Metaphyseal cones in revision total knee arthroplasty: The role of stems.

Metaphyseal tritanium cones can be used to manage the tibial bone loss commonly encountered at revision total knee arthroplasty (rTKA). Tibial stems provide additional fixation and are generally used in combination with cones. The aim of this study was to examine the role of the stems in the overall stability of tibial implants when metaphyseal cones are used for rTKA. This computational study investigates whether stems are required to augment metaphyseal cones at rTKA. Three cemented stem scenarios (no stem, 50 mm stem, and 100 mm stem) were investigated with 10 mm-deep uncontained posterior and medial tibial defects using four loading scenarios designed to mimic activities of daily living. Small micromotions (mean < 12 µm) were found to occur at the bone-implant interface for all loading cases with or without a stem. Stem inclusion was associated with lower micromotion, however these reductions were too small to have any clinical significance. Peak interface micromotion, even when the cone is used without a stem, was too small to effect osseointegration. The maximum difference occurred with stair descent loading. Stress concentrations in the bone occurred around the inferior aspect of each implant, with the largest occurring at the end of the long stem; these may lead to end-of-stem pain. Stem use is also found to result in stress shielding in the bone along the stem. When a metaphyseal cone is used at rTKA to manage uncontained posterior or medial defects of up to 10 mm depth, stem use may not be necessary.

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© 2020 Author(s) et al.

Déclaration de conflit d'intérêts

Conflict of interest statement: All authors report institutional grants (paid to The University of Edinburgh and Royal Infirmary of Edinburgh) partially funded by Stryker with the remainder of funding from the UK’s Engineering and Physical Sciences Research Council (EPSRC), related to this study. R. Burnett reports payment for lectures from Stryker, not related to this study. P. Pankaj reports an institutional grant partially funded by Stryker with the remainder of funding from the UK’s Engineering and Physical Sciences Research Council (EPSRC), related to this study. D. Hamilton reports an institutional grant (paid to The University of Edinburgh) and payment for lectures from Stryker, not related to this study. C. Scott reports consultancy fees from Stryker Orthopaedics and an institutional grant (paid to Royal Infirmary of Edinburgh) from Stryker, all not related to this study.