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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 198 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 3941

Topic: 3. Adult Reconstruction (Hip & Knee)

Metal-on-metal hip resurfacing arthroplasty has specific indications and contraindications. Which of the following patient profiles is associated with the highest risk of early failure and adverse local tissue reactions (ALTR) following this procedure?

. A 45-year-old male with a femoral head size of 54 mm
. A 50-year-old male with primary osteoarthritis
. A 55-year-old male with a history of slipped capital femoral epiphysis
. A 40-year-old female with a femoral head size of 44 mm
. A 35-year-old male with avascular necrosis

Correct Answer & Explanation

. A 40-year-old female with a femoral head size of 44 mm

Explanation

Female gender and small femoral head components (< 48 mm) are major risk factors for failure in metal-on-metal hip resurfacing. Small heads reduce the clearance and fluid film lubrication, increasing wear and ALTR risk.

Question 3942

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, the 'jump distance' is the distance the femoral head must translate laterally to dislocate from the acetabular component. Which of the following component modifications will most effectively increase the jump distance without altering leg length?

. Increasing the femoral neck length
. Decreasing the acetabular cup anteversion
. Increasing the femoral head diameter
. Using a lateralized femoral liner
. Increasing the femoral stem offset

Correct Answer & Explanation

. Increasing the femoral head diameter

Explanation

Jump distance is mathematically defined as the radius of the femoral head. Therefore, increasing the femoral head diameter directly increases the jump distance, significantly reducing the risk of dislocation.

Question 3943

Topic: 3. Adult Reconstruction (Hip & Knee)

Dual mobility components are increasingly utilized in revision THA to prevent instability. What is the primary biomechanical mechanism by which these components reduce the risk of dislocation?

. Decreasing the effective jump distance
. Increasing the effective head size and head-to-neck ratio
. Providing a constrained locking ring around the femoral head
. Shifting the center of rotation medially
. Preventing translation of the inner bearing surface

Correct Answer & Explanation

. Increasing the effective head size and head-to-neck ratio

Explanation

Dual mobility implants consist of a standard femoral head articulating within a large mobile polyethylene liner, which then articulates within a metal shell. This increases the effective head size (the large poly liner) and maximizes the head-to-neck ratio, drastically increasing the jump distance and range of motion before impingement.

Question 3944

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following findings is considered a definitive 'major criterion' for the diagnosis of periprosthetic joint infection (PJI)?

. Two positive periprosthetic cultures with phenotypically identical organisms
. A serum C-reactive protein (CRP) level > 10 mg/L
. A synovial fluid white blood cell (WBC) count > 3,000 cells/uL
. Elevated synovial fluid alpha-defensin
. Positive leukocyte esterase on synovial fluid dipstick

Correct Answer & Explanation

. Two positive periprosthetic cultures with phenotypically identical organisms

Explanation

The 2018 ICM criteria define two major criteria that definitively diagnose PJI: 1) A sinus tract communicating with the joint space, and 2) Two positive periprosthetic tissue/fluid cultures isolating the same organism.

Question 3945

Topic: Total Hip Arthroplasty (THA)

A 58-year-old male undergoes a direct anterior approach THA. Postoperatively, he complains of burning pain and numbness over the anterolateral aspect of his thigh, but his quadriceps motor function is completely intact. Which nerve was most likely injured during the surgical exposure?

. Femoral nerve
. Lateral femoral cutaneous nerve
. Obturator nerve
. Superior gluteal nerve
. Ilioinguinal nerve

Correct Answer & Explanation

. Lateral femoral cutaneous nerve

Explanation

The lateral femoral cutaneous nerve (LFCN) is a pure sensory nerve that crosses over the sartorius muscle and is at high risk of stretch or transection during the direct anterior approach to the hip, leading to anterolateral thigh numbness (meralgia paresthetica).

