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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 94 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 1861

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man presents with a painful right total hip arthroplasty 5 years after surgery. He has a metal-on-polyethylene bearing surface with a 36-mm cobalt-chromium femoral head. Radiographs show a well-fixed stem and cup with no osteolysis. Aspiration reveals fluid with a low white blood cell count. Serum metal ion testing demonstrates significantly elevated cobalt levels with normal chromium levels. What is the most likely diagnosis?

. Adverse local tissue reaction secondary to edge loading
. Periprosthetic joint infection
. Trunnionosis at the head-neck junction
. Polyethylene wear debris disease
. Galvanic corrosion at the modular neck-body junction of a titanium stem

Correct Answer & Explanation

. Trunnionosis at the head-neck junction

Explanation

Elevated cobalt out of proportion to chromium in the setting of a metal-on-polyethylene total hip arthroplasty is classic for mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction. This risk is increased with the use of larger cobalt-chromium heads on titanium stems. Metal-on-metal bearings or edge loading typically present with elevated levels of both cobalt and chromium.

Question 1862

Topic: 3. Adult Reconstruction (Hip & Knee)

When selecting a cementless femoral component for a primary total hip arthroplasty in a patient with Dorr Type A bone, a surgeon chooses a proximally porous-coated, flat tapered wedge stem over a fully porous-coated cylindrical stem. What is the primary biomechanical advantage of the chosen stem in this patient?

. Increased distal fixation and immediate stability
. Decreased risk of periprosthetic fracture during insertion
. Prevention of proximal femoral stress shielding
. Enhanced rotational stability in the diaphyseal bone
. Complete filling of the femoral diaphysis

Correct Answer & Explanation

. Prevention of proximal femoral stress shielding

Explanation

Proximally porous-coated, flat tapered wedge stems achieve proximal fixation, transferring stress proximally to the metaphysis. This minimizes stress shielding and subsequent proximal femoral osteolysis, which is a significant problem with fully porous-coated, diaphyseal-engaging cylindrical stems that bypass the proximal femur and transfer load distally.

Question 1863

Topic: 3. Adult Reconstruction (Hip & Knee)

A 67-year-old man presents with a painful total knee arthroplasty 2 years after his index procedure. Aspiration of the knee yields synovial fluid with a white blood cell count of 2,800 cells/uL (60% neutrophils). Given the equivocal cell count, synovial fluid alpha-defensin testing is ordered and returns positive. What is the physiologic origin of the alpha-defensin molecule in the setting of periprosthetic joint infection?

. Secreted by activated osteoblasts in response to bacterial biofilm
. Released by synovial fibroblasts during matrix degradation
. Produced and released by neutrophils as an antimicrobial peptide
. Synthesized by macrophages during phagocytosis of metal debris
. An exotoxin released directly by Staphylococcus aureus

Correct Answer & Explanation

. Produced and released by neutrophils as an antimicrobial peptide

Explanation

Alpha-defensin is an antimicrobial peptide stored in the azurophilic granules of neutrophils. In the presence of a pathogen, neutrophils migrate to the joint space and release alpha-defensin. It is an excellent biomarker for periprosthetic joint infection (PJI) with high sensitivity and specificity, as it reflects the host's direct immune response to infection.

Question 1864

Topic: 3. Adult Reconstruction (Hip & Knee)

In modern total hip arthroplasty, what is the primary biomechanical rationale for doping highly cross-linked polyethylene (HXLPE) with Vitamin E (alpha-tocopherol) instead of utilizing a traditional post-irradiation remelting process?

. To increase polyethylene wettability and joint lubrication
. To eliminate free radicals without sacrificing mechanical yield strength
. To promote osseointegration of the acetabular shell
. To decrease the incidence of ceramic-on-polyethylene squeaking
. To allow for thinner polyethylene liners by increasing their elasticity

Correct Answer & Explanation

. To eliminate free radicals without sacrificing mechanical yield strength

Explanation

Remelting highly cross-linked polyethylene eliminates free radicals but reduces fatigue and yield strength. Vitamin E doping acts as an antioxidant to scavenge free radicals, preserving the mechanical properties and fatigue resistance of the polyethylene.

Question 1865

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with a painful catching sensation in her knee 8 months after a posterior-stabilized total knee arthroplasty. The catch occurs as the knee actively extends from approximately 40 degrees of flexion. What is the most likely etiology?

. An oversized femoral component in the AP plane
. A fibrous nodule at the superior pole of the patella catching in the intercondylar notch
. Asymmetric polyethylene wear causing medial compartment subsidence
. Patellar maltracking due to an internally rotated tibial component
. Aseptic loosening of the tibial baseplate

Correct Answer & Explanation

. A fibrous nodule at the superior pole of the patella catching in the intercondylar notch

Explanation

This presentation is classic for patellar clunk syndrome, typically seen in posterior-stabilized TKA. It is caused by a fibrous nodule forming at the superior pole of the patella that engages the femoral intercondylar box during flexion and "clunks" out during active extension.

