A new study that forms part of the doctoral research of Dr Antonino Mazzonello has shed light on the possibility of using surface engineering to make hip implants more durable.
Antonino completed his research under the supervision of Prof. Inġ. Bertram Mallia and Prof. Inġ. Joseph Buhagiar at the Department of Metallurgy and Materials Engineering, University of Malta (DMME).
With the rise in global population and life expectancy, more and more people will need surgery to replace the hip joint
The increase in global population and life expectancy mean that more and more people need surgery to replace the hip joint. Antonino explained that the lifetime of the artificial joint depends on different factors including the resistance to material losses at the moving surfaces of the joint.
The sliding movement of the femoral head against the acetabulum liner in the highly
corrosive environment of the fluids inside the human body results in material losses due to the combined action of corrosion and wear.
Mechanical wear and corrosion affect implants’ durability
“Some of the most cost-effective solutions for this type of surgery include metallic implant parts. For instance, Cobalt-Chromium-Molybdenum alloys are typically used, but these wear with time due to the aggressive environment they form part of – you have mechanical wear, but also corrosion caused by chemical components in the body fluids.
This means that if you get a hip replacement at a younger age, the probability of developing complications in later years, and therefore the need of a second operation, increases,” Antonino explained.
Degradation of such metallic implants could potentially lead to the generation of metallic debris and the dissolution of metallic ions into the bloodstream. And this is where Antonino’s doctoral research comes into play…to mitigate the formation of metallic debris and metallic ions via surface engineering such that the durability of metallic implants is improved.
Surface Engineering: A Possible Solution
Antonino told Gadgets that surface engineering involves the alteration of the surface of materials that allows tailoring its properties for the intended application while still benefitting the already good properties of the substrate material. In the case of Cobalt-Chromium-Molybdenum alloys, surface engineering can be aimed towards improving the corrosion-wear performance at the moving surfaces.
Antonino’s doctoral research seeks to improve the performance of metallic implants whilst operating inside the body; in fact, in collaboration with industry giants Bodycote (Germany) and the Danish Technological Institute (Denmark), a Cobalt-Chromium-Molybdenum alloy was surface engineered using commercially available treatments to create a much-improved surface. In his work, Antonino designed and investigated a novel combination of surface engineering treatments involving surface modification by diffusion of carbon followed by an inert ceramic coating application. The surface engineering treatment layers are a tenth of the thickness of an average human hair.
The advantage of ceramic coating is that it doesn’t corrode
Antonino explained the rationale behind the surface engineering treatments: “It is presumed that the dense inert ceramic coating inhibits any pathway for the corrosive media to reach the underlying substrate.
“Furthermore, an advantage of this ceramic coating is that it is inert, meaning that it doesn’t corrode because it doesn’t react with body fluids. Moreover, adding a carbon-based diffusion layer beneath the ceramic coating provides a good bed to the outer inert coating layer. This coating architecture avoids what is known as the thin ice effect – a scenario whereby a thin, brittle layer fractures easily if not well supported.”
Research presented multiple times in international conferences
Antonino has taken pride in the fact that he has presented his research work multiple times in international conferences.
“These were some of the most fulfilling moments. The positive feedback and recognition we repeatedly get is testament to the high quality of research being carried out in Malta.”
What comes next?
Antonino explained that such a surface engineering treatment does not come without its challenges. “As long as a coating is not cracked or damaged, it will fulfil its function perfectly. However, coatings have the risk of peeling off, which could introduce a whole new set of problems.”
“As such, these new surfaces must be tested meticulously against European and American standards. Therefore, as a next step, it would be ideal to coat an actual hip joint implant, and test such implant in a hip-joint simulator.”
Study was possible thanks to a scholarship granted by the Ministry for Education
The research was partially funded by the Endeavour Scholarship Scheme (Malta), part-financed by the European Union – European Social Fund (ESF) – Operational Programme II – Cohesion Policy 2014-2020 ‘Investing in human capital to create more opportunities and promote the well-being of society’.
