3. Adult Reconstruction (Hip & Knee) MCQs

A 68-year-old woman presents to the emergency department with an anterior dislocation of her primary total hip arthroplasty (THA). The index procedure was performed 6 weeks ago via a standard posterior approach. Which of the following component malpositions is most likely responsible for this specific direction of dislocation?

A 72-year-old man presents with severe pain in his right total hip arthroplasty 3 years postoperatively. Radiographs show stable components with no osteolysis. Aspiration of the hip yields synovial fluid with a WBC count of 4,800 cells/µL and 88% polymorphonuclear neutrophils (PMNs). Alpha-defensin testing is positive. Serum CRP is 35 mg/L and ESR is 55 mm/hr. Assuming adequate bone stock and soft tissue coverage, what is the most appropriate next step in management?

A 72-year-old female presents with severe thigh pain after a ground-level fall. Radiographs demonstrate a periprosthetic fracture around a loose femoral stem, but with adequate surrounding bone stock. According to the Vancouver classification, what is the most appropriate surgical management?

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with chronic groin pain and a palpable mass. MRI reveals a solid and cystic pseudotumor. If a tissue sample is taken, which histopathological finding is most characteristic of an Adverse Local Tissue Reaction (ALTR/ALVAL) in this setting?

A patient with a metal-on-polyethylene total hip arthroplasty presents with new-onset groin pain. Serological testing demonstrates significantly elevated serum cobalt levels, while chromium levels remain normal. What is the most likely source of the metal wear?

In patients who have undergone ceramic-on-ceramic total hip arthroplasty, post-operative 'squeaking' is a known complication. Which biomechanical factor is most strongly associated with the development of this phenomenon?

A 72-year-old man presents with chronic right hip pain 3 years after a primary total hip arthroplasty. Laboratory tests show an ESR of 45 mm/hr and a CRP of 18 mg/L. Hip aspiration yields synovial fluid with a WBC count of 3,500 cells/uL and 75% PMNs. Which of the following tests is the most accurate synovial biomarker to confirm a periprosthetic joint infection in this scenario?

A 64-year-old man presents with progressive groin pain and swelling 6 years after a metal-on-polyethylene total hip arthroplasty utilizing a large-diameter cobalt-chromium femoral head on a titanium stem. Serum cobalt levels are markedly elevated (15 ppb) while chromium levels are normal (1.5 ppb). What is the most likely source of the elevated metal ions?

A 55-year-old man reports a new-onset squeaking noise originating from his hip when walking, 4 years after undergoing a primary total hip arthroplasty. Radiographs show a well-fixed uncemented titanium stem and acetabular shell with a ceramic-on-ceramic bearing. Which of the following factors is most strongly associated with the development of squeaking in ceramic-on-ceramic THA?

A 68-year-old woman presents with persistent lateral hip pain and a positive Trendelenburg sign 1 year after a total hip arthroplasty via a direct lateral approach. An MRI with metal artifact reduction sequence (MARS) demonstrates a full-thickness tear of the gluteus medius tendon with 4 cm of retraction and severe fatty atrophy (Goutallier stage 4). What is the most appropriate surgical management?

A 45-year-old patient underwent a total hip arthroplasty with a ceramic-on-ceramic bearing. Two years postoperatively, they complain of a high-pitched squeaking sound during movement but report no pain. What is the most likely biomechanical cause of this phenomenon?

A 68-year-old male presents with a painful THA 3 years postoperatively. Synovial fluid aspiration reveals a WBC count of 3,500 cells/uL with 75% PMNs. Which of the following synovial fluid biomarkers is considered the most specific for confirming a periprosthetic joint infection?

When placing acetabular screws during a total hip arthroplasty, the "safe zone" is located in the posterior-superior quadrant of the acetabulum. What critical neurovascular structure is at highest risk if a screw significantly overpenetrates the anterior-superior quadrant?

Postoperatively, a THA patient complains that their operative leg feels "too long." Radiographs confirm the vertical distance from the teardrop to the lesser trochanter is equal bilaterally, but the horizontal distance is increased by 15 mm on the operative side. What is the most likely clinical consequence?

A 60-year-old female presents with persistent lateral hip pain and a positive Trendelenburg sign 6 months after a posterior approach THA. MRI demonstrates a complete avulsion of the conjoined tendon of the abductors. Where does the primary insertion of the gluteus medius strictly lie?

Highly cross-linked polyethylene (HXLPE) is the modern standard bearing surface in THA. What specific step in its manufacturing process is critical for eliminating free radicals to prevent late oxidative degradation?

A patient with a metal-on-polyethylene THA presents with a painful, swollen hip 5 years postoperatively. Inflammatory markers are normal, and aspiration yields dark, sterile fluid. MRI reveals a large pseudotumor. What is the most likely source of this adverse local tissue reaction (ALTR)?

A 65-year-old undergoes THA. How does increasing femoral offset affect hip biomechanics?