It is unclear how metal augments, polyethylene (PE) liner thickness, and length of cemented stem contribute to load transfer when reconstructing uncontained tibial metaphyseal bone loss of Anderson Orthopedic Research Institute (AORI) Type II defects during revision total knee arthroplasty (rTKA). The aim of this study is to understand the impact of these three variables on load transfer through the tibial baseplate. For a fixed defect depth, we hypothesized that there is a particular combination of liner and augment thickness and stem length that minimizes bone stress, reducing the risk of aseptic loosening.
We conducted a finite element analysis (FEA) to model stresses at the bone-cement interface with different iterations of metal augments, PE liner thicknesses and fully-cemented stems lengths.
For a 20 mm tibial defect, constructs with thicker metal augments and thinner polyethylene liners were superior. Constructs with a fully cemented stem further reduced bone stress on the tibial plateau. Bone stress was lowest when a 100 mm fully-cemented stem was used, while stems between 30 mm – 80 mm produced similar results.
When addressing a tibial bone defect of AORI Type II in rTKA, our FEA model demonstrates that surgeons should opt to use the thickest metal augments in combination with a fully-cemented stem with an added length of at least 30 mm, which allows for surgical flexibility together with the most stable construct. Our study is notably limited by lack of modeling of knee joint moments, which are important when considering micromotion, bone-implant interface and stem effectiveness.
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Published online: December 16, 2022
Accepted: November 26, 2022
Received in revised form: November 20, 2022
Received: April 12, 2022
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