title: Retrospective lifetime estimation of failed and explanted diamond-like carbon coated hip joint balls.
abstract: Diamond-like carbon (DLC) coatings are known to have extremely low wear in many technical applications. The application of DLC as a coating has aimed at lowering wear and to preventing wear particle-induced osteolysis in artificial hip joints. In a medical study femoral heads coated with diamond-like amorphous carbon, a subgroup of DLC, articulating against polyethylene cups were implanted between 1993 and 1995. Within 8.5 years about half of the hip joints had to be revised due to aseptic loosening. The explanted femoral heads showed many spots of local coating delamination. Several of these explanted coated TiAlV femoral heads have been analyzed to investigate the reason for this failure. Raman analysis and X-ray photoelectron spectroscopy (XPS) depth profiling showed that the coating consists of diamond-like amorphous carbon, several Si-doped layers and an adhesion-promoting Si interlayer. Focused ion beam (FIB) transverse cuts revealed that the delamination of the coatings is caused by in vivo corrosion of the Si interlayer. Using a delamination test set-up dissolution of the silicon adhesion-promoting interlayer at a speed of more than 100 μm year(-1) was measured in vitro in solutions containing proteins. Although proteins are not directly involved in the corrosion reactions, they can block existing small cracks and crevices under the coating, hindering the exchange of liquid. This results in a build-up of crevice corrosion conditions in the crack, causing a slow dissolution of the Si interlayer.
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Testing and Research, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland. roland.hauert@empa.ch
authors.forename: R
authors.initials: R
authors.lastname: Hauert
authors.forename: C V
authors.initials: CV
authors.lastname: Falub
authors.forename: G
authors.initials: G
authors.lastname: Thorwarth
authors.forename: K
authors.initials: K
authors.lastname: Thorwarth
authors.forename: Ch
authors.initials: Ch
authors.lastname: Affolter
authors.forename: M
authors.initials: M
authors.lastname: Stiefel
authors.forename: L E
authors.initials: LE
authors.lastname: Podleska
authors.forename: G
authors.initials: G
authors.lastname: Taeger
mesh_terms: D000497:Alloys; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D003343:Corrosion; D003460:Crystallization; D018130:Diamond / Q000494:pharmacology*; D006621:Hip Joint / Q000187:drug effects* / Q000473:pathology; D006622:Hip Prosthesis; D006801:Humans; D008855:Microscopy, Electron, Scanning; D056951:Photoelectron Spectroscopy; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012825:Silicon / Q000494:pharmacology; D013997:Time Factors; D014025:Titanium / Q000494:pharmacology
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; C031462:titanium alloy (TiAl6V4); D018130:Diamond; D014025:Titanium; D012825:Silicon