Superior fixation for implant using AM
The Biomechanics Research Centre at National University of Ireland, Galway (NUI Galway) identified that inadequate primary (immediate) and secondary (long-term) fixation is a major factor in loosening, and thus failure of, orthopaedic implants. Current surface coatings on the market rely on friction for achieving primary fixation of the implant. In some cases, this friction can be inadequate and lead to loosening of the implant and eventual failure. Better primary fixation would lead to more effective long-term bone in-growth and so a longer implant lifetime.
The project aimed to develop a novel surface architecture for improved bone in-growth in orthopaedic implants with the ultimate objective of building a company to commercialise the resulting technology.
NUI Galway approached 3T RPD to further develop the potential benefits of producing a hip stem by additive manufacturing. 3T worked with the university to explain not only the opportunities the technology offers but also to identify and workaround its limitations.
The hip stem design underwent a number of iterations to refine and improve the product to ensure optimal results for the bone/implant interface and to ensure consistent building in Titanium Ti6Al4V on the metal AM machines.
This resulted in OsteoAnchor technology. This is an optimised surface architecture for an implant incorporating a multitude of tiny claw features which embed into the patient’s bone during implantation and a network of interconnected pores beneath the surface of the claws which encourage secondary bone in-growth.
OsteoAnchor technology results in excellent primary fixation of the implant because the claws gently but securely embed into the bone and resist micromotions when the patient starts load bearing. This results in the in-growth of hard bone rather than fibrous tissue into the porous substructure beneath the claws, thereby achieving excellent secondary fixation.
OsteoAnchor technology has been shown to provide an effective solution to primary and secondary fixation problems through the increased mechanical interaction of its unique surface architecture features with the host bone.
Friction testing of OsteoAnchor and two existing technologies – porous tantalum and plasma sprayed surface architectures – has shown that OsteoAnchor provides a resistance to transverse motion under normal pressure which is up to 74% greater than porous tantalum and 246% greater than plasma sprayed coatings. This demonstrates OsteoAnchor’s ability to provide much greater primary fixation compared to other, leading technologies currently on the market.
It would not have been possible to produce the OsteoAnchor features using any other production process because of the complexity of the surface design.
Taking advantage of the one-step nature of additive manufacturing to produce the hip stem meant the complex surface architecture was built integrally with the implant core. This is expected to result in lower total production costs due to the simplified manufacturing process.
Talking about the success of the project, Pat McDonnel, Principal Investigator at the Biomechanics Research Centre at the university said: “The OsteoAnchor project has benefited from the strong relationship that we formed with 3T. This resulted in excellent communication resulting in an outstanding end product with the potential to create improved medical outcomes for patients and to build a sound commercial organisation.”
Having established the success of the concept in a pilot preclinical trial using sheep hemiarthroplasty, NUI Galway is now in talks with a number of organisations with a view to gaining seed capital investment to establish a spin-off company to commercialise the technology.
National University of Ireland, Galway
Ireland’s EU Structural Funds Programmes 2007 – 2013
European Regional Development Fund
Enterprise Ireland, Technology Tunnel Big Ideas’ Poster