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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 285 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 5681

Topic: 3. Adult Reconstruction (Hip & Knee)

A 76-year-old male sustained a periprosthetic fracture of the femur 8 years after a primary cementless total hip arthroplasty. Radiographs show a fracture traversing the stem near the tip. The femoral stem has subsided by 2 cm and is visibly loose. However, the proximal femoral bone stock remains of good quality. According to the Vancouver classification, what is the fracture type and the recommended treatment?

. Vancouver B1; Open reduction and internal fixation with a lateral locking plate
. Vancouver B2; Revision to a long, fully porous-coated or fluted tapered cementless stem
. Vancouver B3; Revision with a proximal femoral replacement (megaprosthesis)
. Vancouver C; Open reduction and internal fixation with a lateral locking plate
. Vancouver A; Non-operative management with protected weight-bearing

Correct Answer & Explanation

. Vancouver B2; Revision to a long, fully porous-coated or fluted tapered cementless stem

Explanation

This is a Vancouver B2 fracture (fracture around the stem, loose implant, good bone stock). The gold standard treatment is bypassing the fracture and revising the loose implant using a long, extensively porous-coated or fluted tapered cementless diaphyseal-engaging stem. B1 fractures have a well-fixed stem (treated with ORIF), while B3 fractures have poor bone stock (requiring proximal femoral replacement or allograft-prosthesis composite).

Question 5682

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with an inability to actively extend her knee 3 months after a primary total knee arthroplasty. Ultrasound confirms a complete mid-substance rupture of the patellar tendon. Primary repair is deemed unfeasible due to poor tissue quality. If an extensor mechanism allograft is utilized for reconstruction, in what position must the allograft be tensioned during fixation to ensure success?

. Full extension
. 30 degrees of flexion
. 60 degrees of flexion
. 90 degrees of flexion
. 120 degrees of flexion

Correct Answer & Explanation

. Full extension

Explanation

Extensor mechanism allograft or synthetic mesh reconstruction for chronic patellar tendon ruptures post-TKA must be tensioned tightly in full extension. Tensioning the graft in any degree of flexion will result in an extensor lag once the patient begins rehabilitation, as the graft inevitably stretches out over time.

Question 5683

Topic: Total Hip Arthroplasty (THA)

A 60-year-old male presents with groin pain and a palpable mass 6 years after a primary metal-on-polyethylene total hip arthroplasty. He received a titanium stem with a 36-mm cobalt-chromium head. Inflammatory markers are normal, and joint aspiration reveals no growth. MRI shows a cystic mass compressing the femoral nerve. Which of the following serum metal ion profiles is most characteristic of his underlying diagnosis?

. Elevated Chromium > Elevated Cobalt
. Elevated Cobalt > Elevated Chromium
. Elevated Titanium and Normal Cobalt
. Normal Cobalt and Normal Chromium
. Elevated Titanium > Elevated Chromium

Correct Answer & Explanation

. Elevated Cobalt > Elevated Chromium

Explanation

The scenario describes mechanically assisted crevice corrosion (MACC), or trunnionosis, at the head-neck junction of a metal-on-polyethylene (MoP) THA, typically involving a large CoCr head on a titanium stem. This produces adverse local tissue reactions (ALVAL). The hallmark serum profile for trunnionosis is elevated Cobalt levels disproportionately higher than Chromium levels (Co >> Cr), whereas metal-on-metal bearing wear typically produces equally elevated Co and Cr.

Question 5684

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, an orthopedic surgeon evaluates the patellar tracking before definitive component implantation. The patella tracks laterally and tends to subluxate during deep flexion. Which of the following component malpositions is the most common iatrogenic cause of this finding?

. External rotation of the femoral component and external rotation of the tibial component
. Internal rotation of the femoral component and internal rotation of the tibial component
. Excessive valgus alignment of the tibial component
. Anterior translation of the femoral component
. Medialization of the patellar 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 and lateralizes the tibial tubercle relative to the trochlear groove, leading to lateral patellar maltracking. To optimize patellar tracking, the femoral and tibial components should be positioned in slight external rotation relative to the posterior condylar and tibial anatomic axes. Medializing (rather than lateralizing) the patellar component actually improves tracking.

