Stability of ceramic coatings on retrieved knee prostheses.

Background: In total knee arthroplasty, femoral components with coated or oxidized surfaces are commonly used as alternative to CoCrMo in metal sensitive patients. Data on the in vivo behaviour of different coating types is, however, rare. Aim of the study was the investigation of coating stability with respect to implant and patient specific parameters.
Methods: Coating thickness and coating thickness reduction, respectively, was measured at 37 retrieved femoral components with TiNbN, TiN, ZrN or oxidized zirconium (OxZr) surface by the crater grinding method. The results were correlated to surface type, manufacturer, time in vivo of the implant, patient body weight and patient activity.
Results: Mean coating thickness reduction in the overall retrieval collection was 0.6 μm ± 0.8 μm. There was no correlation between coating thickness reduction and coating type, time in vivo, patient body weight, and patient activity. If grouped according to manufacturers, implants of one manufacturer showed an increased coating thickness reduction. 10 of 37 retrievals exhibited coating abrasion with exposure of the underlying alloy. TiNbN coatings showed the highest incidence (9/17) of coating abrasion. No coating breakthrough was observed in the ZrN or OxZr surfaces.
Conclusion: Our results indicate that TiNbN coatings should be optimized to improve their wear resistance in the long-term.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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