In Vitro Comparison of Fixed- and Mobile Meniscal–Bearing Unicondylar Knee Arthroplasties: Effect of Design, Kinematics, and Condylar Liftoff
Section snippets
Materials
Six medial and 6 lateral Preservation mobile-bearing UKAs and 6 medial and 6 lateral Preservation fixed-bearing UKAs (DePuy International Ltd) were tested. All UKAs investigated were size 3 systems with Co-Cr-Mo alloy femoral and tibial components interposed by PE inserts of 9.5 mm in designated thickness. Both medial and lateral system PE inserts had been manufactured from GUR 1020 ram extruded bar (DePuy, Leeds, UK), sterilized by gas plasma. In addition, 2 of each PE insert type were used as
Mobile UKA System
Wear of the meniscal system increased as the study progressed. This study consisted of 3 stages: high kinematics (0-5 Mc), intermediate kinematics (5-7 Mc), and intermediate kinematics with induced lateral femoral condylar liftoff (7-9 Mc). Wear of the lateral system was consistently greater than the medial system (Fig. 2); however, this only became significant (ANOVA and Mann-Whitney, P < .05) from 5 Mc onward (during testing under intermediate kinematics). During high-kinematic conditions,
Discussion
Two 9-Mc knee simulator studies were conducted to investigate the mobile- and fixed-bearing variations of a unicompartmental knee device (the Preservation UKA). By assessing the individual and combined UKA systems, the influences of design and the effects of kinematic inputs and femoral condylar liftoff on the in vitro wear and wear performance were assessed.
Conclusion
This study demonstrated that substantially reduced in vitro wear rates can be achieved by mobile- and fixed-bearing UKA devices when compared with clinically successful TKA devices. This study also demonstrated the effects of design, kinematic input, and femoral condylar liftoff on in vitro wear:
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Wear was reduced with the fixed-bearing UKA compared with the mobile-bearing UKA.
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Wear was consistently increased in the lateral side in both UKA designs, indicating that the increased sliding distance
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The Conflict of Interest statement associated with this article can be found at doi:10.1016/j.arth.2012.02.011.
This study was supported by the EPSRC, and the components tested within this study were supplied by DePuy International, Leeds, UK.