Transmission electron microscopy of intracellular particles of polyethylene from joint replacement prostheses: size distribution and cellular response.

Abstract The objectives of this transmission electron microscopy study of peri-implant tissues retrieved at revision arthroplasty were to (1) determine the size distribution of intracellular polyethylene particles, and (2) assess the cellular response to phagocytosed polyethylene particles as revealed by the condition of the cellular organelles. The frequency distributions of intracellular polyethylene particle sizes for 15 cases of total hip replacement showed that more than 75% of the particles had lengths of less than 0.5 μm. More than 90% of the particles were less than 1.0 μm in size. In comparison, the frequency distribution for the particles in cells comprising tissue retrieved from three total knee replacement prostheses showed that only 43% of the particles were less than 0.5 μm in length and 72% were less than 1 μm in size. There was no statistically significant difference in the mean particle length between the specimens from the hip and knee patients. The majority of the cells containing polyethylene were without signs of degeneration. The cytoplasmic and nuclear membranes were intact. Several electron lucent voids which once contained polyethylene particles were seen surrounded by several healthy appearing mitochondria, which displayed sharp membranes and intact cristae. There were no signs of a cytotoxic response to polyethylene at the ultrastructural level.