Effects of implant orientation and implant material on tibia bone strain, implant-bone micromotion, contact pressure, and wear depth due to total ankle replacement.

The aim of this study is to investigate the effects of implant orientation and implant material on tibia bone strain, implant-bone micromotion, maximum contact pressure, and wear depth at the articulating surface due to total ankle replacement. Three-dimensional finite element models of intact and implanted ankle were developed from computed tomography scan data. Four implanted models were developed having varus and valgus orientations of 5° and 10°, respectively. In order to determine the effect of implant material combination on tibia bone strain, micromotion, contact pressure, and wear depth, three other finite element models were developed having a different material combination of the implant. Dorsiflexion, neutral, and plantarflexion positions were considered as applied loading condition, along with muscle force and ligaments. Implant orientation alters the strain distribution in tibia bone. Strain shielding was found to be less in the case of the optimally positioned implant. Apart from the strain, implant orientation also affects implant-bone micromotion, contact pressure, and wear depth. Implant materials have less influence on tibia bone strain and micromotion. However, wear depth was reduced when ceramic and carbon fibre-reinforced polyetheretherketone material combination was used. Proper orientation of the implant is important to reduce the strain shielding. The present result suggested that ceramic can be used as an alternative to metal and carbon fibre-reinforced polyetheretherketone as an alternative to ultra-high molecular weight polyethylene to reduce wear, which would be beneficial for long-term success and fixation of the implant.