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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 44 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 861

Topic: 3. Adult Reconstruction (Hip & Knee)

Synovial fluid analysis is performed to evaluate a painful total knee arthroplasty for periprosthetic joint infection (PJI). An alpha-defensin test is ordered. Alpha-defensin is a highly accurate biomarker for PJI because it is an antimicrobial peptide secreted primarily by which of the following cells in response to pathogens?

. Macrophages
. T-lymphocytes
. B-lymphocytes
. Neutrophils
. Synovial fibroblasts

Correct Answer & Explanation

. Neutrophils

Explanation

Alpha-defensin is an antimicrobial peptide released predominantly by human neutrophils (polymorphonuclear leukocytes) into the synovial fluid when encountering invading pathogens. Its concentration remains high in infected joints regardless of prior antibiotic administration, making it a highly sensitive and specific biomarker for diagnosing periprosthetic joint infection (PJI).

Question 862

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male undergoes a primary total hip arthroplasty using a ceramic-on-ceramic bearing surface. Three years postoperatively, he presents complaining of an audible 'squeaking' sound coming from the hip with normal walking. Radiographs and imaging are obtained. Squeaking in a ceramic-on-ceramic THA is most strongly associated with which of the following mechanical phenomena?

. Third-body wear from retained bone cement particles
. Galvanic corrosion at the head-neck taper
. Edge loading secondary to acetabular component malposition
. Fracture of the ceramic liner
. Excessive offset of the femoral component

Correct Answer & Explanation

. Edge loading secondary to acetabular component malposition

Explanation

Squeaking is a specific complication of ceramic-on-ceramic total hip arthroplasties. It is strongly correlated with edge loading and 'stripe wear' on the retrieved components. Edge loading typically occurs due to suboptimal acetabular component positioning (e.g., excessive cup anteversion or high inclination angle), which shifts the joint contact forces to the very edge of the liner, disrupting the fluid film lubrication and causing the components to vibrate and squeak.

Question 863

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon performs a primary total hip arthroplasty via a direct lateral (Hardinge) approach, which involves splitting the gluteus medius and minimus muscles. Postoperatively, the patient has a severe, unresolving Trendelenburg lurch. Assuming the repair is intact, the surgeon most likely injured a major nerve during the proximal split of the abductor muscles. To avoid this injury, the proximal dissection must stay within what safe distance from the tip of the greater trochanter?

. 1-2 cm
. 3-5 cm
. 7-9 cm
. 10-12 cm
. 14-16 cm

Correct Answer & Explanation

. 3-5 cm

Explanation

The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and tensor fasciae latae. During the direct lateral approach to the hip, splitting the gluteus medius too far proximally risks transecting the inferior branch of the superior gluteal nerve, leading to abductor paralysis and a permanent Trendelenburg gait. The standard safe zone limits the proximal split to 3 to 5 cm (typically quoted as up to 5 cm) proximal to the tip of the greater trochanter.

Question 864

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old osteoporotic female sustains a periprosthetic fracture of the femur around a cemented, polished, tapered total hip stem. Radiographs show a fracture at the tip of the stem with extension proximally, resulting in severe comminution and complete loss of proximal femoral bone stock. The femoral stem is grossly loose. The patient is limited to household ambulation. What is the most reliable surgical treatment option for this Vancouver B3 fracture?

. Open reduction and internal fixation with a lateral locking plate and cerclage cables
. Revision to a long, fully porous-coated cylindrical cementless stem
. Revision using the impaction bone grafting technique with a cemented stem
. Revision to a proximal femoral replacement (tumor prosthesis)
. Cortical strut allografting alone with delayed weight-bearing

Correct Answer & Explanation

. Revision to a proximal femoral replacement (tumor prosthesis)

Explanation

This is a Vancouver B3 periprosthetic fracture (fracture around a loose stem with severely deficient proximal bone stock). In an elderly, low-demand patient with severe osteoporosis and comminution, attempting a complex reconstruction (like impaction grafting or extensively coated stems that rely on poor bone for fixation) carries a high risk of failure and prolonged non-weight-bearing. Proximal femoral replacement (megaprosthesis) provides immediate stability, allows early full weight-bearing, and is the most reliable option.

Question 865

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old female presents with a periprosthetic femur fracture around a cemented femoral stem inserted 15 years ago. Radiographs demonstrate a fracture involving the proximal third of the femur, subsidence of the stem, and severe proximal femoral osteolysis with complete loss of the medial calcar. Which of the following is the most appropriate surgical management?

