Investigations on 3D-printed shoulder implants with custom micro-structured surfaces for wear reduction

In the current orthopaedic practice wear of artificial joints is a well-established problem. These implants wear out, become loose with time and need to be replaced. Therefore, it is necessary to minimise wear and consequently the debris load to improve artificial joint survival. Since inadequate component lubrication in vivo leads to wear of the implant, a novel concept to increase lubrication in orthopaedic implants was developed. This concept consists of providing the metal component with a micro-structured surface using a uniform stiffness random spatial structure. Pilot tests using a simple geometry (disk) implemented with this structure, indicated a reduction of the friction coefficient by 50%. In this PhD project, shoulder implants, hence more complicated geometric structures, will be developed making use of this new concept of micro-structured surfaces. Different designs will be implemented, such as the before mentioned spatial structure, dimpled patterns etc. For the manufacturing of the microstructures, additive manufacturing and laser micromachining will be used. These implants will then be tested with a dedicated five degrees of freedom test machine, because setups with uni- or bidirectional motion proved to underestimate wear in vivo. For lubrication in the test machine, the use of an artificial synovial fluid will be investigated. The final product of this current research project has immediate potential on the orthopaedic implant market.