Ana Laura Puente Reyna*
Ana Laura Puente Reyna1, Jörg Lützner2, Brigitte Altermann1 and Thomas M. Grupp1,3 1Aesculap AG, Research & Development, Tuttlingen, Germany 2Department of Orthopedics, Trauma and Plastic Surgery, University Hospital Carl Gustav Carus, Technische Universität (TU) Dresden, Germany 3Department of Orthopedic and Trauma Surgery, Ludwig Maximilians University Munich, Musculoskeletal University Center Munich (MUM), GermanyFulltext PDF
A ZrN multilayer coated knee implant was retrieved due to early aseptic loosening and showed a greyish coloring instead of its characteristic bright yellow coloring on most of its surface. The first aim of this study was to analyze the surface composition the retrieved implant. Furthermore, as the oxide layer (greyish coloring) might arise the concern of a compromised cement-implant fixation strength, the second aim of this study was to evaluate the implant-cement-bone interface fixation behavior of artificially oxidized ZrN multilayer coated tibial components in an in vitro test set up. A surface composition analysis via scanning electron microscopy with energy dispersive X-Ray was performed in characteristic parts of the femur component and in the gliding surface. The cement-implant fixation strength was evaluated by means of a push-out test performed in artificially oxidized ZrN multilayer tibial components and the results compared to the cement fixation strength of non-oxidized components. The surface analysis showed that the grey coloring was due to oxidation of the most superficial surface of the ZrN multilayer, while the rest of the layers kept their integrity. Moreover, bone cement particles where found embedded in the UHMWPE gliding surfaces, which continuously polished the articulation surface of the femur component until the appearance of a transition layer between the ZrN shield layer and the first CrN intermediate layer. No delamination, roughening nor deep scratches in the ZrN multilayer coating were seen. The artificially oxidized ZrN multilayer coated tibial components showed a similar push-out strength (3 025 N ± 239 N) compared to the non-oxidized components (3 014 N ± 166 N). In conclusion, the grey coloring seen in the retrieved ZrN multilayer coated implant was due to the superficial oxidation of the ZrN shield layer, having no impact in the underlying layers and demonstrating stability of the coating even under worst-case conditions. Finally, even with an oxidized surface, the ZrN multilayer coated tibial components demonstrated a secure cement fixation.
Total knee arthroplasty; Zirconium nitride multilayer; Oxidation; Retrieval analysis; Fixation strength
Ana Laura Puente Reyna, Jörg Lützner, Brigitte Altermann, Thomas M. Grupp. Analysis of the In Vivo Oxidation and Integrity of a Zirconium Nitride Multilayer Coated Knee Implant and Possible Effect of Oxidation on the Implant-Cement-Bone Interface Fixation Strength. Int Case Rep Jour. 2023;3(1):1-16.