. Open reduction and internal fixation with a lateral locking plate and cerclage cables
. Revision to a fully porous-coated cylindrical long stem
. Proximal femoral replacement (tumor prosthesis)
. Impaction bone grafting with a short cemented stem
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. Proximal femoral replacement (tumor prosthesis)

Explanation

This is a Vancouver B3 periprosthetic femur fracture, characterized by a fracture around a loose stem in the setting of poor proximal bone stock. In elderly, low-demand patients with severe proximal bone loss, a proximal femoral replacement (megaprosthesis) allows for immediate weight-bearing and provides a more reliable construct than attempting complex allograft reconstructions.

Question 866

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following conditions is generally considered an absolute contraindication for a Total Ankle Arthroplasty (TAA)?

. End-stage ankle osteoarthritis secondary to a remote pilon fracture
. Age greater than 70 years
. Charcot neuroarthropathy with complete loss of protective sensation
. Concomitant subtalar joint arthritis
. Body Mass Index (BMI) of 32 kg/m2

Correct Answer & Explanation

. Charcot neuroarthropathy with complete loss of protective sensation

Explanation

Charcot neuroarthropathy or severe peripheral neuropathy with loss of protective sensation is an absolute contraindication for Total Ankle Arthroplasty due to the unacceptably high risk of implant failure, aseptic loosening, and progressive joint destruction. Advanced age, prior trauma, subtalar arthritis (which can be fused concurrently), and mild-to-moderate obesity are not absolute contraindications.

Question 867

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male is undergoing primary Total Hip Arthroplasty (THA). He has a history of a multilevel lumbar spinal fusion from L2 to the sacrum. Standing and sitting lateral radiographs reveal that his pelvic tilt changes by less than 5 degrees between the two positions. To minimize the risk of posterior dislocation when sitting, how should the surgeon adjust the acetabular cup positioning compared to a patient with normal spinopelvic mobility?

. Increase target acetabular anteversion and inclination
. Decrease target acetabular anteversion and inclination
. Place the cup in neutral version and neutral inclination
. Use a constrained liner with standard version and inclination
. Decrease femoral offset to reduce impingement

Correct Answer & Explanation

. Increase target acetabular anteversion and inclination

Explanation

Patients with a stiff lumbopelvic junction (e.g., from multilevel fusion) lack normal posterior pelvic rollback when transitioning from standing to sitting. Because the pelvis does not tilt posteriorly to naturally increase functional acetabular anteversion, the anterior femur may impinge on the anterior pelvis/cup, leading to a posterior dislocation. The surgeon must compensate by increasing the structural anteversion and inclination of the acetabular cup.

Question 868

Topic: 3. Adult Reconstruction (Hip & Knee)

Patellar clunk syndrome is a known complication following Total Knee Arthroplasty (TKA). It is most frequently associated with which of the following implant designs?

. Cruciate-retaining with a highly cross-linked polyethylene liner
. Mobile-bearing cruciate-retaining
. Posterior-stabilized with a high intercondylar box ratio
. Symmetric cruciate-retaining with a non-resurfaced patella
. Unicompartmental knee arthroplasty

Correct Answer & Explanation

. Posterior-stabilized with a high intercondylar box ratio

Explanation

Patellar clunk syndrome occurs when a fibrous nodule forms at the superior pole of the patella and catches within the intercondylar notch of the femoral component as the knee extends from a flexed position. It is almost exclusively associated with posterior-stabilized (PS) TKA designs, particularly those with a sharp or high, narrow intercondylar box that irritates the quadriceps tendon.

Question 869

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male presents with groin pain three years after a primary metal-on-polyethylene Total Hip Arthroplasty utilizing a standard titanium stem and a 36-mm cobalt-chrome head. Radiographs show a well-fixed implant without osteolysis. A MARS MRI reveals a large cystic pseudotumor around the hip joint. Laboratory analysis is most likely to show which of the following metal ion profiles?

. Elevated serum titanium, normal serum cobalt and chromium
. Elevated serum chromium, normal serum cobalt
. Elevated serum cobalt and chromium in equal proportions
. Elevated serum cobalt, normal or mildly elevated serum chromium
. Normal serum cobalt, chromium, and titanium

Correct Answer & Explanation

. Elevated serum cobalt, normal or mildly elevated serum chromium

Explanation

This clinical picture describes mechanically assisted crevice corrosion (MACC), or trunnionosis, occurring at the modular head-neck junction of a THA. In metal-on-polyethylene bearings, corrosion at a CoCr head/Titanium neck trunnion typically releases significantly more cobalt than chromium into the serum. In contrast, metal-on-metal articular wear typically produces equally elevated levels of both cobalt and chromium.

Question 870

Topic: 3. Adult Reconstruction (Hip & Knee)

The synovial fluid alpha-defensin test is highly accurate in diagnosing periprosthetic joint infection. Alpha-defensin is an antimicrobial peptide primarily secreted by which of the following cells in response to an infectious pathogen?

