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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 85 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 1681

Topic: 3. Adult Reconstruction (Hip & Knee)
Figure 46 shows the AP radiograph of an active 80-year-old patient with an acetabular fracture. The fracture was initially managed nonsurgically; however, the patient is now scheduled to undergo total hip arthroplasty. What is the treatment of choice for the contained acetabular bone defect?
. Bipolar femoral component
. Acetabular cage
. Large structural allograft
. Use of the femoral head
. Double-bubble acetabular cup

Correct Answer & Explanation

. Use of the femoral head

Explanation

Acetabular fractures can result in a relative or actual acetabular bone defect. The medial blow-out fracture of the acetabulum has united well in this patient. The femoral head may be used as morcellized or structural bone to augment the medial defect and is preferred to structural allograft.

Question 1682

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty for osteoarthritis, trial components are placed. Examination reveals that the knee is perfectly balanced in full extension but is significantly tight in 90 degrees of flexion. Which of the following is the most appropriate step to balance the knee?

. Decrease the posterior slope of the proximal tibial cut.
. Upsize the femoral component.
. Release the posterior capsule from the femur.
. Downsize the femoral component and maintain an anteriorly referenced cut.
. Recut the distal femur to remove more bone.

Correct Answer & Explanation

. Decrease the posterior slope of the proximal tibial cut.

Explanation

A knee that is balanced in extension but tight in flexion typically indicates that the posterior condylar offset of the femoral component is too large, or the PCL (if retaining) is too tight. Downsizing the femoral component (using anterior referencing) decreases the anteroposterior (AP) dimension, thus reducing the posterior condylar prominence and increasing the flexion gap without affecting the extension gap.

Question 1683

Topic: Total Hip Arthroplasty (THA)

A 55-year-old highly active male underwent a primary total hip arthroplasty 2 years ago using a ceramic-on-ceramic bearing. He is very satisfied with his pain relief but complains of an audible 'squeaking' noise from the hip when rising from a chair. Which of the following factors is most strongly associated with this complication?

. Use of an undersized femoral stem
. Component malposition, particularly acetabular cup edge loading
. Femoral head size smaller than 32 mm
. Concurrent use of a highly cross-linked polyethylene liner
. Patient BMI less than 25 kg/m2

Correct Answer & Explanation

. Use of an undersized femoral stem

Explanation

Squeaking is a specific complication of ceramic-on-ceramic (CoC) bearings, occurring in up to 10% of patients. The noise is strongly associated with component malposition (e.g., steep inclination or excessive anteversion of the acetabular cup), which leads to edge loading. This causes micro-separation, disrupts fluid film lubrication, and leads to stripe wear and the resulting squeak.

Question 1684

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old woman with a history of a metal-on-metal total hip arthroplasty performed 8 years ago presents with new-onset groin pain and a palpable anterior thigh mass. Inflammatory markers are normal. MRI demonstrates a thick-walled cystic mass communicating with the joint. What is the classic histopathological finding associated with this condition?

. Massive polymorphonuclear leukocyte infiltration
. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Sheets of foamy macrophages with polyethylene debris
. Multinucleated giant cells containing birefringent crystals
. Monosodium urate crystal deposition

Correct Answer & Explanation

. Massive polymorphonuclear leukocyte infiltration

Explanation

The presentation describes an adverse local tissue reaction (ALTR) or 'pseudotumor' associated with metal-on-metal THA. This is characterized by a delayed Type IV hypersensitivity reaction to metal wear debris (cobalt and chromium ions). The hallmark histological finding is an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL), which includes perivascular lymphocytic infiltration, tissue necrosis, and fibrin deposition.

Question 1685

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with a painful total knee arthroplasty 3 years postoperatively. His serum ESR is 45 mm/hr and CRP is 18 mg/L. Joint aspiration yields a white blood cell count of 4,500 cells/ยตL with 75% PMNs. Which of the following synovial fluid biomarkers currently offers the highest specificity for confirming a periprosthetic joint infection in this patient?

