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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 159 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 3161

Topic: Total Hip Arthroplasty (THA)

A 68-year-old man presents with his third posterior dislocation of a primary THA performed 4 months ago. Radiographs demonstrate the acetabular component is in 35 degrees of abduction and 5 degrees of retroversion. The femoral stem is stable and in neutral version. What is the most appropriate definitive management?

. Closed reduction and application of a hip spica cast for 6 weeks
. Revision of the femoral stem to increase anteversion
. Revision of the acetabular component to increase anteversion
. Application of a constrained acetabular liner
. Conversion to bipolar hemiarthroplasty

Correct Answer & Explanation

. Closed reduction and application of a hip spica cast for 6 weeks

Explanation

The acetabular component is retroverted, which mechanically predisposes the patient to posterior impingement and instability. Revision of the malpositioned acetabular component to an ideal 15-20 degrees of anteversion directly addresses the root cause of the recurrent dislocations.

Question 3162

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old woman presents with worsening right hip pain 2 years after a primary THA. Her inflammatory markers are elevated (ESR 45 mm/hr, CRP 3.2 mg/dL). Synovial fluid aspiration reveals a WBC count of 3,500 cells/uL with 75% PMNs. Which of the following synovial fluid biomarkers has the highest specificity for confirming a periprosthetic joint infection?

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

Correct Answer & Explanation

. Leukocyte esterase

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils and has demonstrated exceptionally high specificity (often >95%) for diagnosing periprosthetic joint infections. Its diagnostic accuracy is notably less affected by prior antibiotic administration than traditional culture methods.

Question 3163

Topic: Total Hip Arthroplasty (THA)

During a posterior approach THA, trial reduction reveals that the leg is lengthened by 1.5 cm and the offset is decreased by 1 cm compared to the preoperative template. Shuck testing shows significant soft tissue laxity. Which modular adjustment will best restore proper offset and soft tissue tension while minimizing further leg lengthening?

. Use a shorter femoral head with a standard neck stem
. Use a longer femoral head with a standard neck stem
. Use a high-offset stem with a shorter femoral head
. Use a standard-offset stem with a longer femoral head
. Advance the stem further into the diaphysis

Correct Answer & Explanation

. Use a shorter femoral head with a standard neck stem

Explanation

A high-offset stem increases femoral offset (tensioning the abductors) without vertically lengthening the leg. Combining a high-offset stem with a shorter femoral head will appropriately restore the necessary offset while reducing the excessive leg length noted on the trial.

Question 3164

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the most common mechanism of failure of a cemented femoral component in total hip arthroplasty?

. Infection
. Aseptic loosening
. Stem fracture
. Dislocation
. Polyethylene wear

Correct Answer & Explanation

. Infection

Explanation

Aseptic loosening is the most common cause of late failure in cemented femoral stems, often due to micro-motion at the cement-bone interface or osteolysis driven by wear debris.

Question 3165

Topic: 3. Adult Reconstruction (Hip & Knee)



Figure 3 shows an AP radiograph of an 80-year-old woman who sustained a low-energy fall. She has a nondisplaced femoral neck fracture. What is the most appropriate definitive management?

. Nonoperative management with strict bed rest
. In situ fixation with cannulated screws
. Bipolar hemiarthroplasty
. Total hip arthroplasty
. Proximal femoral nail

Correct Answer & Explanation

. Nonoperative management with strict bed rest

Explanation

Nondisplaced femoral neck fractures in the elderly are best treated with in situ fixation using cannulated screws to prevent displacement while preserving the native hip.

Question 3166

Topic: 3. Adult Reconstruction (Hip & Knee)



Figure 4 shows a pelvic radiograph of a 65-year-old man who is 5 years status post right total hip arthroplasty. He reports a squeaking sound from his hip. What bearing surface combination was most likely used?

. Metal-on-polyethylene
. Ceramic-on-polyethylene
. Ceramic-on-ceramic
. Metal-on-metal
. Oxinium-on-polyethylene

Correct Answer & Explanation

. Metal-on-polyethylene

Explanation

Squeaking is a specific complication associated with ceramic-on-ceramic bearing surfaces in total hip arthroplasty, often related to stripe wear or component malposition.

