Insert exchange

Abstract

Modularity in tibial components for total knee arthroplasty (TKA) is controversial. Advantages of insert modularity include component inventory management and the potential for late insert exchange to treat instability or polyethylene wear. In addition, prophylactic insert exchange to an improved polyethylene can be accomplished at the time of arthrotomy for a reason unrelated to the tibial component. Disadvantages of modular tibial inserts include outright failure of the locking mechanism or the potential for insert-tray movement leading to backside wear and potential synovitis or osteolysis.1-7 Among the many advances in Total Knee Prosthetic design in the past 30 years has been the incorporation of metal backing and modularity as standard attributes of present-day total knee systems. Metal backing was added to tibial components to improve load transfer across the proximal tibia based on the finite element analysis of Bartel and others.8 Its continued routine use, however, remains controversial. In 1991, Apel et al.9 presented a series of total knee arthroplasties comparing 62 patients with all-polyethylene tibial components with 69 patients with metal-backed tibial components. They reported no significant difference at 6-year follow-up. In fact, they maintained that the incorporation of metal-backing posed the risk of decreased polyethylene thickness and that an all-polyethylene component of 8 to 10mm thickness will have greater durability than a metal-backed component due to more favorable surface wear. © 2005 Springer Science+Business Media, Inc. All rights reserved.