. Alpha-defensin
. Interleukin-6 (IL-6)
. Leukocyte esterase
. C-reactive protein (CRP)
. Calprotectin

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. Multiple meta-analyses have shown that synovial fluid alpha-defensin testing provides exceptionally high sensitivity and specificity (both typically >95%) for diagnosing periprosthetic joint infection (PJI). It outperforms other markers, including leukocyte esterase and synovial CRP, particularly in avoiding false positives from non-infectious inflammatory conditions.

Question 1686

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female sustains a posterior dislocation of her total hip arthroplasty 4 weeks postoperatively. The surgery was performed via a posterior approach. After successful closed reduction, what is the most appropriate bracing strategy to prevent a recurrent posterior dislocation?

. A brace locking the hip in 20 degrees of extension and 10 degrees of adduction
. A brace limiting hip flexion to 70 degrees and preventing internal rotation
. A brace limiting hip extension and preventing external rotation
. A knee immobilizer to prevent hamstring contraction
. An ankle-foot orthosis to control the foot progression angle

Correct Answer & Explanation

. A brace locking the hip in 20 degrees of extension and 10 degrees of adduction

Explanation

Posterior dislocations of a THA most commonly occur when the hip is placed in a position of excessive flexion, adduction, and internal rotation. Therefore, to prevent a recurrent posterior dislocation, an abduction brace should be applied that restricts these 'at-risk' positions. It typically limits hip flexion (e.g., to 70 degrees or less) and prevents internal rotation and adduction.

Question 1687

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male undergoes a primary total knee arthroplasty for severe valgus osteoarthritis (25 degrees of valgus deformity). In the recovery room, he is noted to have a foot drop and decreased sensation over the dorsum of his foot. What is the most appropriate initial management for this complication?

. Immediate surgical exploration of the peroneal nerve
. Removal of all compressive dressings and slightly flexing the knee
. Ordering an emergent MRI of the knee
. Administration of high-dose intravenous corticosteroids
. Application of an ankle-foot orthosis (AFO) and immediate full weight-bearing

Correct Answer & Explanation

. Immediate surgical exploration of the peroneal nerve

Explanation

Peroneal nerve palsy is a severe complication of TKA, especially following the correction of severe valgus or flexion contractures. The nerve experiences traction injury as the lateral side is tensioned. Postoperative swelling and tight dressings can exacerbate the compromise. The immediate first step is to remove all restrictive dressings, splints, and wraps, and to slightly flex the knee to relieve physical tension on the peroneal nerve. Surgical exploration is generally reserved for suspected direct laceration or expanding hematoma.

Question 1688

Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old female presents with a loose right total hip arthroplasty. Radiographs demonstrate superior migration of the acetabular component by 3.5 cm, with massive osteolysis extending medial to the Kohler line and complete destruction of the inferior aspect of the teardrop. This acetabular defect is best classified as:
. Paprosky IIA
. Paprosky IIB
. Paprosky IIIA
. Paprosky IIIB
. Paprosky IIIC

Correct Answer & Explanation

. Paprosky IIIB

Explanation

The Paprosky classification for acetabular defects guides reconstruction. Type IIIB defects are characterized by severe superior migration (>3 cm), medial migration past the Kohler line, and loss of the inferior teardrop, indicating massive bone loss and pelvic discontinuity risk. Type IIIA defects also have >3 cm superior migration but maintain an intact teardrop and Kohler line (the medial wall is intact).

Question 1689

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon performs a trial reduction and notes lateral patellar subluxation during flexion without the tourniquet inflated. Which of the following technical errors could most likely contribute to this finding?

. External rotation of the femoral component
. External rotation of the tibial component
. Internal rotation of the femoral component
. Lateralization of the tibial component
. Lateralization of the femoral component

Correct Answer & Explanation

. External rotation of the femoral component

Explanation

Internal rotation of the femoral component and internal rotation of the tibial component both medialise the trochlear groove or lateralise the tibial tubercle relative to the trochlea, increasing the Q-angle and leading to lateral patellar maltracking. External rotation of the femoral or tibial components, as well as medialization of the tibial tray or patellar button, typically improves patellar tracking.

