title: Friction, lubrication, and polymer transfer between UHMWPE and CoCrMo hip-implant materials: a fluorescence microscopy study.
abstract: The friction coefficients of CoCrMo sliding against UHMWPE and CoCrMo were measured in solutions of albumin and synovial fluid containing fluorescently labeled albumin. No fluorescence could be observed on the CoCrMo disc following incubation in labeled albumin or after sliding against CoCrMo. This was due to quenching of the fluorophore by the metal and indicated that a protein film thicker than 10 nm was not formed on the surface. A more complicated behavior was observed for UHMWPE sliding against CoCrMo. For each lubricating solution and at each load, a bimodal distribution of steady-state friction values was observed, the friction coefficient either remaining constant or decreasing during the early stages of the measurement. As no quenching of the fluorophores occurred on the UHMWPE surface, the fluorescence labeling method could be used to reveal polyethylene (PE) transfer and to show that it correlates with the friction coefficient: Low friction coefficients corresponded to a low density of PE spots on the CoCrMo surface. In addition, it was found that the friction coefficients for UHMWPE sliding against CoCrMo in synovial fluid were not significantly different from those in phosphate-buffered saline (PBS), but that the addition of albumin to PBS did cause a significant increase in the friction coefficient.
authors.affiliation: Empa, Swiss Federal Institute for Material Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland. rowena.crockett@empa.ch
authors.forename: Rowena
authors.initials: R
authors.lastname: Crockett
authors.forename: Marcella
authors.initials: M
authors.lastname: Roba
authors.forename: Marco
authors.initials: M
authors.lastname: Naka
authors.forename: Beat
authors.initials: B
authors.lastname: Gasser
authors.forename: Daniel
authors.initials: D
authors.lastname: Delfosse
authors.forename: Vinzenz
authors.initials: V
authors.lastname: Frauchiger
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Spencer
mesh_terms: D000497:Alloys / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D017276:Friction; D006622:Hip Prosthesis; D008153:Lubrication; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008856:Microscopy, Fluorescence; D011095:Polyethylenes / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013499:Surface Properties; D013582:Synovial Fluid / Q000378:metabolism; D014800:Vitallium / Q000737:chemistry*
chemical_list: D000497:Alloys; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D014800:Vitallium; D012710:Serum Albumin, Bovine