*4.3.3 Bone cement fixation*

The modified surface could result different behavior for cement fixation, which was, therefore, investigated. A study comparing the implant-cement-bone fixation strength between uncoated and ZrN multilayer coated tibial components by means of a push-out test and cementation in polyurethane blocks using different bone cement and cementation times was performed [70]. There were no statistical differences in the bone-cement fixation strength between the uncoated and the ZrN multilayer

*Modern Coatings in Knee Arthroplasty DOI: http://dx.doi.org/10.5772/intechopen.105744*

**Figure 2.**

*Metal ion concentrations measured after 1 million cycles for the uncoated and ZrN coated version of Columbus CR/DD.*

coated tibial components, and mixed failure modes at implant-cement and the cement-foam interface occurred.

Moreover, the fixation strength of the ZrN multilayer coated tibia components was statistically higher than that of a clinically long-term successful implant, whose failure mode was at the implant-cement interface.

#### *4.3.4 Oxidation*

Oxidation of the ZrN multilayer coating is normal behavior, as every metal in contact with biological systems will undergo a process of bio-corrosion [54, 71], and has been reported on in vitro studies before [52]. During the oxidation process, oxygen ions are exchanged with the nitrogen ions of the ZrN layer. This oxidation is visible in the ZrN layer because the color of zirconium alloys varies depending on the amount of oxygen and nitrogen, they contain [72–76]. It has, however, no influence on the biomechanical properties of the coating.
