that is independently diagnostic of a chronic periprosthetic joint infection?

. Synovial fluid leukocyte count of 4,000 cells/mcL
. Synovial fluid polymorphonuclear percentage (PMN%) of 85%
. A positive Alpha-defensin immunoassay test
. A single positive culture for a virulent strain of Staphylococcus aureus
. Two positive periprosthetic tissue cultures yielding phenotypically identical organisms

Correct Answer & Explanation

. Two positive periprosthetic tissue cultures yielding phenotypically identical organisms

Explanation

According to the 2018 ICM (and MSIS) criteria, the two major criteria for diagnosing PJI are: 1) Two positive periprosthetic cultures yielding the same phenotypically identical organism, or 2) The presence of a sinus tract communicating directly with the joint. Either is independently diagnostic. Elevated WBC, high PMN%, Alpha-defensin, and a single positive culture act only as minor criteria.

Question 5667

Topic: 3. Adult Reconstruction (Hip & Knee)

During a cruciate-retaining total knee arthroplasty (CR-TKA), the surgeon inserts the trial components and assesses the gaps. The knee is stable and well-balanced at 90 degrees of flexion, but it is tight in full extension, lacking 10 degrees of full extension. What is the most appropriate next step in surgical management?

. Downsize the femoral component
. Resect more proximal tibia
. Resect more distal femur
. Release the posterior cruciate ligament (PCL)
. Increase the posterior slope of the tibial cut

Correct Answer & Explanation

. Resect more distal femur

Explanation

An isolated tight extension gap with a well-balanced flexion gap is managed by addressing the structures that solely affect extension. Resecting more distal femur increases the extension gap without altering the flexion gap. Downsizing the femoral component or releasing the PCL would primarily affect the flexion gap. Resecting more proximal tibia would increase both the flexion and extension gaps symmetrically, making the knee loose in flexion.

Question 5668

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female sustains a periprosthetic femur fracture around her cemented THA stem after a fall. Radiographs show a transverse fracture at the tip of the stem. The stem is radiographically loose. Furthermore, there is massive osteolysis of the proximal femur with an absent calcar and complete loss of the greater trochanteric bone stock. According to the Vancouver classification, what is the grade and the most appropriate management?

. Vancouver B1; Open reduction internal fixation with cables and a locking plate
. Vancouver B2; Revision to a long cementless diaphyseal-engaging stem
. Vancouver B2; Revision with impaction bone grafting and a cemented stem
. Vancouver B3; Proximal femoral replacement (tumor prosthesis)
. Vancouver C; Open reduction internal fixation with strut allografts

Correct Answer & Explanation

. Vancouver B3; Proximal femoral replacement (tumor prosthesis)

Explanation

This is a Vancouver B3 fracture, defined as a fracture around the stem or just below it (B) with a loose implant (2/3) and severely deficient proximal bone stock (3). While B2 fractures (loose stem, good bone stock) are typically treated with a long cementless fluted tapered stem, B3 fractures often require a proximal femoral replacement (tumor prosthesis) or an extensively porous-coated stem if some distal metaphyseal/diaphyseal bone remains reconstructable.

Question 5669

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with an audible and painful 'clunk' when extending her knee from a flexed position. She underwent a posterior-stabilized (PS) total knee arthroplasty 18 months ago. Nonoperative management has failed. What is the primary pathoanatomic cause of her symptoms?

. Patellar maltracking causing lateral facet impingement
. A fibrotic nodule on the deep surface of the quadriceps tendon engaging the intercondylar box
. A loose body impinging in the posterior recess
. Oversizing of the patellar component resulting in overstuffing of the anterior compartment
. Impingement of the popliteus tendon on the lateral femoral condyle

Correct Answer & Explanation

. A fibrotic nodule on the deep surface of the quadriceps tendon engaging the intercondylar box

Explanation

Patellar clunk syndrome is historically associated with PS total knee arthroplasties. It occurs when a fibrous nodule forms on the deep, posterior surface of the quadriceps tendon, just proximal to the superior pole of the patella. As the knee extends from deep flexion, this nodule catches in the superior aspect of the femoral intercondylar box, causing a painful clunk. Treatment is arthroscopic or open excision of the nodule.

Question 5670

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is classically considered an absolute contraindication for a medial unicompartmental knee arthroplasty (UKA)?

. Age greater than 60 years
. Body mass index (BMI) of 32 kg/m2
. Asymptomatic mild patellofemoral osteoarthritis
. Inflammatory arthropathy (e.g., Rheumatoid Arthritis)
. Fixed flexion contracture of 10 degrees

Correct Answer & Explanation

. Inflammatory arthropathy (e.g., Rheumatoid Arthritis)

Explanation

Inflammatory arthropathy (such as rheumatoid arthritis) is considered an absolute contraindication to UKA due to the systemic, pan-articular nature of the disease, which almost universally leads to progression in the unresurfaced compartments. Age, moderate obesity, asymptomatic patellofemoral OA, and minor flexion contractures (<15 degrees) are not absolute contraindications according to modern criteria.