Question 1866

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female with a primary total hip arthroplasty suffers recurrent posterior dislocations. Radiographs reveal an acetabular cup with 10 degrees of anteversion and 35 degrees of abduction. The femoral component has 5 degrees of retroversion. What is the most appropriate definitive management?

. Prescribe an abduction brace for 12 weeks
. Exchange the polyethylene liner to a constrained liner
. Revise the femoral component to increase anteversion
. Revise the acetabular component to increase abduction
. Perform a greater trochanteric advancement

Correct Answer & Explanation

. Revise the femoral component to increase anteversion

Explanation

The patient has recurrent posterior instability driven by a severely retroverted femoral component. The most appropriate corrective surgery addresses the primary anatomic mechanical flaw, which is revising the femoral stem to restore normal anteversion (typically 10-15 degrees).

Question 1867

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male with an 8-year-old metal-on-metal THA presents with new groin pain. The implants are well-fixed, but serum cobalt/chromium levels are highly elevated. MRI shows a large periarticular cystic mass. What is the most likely histologic finding of the mass?

. Extensive neutrophil infiltration with intra-cellular bacteria
. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Massive sheets of polyethylene-laden macrophages
. Granulomatous inflammation with caseating necrosis
. Dense fibrous tissue with widespread osteoclast activation

Correct Answer & Explanation

. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-metal arthroplasty are typically characterized histologically by an Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesion (ALVAL), representing a delayed type IV hypersensitivity response to metal ions.

Question 1868

Topic: 3. Adult Reconstruction (Hip & Knee)

In total knee arthroplasty, the application of a true kinematic alignment philosophy primarily dictates that the femoral and tibial components are placed to restore which of the following?

. A neutral mechanical axis perpendicular to the floor
. The pre-arthritic native joint lines and individual patient anatomy
. The transepicondylar axis to exactly 3 degrees of external rotation
. A valgus mechanical axis of strictly 5 degrees
. The joint line strictly perpendicular to the mechanical axis of the tibia

Correct Answer & Explanation

. The pre-arthritic native joint lines and individual patient anatomy

Explanation

Kinematic alignment aims to co-align the axes of the prosthetic components with the native kinematic axes of the knee, recreating the patient's specific pre-arthritic joint line and constitutional alignment, rather than enforcing a strict neutral mechanical axis.

Question 1869

Topic: Total Hip Arthroplasty (THA)

When comparing the direct anterior approach (DAA) to the posterior approach for primary total hip arthroplasty, which of the following complications has a definitively higher incidence in the DAA cohort based on recent large registry and meta-analysis data?

. Postoperative hip dislocation
. Sciatic nerve palsy
. Lateral femoral cutaneous nerve neurapraxia
. Deep vein thrombosis
. Symptomatic leg length discrepancy

Correct Answer & Explanation

. Lateral femoral cutaneous nerve neurapraxia

Explanation

The direct anterior approach (DAA) utilizes the internervous plane between the tensor fasciae latae and sartorius. Due to its anatomic proximity in the superficial dissection, the lateral femoral cutaneous nerve is at a significantly higher risk of injury or neurapraxia compared to the posterior approach.

Question 1870

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with recurrent posterior dislocations of her total hip arthroplasty (THA). Radiographic and CT evaluation reveal a well-fixed, ingrown cementless femoral stem with 15 degrees of anteversion, and a well-fixed cementless acetabular component positioned in 10 degrees of retroversion and 45 degrees of abduction. The patient has good remaining bone stock. What is the most appropriate surgical intervention?

. Exchange of the femoral head to a larger diameter head and application of a constrained liner
. Revision of the femoral stem to a modular component to increase anteversion to 30 degrees
. Revision of the acetabular component to increase anteversion to approximately 15-20 degrees
. Conversion to a dual-mobility articulation without altering component positions
. Closed reduction with prolonged spica casting

Correct Answer & Explanation

. Revision of the acetabular component to increase anteversion to approximately 15-20 degrees

Explanation

The patient has a retroverted acetabular component (10 degrees of retroversion), which is a classic cause of posterior instability following THA. Native anatomy and typical THA targets aim for 15-20 degrees of cup anteversion. While constrained liners or dual-mobility cups are tools for instability, addressing the primary underlying malposition of the implant (the retroverted cup) via acetabular revision is the gold standard for long-term stability and prevention of impingement.

