Menu

3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 235 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 4681

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, the use of ceramic-on-ceramic bearing surfaces drastically reduces volumetric wear. Which of the following is a recognized complication uniquely associated with ceramic-on-ceramic bearings compared to metal-on-polyethylene?

. Trunnionosis
. Massive osteolysis from submicron wear particles
. Audible squeaking during range of motion
. Galvanic corrosion at the head-neck junction
. Creep deformation over time

Correct Answer & Explanation

. Audible squeaking during range of motion

Explanation

'Squeaking' is a well-documented clinical phenomenon unique to hard-on-hard bearings, particularly ceramic-on-ceramic total hip arthroplasties. It occurs due to resonance from micro-separation or stripe wear. Trunnionosis and galvanic corrosion are issues at metal-metal junctions. Polyethylene bears the issues of creep and macrophage-induced osteolysis.

Question 4682

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty (TKA), trial components are inserted. Evaluation reveals that the knee is well-balanced and symmetric in full extension, but the joint is significantly tight both medially and laterally in 90 degrees of flexion. Which of the following surgical maneuvers is the most appropriate next step to balance the knee?

. Release the posterior cruciate ligament (PCL)
. Downsize the femoral component
. Resect more distal femur
. Increase the thickness of the polyethylene insert
. Release the posterior capsule

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is balanced in extension but tight in flexion indicates that the flexion gap is too small relative to the extension gap. Options to increase the flexion gap without affecting the extension gap include downsizing the femoral component (which decreases the posterior condylar offset), increasing the posterior tibial slope, or recessing the PCL (if retaining). Downsizing the femoral component is the most direct solution. Resecting more distal femur or releasing the posterior capsule would widen the extension gap.

Question 4683

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria for periprosthetic joint infection (PJI), which of the following synovial fluid biomarkers carries the highest diagnostic weight and serves as a standalone major diagnostic criterion?

. C-reactive protein (CRP)
. Alpha-defensin
. Leukocyte esterase
. Interleukin-6 (IL-6)
. Lactate dehydrogenase (LDH)

Correct Answer & Explanation

. Alpha-defensin

Explanation

A positive synovial fluid alpha-defensin test is highly specific for PJI and is classified as a major criterion in modern scoring systems. Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens.

Question 4684

Topic: 3. Adult Reconstruction (Hip & Knee)

Highly cross-linked polyethylene (HXLPE) is standardly used in modern total hip arthroplasty to reduce wear rates and subsequent osteolysis. What is the primary mechanical trade-off associated with the increased gamma radiation cross-linking of the polyethylene?

. Increased elastic modulus
. Decreased ultimate tensile strength and toughness
. Increased fatigue crack propagation resistance
. Decreased oxidation susceptibility
. Increased creep deformation

Correct Answer & Explanation

. Decreased ultimate tensile strength and toughness

Explanation

While high cross-linking significantly reduces both adhesive and abrasive wear, it alters the mechanical properties of the polyethylene, specifically reducing its toughness, ductility, and resistance to fatigue crack propagation.

Question 4685

Topic: 3. Adult Reconstruction (Hip & Knee)
A patient with a poorly functioning metal-on-metal total hip arthroplasty presents with persistent groin pain and a palpable anterior mass. Advanced imaging reveals a large, cystic pseudotumor. This adverse local tissue reaction (ALVAL) is histologically driven by which specific type of hypersensitivity response?
. Type I (IgE-mediated)
. Type II (Cytotoxic)
. Type III (Immune complex)
. Type IV (Delayed-type cell-mediated)
. Type V (Stimulatory autoantibody)

Correct Answer & Explanation

. Type IV (Delayed-type cell-mediated)

Explanation

Adverse Local Tissue Reaction (ALVAL) generated by metal debris in arthroplasty is primarily a Type IV delayed cell-mediated hypersensitivity reaction. The condition features dense perivascular lymphocytic infiltrates caused by T-lymphocyte sensitization to elevated cobalt and chromium ions.

