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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 183 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 3641

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old man is evaluated for a painful total hip arthroplasty placed 4 years ago. Inflammatory markers show an ESR of 45 mm/hr and a CRP of 22 mg/L. Joint aspiration yields synovial fluid with a white blood cell (WBC) count of 4,500 cells/µL and 85% polymorphonuclear neutrophils (PMNs). An alpha-defensin test is positive. According to the MSIS criteria, what is the most appropriate next step in management?

. One-stage exchange arthroplasty
. Two-stage exchange arthroplasty
. Suppressive antibiotic therapy
. Observation and repeat aspiration in 3 months
. Debridement, antibiotics, and implant retention (DAIR)

Correct Answer & Explanation

. Two-stage exchange arthroplasty

Explanation

The patient meets the criteria for a chronic periprosthetic joint infection (PJI), demonstrated by elevated inflammatory markers, positive alpha-defensin, and synovial WBC >3000 cells/µL with >80% PMNs. For a chronic PJI (diagnosed years after index surgery), the gold standard treatment in North America is a two-stage exchange arthroplasty. DAIR is contraindicated because the biofilm is fully mature.

Question 3642

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man presents with isolated medial compartment osteoarthritis of the knee and is considering a medial unicompartmental knee arthroplasty (UKA). Which of the following is considered an absolute contraindication to performing a medial UKA?

. Anterior cruciate ligament (ACL) deficiency
. Body mass index (BMI) of 32 kg/m2
. 10 degrees of fixed varus deformity correctable on stress views
. Age less than 60 years
. Inflammatory arthropathy

Correct Answer & Explanation

. Inflammatory arthropathy

Explanation

Absolute contraindications to unicompartmental knee arthroplasty (UKA) include inflammatory arthropathy (such as rheumatoid arthritis), as the disease process inherently involves the entire joint. ACL deficiency was traditionally a strict contraindication but is now considered relative. Age, moderate obesity, and correctable varus deformities up to 15 degrees are acceptable indications.

Question 3643

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman presents with worsening groin pain and swelling 5 years after a primary THA utilizing a dual-mobility construct with a cobalt-chromium (CoCr) modular neck and titanium stem. MRI with metal artifact reduction sequence (MARS) demonstrates a thick-walled cystic mass communicating with the joint space. Laboratory evaluation shows highly elevated serum cobalt levels with normal chromium. What is the primary mechanism of implant failure in this patient?

. Polyethylene wear leading to osteolysis
. Galvanic corrosion at the bearing surface
. Mechanically assisted crevice corrosion at the modular junction
. Impingement causing edge loading
. Delayed hypersensitivity to titanium

Correct Answer & Explanation

. Mechanically assisted crevice corrosion at the modular junction

Explanation

The scenario describes trunnionosis or mechanically assisted crevice corrosion (MACC) at the modular neck-stem junction, leading to an adverse local tissue reaction (ALTR) or pseudotumor. This is particularly noted in mixed-metal modular junctions (e.g., CoCr neck on Ti stem). The elevated serum cobalt levels further isolate MACC of the CoCr component as the source.

Question 3644

Topic: Total Hip Arthroplasty (THA)

An 80-year-old woman falls and sustains a periprosthetic femur fracture 10 years after a cemented THA. Radiographs show a transverse fracture around the tip of the stem. The stem demonstrates significant subsidence, and the cement mantle is fractured, but the proximal femoral bone stock remains robust. What is the most appropriate surgical management?

. Open reduction and internal fixation (ORIF) with a lateral locking plate and cables
. Revision THA to a standard length cemented stem
. Cortical strut allograft alone
. Revision THA to a long, fully porous-coated or fluted tapered diaphyseal-engaging stem
. Distal femoral replacement

Correct Answer & Explanation

. Revision THA to a long, fully porous-coated or fluted tapered diaphyseal-engaging stem

Explanation

The patient has a Vancouver B2 periprosthetic fracture, which is defined as a fracture around or just below the stem, with a loose implant, but with adequate remaining bone stock. The standard of care for a Vancouver B2 fracture is revision of the loose stem to a bypass stem (such as a long, extensively porous-coated or modular fluted tapered stem) that bypasses the fracture site by at least 2 cortical diameters.

