Shape and size of virgin ultrahigh molecular weight GUR 4150 HP polyethylene powder

Sizes and shapes of micron- and submicron-sized structures in four lots of virgin GUR 4150 HP ultrahigh molecular weight polyethylene powder were determined by using low-voltage scanning electron microscopy and image analysis, One thousand two hundred micron-sized virgin powder particles and 1200 of their constituent submicron-sized structures were analyzed, The mean maximum diameter of the micron-sized particles was 81.3 mu m, and that of the submicron-sized particles was 0.82 mu m. Particle shapes, as determined by the aspect ratio (maximum diameter divided by minimum diameter), were remarkably consistent from lot to Lot and between the micron- and submicron-sized particles (1.55 versus 1.53, respectively), Significant lot to lot variability was observed in the sizes of the micron-sized particles, and the size distribution of the submicron-sized particles closely follows the size distribution of the submicron-sized particles observed in tissue retrievals, This variability leads to questions about variability in polyethylene quality and in vivo wear performance. Size similarity between the submicron-sized particles retrieved from tissues and that observed in virgin powder supports the hypothesis that polyethylene debris has two origins: particles released from structures retained from the virgin powder, and particles generated de novo by friction and wear. (C) 1996 John Wiley & Sons, Inc.