3. Adult Reconstruction (Hip & Knee) MCQs

A 72-year-old woman sustains a fall 5 years after a cementless THA. Radiographs

demonstrate a fracture around the stem just below the lesser trochanter. On intraoperative assessment, the fully porous-coated stem is found to be grossly loose, but the proximal femur has adequate bone stock. What is the most appropriate management?

A 64-year-old man presents with chronic right hip pain 2 years following a THA. ESR is 45 mm/hr and CRP is 2.5 mg/dL. Hip aspiration yields 2,500 WBC/µL with 75% PMNs. The synovial fluid alpha-defensin test is positive. What is the primary cellular source of the biomarker measured in this specific immunoassay?

A 58-year-old man presents with new-onset groin pain and a palpable mass 6 years after a metal-on-polyethylene THA. He has a 36-mm cobalt-chromium femoral head on a titanium alloy stem. Radiographs show no loosening. Metal ion testing reveals elevated serum cobalt levels with normal chromium levels. MRI demonstrates a large cystic fluid collection around the hip. What is the most likely diagnosis?

A 45-year-old woman underwent a ceramic-on-ceramic THA 3 years ago. She now complains of a high-pitched squeaking noise during gait, without significant pain. Radiographs are unremarkable. Which of the following conditions is most strongly associated with this phenomenon?

In modern total hip arthroplasty, the use of large-diameter femoral heads has increased to reduce the risk of dislocation. However, which of the following is a recognized trade-off when using a large-diameter cobalt-chromium head on a standard titanium femoral stem trunnion?

A 68-year-old man underwent a primary THA 4 weeks ago. He now presents with 3 days of increasing hip pain, fever, and drainage from the surgical site. Synovial fluid aspiration grows Staphylococcus aureus. Radiographs

show well-fixed components. What is the most appropriate indication to proceed with Debridement, Antibiotics, and Implant Retention (DAIR)?

During a direct anterior approach for THA, the surgeon uses fluoroscopy to assess leg length and offset. Which of the following anatomical landmarks provides the most reliable horizontal reference on an AP pelvis radiograph for evaluating leg length discrepancy intraoperatively?

A 70-year-old woman is evaluated for a persistent limp 1 year following a right THA performed via a direct lateral (Hardinge) approach. She complains of lateral hip pain and demonstrates a pronounced Trendelenburg gait. Radiographs show a well-fixed cementless THA. An MRI with metal artifact reduction sequence (MARS) is ordered. What is the most likely finding?

A 35-year-old active man undergoes a total hip arthroplasty with a ceramic-on-ceramic bearing. Two years postoperatively, he complains of a reproducible squeaking noise from the hip when bending to tie his shoes, though he has no pain. Radiographs show a well-fixed stem with an acetabular cup placed in 60 degrees of inclination and 35 degrees of anteversion. What is the most likely cause of the squeaking?

A 72-year-old woman sustains a fall 4 years after a primary cementless total hip arthroplasty. Radiographs reveal a periprosthetic fracture extending from the lesser trochanter to just distal to the tip of the femoral stem. The stem is visibly subsided by 15 mm compared to previous films, but the remaining distal bone stock is good.

According to the Vancouver classification, what is the most appropriate management?

A 65-year-old man presents with chronic dull pain in his left hip 3 years after a primary total hip arthroplasty. His ESR is 45 mm/hr and CRP is 25 mg/L. A hip aspiration is performed. According to the International Consensus Meeting (ICM) criteria, what synovial fluid white blood cell (WBC) count threshold is highly indicative of a chronic periprosthetic joint infection?

A surgeon performs a primary total hip arthroplasty using a direct anterior approach utilizing the inter-nervous plane between the tensor fasciae latae and the sartorius. Postoperatively, the patient notes an area of numbness and dysesthesia over the anterolateral thigh. Which nerve was most likely stretched or injured during the approach?

A 66-year-old man presents with severe right hip pain 8 years after a primary metal-on-polyethylene total hip arthroplasty. Inflammatory markers are normal and aspiration is negative for infection. An MRI with metal artifact reduction sequence (MARS) reveals a large cystic mass communicating with the joint space. Blood tests reveal elevated serum cobalt levels with normal chromium levels. What is the most likely diagnosis?

A 55-year-old woman presents with an apathetic abductor lurch (Trendelenburg gait) 6 months after a primary THA performed via a direct lateral (Hardinge) approach. Physical exam shows profound weakness in hip abduction. Which neurologic structure was most likely injured during the proximal extension of the split in the gluteus medius?

A 60-year-old man with a history of ankylosing spondylitis is scheduled for a bilateral total hip arthroplasty. Given his high risk for heterotopic ossification (HO), what prophylactic regimen is most strongly supported by current evidence?

When preparing the acetabulum during a total hip arthroplasty, the surgeon aims to place the acetabular cup within the classic "Lewinnek safe zone" to minimize the risk of postoperative dislocation. What are the target parameters for this zone?

A 40-year-old man presents with a 4-month history of deep groin pain. MRI reveals osteonecrosis (avascular necrosis) of the femoral head involving 25% of the weight-bearing surface. Plain radiographs show a normal head contour with sclerosis and cystic changes, but no subchondral radiolucent line (crescent sign) or articular collapse. What is the most appropriate initial surgical intervention?

A patient undergoes revision surgery for a painful metal-on-metal total hip arthroplasty. Intraoperatively, extensive solid caseous necrosis and a cystic pseudotumor are found. Histopathological examination of the periarticular tissues would most likely demonstrate which of the following?

A patient complains that their operative leg feels substantially longer following a primary THA. Postoperative anteroposterior pelvic radiographs indicate that the vertical distance from the inter-teardrop line to the lesser trochanter on the operative side is 15 mm greater than on the unoperated side. Global offset is equal bilaterally. Which surgical error most likely caused this leg length discrepancy?