Question 3946

Topic: 3. Adult Reconstruction (Hip & Knee)

Patients with sickle cell disease who undergo total hip arthroplasty for avascular necrosis present unique perioperative challenges. Compared to patients undergoing THA for primary osteoarthritis, sickle cell patients have a significantly higher risk of which of the following complications?

. Aseptic loosening at 1 year
. Heterotopic ossification
. Sciatic nerve palsy
. Perioperative vaso-occlusive crises and periprosthetic infection
. Ceramic liner fracture

Correct Answer & Explanation

. Perioperative vaso-occlusive crises and periprosthetic infection

Explanation

Sickle cell disease patients are at a remarkably high risk for perioperative complications following THA, most notably vaso-occlusive crises (sickle cell crises) triggered by surgical stress/hypoxia, as well as a markedly increased risk of periprosthetic joint infection.

Question 3947

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with severe groin pain 10 years after a revision total hip arthroplasty.

Radiographs demonstrate complete separation of the superior and inferior hemi-pelvis through the acetabulum. Which of the following is the most appropriate management for a chronic, unhealed pelvic discontinuity with adequate remaining bone stock?

. Isolated bone grafting
. Jumbo porous cup alone
. Highly porous revision shell with an ilioischial cage (cup-cage construct)
. Cemented cup in isolated structural allograft
. Girdlestone resection arthroplasty

Correct Answer & Explanation

. Highly porous revision shell with an ilioischial cage (cup-cage construct)

Explanation

Pelvic discontinuity requires spanning the defect and achieving stable fixation in both the ilium and ischium. A cup-cage construct, custom triflange, or distraction with highly porous components provides necessary mechanical stability to allow biological fixation or healing.

Question 3948

Topic: 3. Adult Reconstruction (Hip & Knee)

A 50-year-old male undergoes a primary total hip arthroplasty using a ceramic-on-ceramic bearing surface. Two years postoperatively, he complains of an audible squeaking sound during gait, though he denies any pain. Which of the following factors is most strongly associated with this phenomenon?

. Component malpositioning, particularly acetabular cup retroversion or steep inclination
. Obesity (BMI > 35)
. Impaired renal clearance of ceramic debris
. Oversized femoral head (> 40 mm)
. Use of an uncemented femoral stem

Correct Answer & Explanation

. Component malpositioning, particularly acetabular cup retroversion or steep inclination

Explanation

Squeaking in ceramic-on-ceramic THA is frequently linked to edge loading caused by component malposition, such as cup retroversion or excessive inclination. Other factors include impingement and third-body wear, but cup positioning is the most consistently identified risk factor.

Question 3949

Topic: Total Hip Arthroplasty (THA)

Increasing femoral offset during total hip arthroplasty without changing the vertical leg length will have which of the following biomechanical effects?

. Increased joint reaction force
. Decreased abductor muscle lever arm
. Decreased tension on the abductor musculature
. Increased bending moment on the femoral stem
. Increased risk of bony impingement during abduction

Correct Answer & Explanation

. Increased bending moment on the femoral stem

Explanation

Increasing femoral offset increases the abductor lever arm, which favorably decreases both the required abductor force and the overall joint reaction force. However, increasing the horizontal distance from the center of the head to the stem shaft also increases the bending moment (stress) on the femoral component.

Question 3950

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a metal-on-polyethylene total hip arthroplasty placed 8 years ago presents with new-onset groin pain and a palpable anterior thigh mass. Hip aspiration yields cloudy fluid with 2,500 WBC/uL and a negative Gram stain. Serum cobalt is markedly elevated, while serum chromium is normal. Which of the following is the most likely cause of this patient's symptoms?

. Acute periprosthetic joint infection
. Adverse local tissue reaction secondary to mechanically assisted crevice corrosion
. Polyethylene wear debris causing massive osteolysis
. Impingement of the iliopsoas tendon
. Aseptic loosening of the acetabular component

Correct Answer & Explanation

. Adverse local tissue reaction secondary to mechanically assisted crevice corrosion

Explanation

Mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction results in elevated serum cobalt levels (often out of proportion to chromium) and an adverse local tissue reaction (pseudotumor). The negative Gram stain and modest white blood cell count differentiate this ALTR from an acute infection.

