3. Adult Reconstruction (Hip & Knee) MCQs

A 62-year-old male, 14 months post-anatomic total shoulder arthroplasty, presents with insidious onset of shoulder stiffness and mild pain. Inflammatory markers are strictly normal. Joint aspiration grows Cutibacterium acnes. Which of the following best describes this organism?

A 70-year-old man presents with mild, progressive shoulder pain and stiffness 14 months after a reverse total shoulder arthroplasty. His serum ESR and CRP are within normal limits. Joint aspiration is negative for acute inflammation, but tissue cultures taken during revision surgery grow a slow-growing, anaerobic gram-positive bacillus on day 10. What is the most likely causative organism?

A 65-year-old man presents with aseptic loosening of his cementless total hip arthroplasty 12 years after the index procedure. Radiographs show extensive periprosthetic osteolysis. The primary biological mechanism driving this osteolysis involves the phagocytosis of wear particles by which of the following cell types, leading to the release of TNF-alpha and IL-1?

An orthopedic research team conducts a randomized controlled trial comparing a novel DVT prophylaxis regimen to aspirin after total hip arthroplasty. The study concludes there is no statistically significant difference in VTE events between the two groups (p = 0.15). However, post-market surveillance later proves the novel regimen is genuinely superior. The initial trial's failure to detect this true difference is an example of a Type II error. Which of the following adjustments during the trial's design phase would have most effectively reduced the probability of this specific error?

During revision surgery for a failed total hip arthroplasty, evidence of extensive third-body wear is noted on the polyethylene liner, caused by retained bone cement fragments. This type of wear is characterized by microscopic gouges and scratches. What is the specific term for this wear mechanism?

A new rapid diagnostic biomarker for periprosthetic joint infection (PJI) is evaluated in a population where the prevalence of PJI is 10%. The test has a sensitivity of 90% and a specificity of 90%. What is the approximate positive predictive value (PPV) of this new test in this population?

A 55-year-old man undergoes cementless total hip arthroplasty. During preparation of the femur, a longitudinal crack is propagated in the proximal femur. A cerclage wire is placed to treat the fracture. Which of the following best describes the biomechanical principle of cerclage wire fixation in this scenario?

Osteolysis following total hip arthroplasty is primarily driven by macrophage activation due to wear debris. What is the most biologically active size range of polyethylene particles that stimulates this aggressive inflammatory osteolytic response?

During a posterior (Kocher-Langenbeck) approach to the hip, protection of the main blood supply to the femoral head is critical. The deep branch of the medial femoral circumflex artery (MFCA) courses between which two muscles?

A 72-year-old woman sustains a displaced femoral neck fracture. To understand the risk of avascular necrosis, an orthopedic resident reviews the blood supply to the adult femoral head. Which vessel provides the majority of the blood supply to the weight-bearing portion of the femoral head?

During a posterior approach to the hip for a total hip arthroplasty, identifying the sciatic nerve is critical. What is the most common anatomical relationship of the sciatic nerve to the piriformis muscle in the general population?

During a direct lateral approach (Hardinge) to the hip, the gluteus medius is split. What is the precise anatomic footprint of the gluteus medius tendon insertion on the greater trochanter?

A 22-year-old man sustains a scaphoid waist fracture. Because of the unique vascular anatomy of the scaphoid, he is at high risk for avascular necrosis of the proximal pole. The primary blood supply to the proximal pole of the scaphoid is delivered in a retrograde fashion from which of the following vessels?

A surgeon is performing a posterior approach to the hip for a total hip arthroplasty. To prevent iatrogenic avascular necrosis of the native femoral head in a joint-preserving procedure, the deep branch of the medial femoral circumflex artery (MFCA) must be protected. This critical vessel passes between which two anatomic structures?

A patient is undergoing a total knee arthroplasty and receives an ultrasound-guided saphenous nerve block within the adductor canal (Hunter's canal). Which muscle forms the anterolateral boundary of this canal?

During a posterior approach to the hip, protecting the medial circumflex femoral artery (MFCA) is critical. The main branch of the MFCA runs most consistently between which two muscles before piercing the hip capsule?

A continuous saphenous nerve block is placed in the adductor (Hunter's) canal for postoperative analgesia after total knee arthroplasty. Which of the following muscles forms the anterolateral border of this anatomic canal?

During a posterior approach to the hip for total hip arthroplasty, the surgeon meticulously manages the short external rotators. Which tendon, if left intact, directly protects the deep branch of the medial femoral circumflex artery from iatrogenic injury?