Question 1690

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with a painful total knee arthroplasty 6 weeks after index surgery. Aspiration reveals synovial WBC of 45,000 cells/ยตL with 92% PMNs. Cultures grow methicillin-sensitive Staphylococcus aureus. Radiographs confirm a loose tibial component with a wide radiolucent line. Which of the following is an absolute contraindication to Debridement, Antibiotics, and Implant Retention (DAIR)?

. Infection identified at 6 weeks post-operatively
. Staphylococcus aureus as the infecting organism
. A loose tibial component
. Presence of a well-healed surgical incision
. Patient age greater than 65

Correct Answer & Explanation

. Infection identified at 6 weeks post-operatively

Explanation

DAIR is generally indicated for acute postoperative infections (within 90 days) or acute hematogenous infections (symptoms < 3 weeks) in the setting of a well-fixed prosthesis and a healthy soft tissue envelope. A loose prosthesis is an absolute contraindication to DAIR and necessitates component removal (typically via a 2-stage exchange arthroplasty).

Question 1691

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old male presents with severe groin pain 6 years after an uncomplicated primary THA using a cobalt-chrome head on a titanium stem with a highly cross-linked polyethylene liner. His serum cobalt level is 8 ppb and chromium is 1 ppb. MRI with MARS reveals a large cystic mass communicating with the joint space. What is the most likely diagnosis?

. Polyethylene wear-induced osteolysis
. Adverse local tissue reaction (ALTR) due to trunnionosis
. Periprosthetic joint infection
. Iliopsoas impingement
. Heterotopic ossification

Correct Answer & Explanation

. Polyethylene wear-induced osteolysis

Explanation

In a metal-on-polyethylene THA, an elevated serum cobalt level that is disproportionately higher than the chromium level (Co > Cr) points to mechanically assisted crevice corrosion (MACC) at the head-neck junction (trunnionosis). This corrosion leads to an adverse local tissue reaction (ALTR) or pseudotumor, manifesting as a cystic mass on MRI.

Question 1692

Topic: Total Knee Arthroplasty (TKA)

A 55-year-old male with medial compartment osteoarthritis of the knee is being evaluated for a unicompartmental knee arthroplasty (UKA). Which of the following is historically and contemporarily considered an absolute contraindication to a medial UKA?

. Age less than 60 years
. Weight greater than 90 kg
. Anterior cruciate ligament (ACL) deficiency
. Flexion contracture of 10 degrees
. Inflammatory arthritis

Correct Answer & Explanation

. Age less than 60 years

Explanation

Inflammatory arthritis (such as Rheumatoid arthritis) is a universally accepted absolute contraindication to UKA because the disease is systemic and involves all compartments of the joint, leading to a very high rate of early failure. ACL deficiency was traditionally an absolute contraindication, but it is now considered a relative contraindication (or even acceptable in selected cases with fixed-bearing UKA). Age, weight, and mild flexion contractures (<15 degrees) are not absolute contraindications.

Question 1693

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex revision total hip arthroplasty to extract a well-fixed, fully porous-coated cylindrical femoral stem, the surgeon decides to perform an extended trochanteric osteotomy (ETO). The osteotomy is correctly performed by:

. Osteotomizing the greater trochanter alone from its base
. Splitting the proximal femur in the coronal plane, removing the anterior half
. Removing the lateral one-third of the proximal femur while maintaining the abductor and vastus lateralis attachments
. Removing the medial cortex and lesser trochanter to preserve the lateral tension band
. Performing a transverse osteotomy just distal to the lesser trochanter

Correct Answer & Explanation

. Osteotomizing the greater trochanter alone from its base

Explanation

An extended trochanteric osteotomy (ETO) involves making a controlled osteotomy of the lateral one-third of the proximal femur. This preserves the tendinous insertions of the gluteus medius and minimus proximally and the vastus lateralis distally as a continuous sleeve, maintaining the blood supply and aiding in subsequent healing. It provides excellent exposure for cement or stem removal and allows straight-line reaming for the revision stem.

