Finite element analysis of polycarbonate-urethane coatings for talus implant applications

Total talar replacement is a promising treatment for talar osteonecrosis and collapse. However, current implants fabricated from stiff materials, such as cobalt chrome, are associated with excessive contact pressures that may accelerate wear in the surrounding articular cartilage. Implant coatings such as polycarbonate-urethane (PCU) have been suggested to offer a more physiological joint interface. This study therefore aimed to examine this by evaluating the contact mechanics of talar implants with and without PCU coatings in dorsiflexion and plantarflexion.

Finite element models of four cadaveric ankle joints were generated from CT scans. For each subject, five configurations were simulated in dorsiflexion and plantarflexion: native talus, customized cobalt chrome implant, customized PCU-coated implant, statistical shape model cobalt chrome implant, and statistical shape model PCU-coated implant. A 2000 N compressive load was applied through the tibia, and peak contact pressures and contact areas were quantified at the tibial, fibular, calcaneal, and navicular cartilage surfaces of the talus/implant.

Results indicated that the cobalt chrome implants produced substantially higher peak contact pressures and smaller contact areas relative to the native talus in both dorsiflexion and plantarflexion. Whereas, PCU-coated implants yielded peak contact pressures and contact areas that more closely matched the biological models.

These findings support incorporating compliant coatings into talar implant designs to restore physiological contact mechanics, ultimately preserving cartilage health after total talar replacement.