Abstract
The “keel” is the relatively short part of the undersurface of the tibial component that extends into the medullary canal. Most knee replacement systems have the capacity to attach modular stem extensions for enhanced intra-medullary fixation for revision.
Diaphyseal length, large diameter stems may also guide positioning of trial components and are ideal for accurate surgical technique, even if fully cemented stems are eventually implanted.
Smaller diameter non-modular stem extensions may be used for fully cemented fixation. They do not however guide component position very accurately and do not make sense for uncemented fixation. Revision surgery is different from primary surgery and enhanced fixation with some type of intramedullary fixation is highly appropriate, especially if constrained devices might be required.
Options for enhanced intramedullary fixation are: 1. Fully cemented metaphyseal or shorter stems; 2. Diaphyseal engaging press fit stems; and 3. Very short fully cemented stems with trabecular metal cone fixation.
Metaphyseal length press fit stems do not provide reliable fixation in revision TKA. Revision with primary components or constrained components without any stem extension is not advised.
