Finite element analysis of a total wrist replacement: determining implant lifetime due to fatigue

Abstract

Total wrist replacement is a surgery in which an implant is used to help a patient regain a full range of painless movement in their wrist. However, there is little data to suggest the lifetime of implants when being used, implants should last as long as possible to reduce possible harm to patients and reduce the need of more surgery. This paper aims to use finite element analysis (FEA) to develop a model of a total wrist replacement and therefore develop a fatigue analysis based on the typical use of the implant. Results from the FEA were further corroborated using a rainflow count analysis. It was found that during the wrist movement cycles of radial-ulnar and flexion-extension the implant was suggested to have a lifetime of over 500 years when using loads up to 350N which is far beyond the expected use of the implant. Loads over 350N were suggested to be producing fatigue damage to the implant, with damage being focused at the extreme angles of the cycles. As a result, it is suggested that those with the implant should not lift large loads regularly, or regularly move to the extremes angles of movement, in order to reduce risk of damage to the component.