. Synoviocytes
. Macrophages
. Neutrophils
. T-lymphocytes
. Osteoblasts

Correct Answer & Explanation

. Neutrophils

Explanation

Alpha-defensin is a biomarker utilized for the diagnosis of periprosthetic joint infection (PJI). It is an antimicrobial peptide that is released primarily by activated neutrophils in the presence of pathogens. It integrates into microbial membranes, causing cell death, and its levels remain elevated in synovial fluid even in the presence of concurrent antibiotic therapy.

Question 871

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision Total Knee Arthroplasty for aseptic loosening, the surgeon utilizes a highly constrained implant. Extensive distal femoral bone loss requires the use of distal femoral augments; however, the surgeon inadvertently undersizes the augments and compensates by inserting a significantly thicker tibial polyethylene insert to balance the extension gap. Which of the following postoperative complications is the direct geometric consequence of this technical error?

. True patella baja
. Pseudo-patella baja
. Patella alta
. Hyperextension instability
. Asymmetric valgus instability

Correct Answer & Explanation

. Pseudo-patella baja

Explanation

By not restoring the distal femoral joint line with adequate augments and instead using a thick tibial poly, the joint line is elevated proximally. Because the length of the patellar tendon remains unchanged, the patella is drawn closer to the new, elevated joint line. This creates the radiographic and clinical appearance of a low patella relative to the joint line, known as pseudo-patella baja. True patella baja involves actual shortening of the patellar tendon.

Question 872

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient suffers an extensor mechanism disruption three years after a Total Knee Arthroplasty. Reconstruction utilizing a synthetic mesh (e.g., Marlex) is planned. To optimize the chance of a successful clinical outcome and active extension, what is the critical step during the intraoperative tensioning of the graft?

. Tensioning the mesh with the knee in 90 degrees of flexion
. Tensioning the mesh with the knee in full extension
. Tensioning the mesh with the knee in 30 degrees of flexion
. Anchoring the mesh exclusively to the medial retinaculum
. Leaving 2 cm of laxity to prevent postoperative stiffness

Correct Answer & Explanation

. Tensioning the mesh with the knee in full extension

Explanation

When performing an extensor mechanism reconstruction post-TKA using a synthetic Marlex mesh (or allograft), it is universally recommended to suture the construct under maximal tension with the knee in full extension (0 degrees). Given that these grafts universally stretch out over time, any initial laxity or tensioning in flexion will result in a clinically significant persistent extensor lag.

Question 873

Topic: Total Hip Arthroplasty (THA)
A 14-year-old girl with a 4 cm leg length discrepancy is being evaluated for an intramedullary motorized magnetic lengthening nail. Which of the following is an absolute contraindication to utilizing this specific device technology?
. History of prior external fixation on the contralateral leg
. Leg length discrepancy greater than 3 cm
. Expected postoperative need for frequent MRI screening
. Presence of a closed proximal tibial physis
. Concurrent administration of oral contraceptives

Correct Answer & Explanation

. Expected postoperative need for frequent MRI screening

Explanation

Motorized magnetic lengthening nails (such as the PRECICE nail) contain complex internal magnetic driving mechanisms. Placing a patient with this device into a Magnetic Resonance Imaging (MRI) scanner can lead to implant demagnetization, spontaneous lengthening or shortening, and implant heating or failure. Thus, an absolute requirement for ongoing MRI studies (e.g., for tumor surveillance) is an absolute contraindication for a magnetic lengthening nail.

Question 874

Topic: Total Hip Arthroplasty (THA)

In a metal-on-polyethylene Total Hip Arthroplasty, what specific design factor significantly increases the risk of mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction?

. Use of a highly cross-linked polyethylene liner
. Decreased femoral offset
. Use of a ceramic femoral head
. Increased femoral head diameter
. Use of an uncemented femoral stem

Correct Answer & Explanation

. Increased femoral head diameter

Explanation

Mechanically assisted crevice corrosion (MACC), or trunnionosis, is mediated by micromotion and fretting at the taper junction between the stem and the modular head. The use of larger diameter femoral heads (e.g., >36 mm) increases the frictional torque and lever arm acting on the head-neck junction during gait, significantly increasing the risk of trunnionosis. Ceramic heads are essentially inert and reduce the risk of corrosion.

Question 875

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with recurrent posterior dislocations following a revision total hip arthroplasty (THA). Intraoperative exploration reveals a severely deficient abductor mechanism but well-fixed acetabular and femoral components in acceptable alignment. Which of the following bearing surface options is most appropriate to maximize stability and minimize the risk of mechanical failure in this patient?

. Standard 32-mm metal-on-polyethylene articulation
. Dual mobility articulation
. Constrained acetabular liner
. Large-diameter (40-mm) ceramic-on-ceramic articulation
. Bipolar hemiarthroplasty conversion

Correct Answer & Explanation

. Dual mobility articulation

Explanation

Dual mobility articulations provide high jump distance and excellent stability, making them ideal for patients with abductor deficiency and recurrent instability. Constrained liners have a high risk of mechanical failure and loosening in the setting of absent abductors.

