Polyethylene Wear with Ceramic and Metal Femoral Heads at 5 Years: A Randomized Controlled Trial with RSA

Abstract Background A common bearing combination in THA today is a metal femoral head articulating with polyethylene in the cup. Ceramic heads are thought to be more resistant to third-body damage, and have better wettability and decreased surface roughness, which taken together have been suggested to result in less polyethylene wear. The purpose of this study was to compare the initial creep deformation and following wear pattern, using radiostereometry (RSA), of ceramic and metal femoral heads that articulate with a modern highly cross-linked polyethylene (HXLPE) cup liner. Methods 50 patients with primary osteoarthritis and scheduled for an uncemented THA were randomized 1:1 to either a ceramic (BIOLOX® delta) or a metal (CoCr) femoral head. The patients were followed up for 5 years with repeated RSA examinations (postoperatively, then at 14 days, 3, 12, 24, and 60 months), as well as a hip-specific outcome questionnaire. Results During the first 3 months both groups showed expected creep within the liner of 0.12 mm (SD 0.03) for the ceramic and 0.08 mm (SD 0.02) for the metal heads. Between 3 months and 5 years there was very little wear of the liner in either group, corresponding to 0.003 mm/year for ceramic and 0.007 mm/year for metal heads. There was no difference in cup migration or clinical outcome between the groups and no cups were revised. Conclusion With the introduction of modern HXLPE the ceramic head demonstrates no superiority when it comes to either early deformation or polyethylene wear compared with the metal head.