Question 4686

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon notices that the knee is tight in flexion but balanced and stable in extension. Which of the following is the most appropriate surgical step to balance the knee?

. Resect more distal femur
. Downsize the femoral component
. Release the posterior cruciate ligament (if retaining)
. Upsize the tibial polyethylene insert
. Recut the proximal tibia

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is tight in flexion but stable in extension indicates an isolated tight flexion gap. Downsizing the femoral component increases the anterior-posterior bone cut, which increases the flexion gap without altering the extension gap.

Question 4687

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old active community ambulator sustains a displaced, completely off-ended femoral neck fracture. Which of the following is the most compelling reason to perform a total hip arthroplasty (THA) rather than a hemiarthroplasty?

. Lower dislocation rate
. Lower surgical blood loss
. Decreased risk of long-term acetabular wear and groin pain
. Shorter operative time
. Decreased early mortality

Correct Answer & Explanation

. Decreased risk of long-term acetabular wear and groin pain

Explanation

In active, independently ambulating older adults, THA is favored over hemiarthroplasty for displaced femoral neck fractures. THA significantly reduces the risk of long-term acetabular erosion and persistent groin pain, leading to better long-term functional scores.

Question 4688

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female undergoes a total hip arthroplasty via a posterior approach. Postoperatively, she has a foot drop and cannot actively dorsiflex her ankle or extend her toes, but ankle inversion is preserved. Which nerve or nerve division is most likely injured?

. Femoral nerve
. Obturator nerve
. Sciatic nerve (tibial division)
. Sciatic nerve (peroneal division)
. Superior gluteal nerve

Correct Answer & Explanation

. Sciatic nerve (peroneal division)

Explanation

The peroneal division of the sciatic nerve is located laterally and is more tethered, making it highly susceptible to stretch injury during total hip arthroplasty. Preservation of ankle inversion (innervated by the tibial nerve) confirms an isolated peroneal division injury.

Question 4689

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoing a total knee arthroplasty has a significant preoperative flexion contracture. After initial bone cuts and soft tissue releases, the knee is balanced in extension but remains tight in flexion. Which of the following steps is the most appropriate to address this specific mismatch?

. Resect more distal femur
. Downsize the femoral component
. Upsize the femoral component
. Resect more proximal tibia
. Release the posterior capsule

Correct Answer & Explanation

. Downsize the femoral component

Explanation

If a knee is balanced in extension but tight in flexion, the flexion gap needs to be increased without affecting the extension gap. This is achieved by downsizing the femoral component, which decreases the posterior condylar offset and opens the flexion gap.

Question 4690

Topic: Total Knee Arthroplasty (TKA)

To improve patellar tracking during a total knee arthroplasty without modifying the patellar cut itself, which of the following component position changes is most effective?

. Internal rotation of the femoral component
. Internal rotation of the tibial component
. Medial translation of the femoral component
. Lateralizing the patellar component
. Lateral translation of the femoral component

Correct Answer & Explanation

. Lateral translation of the femoral component

Explanation

To improve patellar tracking, the femoral component can be externally rotated or translated laterally. The tibial component can also be externally rotated, or the patellar component can be medialized. Internal rotation of femoral or tibial components, medialization of the femur, or lateralizing the patella will worsen tracking and increase the Q angle.

Question 4691

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with recurrent posterior dislocation of her total hip arthroplasty. Intraoperatively, the acetabular cup is found to be well-fixed in 30 degrees of abduction and 0 degrees of anteversion. The femoral stem is well-fixed in 15 degrees of anteversion. Which of the following is the most appropriate management?

. Prescribe an abduction brace
. Revise the femoral stem to a retroverted position
. Revise the acetabular cup to increase anteversion
. Perform a greater trochanteric advancement
. Exchange the femoral head to a larger diameter with a longer neck

Correct Answer & Explanation

. Revise the acetabular cup to increase anteversion

Explanation

The safe zone for acetabular cup placement is typically 40 +/- 10 degrees of abduction and 15 +/- 10 degrees of anteversion. The cup in this patient is placed in 0 degrees of anteversion, which predisposes to posterior dislocation. Because the cup position is the primary cause of instability, the most appropriate treatment is revision of the cup to increase anteversion.

Question 4692

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female sustains a periprosthetic femur fracture around a cemented total hip arthroplasty stem. Radiographs demonstrate a fracture at the tip of the stem. The stem is radiographically loose, but there is excellent bone stock proximally and distally. What is the Vancouver classification and appropriate treatment?

. Vancouver B1; ORIF with cables and a plate
. Vancouver B2; Revision to a long uncemented diaphyseal-engaging stem
. Vancouver B3; Revision with a proximal femoral replacement
. Vancouver C; ORIF with a plate
. Vancouver A; Nonoperative management

Correct Answer & Explanation

. Vancouver B2; Revision to a long uncemented diaphyseal-engaging stem

Explanation

Vancouver B2 fractures occur around or just distal to the stem tip, with a loose stem but adequate bone stock. The standard of care is revision arthroplasty bypassing the fracture with a long stem (often a fully porous-coated or fluted tapered stem) to achieve diaphyseal fixation, rather than osteosynthesis alone.

Question 4693

Topic: 3. Adult Reconstruction (Hip & Knee)

In modern total hip arthroplasty, highly cross-linked polyethylene is commonly used to reduce wear. What is the primary purpose of remelting the polyethylene after it undergoes gamma irradiation?

. To increase the crystalline structure
. To decrease the ultimate tensile strength
. To eliminate free radicals and improve oxidation resistance
. To increase the stiffness of the material
. To promote chain scission

Correct Answer & Explanation

. To eliminate free radicals and improve oxidation resistance

Explanation

Gamma irradiation cross-links the polyethylene, significantly increasing its wear resistance. However, it also leaves free radicals within the material structure. If left untreated, these free radicals lead to oxidation and embrittlement in vivo. Remelting (heating above the melting point) quenches these free radicals, preventing oxidation, though it slightly reduces the mechanical strength compared to annealing.

Question 4694

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. Age greater than 70 years
. Weight greater than 90 kg
. Anterior cruciate ligament deficiency
. Patellofemoral osteoarthritis
. Inflammatory arthritis

Correct Answer & Explanation

. Inflammatory arthritis

Explanation

Inflammatory arthritis (e.g., rheumatoid arthritis) remains an absolute contraindication to UKA because the disease systemically affects all compartments of the joint, leading to early failure. The classic Kozinn and Scott criteria included weight, age, patellofemoral arthritis, and ACL deficiency, but these have largely become relative or debated contraindications in modern practice.

Question 4695

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man with a metal-on-metal total hip arthroplasty presents with groin pain and a palpable mass. MRI shows a large cystic mass communicating with the joint. Blood cobalt and chromium levels are significantly elevated. Histopathology of the excised periprosthetic tissue is most likely to show:

. Extensive neutrophil infiltration and acute inflammation
. Perivascular lymphocytic infiltrate and macrophages with metallic debris
. Granulomas with multinucleated giant cells and caseating necrosis
. Sheets of plasma cells and Russell bodies
. Abundant foreign-body giant cells reacting to polyethylene wear particles

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate and macrophages with metallic debris

Explanation

The presentation is classic for an Adverse Local Tissue Reaction (ALTR) or Aseptic Lymphocytic Vasculitis-Associated Lesion (ALVAL) secondary to metal wear debris in a metal-on-metal THA. Histologically, ALVAL is characterized by a dense perivascular lymphocytic infiltrate (indicating a delayed hypersensitivity type IV reaction) alongside macrophages containing fine metallic particulate debris.

Question 4696

Topic: Total Knee Arthroplasty (TKA)

During TKA, the surgeon decides to use an intramedullary guide for distal femoral resection. If the patient has a significant lateral femoral bowing that is not radiographically recognized, what is the most likely error in the coronal plane alignment of the femoral component?

