Finite element stress analysis of the bearing component and bone resected surfaces for total ankle replacement with different implant material combinations

Background

A proper combination of implant materials for Total Ankle Replacement (TAR) may reduce stress at the bearing component and the resected surfaces of the tibia and talus, thus avoiding implant failure of the bearing component or aseptic loosening at the bone-implant interface.

Methods

A comprehensive finite element foot model implanted with the INBONE II implant system was created and the loading at the second peak of ground reaction force was simulated. Twelve material combinations including four materials for tibial and talar components (Ceramic, CoCrMo, Ti6Al4V, CFR-PEEK) and three materials for bearing components (CFR-PEEK, PEEK, and UHMWPE) were analyzed. Von Mises stress at the top and articular surfaces of the bearing component and the resected surfaces of the tibia and talus were recorded.

Results

The stress at both the top and articular surfaces of the bearing component could be greatly reduced with more compliant bearing materials (44.76 to 72.77% difference of peak stress value), and to a lesser extent with more compliant materials for the tibial and talar components (0.94 to 28.09% difference of peak stress value). Peak stresses at both the tibial and talar bone-implant interface could be reduced more strongly by using tibial and talar component materials with smaller material stiffness (7.31 to 66.95% difference of peak stress value) compared with bearing materials with smaller material stiffness (1.11 to 24.77% difference of peak stress value).

Conclusions

Implant components with smaller material stiffness provided a stress reduction at the bearing component and resected surfaces of the tibia and talus. The selection of CFR-PEEK as the material of tibial and talar components and UHMWPE as the material of the bearing component seemed to be a promising material combination for TAR implants. Wear testing and long-term failure analysis of TAR implants with these materials should be included in future studies.