Question 3645

Topic: 3. Adult Reconstruction (Hip & Knee)

A 59-year-old woman is scheduled for a TKA. During her preoperative evaluation, she reports a severe allergic blistering reaction to cheap jewelry. Skin patch testing is positive for nickel. Which of the following femoral component materials is most appropriate for this patient to minimize the risk of a hypersensitivity reaction while maintaining optimal biomechanical wear?

. Standard Cast Cobalt-Chromium
. Oxidized Zirconium
. Standard Titanium alloy
. Stainless Steel
. Uncemented Tantalum

Correct Answer & Explanation

. Oxidized Zirconium

Explanation

Patients with severe metal hypersensitivity, particularly to nickel, are at risk for complications if standard cobalt-chromium (CoCr) implants are used, as CoCr contains trace amounts of nickel. Oxidized zirconium (Oxinium) lacks nickel and is the preferred alternative bearing surface for the femoral component in TKA for patients with metal hypersensitivity. Titanium is an option but has inferior wear characteristics when articulating against polyethylene.

Question 3646

Topic: Total Knee Arthroplasty (TKA)

A 78-year-old man presents with knee pain and swelling 15 years after a primary TKA. Radiographs show significant eccentric wear of the polyethylene bearing. Intraoperatively, the polyethylene insert exhibits large flakes of material separated from the articular surface. Which wear mechanism is primarily responsible for this appearance?

. Abrasive wear
. Delamination wear
. Adhesive wear
. Third-body wear
. Burnishing

Correct Answer & Explanation

. Delamination wear

Explanation

Delamination wear is characterized by large flakes of polyethylene separating from the articular surface. This is caused by subsurface fatigue due to cyclic loading and is historically associated with oxidation of the polyethylene (often seen in legacy gamma-irradiated-in-air polyethylene components). Abrasive wear involves scratching, while adhesive wear involves microscopic transfer of polyethylene to the metal surface.

Question 3647

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with end-stage medial compartment osteoarthritis of the knee is scheduled for a total knee arthroplasty (TKA). He underwent a closing wedge high tibial osteotomy (HTO) 15 years ago. Which of the following is the most likely anatomic challenge encountered during this TKA as a consequence of the prior HTO?

. Patella alta
. Patella baja
. Excessive valgus deformity
. Medial collateral ligament laxity
. Posterior cruciate ligament contracture

Correct Answer & Explanation

. Patella baja

Explanation

Closing or opening wedge high tibial osteotomies often lead to secondary patella baja. This occurs either due to relative elevation of the joint line (in opening wedge) or scarring and contracture of the patellar tendon. This can make eversion of the patella and exposure during subsequent TKA extremely difficult, often requiring a more extensive surgical approach such as a tibial tubercle osteotomy.

Question 3648

Topic: Total Hip Arthroplasty (THA)

A 55-year-old woman undergoes a cementless total hip arthroplasty (THA) with a ceramic-on-ceramic bearing. One year postoperatively, she complains of an audible 'squeaking' sound with walking, though she is otherwise pain-free. Which of the following factors is most strongly associated with the development of squeaking in ceramic-on-ceramic THA?

. Undersized femoral stem
. Decreased femoral offset
. Acetabular component retroversion
. Acetabular component anteversion > 20 degrees
. Use of a 28 mm femoral head

Correct Answer & Explanation

. Acetabular component retroversion

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, microseparation, and component impingement. Acetabular component malposition, specifically retroversion or excessive inclination, leads to edge loading and the loss of fluid film lubrication, which produces the characteristic squeaking phenomenon. Neck-socket impingement can also cause squeaking by transferring metal onto the ceramic head.

Question 3649

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old man presents with a painful total hip arthroplasty 4 years after the index procedure. His ESR is 45 mm/hr and CRP is 2.5 mg/dL. A hip aspiration yields synovial fluid with a white blood cell count of 3,500 cells/µL and 85% neutrophils. Alpha-defensin testing is positive. According to the 2018 International Consensus Meeting (ICM) criteria, what is the next best step in management?

