Background Globally, 1% of the population is affected by arthritis of the foot and ankle. Post-traumatic osteoarthritis, resulting from ankle injury or chronic ankle instability, accounts for more than 50% of these cases. Total ankle replacement (TAR) was developed as an alternative to fusion to treat end-stage arthritis whilst preserving some natural biomechanics. However failure rates are relatively high and are often related to bony damage. Finite element (FE) analysis may be used to investigate the damage to the bone surrounding the TAR implant.
Objective The objective of this study was to develop a FE model of a TAR, which is a sufficiently accurate representation of the real world for further use to examine the failure mechanisms.
Setting Not applicable.
Patients (or participants) Not applicable.
Interventions (or assessment of risk factors) Zenith™ TARs (Corin, UK) were inserted into polyurethane foam blocks (Sawbones, USA) representing the tibial and talar bones. The constructs were loaded in an electromechanical testing machine (Instron, USA) with increasing compressive force until reaching plastic deformation. A corresponding FE model was generated and analysed using Abaqus (Dassault Systèmes, France).
Main outcome measurements Experimental contact pressure, which was captured by pressure mapping sensor (Tekscan, USA), and deformation data were used to validate the FE results.
Results Good agreement was found in the location of damage and average depth of plastic deformation in the synthetic bone (experimental depth was 2.8% smaller than the similar value obtained from analysis). Experimentally, there was some difference in deformation laterally, which corresponded to a difference in contact pressures measured on either side of the mid-plane, illustrating that there was some degree of inclination between the interfaces of the TAR.
Conclusions The good agreement indicates the FE model can be used for further predictions of bone failure. Importantly, the model will be used to investigate clinically relevant misalignment, which this study shows may have an effect on bone damage.
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