Revision total knee arthroplasty: the influence of femoral stems in load sharing and stability.

Restoration of lost bone support and joint stability are the primary challenges in revision total knee arthroplasty (TKA). Normally, the defects type 2B and type 3 are associated with several damaged metaphyseal bone and loss of cortical bone. Structural allografts have been used for the treatment of large, contained, or uncontained osseous defect in revision TKA. Disadvantages of using structural allografts include late resorption or nonunion and risk of disease transmission. Alone, the structural allograft can not provide the initial support for revision implants. In these cases the stems are frequently used to provide the necessary load sharing and increase initial component stability. When evaluating whether stems should be cemented or press-fit, there isn't a simple answer, since there are no clear advantages or disadvantages for each approach. The aim of this study was to evaluate load sharing and stability at bone graft-cement interface under femoral component with use of cemented and press-fit stems after allograft incorporation with host bone. The difficulties encountered or the impossibility on the evaluation of these biomechanical parameters in-vitro make the use of finite element (FE) models a way through this evaluation. The FE results suggest that a press-fit stem could be the adequate choice if structural allografts in femur revision are used.