Fatigue Properties of Additive Manufactured Ti-6Al-4V and CoCr-Alloy Total Ankle Components

Total ankle replacement is an increasingly popular alternative to ankle fusion, because it allows patients to retain mobility of the joint. Additive manufacturing has made the incorporation of porous surfaces a viable option for a variety of orthopedic implants, especially in cases in which the application of a porous metal layer would otherwise be impossible or cost prohibitive. A novel additive manufactured total ankle system using direct metal laser sintering was developed. The tibial component is made from Ti-6Al-4V ELI alloy, and the talar component is made from cobalt-chrome alloy. Both components include a reticulated open porous layer, with a porosity ranging from 60% to 70%. Bending fatigue testing was conducted on finished tibial and talar components and force/number of cycles curves were constructed with a total of five components achieving run-out at 107 cycles with no failures. The results showed that the additive manufactured components met previously established strength requirements for total ankle applications. In addition, it was shown that thermal postprocessing could be effective in eliminating residual or loosely adhered residual powder into the porous structure.