Question 5685

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a cruciate-retaining (CR) total knee arthroplasty complains of the knee 'giving way' when descending stairs. Video fluoroscopy reveals paradoxical anterior sliding of the femur on the tibia during early-to-mid knee flexion. What is the primary biomechanical cause of this phenomenon?

. Cam-post impingement
. Over-tightened posterior cruciate ligament
. Attenuated or incompetent posterior cruciate ligament
. Excessive posterior slope of the tibial component
. Patellar baja

Correct Answer & Explanation

. Attenuated or incompetent posterior cruciate ligament

Explanation

In a native knee and a well-functioning CR TKA, the femur rolls back posteriorly on the tibia during flexion, guided by the tension of the posterior cruciate ligament (PCL). If the PCL is attenuated, ruptured, or functionally incompetent (or if the flexion gap is too loose), the femur fails to roll back and instead slides anteriorly on the tibia during flexion (paradoxical anterior sliding). This leads to a sensation of instability, particularly when descending stairs.

Question 5686

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following conditions is considered an absolute contraindication to utilizing a mobile-bearing medial unicompartmental knee arthroplasty (e.g., Oxford UKA)?

. Age greater than 60 years
. Anterior cruciate ligament deficiency
. Weight greater than 90 kg
. Patellofemoral chondromalacia without anterior knee pain
. Flexion contracture of 10 degrees

Correct Answer & Explanation

. Anterior cruciate ligament deficiency

Explanation

Anterior cruciate ligament (ACL) deficiency is an absolute contraindication for a mobile-bearing unicompartmental knee arthroplasty (UKA). Without an intact ACL, abnormal anteroposterior translation occurs, leading to posterior subluxation of the femur on the tibia in flexion and a high risk of bearing spin-out/dislocation. Age, weight, and asymptomatic patellofemoral chondromalacia are not strict contraindications based on current guidelines.

Question 5687

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) Criteria for Periprosthetic Joint Infection (PJI), which of the following findings is considered a definitive 'Major Criterion' establishing the diagnosis of PJI without the need for further scoring?

. Elevated synovial fluid alpha-defensin
. Elevated serum C-reactive protein > 100 mg/L
. A single intraoperative tissue culture positive for Staphylococcus epidermidis
. A sinus tract communicating with the joint space
. Synovial fluid leukocyte count > 3,000 cells/uL

Correct Answer & Explanation

. A sinus tract communicating with the joint space

Explanation

Under the 2018 ICM criteria, the two major criteria (either of which definitively diagnoses a PJI independently) are: 1) A sinus tract communicating with the joint, and 2) Two positive periprosthetic cultures with phenotypically identical organisms. Elevated alpha-defensin, elevated CRP, elevated synovial WBC, and a single positive culture are minor criteria that contribute points to an aggregate score.

Question 5688

Topic: 3. Adult Reconstruction (Hip & Knee)

In the setting of revision total knee arthroplasty with Anderson Orthopaedic Research Institute (AORI) Type 2B (severe metaphyseal) bone defects, both highly porous cones and metaphyseal sleeves can be used for fixation. What is the primary biomechanical difference in how metaphyseal sleeves engage the construct compared to porous cones?

. Sleeves rely on bone cement for initial fixation to the host bone
. Sleeves connect to the stem/implant via a Morse taper, acting as a modular unit
. Sleeves are independent of the diaphyseal stem and rely on cement for implant attachment
. Cones require diaphyseal-engaging stems, whereas sleeves do not
. Cones are manufactured exclusively from titanium, while sleeves are made of cobalt-chromium

Correct Answer & Explanation

. Sleeves connect to the stem/implant via a Morse taper, acting as a modular unit

Explanation

Metaphyseal sleeves are modular components that interlock with the revision stem and femoral/tibial component via a Morse taper, forming a single, rigidly connected construct that achieves biological fixation to the host bone. Highly porous cones, on the other hand, are implanted independently into the host metaphyseal bone to fill defects, and the revision implant is then cemented into the center of the cone.

Question 5689

Topic: Total Hip Arthroplasty (THA)

During a total hip arthroplasty, the surgeon elects to use an extended offset femoral stem instead of a standard offset stem, without changing the vertical height or leg length. What is the primary biomechanical consequence of increasing femoral offset?

