Polyethylene particle morphology in synovial fluid of failed knee arthroplasty

Synovial fluid from the knees of 16 patients undergoing revision knee arthroplasty for aseptic failure was subjected to base digestion and ultrafiltration. Filtered particles were scanned using scanning electron microscopy and analyzed with an image program. Polyethylene particles were identified visually and confirmed with the use of electron diffraction spectroscopy. Averaging more than 1500 particles per patient sample, 25,148 particles were analyzed. This corresponded to a concentration of 3000 polyethylene particles per milliliter of synovial fluid. Three populations of wear debris were identified in the fluid. Small globular particles with a mean area of 75 mu 2 represented 94% of all particles observed. The particles averaged 10 mu in diameter and often were seen in clumps. Long fibrous particles with a mean area of 1164 mu 2 made up 4% of the particle population. Large rhomboidal particles with an area of 557 mu 2 were observed least commonly and comprised the remainder of the particles visualized. All three particle types were observed in each fluid sample regardless of the wear pattern of the retrieved polyethylene liner. There were no differences in absolute particle counts, particle morphologic characteristics, or particle size between patients with and without gross polyethylene wear.