Stem requirements of tibial augmentations in total knee arthroplasty

Various tibial augmentations have been employed to overcome the problem associated with proximal tibial bony deficiencies mainly in revision total knee arthroplasty (TKA). It has generally been recommended that stem extensions should always be applied to the tibial tray in the event that block augments have been used to compensate for bone loss. The rationale for such routine use of stems has not been clearly established and further this adds to implant costs and may contribute to substantial bone loss if a future revision is required. We investigated the stability of three implant configurations (Deltafit Keel tibial tray only (no bone loss), tray with block augment (with bone loss), and tray with block and extended stem) utilizing both cadaveric human bone as well as commercially available composite tibias. The experimental results revealed that comparable stability can be achieved with the configuration of Deltafit Keel tibial tray and a block as compared to the case of Deltafit Keel tray only without bone loss. Addition of a stem provided moderate improvement of stability but with significant stress shielding. For the amount of bone loss evaluated in this study, a Deltafit Keel tibial tray with a block provided adequate stability and avoided obvious stress shielding.