Question 3167

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient undergoing total hip arthroplasty, placement of the acetabular component in excessive retroversion is most likely to result in which of the following complications?

. Anterior dislocation
. Posterior dislocation
. Leg length discrepancy
. Psoas impingement
. Sciatic nerve palsy

Correct Answer & Explanation

. Anterior dislocation

Explanation

Excessive retroversion of the acetabular component predisposes the hip to posterior dislocation, particularly when combined with flexion, adduction, and internal rotation.

Question 3168

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old woman presents with a displaced femoral neck fracture. She has a history of rheumatoid arthritis and is an independent ambulator. Which of the following is the most appropriate surgical treatment?

. In situ fixation with cannulated screws
. Unipolar hemiarthroplasty
. Bipolar hemiarthroplasty
. Total hip arthroplasty
. Cephalomedullary nail

Correct Answer & Explanation

. In situ fixation with cannulated screws

Explanation

Total hip arthroplasty is the preferred treatment for displaced femoral neck fractures in independent, active elderly patients, particularly those with preexisting joint disease like rheumatoid arthritis.

Question 3169

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the most accurate method to diagnose an adverse local tissue reaction (ALTR) in a patient with a metal-on-metal total hip arthroplasty?

. Joint aspiration for cell count
. Serum cobalt and chromium levels
. Metal artifact reduction sequence (MARS) MRI
. Bone scan
. Plain radiography

Correct Answer & Explanation

. Joint aspiration for cell count

Explanation

MARS MRI is the most sensitive and specific imaging modality for diagnosing and evaluating the extent of ALTR or pseudotumors in patients with metal-on-metal bearings.

Question 3170

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old man presents with groin pain 7 years after total hip arthroplasty. Radiographs show eccentric wear of the polyethylene liner and osteolysis in Gruen zones 1 and 7. What is the primary biological mediator responsible for this osteolysis?

. Interleukin-1 (IL-1) and TNF-alpha activated macrophages
. Polymorphonuclear leukocytes
. T-lymphocytes
. B-lymphocytes
. Eosinophils

Correct Answer & Explanation

. Interleukin-1 (IL-1) and TNF-alpha activated macrophages

Explanation

Polyethylene wear particles are phagocytosed by macrophages, which then release inflammatory cytokines like IL-1, IL-6, and TNF-alpha, leading to osteoclast activation and periprosthetic osteolysis.

Question 3171

Topic: Total Hip Arthroplasty (THA)

During a posterior approach to the hip, which muscle is most critical to protect and repair to minimize the risk of postoperative dislocation?

. Piriformis
. Obturator internus
. Gluteus maximus
. Quadratus femoris
. Gluteus medius

Correct Answer & Explanation

. Piriformis

Explanation

The short external rotators, particularly the obturator internus and piriformis, along with the posterior capsule, should be meticulously repaired during a posterior approach to enhance stability.

Question 3172

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is considered the "safe zone" for acetabular component placement in total hip arthroplasty as described by Lewinnek?

. 20-30 degrees of abduction, 5-15 degrees of anteversion
. 30-50 degrees of abduction, 5-25 degrees of anteversion
. 40-60 degrees of abduction, 15-35 degrees of anteversion
. 30-50 degrees of abduction, 0-10 degrees of retroversion
. 45-55 degrees of abduction, 20-40 degrees of anteversion

Correct Answer & Explanation

. 20-30 degrees of abduction, 5-15 degrees of anteversion

Explanation

Lewinnek's safe zone for acetabular cup placement is historically defined as 40 +/- 10 degrees of abduction (inclination) and 15 +/- 10 degrees of anteversion to minimize dislocation risk.

Question 3173

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old woman complains of lateral hip pain after an uncomplicated total hip arthroplasty performed via a direct anterior approach. What structure is most likely contributing to her symptoms?

. Tensor fasciae latae
. Gluteus medius
. Rectus femoris
. Sartorius
. Iliopsoas

Correct Answer & Explanation

. Tensor fasciae latae

Explanation

The direct anterior approach uses the internervous plane between the tensor fasciae latae (TFL) and sartorius. Retraction and trauma to the TFL can lead to postoperative lateral hip pain.