. Decreases the abductor moment arm and increases the joint reaction force
. Increases the abductor moment arm and decreases the joint reaction force
. Decreases soft tissue tension leading to increased risk of dislocation
. Medializes the greater trochanter relative to the center of rotation
. Increases the risk of sciatic nerve traction palsy

Correct Answer & Explanation

. Increases the abductor moment arm and decreases the joint reaction force

Explanation

Increasing femoral offset moves the femur laterally away from the center of rotation (without altering leg length). This increases the abductor moment arm (lever arm), which means the abductor muscles need to generate less force to maintain a level pelvis. Consequently, the overall joint reaction force across the hip is decreased. It also increases soft-tissue tension, reducing the risk of impingement and dislocation.

Question 5690

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with the sudden onset of severe medial knee pain while walking. She denies any trauma. Radiographs of the knee are unremarkable. MRI reveals bone marrow edema in the medial femoral condyle with a focal subchondral hypointense crescent. Which of the following is the most appropriate initial management for this condition?

. Immediate unicompartmental knee arthroplasty
. Core decompression of the medial femoral condyle
. Non-weight bearing with crutches and analgesia
. Intra-articular corticosteroid injection
. Arthroscopic meniscectomy

Correct Answer & Explanation

. Non-weight bearing with crutches and analgesia

Explanation

The clinical presentation and MRI findings are classic for spontaneous osteonecrosis of the knee (SPONK), now more accurately termed a subchondral insufficiency fracture of the knee (SIFK). It overwhelmingly affects older females in the medial femoral condyle. Initial management is non-operative, focusing on protected weight-bearing and analgesia, as a significant portion will heal without surgical intervention. Surgery is reserved for collapse and secondary osteoarthritis.

Question 5691

Topic: Total Hip Arthroplasty (THA)

A 45-year-old patient undergoes a ceramic-on-ceramic total hip arthroplasty. Three years later, the patient complains of an audible squeaking noise from the hip during ambulation. What surgical factor is most strongly associated with the development of this complication?

. Use of a 28 mm ceramic head instead of a 36 mm head
. Acetabular cup inclination greater than 50 degrees
. Femoral stem anteversion less than 10 degrees
. Failure to use a cemented femoral stem
. Utilization of a highly cross-linked polyethylene liner

Correct Answer & Explanation

. Acetabular cup inclination greater than 50 degrees

Explanation

Squeaking is a well-known complication unique to hard-on-hard bearings, particularly ceramic-on-ceramic (CoC) THA. It is strongly associated with edge loading and stripe wear, which result from component malposition. Specifically, steep acetabular cup inclination (often >50 degrees) or version mismatches lead to the femoral head loading on the edge of the ceramic liner, disrupting fluid film lubrication and causing the squeak.

Question 5692

Topic: 3. Adult Reconstruction (Hip & Knee)
An 82-year-old female presents with a displaced supracondylar femur fracture just proximal to a posterior-stabilized total knee arthroplasty. Radiographs indicate that the femoral component has subsided and is grossly loose. According to the Rorabeck classification, what is the grade of this fracture, and what is the definitive surgical treatment?
. Rorabeck Type I; Retrograde intramedullary nailing
. Rorabeck Type II; Open reduction and internal fixation with a lateral locked plate
. Rorabeck Type II; Distal femoral replacement
. Rorabeck Type III; Distal femoral replacement
. Rorabeck Type III; Open reduction and internal fixation with dual plating

Correct Answer & Explanation

. Rorabeck Type III; Distal femoral replacement

Explanation

The Rorabeck classification is used for periprosthetic femur fractures above a TKA. Type I: undisplaced, implant stable. Type II: displaced, implant stable. Type III: implant loose, regardless of displacement. Because the femoral component in this patient is grossly loose, it is a Rorabeck Type III. The standard treatment is revision arthroplasty using a distal femoral replacement (megaprosthesis) or a revision TKA with diaphyseal engaging stems, as ORIF will fail if the implant is loose.

Question 5693

Topic: Total Knee Arthroplasty (TKA)

Which of the following describes the fundamental goal of 'Kinematic Alignment' in total knee arthroplasty compared to traditional 'Mechanical Alignment'?