. Oral antibiotics for 6 weeks
. One-stage revision arthroplasty
. Two-stage revision arthroplasty
. Debridement, antibiotics, and implant retention (DAIR)
. Repeat aspiration in 6 weeks

Correct Answer & Explanation

. Two-stage revision arthroplasty

Explanation

The patient has a definitive chronic periprosthetic joint infection (PJI) based on elevated inflammatory markers, synovial WBC > 3,000 cells/µL, PMN > 80%, and a positive alpha-defensin test. For chronic PJI (symptoms > 3 weeks or occurring > 4 weeks postoperatively), a two-stage revision arthroplasty remains the gold standard in North America to completely eradicate the infection. DAIR is strictly indicated only for acute infections with well-fixed implants.

Question 3650

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female undergoes a right total knee arthroplasty. During the trial reduction, the patella tracks laterally and tends to dislocate with deep flexion. The surgeon suspects component malrotation. Which of the following combinations of component positioning would most likely cause this patellar maltracking?

. Internal rotation of the femoral component and internal rotation of the tibial component
. Internal rotation of the femoral component and external rotation of the tibial component
. External rotation of the femoral component and internal rotation of the tibial component
. External rotation of the femoral component and external rotation of the tibial component
. Excessive valgus alignment of the tibial component

Correct Answer & Explanation

. Internal rotation of the femoral component and internal rotation of the tibial component

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, exacerbating lateral patellar tracking. Internal rotation of the femoral component mediatizes the trochlear groove, while internal rotation of the tibial component lateralizes the tibial tubercle relative to the trochlea. Therefore, combined internal rotation of both components synergistically worsens lateral patellar subluxation.

Question 3651

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male presents with persistent groin pain two years after a primary metal-on-polyethylene total hip arthroplasty. Radiographs show a well-fixed cementless stem and cup. Serum cobalt levels are markedly elevated, while serum chromium levels are within normal limits. Which of the following is the most likely underlying cause of his symptoms and laboratory findings?

. Polyethylene wear
. Trunnionosis
. Acetabular loosening
. Impingement of the neck on the acetabular rim
. Intra-articular third-body wear

Correct Answer & Explanation

. Trunnionosis

Explanation

An isolated marked elevation of serum cobalt with normal or only slightly elevated chromium in a patient with a metal-on-polyethylene THA strongly suggests mechanically assisted crevice corrosion (MACC) at the head-neck junction, commonly referred to as trunnionosis. This corrosion primarily releases cobalt ions from the cobalt-chromium femoral head where it interacts with the titanium stem taper.

Question 3652

Topic: 3. Adult Reconstruction (Hip & Knee)

When evaluating a patient for unicompartmental knee arthroplasty (UKA), which of the following is generally considered an acceptable indication rather than a contraindication?

. Asymptomatic patellofemoral chondromalacia
. Absent anterior cruciate ligament (ACL)
. Inflammatory arthritis (e.g., Rheumatoid Arthritis)
. Fixed varus deformity of 20 degrees
. Fixed flexion contracture of 25 degrees

Correct Answer & Explanation

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

Explanation

Modern criteria for medial unicompartmental knee arthroplasty (UKA) permit the procedure in the presence of asymptomatic, incidental patellofemoral chondromalacia or cartilage wear. Classic contraindications include inflammatory arthritis, an absent or incompetent ACL (which causes abnormal kinematics and early failure), fixed varus or valgus deformities that are not passively correctable, and flexion contractures greater than 15 degrees.

Question 3653

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female undergoes total knee arthroplasty utilizing a posterior stabilized (PS) implant. During trial range of motion, the surgeon notes that the tibial post impinges on the anterior aspect of the femoral cam/box when the knee is brought into full extension. What is the most appropriate intraoperative step to correct this?

. Upsize the femoral component
. Downsize the femoral component
. Increase the posterior slope of the tibial cut
. Decrease the posterior slope of the tibial cut
. Recut the distal femur to add more valgus

Correct Answer & Explanation

. Decrease the posterior slope of the tibial cut

Explanation

Anterior impingement of the tibial post on the femoral box or cam in full extension with a posterior stabilized TKA is typically caused by excessive posterior tibial slope. Excessive slope effectively pitches the tibial post forward relative to the femur when the knee extends. Decreasing the posterior slope of the tibial cut or using an insert that corrects this will resolve the impingement.