Question 3951

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male with a history of multiple revision total hip arthroplasties presents with massive proximal femoral bone loss (Paprosky Type IV).

The decision is made to perform a proximal femoral replacement (megaprosthesis). Which of the following is the most common major complication associated with this procedure for non-oncologic indications?

. Periprosthetic fracture of the distal femur
. Sciatic nerve palsy
. Instability and dislocation
. Aseptic loosening of the acetabular component
. Symptomatic heterotopic ossification

Correct Answer & Explanation

. Instability and dislocation

Explanation

Instability and dislocation are the most common complications following proximal femoral replacement for non-oncologic indications, with rates often exceeding 15-20%. This complication is primarily driven by the extensive loss of soft tissue attachments, particularly the abductor mechanism.

Question 3952

Topic: 3. Adult Reconstruction (Hip & Knee)

A 38-year-old asthmatic patient on chronic oral corticosteroids presents with 3 months of progressive groin pain.

MRI reveals a well-demarcated area of osteonecrosis in the anterosuperior femoral head involving 20% of the weight-bearing surface. Plain radiographs show no evidence of subchondral collapse or crescent sign. What is the most appropriate joint-preserving surgical intervention?

. Vascularized free fibular grafting
. Core decompression
. Proximal femoral rotational osteotomy
. Total hip arthroplasty
. Hip resurfacing arthroplasty

Correct Answer & Explanation

. Core decompression

Explanation

In early-stage (Ficat Stage I or II) osteonecrosis of the femoral head with a small to medium-sized lesion and no subchondral collapse, core decompression is the preferred initial surgical treatment. The goal is to reduce intraosseous pressure, alleviate pain, and potentially promote revascularization.

Question 3953

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old woman presents with recurrent posterior dislocations following a primary total hip arthroplasty. Radiographs demonstrate a well-fixed femoral stem with appropriate anteversion, but the acetabular component is retroverted.

Which of the following is the most appropriate surgical intervention?

. Exchange to a larger femoral head
. Acetabular component revision
. Femoral component revision
. Application of a constrained liner
. Trochanteric advancement

Correct Answer & Explanation

. Acetabular component revision

Explanation

Posterior instability resulting from acetabular retroversion is a component malpositioning issue. Revision of the malpositioned acetabular cup to the correct anteversion is required rather than simply increasing head size or using a constrained liner.

Question 3954

Topic: 3. Adult Reconstruction (Hip & Knee)

A 32-year-old man with systemic lupus erythematosus on chronic corticosteroids presents with severe bilateral groin pain. MRI reveals pre-collapse avascular necrosis of both femoral heads (Ficat stage II) with edema. What is the most appropriate initial surgical management?

. Total hip arthroplasty
. Bipolar hemiarthroplasty
. Core decompression
. Proximal femoral osteotomy
. Hip arthroscopy with labral debridement

Correct Answer & Explanation

. Core decompression

Explanation

Core decompression is indicated for early-stage (pre-collapse) osteonecrosis of the femoral head. It relieves intraosseous pressure, decreases pain, and may promote revascularization, which is ideal in young patients to delay arthroplasty.

Question 3955

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man presents with groin pain and a palpable anterior thigh mass 6 years after a metal-on-metal total hip arthroplasty. Serum cobalt and chromium levels are significantly elevated. MARS MRI demonstrates a large cystic pseudotumor. What is the most appropriate next step in management?

. CT-guided aspiration of the mass
. Observation with serial MRIs
. Revision to a ceramic-on-polyethylene bearing
. Resection of the mass only
. Administration of oral metal chelators

Correct Answer & Explanation

. Revision to a ceramic-on-polyethylene bearing

Explanation

Symptomatic adverse local tissue reaction (ALTR) with elevated metal ions and a pseudotumor in a metal-on-metal THA requires revision. The bearing surfaces must be exchanged to non-metal alternatives, typically combined with excision of the necrotic tissue.

