Structural optimisation for medical implants through additive manufacturing

Advanced manufacturing techniques are being explored to fabricate degradable and non-degradable, porous or non-porous implants for medical applications. These implants have been designed using standard computer-aided design (CAD) and computer-aided engineering (CAE) tools and produced in a multitude of materials. The recent use of optimisation techniques, mainly topology optimisation, allows the development of additive manufactured medical devices with improved performance. This review discusses the combined use of optimisation techniques and additive manufacturing to produce biocompatible and biodegradable scaffolds for tissue engineering with improved mechanical and permeability properties; metallic lattice structures with reduced weight and minimal stress shielding effect; and lightweight personalised orthopaedic implants. Three optimisation routes are considered: topology optimisation; triply periodic minimal surfaces that can be manipulated by means of the equations parameters to optimise the overall performance; and the use of repetitive structures that are optimised as unit cells under certain conditions to compose a bulk object. Major limitations and research challenges are highlighted and discussed.