Question 3654

Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old woman is evaluated for a painful total hip arthroplasty. Radiographs demonstrate massive osteolysis around the acetabular component with 4 cm of superior migration. During revision surgery, a large cavitary and segmental bone defect is noted in the superior acetabulum with intact Kohler's line (Paprosky Type IIIA). Which of the following reconstruction methods is most appropriate to achieve durable, long-term fixation?
. Cemented all-polyethylene cup
. Jumbo uncemented hemispherical cup with screws
. Porous metal cup with structural augments and multi-hole screw fixation
. Anti-protrusio cage with a cemented cup
. Bipolar hemiarthroplasty

Correct Answer & Explanation

. Porous metal cup with structural augments and multi-hole screw fixation

Explanation

Paprosky IIIA defects involve >30% bone loss with significant superior migration of the hip center (>3 cm) while Kohler's line remains intact. These severe defects are best managed with highly porous metal components and structural trabecular metal augments. This construct provides excellent immediate mechanical stability and the potential for long-term biologic fixation (osteointegration), which has proven superior to traditional anti-protrusio cages that rely purely on mechanical fixation.

Question 3655

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old patient presents 6 weeks after a primary total knee arthroplasty with complaints of stiffness. Her range of motion is 15 degrees to 75 degrees. Radiographs demonstrate that the prosthetic joint line is elevated by 8 mm compared to her preoperative films. Which of the following intraoperative technical errors is the most likely cause of this elevated joint line?

. Over-resection of the distal femur and under-resection of the proximal tibia
. Under-resection of the distal femur and over-resection of the proximal tibia
. Excessive external rotation of the femoral component
. Undersizing the femoral component in the anteroposterior dimension
. Oversizing the femoral component in the anteroposterior dimension

Correct Answer & Explanation

. Over-resection of the distal femur and under-resection of the proximal tibia

Explanation

Joint line elevation in TKA commonly occurs when the surgeon over-resects the distal femur. This widens the extension gap. To achieve stability in extension, the surgeon is then forced to use a thicker polyethylene insert. The combination of a resected distal femur and a thicker poly insert pushes the entire tibiofemoral articulation proximally, elevating the joint line. Under-resecting the proximal tibia further contributes to joint line elevation by failing to lower the base upon which the thick insert sits.

Question 3656

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active man underwent a cementless total hip arthroplasty with a ceramic-on-ceramic bearing 3 years ago. He presents complaining of a new squeaking noise emanating from his hip during activities such as bending to tie his shoes or climbing stairs. He denies pain, feelings of instability, or constitutional symptoms. Radiographs show well-fixed components with no evidence of osteolysis. What is the most likely biomechanical cause of the squeaking in this patient?

. Aseptic loosening of the acetabular component
. Impingement and edge loading of the ceramic bearing
. Micro-fracture of the ceramic liner
. Third-body wear from retained cement debris
. Fretting and corrosion at the trunnion (trunnionosis)

Correct Answer & Explanation

. Impingement and edge loading of the ceramic bearing

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is a well-documented phenomenon. It is most strongly associated with edge loading of the bearing surfaces, which typically occurs due to suboptimal positioning of the acetabular component (such as excessive inclination or abnormal version) or due to component impingement. This leads to a loss of fluid film lubrication and high friction, producing the characteristic squeak. Since the patient is asymptomatic and radiographs show well-fixed components, aseptic loosening or catastrophic failure (fracture) are unlikely.

Question 3657

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, a surgeon utilizes trial components to assess the gap kinematics. With the trials in place, the knee is well-balanced and symmetric in extension. However, the knee is symmetrically tight in 90 degrees of flexion, limiting the range of motion and preventing full flexion. Which of the following intraoperative maneuvers is the most appropriate next step to balance the knee?

