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arthroplasty

Aseptic Loosening of Total Knee Arthroplasty

advanced
6 min
18 marks
6 questions
Clinical Scenario
A 68-year-old female presents with progressive right knee pain 8 years after primary TKA for osteoarthritis. Initially had excellent pain relief for 6 years. Now has start-up pain, pain with stairs, and night pain. CRP is 5 mg/L. On examination, there is a small effusion, full extension, flexion to 100°, and tenderness over the medial tibial plateau. Radiographs show tibial component subsidence with progressive radiolucent lines.
AP and lateral radiographs of TKA showing progressive radiolucent lines around tibial component with subsidence and varus collapse. Femoral component appears well-fixed. Evidence of tibial bone loss medially.
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AP and lateral radiographs of TKA showing progressive radiolucent lines around tibial component with subsidence and varus collapse. Femoral component appears well-fixed. Evidence of tibial bone loss medially.

Source: Treatment for Wear and Osteolysis in Well-Fixed Uncemented TKR • PMC4045342 • CC-BY

Questions

Question 1 (3 marks)

What are the causes of aseptic loosening in TKA and how do you differentiate from septic loosening?

Question 2 (3 marks)

Describe the AORI (Anderson Orthopaedic Research Institute) classification for bone defects in revision TKA.

Question 3 (4 marks)

What are the options for managing bone defects in revision TKA? Discuss cones, sleeves, and augments.

Question 4 (3 marks)

The tibial component is loose but the femoral component is well-fixed. What are your options?

Question 5 (3 marks)

What factors predict poorer outcomes in revision TKA for aseptic loosening?

Question 6 (2 marks)

What constraint level would you choose for this revision?

Exam Day Cheat Sheet

Must Mention

  • •EXCLUDE INFECTION before aseptic revision (aspiration, CRP, alpha-defensin)
  • •AORI classification (1, 2A, 2B, 3) guides reconstruction
  • •Cones and sleeves for metaphyseal bone loss (Type 2)
  • •Constraint ladder: PS → VVC → Rotating Hinge
  • •Use minimum constraint necessary
  • •Each revision has worse outcomes than previous

Common Pitfalls

  • •Revising without excluding infection
  • •Over-constraining from the start
  • •Not assessing femoral component properly
  • •Forgetting to assess ligament integrity
  • •Not having backup implant options