Comparison of the biological activity of grade GUR 1120 and GUR 415HP UHMWPE wear debris.

This study evaluated the in vitro response of murine macrophages to clinically relevant polyethylene particles from two grades of UHMWPE at varying volume doses. Clinically relevant UHMWPE wear debris was generated in vitro using a tri-pin-on-disc tribometer. The debris was observed using a scanning electron microscope and analysed by image analysis. There was no significant difference in the wear rates of the two grades of UHMWPE. Analysis of the wear debris showed that GUR 415HP produced a higher percentage of mass of debris in the submeter size range compared to GUR 1120. The wear debris was co-cultured with C3H murine peritoneal macrophages at particle volume (microm(3)): cell number ratios of 100 :1, 50 :1, 10 :1 and 1 :1 for both grades of UHMWPE and additionally at 0.5 :1 and 0.1 :1 for grade GUR 415HP. The secretion of TNF-alpha was determined by ELISA. Significantly elevated levels of TNF-alpha were secreted at 100 :1 ratio when macrophages were challenged with wear debris from GUR 1120 and at 10 :1 and 1 :1 for debris from GUR 415HP. The results suggested that the greater percentage mass of debris in the submicrometer size range from GUR 415HP lead to a substantial increase in biological activity for this grade of UHMWPE on a volume for volume basis when compared with GUR 1120.