Question 5671

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a non-metal-on-metal (MoM) total hip arthroplasty (titanium stem, cobalt-chromium head, highly cross-linked polyethylene liner) presents 6 years postoperatively with groin pain. Imaging reveals a large periprosthetic fluid collection. Aspiration shows cloudy fluid with a low neutrophil count but high cobalt levels. What combination of implant factors most significantly increases the risk of this complication?

. A small diameter femoral head on a rough-machined trunnion
. A large diameter cobalt-chromium femoral head on a standard titanium trunnion
. A ceramic femoral head on a titanium trunnion
. A cobalt-chromium head coupled with a cobalt-chromium stem
. An un-cemented polished tapered slip (PTS) stem

Correct Answer & Explanation

. A large diameter cobalt-chromium femoral head on a standard titanium trunnion

Explanation

This patient has trunnionosis (mechanically assisted crevice corrosion at the head-neck taper). The use of large-diameter heavy cobalt-chromium (CoCr) heads on standard or thin titanium trunnions increases the lever arm and torque at the taper junction, exacerbating fretting and corrosion. This can lead to an adverse local tissue reaction (ALTR) or pseudotumor despite a metal-on-polyethylene bearing surface.

Question 5672

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty for a severe fixed valgus deformity, the surgeon notes that the knee is perfectly balanced in flexion, but remains excessively tight laterally in full extension. Which of the following structures is the primary restraint to lateral opening in extension and should be the first targeted for release?

. Popliteus tendon
. Posterior cruciate ligament
. Iliotibial (IT) band
. Lateral collateral ligament (LCL)
. Biceps femoris tendon

Correct Answer & Explanation

. Iliotibial (IT) band

Explanation

When correcting a valgus knee, the IT band is tight in extension and relatively lax in flexion. If the knee is tight laterally only in extension, releasing or pie-crusting the IT band will correct the extension gap without affecting the flexion gap. The popliteus is tight in flexion, and the LCL is a primary stabilizer in both flexion and extension.

Question 5673

Topic: 3. Adult Reconstruction (Hip & Knee)

A 28-year-old male is diagnosed with pre-collapse (ARCO Stage II) avascular necrosis of the femoral head. He is scheduled for a free vascularized fibular graft (FVFG). What is the primary vascular pedicle harvested with the fibular graft for this procedure?

. Anterior tibial artery
. Posterior tibial artery
. Peroneal artery
. Sural artery
. Popliteal artery

Correct Answer & Explanation

. Peroneal artery

Explanation

The free vascularized fibular graft (FVFG) relies on the peroneal artery and its venae comitantes as its vascular pedicle. The graft is typically anastomosed to the lateral femoral circumflex artery and its corresponding veins to provide structural support and a new blood supply to the necrotic femoral head.

Question 5674

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with an inability to perform a straight leg raise 3 years after a primary total knee arthroplasty. Imaging and clinical exam confirm a chronic, retracted patellar tendon rupture. Given the high failure rate of primary repair in this setting, what is the most reliable and durable reconstructive option?

. Direct primary repair with cerclage wire augmentation
. Semitendinosus and gracilis autograft reconstruction
. Extensor mechanism allograft with a tibial bone block
. Revision to a rotating hinge knee arthroplasty without extensor repair
. Gastrocnemius rotational flap

Correct Answer & Explanation

. Extensor mechanism allograft with a tibial bone block

Explanation

Chronic extensor mechanism disruption after TKA is a catastrophic complication. Primary repair, even with augmentation, has unacceptably high failure rates in the chronic setting. The gold standard for reconstruction is an extensor mechanism allograft (comprising the tibial tubercle, patellar tendon, patella, and quadriceps tendon), rigidly fixed to the host tibia and tensioned tightly in full extension.

Question 5675

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex revision total knee arthroplasty for a failed aseptic TKA, the surgeon encounters severe, uncontained metaphyseal bone loss (AORI Type 2b defect). The surgeon decides to use highly porous metaphyseal metal cones. What is the correct principle of fixation regarding the interface between the cone, the host bone, and the revision tibial baseplate/stem?

. The cone is press-fit to the host bone and mechanically locked via a Morse taper to the tibial stem
. The cone is cemented to the host bone and cemented to the tibial baseplate/stem
. The cone achieves biologic ingrowth with the host bone and is cemented to the tibial baseplate/stem
. The cone achieves biologic ingrowth with the host bone and requires a cementless stem to lock into place
. The cone requires screw fixation to the host bone and a polyethylene liner for modularity

Correct Answer & Explanation

. The cone achieves biologic ingrowth with the host bone and is cemented to the tibial baseplate/stem

Explanation

Metaphyseal cones (made of highly porous metal like tantalum or 3D-printed titanium) are distinct from metaphyseal sleeves. Cones are implanted independently of the final components and rely on press-fit into the host bone for primary stability and eventual biologic ingrowth. The revision tibial baseplate and stem are then cemented into the center of the cone. In contrast, sleeves are modularly locked to the stem via a taper.

Question 5676

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female undergoes a revision THA for aseptic loosening. Intraoperatively, the surgeon identifies a complete transverse separation between the superior and inferior halves of the acetabulum, with the inferior hemipelvis moving independently of the ilium. Which of the following reconstructive strategies is considered the most reliable modern approach to address this specific defect?

