Finite-element analysis of the influence of tibial implant fixation design of total ankle replacement on bone-implant interfacial biomechanical performance.

PURPOSE: Implant loosening in tibia after primary total ankle replacement (TAR) is one of the common postoperative problems in TAR. Innovations in implant structure design may ideally reduce micromotion at the bone-implant interface and enhance the bone-implant fixation and initial stability, thus eventually prevents long-term implant loosening. This study aimed to investigate (1) biomechanical characteristics at the bone-implant interface and (2) the influence of design features, such as radius, height, and length.
METHODS: A total of 101 finite-element models were created based on four commercially available implants. The models predicted micromotion at the bone-implant interface, and we investigated the impact of structural parameters, such as radius, length, and height.
RESULTS: Our results suggested that stem-type implants generally required the highest volume of bone resection before implantation, while peg-type implants required the lowest. Compared with central fixation features (stem and keel), peripherally distributed geometries (bar and peg) were associated with lower initial micromotions. The initial stability of all types of implant design can be optimized by decreasing fixation size, such as reducing the radius of the bars and pegs and lowering the height.
CONCLUSION: Peg-type tibial implant design may be a promising fixation method, which is required with a minimum bone resection volume and yielded minimum micromotion under an extreme axial loading scenario. Present models can serve as a useful platform to build upon to help physicians or engineers when making incremental improvements related to implant design.