A randomised prospective study of 4 bearing surfaces in hip replacements is being conducted. The primary objective is to identify the best long term bearing surface clinically and radiographically, and metal ion levels have been measured in all cases.

Patieents have been randomised to the 4 bearing surfaces viz. Ceramic on XLinked Poly, Ceramic on Ceramic, Metal on Metal and Ceramic on Metal. Pre operative blood samples and follow up blood samples for metal ion analysis using the ICPMS method have been taken in all patients. As at February 2008 187 patients have been recruited, and metal ion levels at 1 year are available in 52 patients.

Metal ion levels are not increased with Ceramic on XLinked Poly or Ceramic on Ceramic bearings. At 1 year follow up the metal ion levels in Ceramic on Metal bearings is half that of Metal on Metal bearings using the mean levels, and one third using the madian levels. Of note is that the chromium levels in Ceramic on Metal bearings is the least elevated.

Due to laboratory evidence that Ceramic on Metal bearings have the best surface wear characteristics with no head stripe wear, and laboratory and clinical evidence of lower metal ion blood levels, Ceramic on Metal hip replacements could be a bearing surface of the future.