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arthroplasty

Bearing Surfaces, Polyethylene Wear, and Osteolysis

advanced
6 min
22 marks
6 questions
Clinical Scenario
A 60-year-old man with a 15-year-old uncemented THA presents for routine follow-up. He is asymptomatic with excellent function. X-rays show eccentric position of the femoral head within the acetabular component and progressive periacetabular osteolysis that was not present 2 years ago. Components appear well-fixed. Additionally, a 48-year-old active male construction worker is discussing THA options and is concerned about implant longevity.
AP pelvis radiograph showing left uncemented THA with eccentric femoral head position indicating polyethylene wear. Expansile lytic lesions visible around acetabular component in DeLee-Charnley zones 1-2. Components remain well-fixed.
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AP pelvis radiograph showing left uncemented THA with eccentric femoral head position indicating polyethylene wear. Expansile lytic lesions visible around acetabular component in DeLee-Charnley zones 1-2. Components remain well-fixed.

Source: The Usefulness of 3D CT as an Assessment of Periacetabular Osteolysis • PMC4972632 • CC-BY

Questions

Question 1 (3 marks)

What bearing surface options are available for THA and what are the key characteristics of each?

Question 2 (3 marks)

Explain the pathophysiology of periprosthetic osteolysis.

Question 3 (4 marks)

How has polyethylene technology evolved and what is the evidence for highly cross-linked polyethylene?

Question 4 (4 marks)

The 60-year-old patient has progressive osteolysis around a well-fixed cup. What are your management options?

Question 5 (4 marks)

For the 48-year-old active construction worker, what bearing surface would you recommend and why?

Question 6 (4 marks)

What is the role of femoral head size selection and what factors influence your choice?

Exam Day Cheat Sheet

Must Mention

  • •Osteolysis: wear particles → macrophage activation → RANKL → osteoclasts
  • •HXLPE reduces wear by 50-90%
  • •Eccentric head position on X-ray = polyethylene wear
  • •CoC = lowest wear but squeaking/fracture risks
  • •MoM largely abandoned (ARMD)
  • •Exclude infection before any revision
  • •Progressive osteolysis = early intervention preserves bone

Common Pitfalls

  • •Not excluding infection before revision
  • •Recommending MoM (abandoned)
  • •Large metal heads (trunnion corrosion)
  • •Ignoring progressive osteolysis
  • •Revising well-fixed cup unnecessarily