Question 1871

Topic: Total Hip Arthroplasty (THA)

During the posterior approach to the hip (Kocher-Langenbeck), preservation of the blood supply to the femoral head is a critical consideration if the femoral head is to be retained. The deep branch of the medial femoral circumflex artery (MFCA) is protected primarily by which of the following intact structures?

. Piriformis tendon
. Obturator internus tendon
. Obturator externus tendon
. Quadratus femoris muscle
. Superior gemellus muscle

Correct Answer & Explanation

. Obturator internus tendon

Explanation

Anatomical studies by Gautier et al. demonstrated that the deep branch of the medial femoral circumflex artery (MFCA) runs posterior to the obturator externus tendon. Preserving the obturator externus during surgical dislocation or a posterior approach provides a protective barrier for the MFCA, which supplies the majority of blood to the femoral head.

Question 1872

Topic: 3. Adult Reconstruction (Hip & Knee)
According to the 2018 International Consensus Meeting (ICM) / Musculoskeletal Infection Society (MSIS) criteria for diagnosing periprosthetic joint infection (PJI), which of the following findings is considered a 'major' (absolute) criterion that essentially confirms a PJI?
. A single positive tissue culture with a virulent organism like Staphylococcus aureus
. Two positive periprosthetic cultures yielding phenotypically identical organisms
. Synovial fluid white blood cell (WBC) count > 3,000 cells/μL
. Elevated serum C-reactive protein (CRP) > 10 mg/L and D-dimer > 860 ng/mL
. Purulence in the joint observed during the surgical approach

Correct Answer & Explanation

. Two positive periprosthetic cultures yielding phenotypically identical organisms

Explanation

Under the widely accepted ICM/MSIS criteria, the presence of two 'major' criteria can independently definitively diagnose a PJI: (1) a sinus tract communicating with the prosthesis, or (2) two positive periprosthetic cultures with phenotypically identical organisms. Purulence, elevated ESR/CRP, elevated synovial WBC, and a single positive culture are considered 'minor' criteria, requiring a cumulative score to confirm the diagnosis.

Question 1873

Topic: 3. Adult Reconstruction (Hip & Knee)

A 79-year-old female sustains a fall and presents with a periprosthetic fracture of the femur around a cemented total hip arthroplasty implanted 10 years ago. Radiographs show a transverse fracture at the tip of the stem. The cement mantle is extensively fractured, and the stem is frankly loose. However, cortical thickness in the proximal femur remains robust. According to the Vancouver classification, what is the fracture type and the most appropriate standard surgical management?

. Vancouver B1; Open reduction and internal fixation with locking plate and cables
. Vancouver B2; Revision to a long cementless, extensively porous-coated or fluted tapered stem bypassing the fracture
. Vancouver B3; Revision with a proximal femoral replacement (megaprosthesis)
. Vancouver C; Open reduction and internal fixation utilizing cortical allograft struts
. Vancouver A; Conservative management with protected weight-bearing

Correct Answer & Explanation

. Vancouver B2; Revision to a long cementless, extensively porous-coated or fluted tapered stem bypassing the fracture

Explanation

The Vancouver classification for periprosthetic femur fractures defines a B2 fracture as being around or just below the stem tip with a loose implant, but with adequate remaining proximal bone stock. The standard of care for a Vancouver B2 fracture is revision arthroplasty using a long-stemmed prosthesis (often an extensively porous-coated or fluted tapered diaphyseal-engaging stem) that bypasses the fracture site by at least two cortical diameters to achieve stability. B1 is a stable stem (managed with ORIF), and B3 implies a loose stem with poor bone stock (often needing a proximal femoral replacement or allograft-prosthetic composite).

Question 1874

Topic: 3. Adult Reconstruction (Hip & Knee)

Which patient or implant factor is most strongly associated with the complication of squeaking following a ceramic-on-ceramic (CoC) total hip arthroplasty?

. High body mass index (BMI)
. Malpositioned acetabular component leading to edge loading
. Short femoral neck offset
. Use of a 28 mm femoral head
. Cemented fixation of the femoral stem

Correct Answer & Explanation

. Malpositioned acetabular component leading to edge loading

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is strongly correlated with edge loading, typically due to acetabular cup malposition (such as excessive anteversion or vertical cup placement). This leads to stripe wear, loss of fluid-film lubrication, and subsequent micro-separation and noise generation. While younger age and high activity levels are clinical risk factors, mechanical edge loading from component malposition is the primary biomechanical cause.