. Release the posterior capsule
. Resect more distal femur
. Downsize the femoral component using a posterior referencing guide
. Increase the posterior slope of the tibial cut
. Resect an additional 2 mm from the proximal tibia

Correct Answer & Explanation

. Increase the posterior slope of the tibial cut

Explanation

The clinical scenario describes a knee that is balanced in extension but tight in flexion (tight flexion gap, normal extension gap). To address a tight flexion gap without altering the extension gap, the surgeon must remove more bone from areas that articulate exclusively in flexion. Increasing the posterior slope of the tibial cut lowers the posterior tibia, effectively increasing the flexion gap while minimally affecting the extension gap. Alternatively, downsizing the femoral component using an anterior referencing system (which increases the posterior femoral resection) would also work, but posterior referencing preserves the posterior cut and would not increase the flexion gap. Releasing the posterior capsule or resecting more distal femur would alter the extension gap. Resecting more proximal tibia would equally enlarge both the flexion and extension gaps.

Question 3658

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman presents with persistent right hip pain 2 years after a primary total hip arthroplasty. Her erythrocyte sedimentation rate (ESR) is 45 mm/hr and C-reactive protein (CRP) is 2.5 mg/dL. Aspiration of the hip yields synovial fluid with a white blood cell (WBC) count of 3,500 cells/uL and 75% polymorphonuclear leukocytes (PMNs). According to recent guidelines, which of the following synovial fluid biomarkers provides the highest specificity for confirming the diagnosis of a periprosthetic joint infection (PJI)?

. Interleukin-6 (IL-6)
. Alpha-defensin
. Leukocyte esterase
. Synovial fluid C-reactive protein (CRP)
. Procalcitonin

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to infection. It has been extensively studied and validated as a highly specific and sensitive biomarker for periprosthetic joint infection (PJI). While leukocyte esterase is a useful and inexpensive point-of-care test, alpha-defensin (measured via laboratory immunoassay) demonstrates superior specificity and is incorporated into the 2018 International Consensus Meeting (ICM) criteria as a major definitive marker for PJI.

Question 3659

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old woman presents 8 months after a primary posterior-stabilized total knee arthroplasty with a complaint of a painful 'catching' or 'popping' sensation in her knee. This reliably occurs as she extends her knee from a flexed position, specifically around 30 to 45 degrees of flexion. Physical examination reveals a palpable clunk during active extension. Radiographs show well-positioned components without loosening. What is the most appropriate definitive management for this condition?

. Revision of the patellar component with a thicker button
. Revision to a constrained non-modular (hinge) prosthesis
. Arthroscopic or open debridement of the retropatellar fibrous nodule
. Botulinum toxin injection into the quadriceps tendon
. Manipulation under anesthesia to break intra-articular adhesions

Correct Answer & Explanation

. Arthroscopic or open debridement of the retropatellar fibrous nodule

Explanation

The patient is describing patellar clunk syndrome, a recognized complication following posterior-stabilized total knee arthroplasty. It is caused by the formation of a fibrous nodule at the superior pole of the patella. As the knee extends from deep flexion, this nodule catches in the intercondylar box of the femoral component, popping out with a palpable and painful 'clunk' at approximately 30-45 degrees of flexion. The definitive and most effective treatment is excision of the fibrotic nodule, which can be performed arthroscopically or open.

Question 3660

Topic: Total Hip Arthroplasty (THA)

During a primary total hip arthroplasty, the surgeon opts to use a high-offset femoral stem, effectively increasing the femoral offset by 10 mm compared to the patient's native anatomy, while maintaining equal leg lengths. What is the primary biomechanical effect of this increase in femoral offset?

. Increased joint reaction force across the hip
. Decreased tension on the abductor musculature
. Increased risk of bony impingement between the greater trochanter and ilium
. Increased tension on the abductor musculature
. Decreased global range of motion of the hip

Correct Answer & Explanation

. Increased tension on the abductor musculature

Explanation

Femoral offset is the horizontal distance from the center of rotation of the femoral head to the anatomical axis of the femur. Increasing the femoral offset increases the lever arm of the abductor mechanism. This restores or increases tension on the abductor musculature, which improves their mechanical advantage. As a result, less abductor muscle force is required to maintain a level pelvis during single-leg stance, which paradoxically decreases the overall joint reaction force across the hip joint. It also moves the femur laterally, reducing the risk of bony impingement and improving the range of motion.

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