title: Discerning alumina ball wear from confounding metal transfer artifact.
abstract: On dismounting a ceramic femoral ball from its metal trunnion, there is usually a range of gray metallic bands transferred to the trunnion bore inside the ball. This creates an artifact that may compromise detection by weight of the exceedingly low wear rates of ceramic balls. The objective of this study was to compare the weight trending of the metal trunnions and their ceramic balls during conditioning studies. Our hypothesis was that a pretest conditioning protocol would eliminate or greatly reduce the metal transfer artifact. The balls and tapers were placed on a hip simulator under 300-600 load cycles but with no articulation. The balls were then dismounted from the trunnions, and both were cleaned and weighed. This was repeated 6-23 times. We developed a novel hydraulic method for dismounting balls from trunnions that proved to be safe and efficient. There was significant weight loss in the trunnions after the ball removal, but there was no corresponding weight gain in the alumina balls. The weight effect of the metal transfer appeared to have been removed from the balls with our standard cleaning procedures. Therefore, wear rates for alumina balls may be gravimetrically determined without compensating for the metal transfer from trunnion to ball.
authors.affiliation: Peterson Tribology Lab, Orthopaedic Research Center, Loma Linda University Medical Center, Department of Orthopaedic Surgery, 11406 Loma Linda Drive #606, Loma Linda, California 92354, USA. sbrown@som.Ilu.edu
authors.forename: S S
authors.initials: SS
authors.lastname: Brown
authors.forename: K
authors.initials: K
authors.lastname: Kawanabe
authors.forename: M
authors.initials: M
authors.lastname: Manaka
authors.forename: P
authors.initials: P
authors.lastname: Williams
authors.forename: V
authors.initials: V
authors.lastname: Good
authors.forename: I C
authors.initials: IC
authors.lastname: Clarke
mesh_terms: D000537:Aluminum Oxide; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation; D001672:Biocompatible Materials; D008422:Materials Testing / Q000295:instrumentation* / Q000379:methods*; D014025:Titanium; D015040:Zirconium
chemical_list: D001672:Biocompatible Materials; D015040:Zirconium; D014025:Titanium; D000537:Aluminum Oxide