Question 876

Topic: Total Hip Arthroplasty (THA)

In the preoperative planning for a high tibial osteotomy to correct a varus deformity, the surgeon applies Osteotomy Rule 1. According to this principle, what is the expected geometric outcome if both the osteotomy cut and the mechanical hinge are located exactly at the center of rotation of angulation (CORA)?

. Pure angulation without translation
. Angulation with simultaneous medial translation
. Pure translation without angulation
. Angulation with simultaneous lateral translation
. Correction of both angulation and leg length discrepancy

Correct Answer & Explanation

. Pure angulation without translation

Explanation

Osteotomy Rule 1 states that if the osteotomy and the mechanical hinge are both placed at the CORA, the bone ends will angulate purely without any translational deformity.

Question 877

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female undergoes a primary total knee arthroplasty (TKA). Postoperatively, she develops lateral patellar subluxation. Radiographic and CT evaluation reveals that the tibial component was inadvertently placed in excessive internal rotation. How does this specific malrotation alter the biomechanics of the extensor mechanism?

. It medialize the tibial tubercle relative to the trochlear groove, decreasing the Q angle.
. It increases tension on the medial patellofemoral ligament, causing medial subluxation.
. It lateralizes the tibial tubercle relative to the trochlear groove, increasing the Q angle.
. It inherently causes patella baja, resulting in lateral tracking.
. It decreases the patellofemoral contact pressure, leading to patellar instability.

Correct Answer & Explanation

. It lateralizes the tibial tubercle relative to the trochlear groove, increasing the Q angle.

Explanation

Internal rotation of the tibial component effectively lateralizes the tibial tubercle relative to the femoral trochlea. This increases the Q angle, directly causing lateral patellar maltracking and subluxation.

Question 878

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old male presents with acute thigh pain and inability to bear weight after a mechanical fall. Radiographs demonstrate a fracture around the stem of his cementless total hip arthroplasty, with obvious subsidence of the femoral component. The fracture extends just distal to the lesser trochanter. What is the most appropriate surgical management?

. Open reduction internal fixation with a locking plate and cerclage wires alone
. Revision to a cemented standard-length femoral stem
. Nonoperative management with traction for 6 weeks
. Revision to a fully porous-coated long diaphyseal-engaging stem bypassing the fracture by 2 cortical diameters
. Proximal femoral replacement (megaprosthesis)

Correct Answer & Explanation

. Revision to a fully porous-coated long diaphyseal-engaging stem bypassing the fracture by 2 cortical diameters

Explanation

This is a Vancouver B2 periprosthetic fracture (fracture around a loose stem with adequate proximal bone stock). The standard of care is revision to a longer, distally engaging stem that bypasses the most distal fracture line by at least two cortical diameters.

Question 879

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male presents with groin pain 7 years after a primary metal-on-polyethylene total hip arthroplasty. Aspiration is negative for infection, but serum metal ions show an elevated Cobalt level with a relatively normal Chromium level. MRI demonstrates a large pseudotumor. What is the primary pathophysiologic mechanism for this failure?

. Abrasive wear of the polyethylene liner
. Galvanic corrosion at the interface of the titanium shell and cobalt-chromium liner
. Mechanically assisted crevice corrosion at the head-neck junction
. Third-body wear from retained bone cement
. Impingement of the femoral neck on the acetabular rim

Correct Answer & Explanation

. Mechanically assisted crevice corrosion at the head-neck junction

Explanation

Elevated Cobalt out of proportion to Chromium in a metal-on-polyethylene THA strongly indicates trunnionosis. This is caused by mechanically assisted crevice corrosion (MACC) at the modular head-neck taper junction.

Question 880

Topic: 3. Adult Reconstruction (Hip & Knee)

When utilizing a high-offset femoral stem in primary total hip arthroplasty, which of the following describes the resulting biomechanical effect compared to a standard-offset stem, assuming vertical height remains unchanged?

. It decreases the abductor moment arm and increases joint reactive forces.
. It decreases the abductor moment arm and decreases joint reactive forces.
. It increases the abductor moment arm and increases joint reactive forces.
. It increases the abductor moment arm and decreases joint reactive forces.
. It has no effect on joint reactive forces but increases the risk of posterior dislocation.

Correct Answer & Explanation

. It increases the abductor moment arm and decreases joint reactive forces.

Explanation

Increasing femoral offset lateralizes the femur, which directly increases the abductor moment arm. A longer abductor lever arm requires less abductor muscle force to maintain pelvic stability, thereby decreasing the overall joint reactive forces across the hip.

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