MOLECULAR ANATOMY OF FREEZE-FRACTURED ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE AS DETERMINED BY LOW-VOLTAGE SCANNING ELECTRON-MICROSCOPY

Morphological similarities between virgin ultrahigh-molecular-weight p olyethylene (UHMWPE) powder and debris retrieved from failed UHMWPE to tal joint implants motivated this study's objective: to establish the internal microstructural features of consolidated UHMWPE. Cylindrical specimens were cored from a gamma-irradiation sterilized tibial compon ent (extruded from GUR 415 resin), and then these specimens were freez e-fractured at high strain rates. Low-voltage scanning electron micros copy was used to examine these surfaces. Two types of areas were obser ved. The first were uniform, homogeneous, and continuous with microrid ge structures (45-70 nm wide) and hillocks (0.1-0.3 mu m in diameter). The second was nonhomogeneous and discontinuous with fibrils (10-200 nm long), microridges, fenestra as small as 20 nm, and large crater-li ke structures (6-12 mu m in diameter). Many of the submicron-sized str uctures observed were similar to the structures observed in virgin pow der, as well as those observed by others from wear debris retrieval st udies. These data support the hypotheses that wear debris originates, in part, from structures originally present in the powder resin, and t hat these structures retain their identity throughout consolidation, m achining, and in vivo wear, and are released into periprosthetic tissu es as wear debris. (C) 1997 John Wiley & Sons, Inc.