. A hemispherical jumbo cup with multiple screws
. Impaction bone grafting with a cemented polyethylene cup
. A cup-cage construct or custom triflange acetabular component
. A standard porous-coated cup with a bilobed structural allograft
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. A cup-cage construct or custom triflange acetabular component

Explanation

The clinical description is pathognomonic for a pelvic discontinuity. In the setting of a chronic pelvic discontinuity, bridging the defect and providing rigid stability between the superior and inferior halves of the pelvis is required. Modern, reliable treatments utilize highly porous metal, such as a cup-cage construct or a custom 3D-printed triflange implant, which stabilizes the discontinuity and allows for bone ingrowth.

Question 5677

Topic: 3. Adult Reconstruction (Hip & Knee)
A 66-year-old male presents with a painful total knee arthroplasty 4 years postoperatively. Blood work shows an ESR of 35 mm/hr and CRP of 18 mg/L. Aspiration yields 2,500 WBC/μL with 65% neutrophils. To definitively support a diagnosis of periprosthetic joint infection (PJI), the synovial fluid is sent for biomarker analysis. Which of the following synovial biomarkers is highly specific for PJI and acts by disrupting bacterial cell membranes?
. Interleukin-6 (IL-6)
. Procalcitonin
. Alpha-defensin
. C-reactive protein (CRP)
. Leukocyte esterase

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to infection. It works by inserting into and disrupting bacterial cell membranes. It has been shown to be highly sensitive and specific for the diagnosis of PJI, performing well even in cases where traditional inflammatory markers or cell counts are borderline. It is recognized as a major criterion in the MSIS/ICM definition of PJI.

Question 5678

Topic: 3. Adult Reconstruction (Hip & Knee)
Adverse local tissue reaction (ALTR) or Aseptic Lymphocytic Vasculitis Associated Lesions (ALVAL) is a known complication of metal-on-metal hip arthroplasty. Histologically, this phenomenon is characterized by an extensive perivascular lymphocytic infiltrate. What is the underlying immunological mechanism of this specific reaction?
. Type I IgE-mediated hypersensitivity
. Type II cytotoxic hypersensitivity
. Type III immune complex-mediated hypersensitivity
. Type IV delayed-type T-cell mediated hypersensitivity
. Innate macrophage-mediated foreign body reaction

Correct Answer & Explanation

. Type IV delayed-type T-cell mediated hypersensitivity

Explanation

ALVAL (Aseptic Lymphocytic Vasculitis Associated Lesions) is widely accepted to be a Type IV delayed-type hypersensitivity reaction to metal ions (specifically cobalt and chromium). It is mediated by T-lymphocytes, leading to the characteristic perivascular lymphocytic infiltrate seen on histology. This is distinct from the macrophage-dominated foreign body reaction seen in particulate polyethylene wear (osteolysis).

Question 5679

Topic: 3. Adult Reconstruction (Hip & Knee)

A 74-year-old female presents for revision of a failed total hip arthroplasty. Preoperative radiographs and intraoperative findings demonstrate severe acetabular bone loss with a transverse defect separating the superior and inferior hemipelvis, indicating independent movement of the lower half of the pelvis. According to the Paprosky classification, this is a Type 3B defect with pelvic discontinuity. What is the most reliable reconstructive option to achieve stable fixation in this scenario?

. Standard hemispherical jumbo cup with multiple screws
. Impaction bone grafting with a cemented polyethylene cup
. Cup-cage construct or custom triflange acetabular component
. High hip center reconstruction using a standard porous-coated cup
. Bipolar hemiarthroplasty

Correct Answer & Explanation

. Cup-cage construct or custom triflange acetabular component

Explanation

Pelvic discontinuity requires stabilization of the superior and inferior halves of the pelvis while providing a stable socket for the femoral head. A cup-cage construct, custom triflange acetabular component, or distraction with a highly porous metal cup are the most reliable methods to span the discontinuity and achieve rigid fixation. Jumbo cups and high hip centers do not inherently stabilize the discontinuity, leading to high failure rates.

Question 5680

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary posterior-stabilized total knee arthroplasty, the trial reduction reveals that the knee is symmetric and well-balanced in full extension, but the medial and lateral compartments are both excessively tight in 90 degrees of flexion. Which of the following adjustments is the most appropriate next step?

. Resect an additional 2 mm of the distal femur
. Downsize the femoral component using an anterior referencing system
. Increase the posterior slope of the tibial cut
. Release the posterior capsule
. Upsize the femoral component using a posterior referencing system

Correct Answer & Explanation

. Downsize the femoral component using an anterior referencing system

Explanation

A knee that is tight in flexion but balanced in extension has a tight flexion gap. Resecting more distal femur or releasing the posterior capsule affects the extension gap. Increasing the tibial slope increases the flexion gap but alters tibial bone stock and kinematics. Downsizing the femoral component using an anterior referencing system reduces the AP dimension of the femur (thinner posterior condyles), thereby increasing the flexion gap without altering the extension gap.

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