Quantitative characterization of polyethylene debris isolated from periprosthetic tissue in early failure knee implants and early and late failure Charnley hip implants

This study isolated and characterized UHMWPE particles from 3 explant group s: early Charnley hip failures (ECE; < 10 years), late Charnley hip failure s (LCE; > 10 years) and early knee failures (EKE; < 10 years). Debris isola ted from the 3 groups had percentage particle number and percentage volumet ric concentration distributions that were not significantly different. The greatest number of particles were found in the 0.1-0.5 mum size range and 1 9-20.6% of the volumetric concentration was below 1 mum in size in all grou ps. However, there were significant differences in the total volumetric con centration of debris isolated per g of tissue. LCE had significantly higher volumes of debris than ECE and EKE, there was no significant difference in the volume of debris from the EKE and ECE, The mean aspect ratio and mean irregularity ratio of the LCE group were also significantly higher than the ECE and EKE, suggesting that different wear mechanisms were occurring in t he late Charnley group compared to the early Charnley and knee groups. Thes e results also suggest that early knees, with normal surface wear, may have similar wear mechanisms to early Charnley hips and indicate that similar v olumes of biologically active micrometer and sub-micrometer UHMWPE particle s were produced, This may have important implications in the longer-term ou tcome of total knee arthroplasties, because it indicates a similar potentia l for osteolysis induced by wear debris. (C) 2001 John Wiley & Sons, Inc.