Serial radiographs of a total hip replacement show progressive periprosthetic osteolysis around the acetabulum. Wear analysis of the polyethylene liner estimates a steady linear wear rate. Above which annual linear wear rate is the risk of osteolysis considered significantly increased?

• A 0.05 mm per year
• B 0.1 mm per year ✓
• C 0.5 mm per year
• D 1.0 mm per year

Explanation

A linear polyethylene wear rate exceeding approximately 0.1 millimetre per year generates a volumetric particle load sufficient to activate macrophages and trigger cytokine-mediated periprosthetic osteolysis; rates below this threshold are rarely associated with lytic lesions. This threshold explains why highly cross-linked polyethylene, with wear rates often under 0.05 millimetre per year, sharply reduced osteolysis. Options C and D describe catastrophic wear seen only with frank malfunction, far beyond the biological threshold for lysis.

Reference: Miller's Review of Orthopaedics, 8th ed.

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