Artificial lifelong joints can become a reality

Previous attempts to increase the functional lifetime of hip and knee artificial joints focused on using wear-resistant materials. The project ‘LifeLongJoints: Silicon nitride coatings for improved implant function' (LIFELONGJOINTS) explores a different concept. It aims to develop a harder wearing coating that also produces soluble debris with decreased impact on surrounding biological tissues. New silicon nitride low-wear coating for articulating surfaces and interfaces will result in implants with improved wear characteristics.


LIFELONGJOINTS hopes to achieve longer-lasting and more robust implants and reductions in implant failures. The 5-year effort, to be completed in 2018, involves a consortium of 15 centres of excellence within the European research and technology community.


In addition to design and characterisation of a novel wear-resistant silicon nitride-based coating for articulating and non-articulating bearing surfaces, the project has several other objectives. These include development of advanced methodologies for simulating activities of daily living using mechanical and software systems, which predict wear and allow the pre-clinical testing of a series of prototype devices. These newly developed tests will challenge the coating beyond the current standards and will include activities such stair climbing and stumbling. Laboratory studies will also address the effects of silicon nitride on living cell to ascertain whether there are any toxic effects. It is expected that silicon nitride coating will also reduce corrosion, decreasing adverse biological responses.


During the first year, LIFELONGJOINTS partners identified deposition process parameters with regards to silicon nitride coating properties. Silicon nitride-coated cobalt chromium samples were then tested. Testing included adhesion, roughness, hardness, wear resistance and tribocorrosion. The scientists investigated the reasons leading to failure of implants, specifically the fretting wear around the taper junction of the hip implants. State-of-the art simulators are currently being developed that mimic the 'real-life' cycles that cause adverse loading and motions.


The project has had a promising start. The new coatings should lead to improved therapeutic outcomes of joint replacement procedures and increased patient benefits.