In Vitro Wear Simulation of a Kinematically Aligned Knee Implant Tilted at an Angle of 8°

Despite promising results of kinematic alignment (KA), there are still concerns regarding the wear behavior of KA knee implants. In a previous study, mechanically aligned (MA), KA and malaligned (MalA) knee implants were tested in a wear simulation study using Attune knee implant systems. The results showed no increased wear rate for a mild KA (KA4°) and MalA (MalA4°) condition in comparison to MA (MA0°) knee implants. This study analyzes the wear behavior of a KA condition of 8° (KA8°). The test setup was adapted accordingly. In addition, all tests of the previous study (MA0°, MalA4° and KA4°) and the KA8° condition were replicated using PFC implant systems to indicate if the previous results can be transferred to the predecessor model of the Attune knee implant system. The KA8° using the Attune knee implant system did not lead to a higher wear rate (2.4 ± 0.1 mg/10⁶ cycles) in comparison to the wear results of the previous study (3.8 ± 0.5 mg/10⁶ cycles for MA0°; 2.7 ± 0.2 mg/10⁶ cycles for MalA4° and 4.1 ± 0.2 mg/10⁶ cycles for KA4°). The PFC implant system led to higher wear rates than the Attune implant system but showed the same trend for the different alignment methods (5.1 ± 0.4 mg/10⁶ cycles for MA0°; 3.9 ± 0.1 mg/10⁶ cycles for MalA4°, 5.1 ± 0.8 mg/10⁶ cycles for KA4° and 3.5 ± 1.0 mg/10⁶ cycles for KA8°). KA8° did not show wear related problems but further in vitro and in vivo studies are necessary.