. To cut the femur and tibia strictly perpendicular to their mechanical axes
. To intentionally create a postoperative limb alignment of exactly 0 degrees mechanical axis
. To co-align the transverse axes of the components with the three kinematic axes of the normal knee
. To externally rotate the femoral component 3 degrees off the posterior condylar axis in all patients
. To release the medial collateral ligament to achieve rectangular flexion and extension gaps

Correct Answer & Explanation

. To co-align the transverse axes of the components with the three kinematic axes of the normal knee

Explanation

Kinematic alignment (KA) aims to restore the pre-arthritic constitutional alignment and kinematics of the knee by co-aligning the transverse axes of the TKA components with the native kinematic axes of the joint. This often involves placing the tibial component in slight varus and the femoral component in slight valgus (matching the native joint line), minimizing the need for soft-tissue releases. Mechanical alignment aims for a neutral (0 degree) mechanical axis with cuts perpendicular to the mechanical axes of the tibia and femur.

Question 5694

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a history of a metal-on-metal hip resurfacing arthroplasty undergoes revision surgery for a suspected pseudotumor. Intraoperative tissue samples are sent for histopathological analysis. Which of the following histologic findings is the hallmark of an adverse local tissue reaction (ALVAL) associated with metal-on-metal wear debris?

. Massive infiltration of polymorphonuclear neutrophils (PMNs)
. Birefringent particulate debris surrounded by foreign body giant cells
. Perivascular lymphocytic infiltrate with varying degrees of tissue necrosis
. Non-caseating granulomas with epithelioid macrophages
. Abundant chondroid metaplasia with woven bone formation

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate with varying degrees of tissue necrosis

Explanation

Adverse local tissue reaction (ALVAL - aseptic lymphocyte-dominated vasculitis-associated lesion) is a type IV delayed hypersensitivity reaction to metal ions (cobalt and chromium). The classic histological hallmark is a dense perivascular infiltrate of lymphocytes (T-cells) along with tissue necrosis and fibrin exudation. Birefringent particles and foreign body giant cells are characteristic of polyethylene wear (osteolysis), not metal-on-metal ALVAL.

Question 5695

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female presents with an audible and palpable 'clunk' at 40 degrees of flexion as she extends her knee, 1 year after a posterior-stabilized TKA. Which of the following implant design factors is most directly associated with the development of patellar clunk syndrome?

. High ratio of the femoral intercondylar box height to the patellar button diameter
. Anterior placement of the femoral component
. Thickening of the patellar component
. A sharp, square anterior-superior edge of the femoral intercondylar box
. A lowered joint line during tibial preparation

Correct Answer & Explanation

. A sharp, square anterior-superior edge of the femoral intercondylar box

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA due to the formation of a fibrous nodule at the superior pole of the patella. This nodule catches in the intercondylar box of the femoral component during extension (typically around 30-45 degrees of flexion). Older PS designs with a sharp, square anterior-superior edge of the intercondylar box were highly associated with this complication. Modern designs have lowered and rounded this edge, decreasing the incidence.

Question 5696

Topic: 3. Adult Reconstruction (Hip & Knee)

A 64-year-old male presents with groin pain 6 years after a primary metal-on-polyethylene THA with a large-diameter cobalt-chromium head. Inflammatory markers are normal, but MARS MRI reveals a solid, thick-walled soft tissue mass compressing the femoral vein. Aspiration yields sterile, turbid fluid. What is the most likely primary source of this complication?

. Fretting and crevice corrosion at the head-neck junction
. Polyethylene wear debris from the bearing surface
. Galvanic corrosion between the titanium cup and screws
. Undiagnosed indolent Cutibacterium acnes infection
. Third-body wear from retained bone cement

Correct Answer & Explanation

. Fretting and crevice corrosion at the head-neck junction

Explanation

The patient has an Adverse Local Tissue Reaction (ALTR) or pseudotumor, which in a metal-on-polyethylene THA is typically caused by trunnionosis (fretting and crevice corrosion at the modular head-neck junction). Risk factors include a large diameter head (>36mm), cobalt-chromium heads on titanium stems, increased head offset, and higher BMI. It leads to metal ion release (elevated serum Co and Cr) and a local hypersensitivity/toxicity reaction.

