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Session: Poster session 2 (Odd numbers)
Session starts: Friday 27 January, 10:00
Presentation starts: 10:00

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Corine Post (Radboudumc)
Thom Bitter (Radboudumc)
Inger van Langen (Radboudumc)
Adam Briscoe (Invibio Ltd.)
Nico Verdonschot (Radboudumc)
Dennis Janssen (Radboudumc)

Abstract:
Introduction: Cementless polyetheretherketone (PEEK-OPTIMATM) knee components are of interest due to its stiffness properties being more similar to the properties of bone than titanium. This may potentially avoid stress-shielding. The primary fixation of cementless knee components are crucial for the long-term fixation, with the micromotions and gaps as important quantifications. The interference fit and coefficient of friction both influence the primary fixation and therefore need to be researched in cementless PEEK tibial components. In this finite element (FE) study, the effect of varying the interference fit and coefficient of friction on the micromotions of a cementless PEEK and titanium tibial component was investigated. Methods: Nine FE models were created of the tibia and PEEK or titanium tibial tray including polyethylene insert (5L, 4R). Gait and squat activities were simulated. Two variations of interference fit (500, 750 µm), defined through the contact algorithm and applied at the bone-implant interface, and two variations of coefficient of friction (0.5, 1.5) were investigated. To quantify the primary fixation, the 95th percentile of the resulting shearing micromotions, resulting normal gaps and resultant (vectorial) micromotions were analyzed for each FE simulation. Results: Both the interference fit and coefficient of friction did not have a large impact on the shearing micromotions. The high interference fit resulted in slightly larger normal gaps and resultant micromotions. Additionally, the micromotion and gap values of the cementless PEEK tibial component were similar to the micromotion and gap values of the more traditional cementless titanium tibial component. Conclusion: This study showed that the shearing micromotions of a cementless tibial component has minor effects caused by the in this study researched variations of interference fit, coefficient of friction and implant material. The interference fit has small effects on the normal gaps and resultant micromotions. The current FE simulations give understanding of the influence of interference fit and coefficient of friction on the micromotions and gaps. This may be further assessed in a larger population of models to analyze the sensitivity of patient related characteristics on micromotion outliers. Acknowledgements: PEEK-OPTIMATM is a trademark of Invibio Ltd. Implant geometry was supplied by Maxx Orthopaedics Inc.