Question 3956

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old woman presents with persistent hip pain 2 years following a total hip arthroplasty. Aspiration of the hip yields a synovial white blood cell count of 4,500 cells/ยตL with 85% polymorphonuclear leukocytes (PMNs). What is the most appropriate definitive management?

. Observation and physical therapy
. Chronic suppressive oral antibiotics
. Two-stage revision arthroplasty
. One-stage revision arthroplasty without tissue cultures
. Arthroscopic washout and liner exchange

Correct Answer & Explanation

. Two-stage revision arthroplasty

Explanation

A synovial WBC >3,000 cells/ยตL and >80% PMNs is highly diagnostic of chronic periprosthetic joint infection in a THA over 90 days out. Two-stage exchange arthroplasty remains the gold standard treatment in North America.

Question 3957

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following patients has an absolute contraindication for a metal-on-metal hip resurfacing arthroplasty?

. A 50-year-old male with primary osteoarthritis
. A 45-year-old male with FAI-induced secondary osteoarthritis
. A 60-year-old female with advanced chronic kidney disease
. A 55-year-old male with osteonecrosis and minimal head collapse
. A 48-year-old male with post-traumatic osteoarthritis

Correct Answer & Explanation

. A 60-year-old female with advanced chronic kidney disease

Explanation

Advanced renal disease is an absolute contraindication for MoM hip resurfacing due to the inability of the kidneys to properly clear cobalt and chromium ions. Women of childbearing age and patients with severe osteoporosis are also contraindicated.

Question 3958

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old woman sustains a fall 8 years after a cemented THA. Radiographs show a fracture occurring 5 cm distal to the tip of the femoral stem.

The stem remains well-fixed. According to the Vancouver classification, what is the proper classification and management?

. Type A, manage conservatively
. Type B1, manage with open reduction and internal fixation
. Type B2, manage with revision to a long stem
. Type C, manage with open reduction and internal fixation
. Type C, manage with revision to a distal femoral replacement

Correct Answer & Explanation

. Type C, manage with open reduction and internal fixation

Explanation

A Vancouver Type C fracture occurs entirely distal to the tip of the prosthesis. The standard treatment is open reduction and internal fixation using plates and screws, ensuring the fixation overlaps the prosthesis tip.

Question 3959

Topic: 3. Adult Reconstruction (Hip & Knee)

A 25-year-old woman presents with symptomatic hip dysplasia. Her center-edge angle is 12 degrees. The triradiate cartilage is closed, and there is no evidence of advanced osteoarthritis. Which of the following procedures is most appropriate?

. Salter osteotomy
. Dega osteotomy
. Bernese periacetabular osteotomy (PAO)
. Total hip arthroplasty
. Chiari osteotomy

Correct Answer & Explanation

. Bernese periacetabular osteotomy (PAO)

Explanation

The Bernese PAO is the procedure of choice for symptomatic acetabular dysplasia in young adults with closed triradiate cartilage. It allows for powerful multiplanar correction while preserving the integrity of the posterior column.

Question 3960

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man presents with groin pain 5 years after an uncomplicated metal-on-polyethylene total hip arthroplasty using a large-diameter cobalt-chromium femoral head on a titanium stem. Laboratory tests show significantly elevated serum cobalt levels with normal serum chromium levels. What is the most likely diagnosis?

. Polyethylene wear
. Trunnionosis (Mechanically assisted crevice corrosion)
. Periprosthetic joint infection
. Aseptic loosening of the femoral stem
. Iliopsoas impingement

Correct Answer & Explanation

. Trunnionosis (Mechanically assisted crevice corrosion)

Explanation

Trunnionosis occurs at the modular head-neck junction due to mechanically assisted crevice corrosion. It is classically characterized by elevated serum cobalt levels disproportionate to chromium in metal-on-polyethylene bearings, leading to adverse local tissue reactions.

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