Question 1694

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female undergoes a primary posterior-stabilized total knee arthroplasty. During trial reduction with the thinnest available polyethylene insert, the knee is found to be symmetrically tight in both full extension and 90 degrees of flexion. What is the most appropriate next step to achieve a balanced gap?

. Resect more distal femur
. Downsize the femoral component
. Resect more proximal tibia
. Recut the distal femur with more valgus
. Release the posterior capsule

Correct Answer & Explanation

. Resect more distal femur

Explanation

When a total knee arthroplasty is symmetrically tight in both flexion and extension, the overall joint space is too small. Because the tibial cut affects both the flexion and extension gaps equally, resecting more proximal tibia (or using a thinner polyethylene insert, if one were available) will increase both gaps simultaneously and achieve balance. Resecting more distal femur only increases the extension gap, while downsizing the femoral component primarily affects the flexion gap.

Question 1695

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with a painful total knee arthroplasty 3 years postoperatively. Synovial fluid analysis reveals a WBC count of 3,500 cells/uL with 75% PMNs. An alpha-defensin test is ordered and returns positive. Which of the following best describes the nature and clinical utility of alpha-defensin in diagnosing periprosthetic joint infection (PJI)?

. It is an antimicrobial peptide released by neutrophils and is highly sensitive and specific for PJI
. It is an acute phase reactant produced by the liver and is a non-specific marker of inflammation
. It is an enzyme produced by bacteria that degrades the extracellular matrix
. Its diagnostic accuracy is significantly diminished by the prior administration of antibiotics
. It is produced exclusively by synovial fibroblasts in response to prosthetic wear debris

Correct Answer & Explanation

. It is an antimicrobial peptide released by neutrophils and is highly sensitive and specific for PJI

Explanation

Alpha-defensin is a biomarker used in the diagnosis of periprosthetic joint infection (PJI). It is an antimicrobial peptide released primarily by human neutrophils in response to pathogens. The synovial fluid alpha-defensin test has been shown to be highly sensitive and specific for PJI. A key advantage of the test is that its accuracy is not significantly diminished by prior systemic antibiotic administration, unlike traditional synovial fluid cultures.

Question 1696

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old male presents with isolated medial compartment knee osteoarthritis. He is considering a medial unicompartmental knee arthroplasty (UKA). Which of the following conditions represents an absolute contraindication to proceeding with a UKA?

. Patient age less than 60 years
. Patient weight greater than 90 kg
. An intact anterior cruciate ligament (ACL)
. Inflammatory arthropathy (e.g., Rheumatoid arthritis)
. Asymptomatic patellofemoral chondromalacia noted on MRI

Correct Answer & Explanation

. Patient age less than 60 years

Explanation

Inflammatory arthropathies, such as rheumatoid arthritis, are generally considered absolute contraindications for unicompartmental knee arthroplasty due to the systemic, progressive nature of the disease, which will almost certainly affect the remaining un-resurfaced compartments of the knee. Historically, age <60, weight >90kg, and patellofemoral changes were contraindications (Kozinn and Scott criteria), but modern literature has largely debunked these as absolute contraindications. An intact ACL is a requirement (an indication), not a contraindication, for a standard UKA.

Question 1697

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old female is 8 years post-operative from a metal-on-metal total hip arthroplasty. She presents with new-onset, progressive anterior groin pain and a palpable soft tissue mass. Serum cobalt and chromium levels are elevated. MRI with MARS sequencing reveals a large periarticular cystic mass. Tissue biopsy of the periarticular soft tissues would most likely reveal which of the following characteristic histologic findings?

