title: Advances in tribological testing of artificial joint biomaterials using multidirectional pin-on-disk testers.
abstract: The introduction of numerous formulations of Ultra-high molecular weight polyethylene (UHMWPE), which is widely used as a bearing material in orthopedic implants, necessitated screening of bearing couples to identify promising iterations for expensive joint simulations. Pin-on-disk (POD) testers capable of multidirectional sliding can correctly rank formulations of UHMWPE with respect to their predictive in vivo wear behavior. However, there are still uncertainties regarding POD test parameters for facilitating clinically relevant wear mechanisms of UHMWPE. Studies on the development of POD testing were briefly summarized. We systematically reviewed wear rate data of UHMWPE generated by POD testers. To determine if POD testing was capable of correctly ranking bearings and if test parameters outlined in ASTM F732 enabled differentiation between wear behavior of various formulations, mean wear rates of non-irradiated, conventional (25-50kGy) and highly crosslinked (≥90kGy) UHMWPE were grouped and compared. The mean wear rates of non-irradiated, conventional and highly crosslinked UHMWPEs were 7.03, 5.39 and 0.67mm(3)/MC. Based on studies that complied with the guidelines of ASTM F732, the mean wear rates of non-irradiated, conventional and highly crosslinked UHMWPEs were 0.32, 0.21 and 0.04mm(3)/km, respectively. In both sets of results, the mean wear rate of highly crosslinked UHMPWE was smaller than both conventional and non-irradiated UHMWPEs (p<0.05). Thus, POD testers can compare highly crosslinked and conventional UHMWPEs despite different test parameters. Narrowing the allowable range for standardized test parameters could improve sensitivity of multi-axial testers in correctly ranking materials.
authors.affiliation: School of Biomedical Engineering, Drexel University, USA. Electronic address: db434@drexel.edu.
authors.forename: D
authors.initials: D
authors.lastname: Baykal
authors.affiliation: Exponent Inc., USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Siskey
authors.affiliation: Department of Orthopaedic Surgery and Rehabilitation, University of Nebraska Medical Center, USA.
authors.forename: H
authors.initials: H
authors.lastname: Haider
authors.affiliation: Department of Engineering Design and Production, Aalto University School of Engineering, Finland.
authors.forename: V
authors.initials: V
authors.lastname: Saikko
authors.affiliation: VTT Technical Research Centre of Finland, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Ahlroos
authors.affiliation: School of Biomedical Engineering, Drexel University, USA; Exponent Inc., USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Kurtz
mesh_terms: D016880:Anisotropy; D001672:Biocompatible Materials / Q000032:analysis / Q000737:chemistry*; D019544:Equipment Failure Analysis / Q000295:instrumentation*; D017276:Friction; D007595:Joint Prosthesis; D008422:Materials Testing / Q000295:instrumentation*; D011095:Polyethylenes / Q000032:analysis / Q000737:chemistry*; D013314:Stress, Mechanical
chemical_list: D001672:Biocompatible Materials; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene