Finite element analysis of total ankle replacement

Lead Research Organisation: University of Leeds
Department Name: Mechanical Engineering

Abstract

It is estimated that osteoarthritis of the ankle affects more than 70 million people worldwide. Total ankle replacement (TAR) has been a clinical solution to ankle arthritis since development in the 1970s. However, clinical performance compared to hip or knee replacement is far less successful, with only 77% of TARs functioning beyond ten years. Despite a clear clinical need, ankle replacement is used less frequently than hip or knee replacement due to concerns over clinical performance. As ankle arthritis is primarily associated with prior trauma, patients tend to be younger and more active than hip or knee patients, therefore there is a significant need to address the failure of TAR and deliver underpinning research to support the understanding of TAR function. Implant failure is often associated with osteolytic lesions around both the tibial and talar components. Wear debris induced osteolysis is a well-documented phenomena in hip and knee replacement failure, however studies of TAR wear performance and TAR retrieval analysis within the iMBE ankle group have indicated that polyethylene wear may not be the primary cause of failure. A recent PhD project within iMBE has developed an initial finite element model of total ankle replacement, and identified elevated stress within the tibial bone surrounding the implant. Anecdotal discussion with our local collaborating surgeon (Mr Ktistakis) has also suggested there is a wide difference in perceived mechanical properties/condition of the bone in which the TAR devices are implanted. Development of an enhanced finite element model to explore the influence of fixation and surgical positioning of the TAR, incorporating a stratified range of bony geometries and properties will enable better indicators of patient suitability for TAR, and improved TAR implant design and instrumentation to reduce the likelihood of bony failure.

The overall aim of this PhD is to develop a stratified range of finite element models of total ankle replacement to explore the effects of bone quality, geometry and surgical positioning on the contact mechanics of a TAR and the localised stresses around the implant. This project will build upon the previous PhD study (which modelled tibial interface only), and include experimental validation. Specific objectives will include:
CT measurement and mechanical evaluation of cadaveric human ankle bone tissues (tibia and talus)
Development of finite element models of the natural ankle using methods developed at Leeds to derive both the geometry and material properties from the CT image data
Implantation of a TAR device within the model under a range of conditions
Standard surgical technique as defined within manufacturers instructions
Rotational and translational implant offset as defined by retrieval analysis and consultation with local ankle surgeon
Experimental and computational contact mechanics studies of TAR under a range of conditions representative of daily activities

The project fits to the priority areas for the IMBE set out in the school research strategy, ('(i) extend our joint simulation techniques to other joints (e.g. ankle joints)' and '(v) pro-actively develop the independent research profiles of our talented, younger staff within iMBE such as the new UAF (Brockett)'. This PhD would join a new and developing research group within iMBE, led by Dr Brockett (UAF) and align with the developing area of total ankle replacement simulation. Two industrial partners have previously supported Dr Brockett's research area through CASE studentship support and provision of materials, and we would seek to gain further collaborative support for this project. Dr Brockett will be submitting an EPSRC first grant proposal in December 2016 focussed on development of novel and clinically relevant experimental simulation of total ankle replacement, and this PhD project would articulate well with the planned research.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509681/1 01/10/2016 30/09/2021
1970957 Studentship EP/N509681/1 01/01/2018 31/10/2021 Bryony Jocelin Halcrow