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Session: Poster Session 1 (Even numbers)
Session starts: Thursday 26 January, 16:00
Presentation starts: 16:00

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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: Polyetheretherketone (PEEK-OPTIMATM) is used as an alternative material for total knee arthroplasty (TKA) components as its stiffness characteristics more closely resemble the stiffness characteristics of human bone compared to the currently used metal alloys. This on the long-term may avoid stress-shielding of the TKA. Earlier research on a cementless PEEK femoral component suggested that larger bone-implant interface micromotions were found relative to a cementless cobalt-chrome femoral component. Porous titanium has been widely used for facilitating bone ingrowth and therefore, a titanium inlay on the inside of a cementless PEEK femoral component may reduce the micromotions as well as preserving the beneficial (low) stiffness characteristics. Therefore, the objective of this study was to assess the effect of varying the thickness and stiffness of a titanium inlay on the inner surface of a cementless PEEK femoral component on the primary fixation and bone stress-shielding using finite element (FE) analysis. Methods: FE models of the femur and femoral component were created with five variants of titanium inlays: thin, medium, thick, distal thick – proximal thin, and distal thin – proximal thick. The axial forces of a jogging activity from the Orthoload database were applied on the medial and lateral femoral condyles. The 95th percentile of the maximum resulting micromotions and the strain energy density (SED) were quantified as outcome measures. Results: The addition of a titanium inlay reduced the micromotions. The largest micromotions arose on the medial side of the anterior flange. The distal thick – proximal thin variant showed the lowest micromotions. The SED mainly decreased in the distal region. This was more pronounced for a stiff and thick inlay. Conclusion: This study showed that the combined distal thick – proximal thin inlay gives the best trade-off between reducing micromotions and prevention of periprosthetic stress-shielding. The addition of a titanium inlay on the inner surface of a cementless PEEK femoral component may therefore result in a longer lifespan of the femoral component. Acknowledgements: PEEK-OPTIMATM is a trademark of Invibio Ltd. Implant geometry was supplied by Maxx Orthopaedics Inc.