. Abundant polymorphonuclear leukocytes and intracellular bacteria
. Dense sheets of polyethylene wear debris with foreign body giant cells
. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Massive deposition of monosodium urate crystals
. Osteoclast-rich granulomas containing birefringent pyrophosphate crystals

Correct Answer & Explanation

. Abundant polymorphonuclear leukocytes and intracellular bacteria

Explanation

The clinical scenario describes an adverse local tissue reaction (ALTR) or pseudotumor associated with a metal-on-metal (MoM) total hip arthroplasty. The characteristic histologic hallmark of this condition is the Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion (ALVAL), which represents a delayed type IV hypersensitivity immune response to metal ions (cobalt and chromium).

Question 1698

Topic: Total Hip Arthroplasty (THA)

During a total hip arthroplasty via a posterior approach, the surgeon inadvertently utilizes a femoral component with significantly less femoral offset than the patient's native anatomy, though leg lengths are perfectly restored. Postoperatively, the patient experiences recurrent posterior dislocations. Decreasing femoral offset contributes to joint instability primarily through which of the following mechanisms?

. Increasing the distance between the greater trochanter and the center of rotation
. Lengthening the limb disproportionately relative to the contralateral side
. Lateralizing the center of rotation of the hip
. Increasing tension on the iliopsoas tendon
. Decreasing the tension of the abductor musculature

Correct Answer & Explanation

. Increasing the distance between the greater trochanter and the center of rotation

Explanation

Femoral offset is the horizontal distance from the center of rotation of the femoral head to a line bisecting the long axis of the femur. Decreasing femoral offset shortens the lever arm of the abductor musculature. This results in relative soft tissue laxity and weakness of the abductors, which significantly decreases the stability of the hip joint and increases the risk of dislocation. It can also lead to earlier bony impingement between the greater trochanter and the pelvis.

Question 1699

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with a painful 'catching' or 'popping' sensation in her knee 14 months after undergoing a posterior-stabilized total knee arthroplasty. She notes the catching occurs consistently as she extends her knee from a flexed position, typically around 30 to 45 degrees of flexion. Which of the following is the underlying pathophysiology of this specific phenomenon?

. Aseptic loosening of the patellar component
. Overstuffing of the anterior compartment leading to patellofemoral impingement
. Formation of a fibrosynovial nodule at the superior pole of the patella that catches in the intercondylar notch
. Impingement of the popliteus tendon on an oversized posterolateral tibial baseplate
. Severe, asymmetric polyethylene wear of the tibial insert

Correct Answer & Explanation

. Aseptic loosening of the patellar component

Explanation

The clinical presentation describes 'patellar clunk syndrome,' a known complication primarily associated with posterior-stabilized (PS) total knee arthroplasty designs. It is caused by the development of a fibrosynovial nodule at the junction of the quadriceps tendon and the superior pole of the patella. As the knee extends from flexion, this nodule drops into the intercondylar box of the femoral component and then forcefully 'clunks' or pops out as extension continues (usually between 30 and 45 degrees of flexion). Treatment is arthroscopic excision of the nodule.

Question 1700

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male with a metal-on-polyethylene total hip arthroplasty (modular unipolar femoral head) placed 6 years ago presents with new-onset anterior groin pain. Radiographs show well-fixed components. Serum metal ion testing reveals a Cobalt level of 18 ppb and a Chromium level of 1.2 ppb. What is the most likely etiology of his symptoms?

. Polyethylene wear induced osteolysis
. Aseptic loosening of the femoral stem
. Adverse local tissue reaction due to trunnionosis
. Periprosthetic joint infection
. Impingement of the iliopsoas tendon

Correct Answer & Explanation

. Polyethylene wear induced osteolysis

Explanation

Elevated serum cobalt levels with normal or slightly elevated chromium levels in the setting of a metal-on-polyethylene THA is classic for mechanically assisted crevice corrosion (trunnionosis) at the head-neck junction. This leads to an adverse local tissue reaction (ALTR).

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