Question 3174

Topic: 3. Adult Reconstruction (Hip & Knee)

When converting an ankylosed (arthrodesed) hip to a total hip arthroplasty, the patient should be counseled about an increased risk of which of the following complications compared to primary THA?

. Sciatic nerve palsy
. Aseptic loosening of the acetabular component
. Infection
. Venous thromboembolism
. Periprosthetic fracture

Correct Answer & Explanation

. Sciatic nerve palsy

Explanation

Conversion of a hip arthrodesis to a total hip arthroplasty carries a significantly higher risk of nerve injury, particularly to the sciatic nerve, due to altered anatomy and the need to restore leg length.

Question 3175

Topic: 3. Adult Reconstruction (Hip & Knee)

Highly cross-linked polyethylene is primarily used in total hip arthroplasty to reduce which of the following?

. Dislocation rate
. Volumetric wear
. Oxidation rate
. Squeaking
. Cost of the implant

Correct Answer & Explanation

. Dislocation rate

Explanation

Highly cross-linked polyethylene (HXLPE) was developed to significantly reduce volumetric wear rates compared to conventional polyethylene, decreasing the incidence of wear particle-induced osteolysis.

Question 3176

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male is evaluated for a painful THA. Aspiration yields a synovial fluid white blood cell (WBC) count of 4,500 cells/uL with 85% polymorphonuclear leukocytes. What is the most appropriate next step?

. Immediate single-stage revision
. Two-stage revision arthroplasty
. Prescribe oral antibiotics for 6 weeks
. Obtain a bone scan
. Perform a core biopsy

Correct Answer & Explanation

. Immediate single-stage revision

Explanation

A synovial WBC > 3,000 cells/uL with > 80% PMNs in a hip more than 6 weeks post-op is highly suggestive of a periprosthetic joint infection (PJI), making two-stage revision the gold standard treatment.

Question 3177

Topic: 3. Adult Reconstruction (Hip & Knee)

Increasing femoral offset in a total hip arthroplasty has what primary biomechanical effect on the joint?

. Decreases abductor tension
. Increases the joint reaction force
. Decreases the abductor moment arm
. Increases the abductor moment arm
. Increases the incidence of bony impingement

Correct Answer & Explanation

. Decreases abductor tension

Explanation

Increasing femoral offset lengthens the abductor moment arm, which decreases the force required by the abductors to stabilize the pelvis. This consequently decreases the overall joint reaction force on the hip.

Question 3178

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old active community ambulator sustains a displaced femoral neck fracture. Compared to hemiarthroplasty, total hip arthroplasty for this patient is associated with:

. A lower risk of postoperative dislocation
. A lower risk of reoperation
. Shorter operative time
. Decreased intraoperative blood loss
. Higher mortality at 1 year

Correct Answer & Explanation

. A lower risk of postoperative dislocation

Explanation

In active older adults, total hip arthroplasty for displaced femoral neck fractures has a lower reoperation rate and better functional scores than hemiarthroplasty. This benefit comes despite a higher dislocation risk and increased surgical time and blood loss.

Question 3179

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old woman presents with a periprosthetic femur fracture around a cementless THA stem. Radiographs show a fracture at the tip of the stem, and the stem is radiographically loose. According to the Vancouver classification, what is the most appropriate management?

. Open reduction internal fixation with cerclage cables
. Nonoperative management with a brace
. Revision to a long cementless diaphyseal engaging stem
. Revision to a cemented stem
. Strut allografting alone

Correct Answer & Explanation

. Open reduction internal fixation with cerclage cables

Explanation

This describes a Vancouver B2 fracture (fracture around the stem, loose prosthesis, adequate bone stock). The standard of care is revision arthroplasty utilizing a long bypass stem to achieve stable diaphyseal fixation past the fracture site.

Question 3180

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old man with a metal-on-metal total hip arthroplasty presents with groin pain 5 years postoperatively. Workup reveals a solid pseudotumor and elevated serum cobalt and chromium levels. This reaction is primarily mediated by which type of hypersensitivity?

. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type I

Explanation

Adverse local tissue reaction (ALTR) or ALVAL in metal-on-metal implants is primarily mediated by a Type IV delayed hypersensitivity reaction. It is a T-cell mediated response to metal ions (cobalt and chromium).

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