ORGANISATION NAMEnorthumbria university
ORGANISATION COUNTRYUnited Kingdom
RESEARCH FIELDFormal sciencesProfessions and applied sciences
Fully funded PhD position for students worldwide.
Title: Failure analysis and design optimisation of the magnetic expansion controlled growing spinal rod medical implant
Supervisors: Dr Farnoosh Farhad, Prof Tom Joyce, Dr Martin Birkett
About the Project
Medical implants have improved the quality of life for millions of human beings. However, the failure of the implants can be disastrous to the patients. This emphasises the need in the study of failed implants and development in the products that expands their lifecycle. Magnetically controlled growing rods are the medical implants that are increasingly used in the treatment of early-onset scoliosis (i.e. curvature of the spine >10°) in children. The MAGnetic Expansion Control (MAGEC) system is one such implant that has been licenced for use in Europe since 2009. It has the advantage of being lengthened using an external remote control and therefore significantly reduces the number of surgeries and consequently improves the experience of the patient compared with conventional growing rods, which require surgery every 6-9 months. However, mechanical failure with MAGEC system have been reported. Failure is likely due to multiple factors including over-loading, fatigue, and corrosion. However, the relative importance of each of these factors, and therefore how to mitigate them remains a critical and limiting knowledge gap. This project aims to optimise the design of rods in two phases, phase one is an evaluation of the failure mechanism and phase two is the assessment and ultimate improvement of the design of the rod. The specific objectives of this study are:
- To analyse the explanted MAGEC rods by means of microscopy techniques and evaluate common failure mechanisms
- To assess the failure mode of MAGEC rods by performing finite element stress analysis
- To optimise the MAGEC rods
- To experimentally examine the life cycle of newly designed rods using a new bespoke corrosion-fatigue test replicating body fluid
Several MAGEC rod implants have been explanted and are available from Newcastle University [6-10]. Specialist support will also be provided by an industrial collaborator, ExplantLab, https://www.explantlab.com/ with expertise in the analysis of a range of medical implants. Scanning Electron Microscopy (SEM) of the failed drive pins will be undertaken to understand their failure mechanisms. The stress analysis of the rods and drive pins using numerical simulation (by ABAQUS/ANSYS software) will provide valuable new insights into the failure mode [2-3]. Based upon the identification of the failure mechanism(s) and analysed life span of the explanted rods, a new optimised design will be proposed. To physically test the optimised version, a bespoke corrosion fatigue vessel that previously was developed in [1,4-5] will be modified for this application and the life cycle of the implant will be examined in a replicated body environment in the laboratory.
The Principal Supervisor for this project is Dr Farnoosh Farhad.
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