Question 5697

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision TKA for aseptic loosening, the surgeon utilizes a large distal femoral augment to compensate for bone loss and subsequently inserts a polyethylene liner that is 4 mm thicker than the original to achieve stability. Postoperatively, the patient has limited knee flexion and anterior knee pain. What is the most likely biomechanical consequence of elevating the joint line in this manner?

. Patella alta with an increased Q angle
. Decreased tension on the collateral ligaments in mid-flexion
. Patella baja with secondary impingement of the patella against the tibial insert
. Increased mechanical advantage of the quadriceps mechanism
. Anterior shift of the tibiofemoral contact point in deep flexion

Correct Answer & Explanation

. Patella baja with secondary impingement of the patella against the tibial insert

Explanation

Elevating the joint line during TKA (often due to over-resecting the distal femur and compensating with a thicker poly, or failing to restore distal femoral bone loss in revision) leads to relative/pseudo patella baja. The distance between the tibial tubercle and the joint line is decreased. This causes altered patellofemoral kinematics, restricted knee flexion, anterior knee pain, and potential impingement of the patella or patellar tendon against the anterior lip of the tibial polyethylene insert.

Question 5698

Topic: Total Hip Arthroplasty (THA)

A surgeon is performing a THA using the direct lateral (Hardinge) approach. To protect the superior gluteal nerve, the proximal split in the gluteus medius should not extend beyond a certain distance from the tip of the greater trochanter. What is the generally accepted safe distance limit for this split?

. 1 cm
. 3 cm
. 5 cm
. 7 cm
. 9 cm

Correct Answer & Explanation

. 5 cm

Explanation

The superior gluteal nerve innervates the gluteus medius, minimus, and tensor fasciae latae. During a direct lateral approach, the gluteus medius is split longitudinally. The main trunk of the superior gluteal nerve lies approximately 5 cm proximal to the tip of the greater trochanter. Extending the split further than 5 cm proximally puts the nerve at high risk of iatrogenic injury, which would result in a permanent Trendelenburg gait.

Question 5699

Topic: 3. Adult Reconstruction (Hip & Knee)

A 59-year-old female presents with unexplained chronic pain, stiffness, and recurrent knee effusions 2 years after a primary TKA. Infection workup is negative, and radiographs show well-fixed components. She reports a history of severe skin reactions to cheap jewelry. Which of the following tests is currently considered the most appropriate initial diagnostic step for suspected metal hypersensitivity in this context?

. Lymphocyte transformation testing (LTT)
. Skin patch testing with standard metal panels
. Serum cobalt and chromium ion levels
. Synovial fluid analysis for eosinophils
. Bone scan with technetium-99m

Correct Answer & Explanation

. Skin patch testing with standard metal panels

Explanation

In cases of suspected metal hypersensitivity post-TKA, after ruling out infection, instability, and aseptic loosening, cutaneous patch testing remains the most widely accepted and accessible first-line test, despite its limitations in predicting deep joint reactions. LTT is available but often considered a second-line or adjunctive test due to cost and varying standardization. However, the diagnosis remains largely clinical and of exclusion. Many boards test skin patch testing as the classic 'next step' to confirm a cutaneous allergy to nickel/cobalt, followed by considering revision if the suspicion is high enough.

Question 5700

Topic: Total Hip Arthroplasty (THA)

A 45-year-old male complains of a loud 'squeaking' noise coming from his hip while walking, 4 years following a ceramic-on-ceramic THA. Which of the following biomechanical factors is most strongly associated with the development of squeaking in ceramic-on-ceramic hips?

. Decreased femoral offset
. Excessive acetabular cup anteversion (>25 degrees)
. Stripe wear from edge loading due to component malposition
. Third-body wear from retained polymethylmethacrylate
. Galvanic corrosion at the head-neck junction

Correct Answer & Explanation

. Stripe wear from edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic (CoC) THA is a well-documented phenomenon. It is most commonly associated with 'stripe wear' which results from edge loading. Edge loading occurs when the femoral head contacts the rim of the acetabular liner, resulting in localized wear and loss of fluid film lubrication. This is typically caused by component malposition, specifically high cup inclination (>50 degrees) or extremes of anteversion.

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