Question 1875

Topic: 3. Adult Reconstruction (Hip & Knee)
In a patient with early-stage non-traumatic osteonecrosis of the femoral head, which of the following is considered the most reliable prognostic indicator for the success of a core decompression procedure?
. Preoperative Harris Hip Score
. Patient age at the time of symptom onset
. Size and location of the necrotic lesion on MRI
. The specific underlying etiology of osteonecrosis
. Presence of a crescent sign on anteroposterior plain radiographs

Correct Answer & Explanation

. Size and location of the necrotic lesion on MRI

Explanation

The success of core decompression in treating avascular necrosis (AVN) of the femoral head heavily depends on the size and location of the necrotic lesion, typically evaluated by the Kerboul angle or modified Steinberg/Ficat staging on MRI. Lesions involving <15% of the head and located medially or centrally have a significantly higher success rate than large, laterally located lesions. The presence of a crescent sign (Ficat stage III) indicates subchondral collapse and is generally considered a contraindication to core decompression.

Question 1876

Topic: 3. Adult Reconstruction (Hip & Knee)
In revision total hip arthroplasty, a 'jumbo' acetabular cup is occasionally utilized to manage large cavitary bone defects. Based on the widely accepted orthopedic literature definition, what minimal outer diameter constitutes a jumbo cup in male and female patients, respectively?
. Males >60 mm, Females >56 mm
. Males >66 mm, Females >62 mm
. Males >54 mm, Females >50 mm
. Males >70 mm, Females >66 mm
. Males >58 mm, Females >54 mm

Correct Answer & Explanation

. Males >66 mm, Females >62 mm

Explanation

In the context of revision total hip arthroplasty, a 'jumbo' cup is generally defined as an uncemented hemispherical acetabular shell with an outer diameter of ≥66 mm in males and ≥62 mm in females. These oversized cups maximize contact with host bone, achieving initial stability and promoting osseointegration across large cavitary defects without the absolute need for bulk allografts.

Question 1877

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with groin pain. Serum cobalt levels are elevated at 12 ppb, and MARS MRI reveals a solid pseudotumor compressing the femoral vein. What is the most appropriate surgical management?

. Revision of the acetabular and femoral components to a ceramic-on-polyethylene bearing
. Aspiration of the hip joint and isolated liner exchange
. Open debridement with retention of the metal-on-metal components
. Revision to a dual-mobility metal-on-polyethylene bearing using the same stem
. Prescription of systemic metal chelating agents and observation

Correct Answer & Explanation

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

Explanation

Symptomatic adverse local tissue reactions (ALTR/ALVAL) from metal-on-metal implants with elevated metal ions and pseudotumor require revision surgery. The bearing surface must be changed to eliminate the metal-on-metal articulation, typically utilizing a ceramic or metal head on a highly cross-linked polyethylene liner.

Question 1878

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a metal-on-polyethylene THA presents with groin pain and an enlarging cystic mass. Aspirate shows dark fluid, high cobalt and chromium levels, and negative infection markers. Pathology of the tissue shows ALVAL. What is the most likely source of this reaction?

. Head-neck junction wear
. Articular bearing wear
. Acetabular shell loosening
. Femoral stem osteolysis
. Iliopsoas impingement

Correct Answer & Explanation

. Head-neck junction wear

Explanation

Trunnionosis occurs at the modular head-neck junction, leading to mechanically assisted crevice corrosion and ALVAL, even in metal-on-polyethylene bearings. High serum or fluid cobalt levels with a pseudotumor are characteristic.

Question 1879

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male presents with chronic insidious shoulder pain and stiffness 18 months after an anatomic total shoulder arthroplasty. Inflammatory markers (ESR, CRP) are normal. Preoperative aspiration grows Cutibacterium acnes after 10 days of incubation. What is the most appropriate management?

. Arthroscopic debridement and retain components
. Single-stage revision with antibiotic-loaded cement
. Two-stage revision arthroplasty
. Long-term suppressive oral antibiotics
. Polyethylene exchange alone

Correct Answer & Explanation

. Two-stage revision arthroplasty

Explanation

Chronic periprosthetic joint infections of the shoulder, particularly with C. acnes, are definitively managed with a two-stage revision using an antibiotic spacer. This approach provides the most reliable eradication of the biofilm.

Question 1880

Topic: 3. Adult Reconstruction (Hip & Knee)

During a direct anterior approach for a total hip arthroplasty, the surgeon dissects between the tensor fasciae latae and the sartorius. Which vessel must typically be identified and ligated within this interval to prevent postoperative hematoma?

. Medial femoral circumflex artery
. Lateral femoral circumflex artery ascending branches
. Deep femoral artery
. Superior gluteal artery
. Inferior gluteal artery

Correct Answer & Explanation

. Lateral femoral circumflex artery ascending branches

Explanation

The direct anterior approach utilizes the Smith-Petersen internervous plane. The ascending branches of the lateral femoral circumflex artery cross this interval and must be ligated to prevent excessive bleeding.

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