Finite Element Analysis in Bioactive-coated Tibial Components

Abstract

The stability of the components is vital for successful, long-term results of total knee arthroplasty (TKA). The loosening of the tibial component is more common than that of the femoral component. Therefore, methods to improve the fixation of the tibial component have been continually developing. Roentgenstereometric analysis (RSA) has shown that early migration can predict loosening of tibial component (1, 2). In cemented TKA, initial postoperative migration occurs as a result of the operative trauma, such as thermal bone necrosis from cementing or sawing. In cementless TKA, initial instability may be due not only to operative trauma from sawing, but also to irregularities of the cut surface. To fill the gap between component and cut surface, bioactive coating or clay, such as hydroxyapatite (HA) or tri-calcium phosphate (TCP), was developed. Some animal studies have shown that hydroxyapatite coating (3) or clay ( 4) enhances the fixation of unstable cementless implants. In clinical studies, some authors showed successful use of bioactive coated implants (5, 6). However, some authors reported early failure due to separation of the coating (7). The objective of the present study is to assess the effectiveness of bioactive coating with tibial components. For this objective, finite element method (FEM) was employed for four different modalities of fixation with the same stem-type design, I) rigid interface, 2) rigid interface only at tibial tray, 3) early stage of bioactive coating, and 4) fibrous fixation.