• Andreas Ficklscherer, Bernd Wegener, Thomas Niethammer, Matthias F Pietschmann, Peter E Müller, Volkmar Jansson, and Hans-Heinrich Trouillier.
• Department of Orthopaedic Surgery, University Hospital of Munich (LMU), Munich, Germany. andreas.ficklscherer@med.uni-muenchen.de
• Ulus Travma Acil Cer. 2013 Mar 1;19(2):98-102.

BackgroundRecent literature has shown a persistently high rate of aseptic loosening of the tibial component in total ankle prostheses.MethodsWe analyzed the interface between the tibial bone and tibial component with a thermoelastic stress analysis to demonstrate load transmission onto the distal tibia. In this regard, we used two established ankle prostheses, which were implanted in two human cadaveric and in two third-generation composite tibia bones (Sawbones®, Sweden). Subsequently, the bones were attached to a hydropulser and a sinusoidal load of 700 N was applied.ResultsBoth prostheses had an inhomogeneous load transmission onto the distal tibia. Instead of distributing load equally to the subarticular bone, forces were focused around the bolting stem, accumulating as stress maxima with forces up to 90 MPa. Furthermore, we were able to demonstrate load transmission into the metaphysis of the bone.ConclusionAs demonstrated in this study, anchoring systems with stems used in all established total ankle prostheses lead to an inhomogeneous load transmission onto the distal tibia, and furthermore, to a distribution of load into the weaker metaphyseal bone. For these reasons, we favor a prosthetic design with minimal bone resection and without any stem or stem-like anchoring system, which facilitates a homogeneous load transmission onto the distal tibia. Thermoelastic stress analysis proved to be a fast and easy-to-perform method to visualize load transmission.

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