Novel bone fixation implants minimising stress shielding

Abstract

In ageing countries, where the population is above the median age, the national health services are under enormous pressure to address problems related to bone fractures due to accidents or diseases. More effective and personalised medical treatments are critical, not only to improve the outcome of the clinical treatment but also to reduce costs. Bone fractures require the use of fixation plates to stabilise the fracture and promote bone healing. These plates are produced using biocompatible metallic materials, presenting a significant stiffness mismatch in comparison to bone. This often results in lack of bone stimulation in the vicinity of the plate causing bone loss and plate instability. Moreover, commercial fixation plates are mass produced using conventional manufacturing methods and consequently not feasible for personalised medical strategies. In order to solve these limitations, this research proposes a strategy based on the use of topology optimisation and bone remodeling together with powder bed fusion additive manufacturing. The aim is to design lightweight plates with reduced stress shielding and additive manufacturing (the ideal technology for mass personalisation) to produce optimised plates. Bone fixation plates were successfully optimised considering different loading conditions and volume reductions. Electron Beam Melting and Selective Laser Melting were used to produce the optimised plates. Non-processed additive manufactured plates were mechanically, biologically and tribologically characterised. Results show that by increasing the volume reduction, the stress shielding problem is minimised, and it was also possible to obtain plate designs presenting mechanical properties in the range of cortical bone. Additive manufactured plates are also able to support cell attachment and to promote cell proliferation, showing significantly better biological performance than commercial plates.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Paulo Jorge Da Silva Bartolo (Supervisor) & Marco Domingos (Supervisor)