Early metal ion levels in ceramic-on-polyethylene and metal-on-polyethylene total hip arthroplasty

Presenting Author - Sol Qurashi
Background Trunnionosis in total hip arthroplasty (THA) is the mechanical wear or corrosion occurring at femoral modular head-neck interfaces. Trunnionosis has been attributed to elevated serum levels of cobalt and chromium in metal-on-polyethylene THAs. It has been gaining recognition as a cause of failure in THAs as the release of metal ions has the potential to lead to adverse local tissue reaction, persistent pain, increased wear, and physiological dysfunction requiring revision surgery. The purpose of our research was to investigate the early signs of trunnionosis at 6 months post-surgery by evaluating serum cobalt and chromium in the blood. Our secondary aim was to compare metal on polyethylene versus ceramic on polyethylene in THA. To date there is a paucity of research data evaluating metal ion levels at intervals of less than 12 months with most studies either evaluating them at 1 ,2 or 5 years. Methods 100 consecutive patients undergoing an elective primary THA for osteoarthritis using uncemented femoral stem and acetabular components were assessed. All THAs received a 28mm, 32mm or 36mm metal (CoCr on Ti) or ceramic (BioloxDelta on Ti)femoral head matched with a highly cross-linked polyethylene (HCPE) liner. Assembly of the heads was performed by in situ reduction and no impaction. Patients were split into two groups, metal-on-polyethylene (n=50) and ceramic-on-polyethylene (n=50), in a time series fashion. Serum cobalt and chromium levels were measuredbetween 5-7 tomonthspost operatively. Results Serum cobalt and chromium in the blood at 5-7 months post-surgery did not show any detectable abnormal rise in either bearing combinations. Further, there was not statistically significant difference between the two groups. Conclusion Early results of CoCr v/s Ceramic on HCPE do not show any increase or difference in serum metal ion levels.