. Excessive flexion
. Excessive extension
. Excessive valgus
. Excessive varus
. Excessive internal rotation

Correct Answer & Explanation

. Excessive valgus

Explanation

An intramedullary guide references the anatomic axis of the distal femur. In the presence of significant lateral (varus) femoral bowing, the anatomic axis of the distal segment deviates laterally relative to the true mechanical axis of the entire femur. If the standard 5-7 degree valgus cut angle is blindly applied using the intramedullary guide, the distal cut will be in excessive valgus relative to the true mechanical axis.

Question 4697

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with pain and swelling 5 years after a primary THA utilizing a large metal head on a highly cross-linked polyethylene liner with a titanium stem. Joint aspiration is negative for infection, but serum cobalt levels are markedly elevated while chromium levels are normal or slightly elevated. What is the most likely source of the metal ions?

. Bearing surface wear
. Acetabular shell fretting
. Head-neck junction (mechanically assisted crevice corrosion)
. Proximal stem coating delamination
. Impingement of the neck on the acetabular rim

Correct Answer & Explanation

. Head-neck junction (mechanically assisted crevice corrosion)

Explanation

In a metal-on-polyethylene THA, elevated serum cobalt levels with normal or near-normal chromium levels are the classic signature of mechanically assisted crevice corrosion (MACC) at the head-neck taper junction (trunnionosis). Bearing surface wear does not produce this ion profile in a non-metal-on-metal articulation.

Question 4698

Topic: 3. Adult Reconstruction (Hip & Knee)
In revision total hip arthroplasty, a Paprosky Type IIIB acetabular defect is specifically characterized by which of the following findings?
. Intact rim, no superior migration, teardrop intact
. Superomedial migration of the hip center, teardrop absent, intact Kohler's line
. Superolateral migration >3 cm, teardrop absent, severe ischial osteolysis
. Severe pelvic discontinuity with complete separation of the superior and inferior pelvis
. Superior migration <3 cm, intact teardrop, and normal Kohler's line

Correct Answer & Explanation

. Superolateral migration >3 cm, teardrop absent, severe ischial osteolysis

Explanation

Paprosky Type IIIB defects involve severe acetabular bone loss with non-supportive rims. They are defined by superior migration of the hip center >3 cm, medial migration (often violating Kohler's line), an absent teardrop, and severe ischial osteolysis. Type IIIC indicates pelvic discontinuity.

Question 4699

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female is undergoing a revision total knee arthroplasty. Intraoperatively, she is found to have a completely deficient medial collateral ligament (MCL) but an intact lateral collateral ligament (LCL) and extensor mechanism. Which of the following constraint levels is required for her revision prosthesis?

. Posterior-stabilized (PS)
. Cruciate-retaining (CR)
. Constrained non-hinged (CCK)
. Rotating hinge
. Fixed hinge

Correct Answer & Explanation

. Rotating hinge

Explanation

A grossly incompetent or absent MCL in the setting of TKA is a strict indication for a hinged prosthesis (typically a rotating hinge). A Constrained Condylar Knee (CCK) relies on functional collateral ligaments to provide a checkrein to its varus-valgus post; if the MCL is completely deficient, a CCK is contraindicated as the post will fail from repetitive stress.

Question 4700

Topic: Total Hip Arthroplasty (THA)

Which of the following statements best describes the mechanical design principle of a 'taper-slip' cemented femoral stem (e.g., Exeter stem)?

. It is designed with a broad collar to load the medial calcar directly.
. It has a roughened or matte surface finish to mechanically interlock with the cement.
. It relies on controlled subsidence into the cement mantle to increase radial compressive forces.
. It is designed to be fully unbonded to allow toggling in the sagittal plane.
. It transfers load primarily through proximal shear forces at the cement-bone interface.

Correct Answer & Explanation

. It relies on controlled subsidence into the cement mantle to increase radial compressive forces.

Explanation

Taper-slip cemented stems are collarless, highly polished, and double-tapered. They are engineered to slightly subside within the cement mantle under axial load. This subsidence acts like a wedge, creating radial compressive forces that strengthen the cement-bone interface and transform shear forces into more favorable compressive forces on the surrounding bone.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page